Brazing Handbook-1-400.pdf

Brazing Handbook Fifth Edition Supersedes Brazing Handbook, 4th Edition, 1991 Prepared by the American Welding Society (AWS) C3 Committee on Brazing and Soldering Under the Direction of the...

Brazing Handbook Fifth Edition Supersedes Brazing Handbook, 4th Edition, 1991 Prepared by the American Welding Society (AWS) C3 Committee on Brazing and Soldering Under the Direction of the AWS Technical Activities Committee Approved by the AWS Board of Directors  International Standard Book Number: 978-0-87171-046-8 American Welding Society 550 N.W. LeJeune Road, Miami, FL 33126 © 2007 by American Welding Society All rights reserved Printed in the United States of America Errata: 2nd Printing, June 2011 Photocopy Rights. No portion of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, including mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright owner. Authorization to photocopy items for internal, personal, or educational classroom use only or the internal, personal, or educational classroom use only of specific clients is granted by the American Welding Society provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; tel: (978) 750-8400; Internet:. The information and data presented in the Brazing Handbook are intended for informational purposes only. Reasonable care is exercised in the compilation and publication of the Brazing Handbook to ensure the authenticity of the contents. However, no representation is made as to the accuracy, reliability, or completeness of this infor- mation, and an independent, substantiating investigation of the information should be undertaken by the user. The information contained in the Brazing Handbook shall not be construed as a grant of any right of manufacture, sale, use, or reproduction in connection with any method, process, apparatus, product, composition, or system, which is covered by patent, copyright, or trademark. Also, it shall not be construed as a defense against any liability for such infringement. Whether the use of any information in the Brazing Handbook would result in an infringement of any patent, copyright, or trademark is a determination to be made by the user. ii  Preface This preface is not part of the Brazing Handbook, but is included for informational purposes only. Knowledge of the ancient art of brazing is continuously being supplemented by an ever-increasing amount of technical information about metals and their behavior, so that today brazing must be considered both an art and a science. This Fifth Edition of the Brazing Handbook (formerly the Brazing Manual) addresses the fundamental concepts of brazing and incorporates the many advances made since the Brazing Manual was first published. The American Welding Society defines brazing as “a group of joining processes that produces coalescence of materials by heating them to the brazing temperature in the presence of a filler metal having a liquidus above 840°F (450°C) and below the solidus of the base metal. The filler metal is distributed between the closely fitted faying surfaces of the joint by capillary action.” Brazing then must meet each of three criteria: 1. The parts must be joined without melting the base metals. 2. The filler metal must have a liquidus temperature above 840°F (450°C). 3. The filler metal must wet the base metal surfaces and be drawn into or held in the joint by capillary action. To achieve a good joint using any of the various brazing processes described in this Brazing Handbook, the parts must be properly cleaned and must be protected, either by fluxing or protective atmosphere during the heating process, to prevent excessive oxidation. The parts must be designed to afford a capillary for the filler metal when properly aligned, and a heating process must be selected that will provide the proper brazing tem- perature and heat distribution. No analysis of a subject that is continuously being improved can hope to be complete, nor can the subject be covered with a thoroughness that would satisfy the specialist. For this reason, most chapters provide a list of references that give additional and more detailed information on the subject. Yet even after the additional research, trial and error may be required to successfully complete unusual applications. It is hoped, however, that the trials and errors will be fewer for having this Brazing Handbook as a guide. Comments, inquiries, and suggestions for future revisions of the Brazing Handbook are welcome. They should be sent to the Secretary, AWS C3 Committee on Brazing and Soldering, American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126. xiii  Foreword This foreword is not part of the Brazing Handbook, but is included for informational purposes only. Welcome to the new and improved Brazing Handbook, 5th edition. The Brazing Handbook has been substantively updated from the previous edition. For your convenience, the current edition has been reorganized into three main sections—Fundamentals, Processes, and Applications. There are two new chapters, Chapter 11, “Introduction to the Brazing Processes” and Chapter 36, “Diamond.” The new edition covers cutting edge process technologies and new materials. Updating and expanding the chapter on brazing and operator safety has also been a key initiative. The new edition has taken several years to complete, requiring the collaboration and support of many individuals and companies; their contribution has been invaluable! The AWS Handbook Committee members have risen to this challenge and responded with an outstanding technical reference for the brazing industry. You will notice that each chapter was assigned to a reviewer who was responsible for its final technical criteria. Many reviewers had assistance from others at their respective company or within the industry. Without their collaboration, the book would not have been possible. Special thanks go to the members of the AWS C3 Committee on Brazing and Soldering and AWS C3A Sub- committee for the Brazing Handbook who addressed the many challenges that accompany such an undertaking. Carmen Paponetti Chair, C3A Subcommittee for the Brazing Handbook Errata AWS BRH:2007, Brazing Handbook The following Erratum has been identified and will be incorporated into the next reprinting of this document. Page 61, under Inspection, 3rd, 4th, and 5th paragraphs: Replace the following: Class A joints are those joints subjected to high stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property or significant operational failure. Class B joints are those joints subjected to low or moderate stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property significant operational failure. Class C joints are those joints subjected to low or moderate stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property, or significant operational failure. With the following: Class A is typically chosen for joints subjected to high stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property, or in significant operational failure. Class B is frequently chosen for joints subjected to low or moderate stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property, or in significant operational failure. Class C is frequently chosen for joints subjected to low or moderate stresses, cyclic stresses, or both, the failure of which would have no significant detrimental effect. xi  Personnel AWS C3 Committee on Brazing and Soldering P. T. Vianco, Chair Sandia National Laboratories R. W. Smith, Vice Chair Materials Resources International S. N. Borrero, Secretary American Welding Society G. L. Alexy The Prince & Izant Company R. Aluru Chromalloy Gas Turbine Corporation B. Barten Delphi Thermal & Interior D. W. Bucholz Conforma Clad, Incorporated D. E. Budinger General Electric Aviation C. F. Darling Lucas-Milhaupt, Incorporated W. J. Engeron EAS Training & Consulting Services S. L. Feldbauer Abbott Furnace Company Y. Flom NASA Goddard Space Flight Center D. Fortuna Sulzer Metco (U.S.), Incorporated Y. P. Gao Pratt & Whitney Rocketdyne R. A. Gross Gourley Curtiss-Wright S. R. Hazelbaker The Prince & Izant Company T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated F. M. Hosking Sandia National Laboratories J. R. Jachna Modine Manufacturing Company D. A. Javernick Los Alamos National Laboratory D. Kane ADB Industries G. F. Kayser Pratt & Whitney Rocketdyne M. J. Kuta Lucas-Milhaupt, Incorporated E. Liguori Scarrott Metallurgical M. J. Lucas, Jr. General Electric Aviation R. P. McKinney The Prince & Izant Company C. R. Moyer Bodycote Thermal Processing T. Oyama WESGO Metals C. A. Paponetti, Sr. Expert Brazing & Heat Treating, Incorporated R. L. Peaslee Wall Colmonoy Corporation A. Rabinkin Metglas, Incorporated/Hitachi Metals A. E. Shapiro Titanium Brazing, Incorporated C. Walker Sandia National Laboratories Advisors to the C3 Committee on Brazing and Soldering A. Belohlav Lucas-Milhaupt, Incorporated S. S. Bhargava General Motors S. Christy Pratt and Whitney N. C. Cole NCC Engineering C. E. Fuerstenau Lucas-Milhaupt, Incorporated P. K. Gupta Honeywell Aerospace M. J. Higgins Pratt and Whitney v Advisors to the C3 Committee on Brazing and Soldering (Continued) H. Lichtenberger Williams Advanced Materials E. Lugscheider Aachen University of Technology W. D. Rupert Wolverine Joining Technologies AWS C3A Subcommittee on the Brazing Handbook C. A. Paponetti, Chair Expert Brazing & Heat Treating E. Liguori, Vice Chair Scarrott Metallurgical S. N. Borrero, Secretary American Welding Society G. L. Alexy The Prince & Izant Company R. Aluru Chromalloy Gas Turbine Corporation D. W. Bucholz Conforma Clad, Incorporated D. E. Budinger General Electric Aviation W. J. Engeron EAS Training & Consulting Services S. L. Feldbauer Abbott Furnace Company Y. Flom NASA Goddard Space Flight Center C. E. Fuerstenau Lucas-Milhaupt, Incorporated S. R. Hazelbaker The Prince & Izant Company T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated C. H. Holwerk Conforma Clad, Incorporated F. M. Hosking Sandia National Laboratories J. R. Jachna Modine Manufacturing Company G. F. Kayser Pratt & Whitney Rocketdyne M. J. Kuta Lucas-Milhaupt, Incorporated M. J. Lucas, Jr. General Electric Aviation T. Oyama WESGO Metals R. L. Peaslee Wall Colmonoy Corporation A. Rabinkin Metglas, Incorporated/Hitachi Metals A. E. Shapiro Titanium Brazing, Incorporated R. W. Smith Materials Resources International P. T. Vianco Sandia National Laboratories C. M. Volpe Wolverine Joining Technologies C. Walker Sandia National Laboratories Advisors to the C3A Subcommittee on the Brazing Handbook B. Barten Delphi Thermal & Interior A. Belohlav Lucas-Milhaupt, Incorporated S. S. Bhargava General Motors N. C. Cole NCC Engineering P. K. Gupta Honeywell Aerospace M. J. Higgins Pratt and Whitney T. A. Kern Consultant H. H. Lang York International Corporation H. Lichtenberger Williams Advanced Materials W. D. Rupert Wolverine Joining Technologies A. Severin Bradley Corporation R. W. Walls Walls Engineering vi  AWS C3B Subcommittee on Soldering F. M. Hosking, Chair Sandia National Laboratories S. N. Borrero, Secretary American Welding Society R. Aluru Chromalloy Gas Turbine Corporation C. F. Darling Lucas-Milhaupt, Incorporated A. Rabinkin Metglas, Incorporated/Hitachi Metals J. P. Sands Wolverine Joining Technologies A. E. Shapiro Titanium Brazing, Incorporated R. W. Smith Materials Resources International P. T. Vianco Sandia National Laboratories C. M. Volpe Wolverine Joining Technologies C. Walker Sandia National Laboratories Advisors to the C3B Subcommittee on Soldering N. C. Cole NCC Engineering C. E. Fuerstenau Lucas-Milhaupt, Incorporated P. K. Gupta Honeywell Aerospace T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated M. J. Lucas, Jr. General Electric Aviation AWS C3C Subcommittee on Education and Safety G. L. Alexy, Chair The Prince & Izant Company S. N. Borrero American Welding Society R. Aluru Chromalloy Gas Turbine Corporation C. F. Darling Lucas-Milhaupt, Incorporated W. J. Engeron EAS Training & Consulting Services D. Fortuna Sulzer Metco (US), Incorporated T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated D. J. Javernick Los Alamos National Laboratory M. J. Lucas, Jr. General Electric Aviation R. P. McKinney The Prince & Izant Company R. L. Peaslee Wall Colmonoy Corporation J. P. Sands Wolverine Joining Technologies C. Wohlmuth Consultant Advisors to the C3C Subcommittee on Education and Safety A. B. Cedilote WABCO N. C. Cole NCC Engineering V. R. Dave Los Alamos National Laboratory P. K. Gupta Honeywell Aerospace F. M. Hosking Sandia National Laboratories H. H. Lang York International Corporation A. Severin Bradley Corporation R. W. Smith Materials Resources International vii AWS C3D Subcommittee on Brazing Specifications J. R. Jachna, Chair Modine Manufacturing Company S. R. Hazelbaker, Vice Chair The Prince & Izant Company S. N. Borrero, Secretary American Welding Society R. Aluru Chromalloy Gas Turbine Corporation D. E. Budinger General Electric Aviation S. L. Feldbauer Abbott Furnace Company Y. Flom NASA Goddard Space Flight Center C. E. Fuerstenau Lucas-Milhaupt, Incorporated Y. P. Gao Pratt and Whitney Rocketydyne R. A. Gross Gourley Curtiss-Wright T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated F. M. Hosking Sandia National Laboratories D. Kane ADB Industries G. F. Kayser Pratt & Whitney Rocketdyne M. J. Kuta Lucas-Milhaupt, Incorporated E. Liguori Scarrott Metallurgical J. A. Liguori Scarrott Metallurgical M. J. Lucas, Jr. General Electric Aviation R. P. McKinney The Prince & Izant Company C. R. Moyer Bodycote Thermal Processing J. Newman Laser Technology, Incorporated T. Oyama WESGO Metals C. A. Paponetti, Sr. Expert Brazing and Heat Treating, Incorporated R. L. Peaslee Wall Colmonoy Corporation M. J. Pohlman Honeywell R. W. Smith Materials Resources International P. T. Vianco Sandia National Laboratories C. M. Volpe Wolverine Joining Technologies C. Walker Sandia National Laboratories C. Wohlmuth Consultant Advisors to the C3D Subcommittee on Brazing Specifications B. Barten Delphi Thermal & Interior A. B. Cedilote Wabco, Incorporated N. C. Cole NCC Engineering P. K. Gupta Honeywell Aerospace M. J. Higgins Pratt and Whitney T. A. Kern Consultant H. H. Lang York International Corporation H. Mizuhara H Mizuhara Consulting Services W. D. Rupert Wolverine Joining Technologies A. Severin Bradley Corporation K. P. Thornberry Care Medical, Incorporated R. W. Walls Walls Engineering viii AWS C3E Subcommittee on Brazing Conferences R. W. Smith, Chair Materials Resources International A. Rabinkin, Vice Chair Metglas, Incorporated/Hitachi Metals S. N. Borrero, Secretary American Welding Society G. L. Alexy The Prince & Izant Company R. Aluru Chromalloy Gas Turbine Corporation D. W. Bucholz Conforma Clad, Incorporated C. F. Darling Lucas-Milhaupt, Incorporated S. L. Feldbauer Abbott Furnace Company Y. Flom NASA Goddard Space Flight Center D. Fortuna Sulzer Metco (US), Incorporated F. M. Hosking Sandia National Laboratories D. A. Javernick Los Alamos National Laboratory M. J. Lucas, Jr. General Electric Aviation T. Oyama WESGO Metals C. A. Paponetti Expert Brazing & Heat Treating J. P. Sands Wolverine Joining Technologies P. T. Vianco Sandia National Laboratories C. Walker Sandia National Laboratories Advisors to the C3E Subcommittee on Brazing Conferences N. C. Cole NCC Engineering K. L. Gustafson Consultant M. J. Higgins Pratt and Whitney T. P. Hirthe Kru-Mar Manufacturing Services, Incorporated H. Mizuhara H Mizuhara Consulting Services W. D. Rupert Wolverine Joining Technologies M. L. Santella Oak Ridge National Laboratories A. Severin Bradley Corporation K. P. Thornberry Care Medical, Incorporated C. Wohlmuth Consultant Special Contributor C. L. Jenney American Welding Society ix  Table of Contents Page No. Dedications................................................................................................................................................. iii Personnel.......................................................................................................................................................v Foreword..................................................................................................................................................... xi Preface....................................................................................................................................................... xiii List of Tables........................................................................................................................................... xxiii List of Figures..........................................................................................................................................xxvii CHAPTER 1—BASICS OF BRAZING.................................................................................................. 1 Introduction................................................................................................................................................. 2 Historical Perspective................................................................................................................................... 3 Physics of Brazing......................................................................................................................................... 6 Factors Controlling the Properties of the Brazement..................................................................................... 9 The Five Elements of Brazing...................................................................................................................... 12 Bibliography............................................................................................................................................... 20 Suggested Reading List............................................................................................................................... 20 CHAPTER 2—BRAZEMENT DESIGN............................................................................................... 21 Introduction............................................................................................................................................... 22 Design Variables......................................................................................................................................... 22 Base Metal.................................................................................................................................................. 23 Joint Design................................................................................................................................................ 23 Fluxes and Protective Atmospheres............................................................................................................. 32 Stress Distribution...................................................................................................................................... 33 Service Requirements.................................................................................................................................. 38 Brazing Filler Metal.................................................................................................................................... 48 Brazing Process Variables............................................................................................................................ 52 Prebraze and Postbraze Cleaning................................................................................................................ 53 Postbraze Heat Treatment........................................................................................................................... 53 Testing of Brazed Joints to Attain Design Data............................................................................................ 54 Inspection................................................................................................................................................... 61 Drafting Conventions................................................................................................................................. 61 Bibliography............................................................................................................................................... 66 Suggested Reading List............................................................................................................................... 66 CHAPTER 3—BRAZING FILLER METALS...................................................................................... 67 Introduction............................................................................................................................................... 68 Melting of Brazing Filler Metals................................................................................................................. 68 Brazing Filler Metal–Base Metal Interaction............................................................................................... 74 Brazing Filler Metal Selection..................................................................................................................... 74 Brazing Filler Metal Classifications............................................................................................................. 81 Bibliography............................................................................................................................................... 98 Suggested Reading List............................................................................................................................... 99 CHAPTER 4—FLUXES AND ATMOSPHERES.............................................................................. 101 Introduction............................................................................................................................................. 102 Fluxes....................................................................................................................................................... 102 Controlled Brazing Atmospheres.............................................................................................................. 110 Bibliography............................................................................................................................................. 126 Suggested Reading List............................................................................................................................. 126 xv  Page No. CHAPTER 5—PRECLEANING AND SURFACE PREPARATION............................................... 127 Introduction.............................................................................................................................................. 128 Cleaning Processes.................................................................................................................................... 128 Surface Pretreatments................................................................................................................................ 133 Braze Flow Inhibitors................................................................................................................................ 134 Maintaining Cleanliness............................................................................................................................ 134 Suggested Reading List.............................................................................................................................. 135 CHAPTER 6—ASSEMBLY AND FIXTURING................................................................................ 137 Introduction.............................................................................................................................................. 138 Assembly................................................................................................................................................... 138 Fixturing................................................................................................................................................... 139 Suggested Reading List.............................................................................................................................. 143 CHAPTER 7—CORROSION OF BRAZED JOINTS...................................................................... 145 Introduction.............................................................................................................................................. 146 Fundamentals............................................................................................................................................ 146 Types of Corrosion.................................................................................................................................... 147 Proper Brazing Procedures to Minimize Corrosion................................................................................... 160 Removing Source of Corrosion................................................................................................................. 161 Corrosion Resistance................................................................................................................................ 163 Bibliography............................................................................................................................................. 166 Suggested Reading List.............................................................................................................................. 166 CHAPTER 8—INSPECTION OF BRAZED JOINTS...................................................................... 169 Introduction.............................................................................................................................................. 170 Acceptance Criteria................................................................................................................................... 170 Discontinuities in Brazed Joints................................................................................................................. 170 Inspection Methods................................................................................................................................... 171 Critical Brazed Components..................................................................................................................... 177 Bibliography............................................................................................................................................. 178 CHAPTER 9—CODES AND OTHER STANDARDS....................................................................... 179 Introduction.............................................................................................................................................. 180 Applications.............................................................................................................................................. 180 Standards-Developing Organizations........................................................................................................ 181 Manufacturer Associations....................................................................................................................... 192 CHAPTER 10—SAFETY AND HEALTH.......................................................................................... 193 Introduction.............................................................................................................................................. 194 Historical Background.............................................................................................................................. 194 Safety Management................................................................................................................................... 195 General Work Area Safe Practices............................................................................................................. 198 Personal Protective Equipment.................................................................................................................. 201 Protection against Fumes and Gases.......................................................................................................... 202 Safe Handling of Compressed Gases, Gas Cylinders, and Containers........................................................ 208 Electrical Safety......................................................................................................................................... 212 Fire Prevention and Protection.................................................................................................................. 214 Noise Hazards.......................................................................................................................................... 214 Ergonomics............................................................................................................................................... 215 Process-Specific Safe Practices................................................................................................................... 216 Combustibility of Metal Powders.............................................................................................................. 222 Bibliography............................................................................................................................................. 224 xvi  Page No. Suggested Reading List............................................................................................................................. 225 CHAPTER 11—INTRODUCTION TO THE BRAZING PROCESSES........................................ 227 Introduction............................................................................................................................................. 228 Process Classification................................................................................................................................ 228 Process Selection....................................................................................................................................... 228 Process Development................................................................................................................................ 230 Process Maintenance................................................................................................................................ 232 Bibliography............................................................................................................................................. 233 CHAPTER 12—TORCH BRAZING................................................................................................... 235 Introduction............................................................................................................................................. 236 Process Fundamentals............................................................................................................................... 236 Manual Operations.................................................................................................................................. 237 Mechanized, Semiautomated, and Automated Operations........................................................................ 240 Robotic Operations.................................................................................................................................. 245 Materials and Consumables...................................................................................................................... 246 Joint Design.............................................................................................................................................. 250 Process Techniques................................................................................................................................... 250 Applications............................................................................................................................................. 252 Safe Practices............................................................................................................................................ 253 Bibliography............................................................................................................................................. 253 Suggested Reading List............................................................................................................................. 253 CHAPTER 13—INDUCTION BRAZING.......................................................................................... 256 Introduction............................................................................................................................................. 256 Process Fundamentals............................................................................................................................... 256 Equipment................................................................................................................................................ 259 Materials and Consumables...................................................................................................................... 265 Process Considerations............................................................................................................................. 267 Applications............................................................................................................................................. 271 Safe Practices............................................................................................................................................ 271 Bibliography............................................................................................................................................. 274 Suggested Reading List............................................................................................................................. 274 CHAPTER 14—FURNACE BRAZING............................................................................................. 275 Introduction............................................................................................................................................. 276 Historical Overview.................................................................................................................................. 276 Brazing Furnaces...................................................................................................................................... 277 Fluxes Employed in Furnace Brazing........................................................................................................ 287 Protective-Atmosphere Furnace Brazing.................................................................................................... 288 Process Requirements............................................................................................................................... 308 Inspection................................................................................................................................................. 311 Safety Considerations............................................................................................................................... 312 Bibliography............................................................................................................................................. 312 Supplementary Reading List..................................................................................................................... 312 CHAPTER 15—DIP BRAZING.......................................................................................................... 313 Introduction............................................................................................................................................. 314 Molten-Metal Dip Brazing........................................................................................................................ 314 Chemical-Bath Dip Brazing....................................................................................................................... 314 Safety Precautions..................................................................................................................................... 323 Bibliography............................................................................................................................................. 325 xvii  Page No. Suggested Reading List.............................................................................................................................. 325 CHAPTER 16—RESISTANCE BRAZING........................................................................................ 327 Introduction.............................................................................................................................................. 328 Equipment................................................................................................................................................ 329 Materials................................................................................................................................................... 332 Modes of Operation.................................................................................................................................. 334 Process Requirements................................................................................................................................ 335 Applications.............................................................................................................................................. 337 Safety Considerations................................................................................................................................ 338 Bibliography............................................................................................................................................. 339 Suggested Reading List.............................................................................................................................. 339 CHAPTER 17—DIFFUSION BRAZING........................................................................................... 341 Introduction.............................................................................................................................................. 342 Process Description................................................................................................................................... 342 Equipment................................................................................................................................................ 343 Materials and Consumables...................................................................................................................... 344 Process Variables....................................................................................................................................... 346 Test Method to Determine the Diffusion Cycle......................................................................................... 348 Brazed Joint Quality................................................................................................................................. 349 Applications.............................................................................................................................................. 349 Bibliography............................................................................................................................................. 350 CHAPTER 18—OTHER BRAZING PROCESSES.......................................................................... 351 Introduction.............................................................................................................................................. 352 Electron Beam Braze Welding................................................................................................................... 352 Exothermic Brazing................................................................................................................................... 353 Infrared Brazing........................................................................................................................................ 354 Laser Beam Braze Welding........................................................................................................................ 354 Microwave Brazing................................................................................................................................... 355 Obsolete Processes.................................................................................................................................... 356 CHAPTER 19—BRAZE WELDING................................................................................................... 359 Introduction.............................................................................................................................................. 360 Process Fundamentals............................................................................................................................... 360 Equipment................................................................................................................................................ 361 Materials and Consumables...................................................................................................................... 361 Process Variables....................................................................................................................................... 363 Process Considerations.............................................................................................................................. 363 Applications.............................................................................................................................................. 366 Quality of Braze Welds............................................................................................................................. 367 Safe Practices............................................................................................................................................ 367 Bibliography............................................................................................................................................. 367 CHAPTER 20—ALUMINUM AND ALUMINUM ALLOYS............................................................ 369 Introduction.............................................................................................................................................. 370 Materials................................................................................................................................................... 370 Material Preparation................................................................................................................................. 373 Joint Types................................................................................................................................................ 373 Performance of Joints................................................................................................................................ 375 Corrosion Resistance................................................................................................................................ 376 Applicable Brazing Processes..................................................................................................................... 376 xviii  Page No. Dissimilar Metal Brazing.......................................................................................................................... 378 Postbraze Cleaning................................................................................................................................... 378 Bibliography............................................................................................................................................. 379 Suggested Reading List............................................................................................................................. 379 CHAPTER 21—GRAPHITE AND CARBON-CARBON COMPOSITES..................................... 381 Introduction............................................................................................................................................. 382 Applications............................................................................................................................................. 382 Base Materials.......................................................................................................................................... 383 Brazing Characteristics.............................................................................................................................. 388 Brazing Filler Metal Compositions and Brazing Methods......................................................................... 397 Prebrazing Treatment and the Brazing Procedure...................................................................................... 400 Diffusion Brazing of Graphite to Steel without Adding a Brazing Filler Metal.......................................... 402 Diffusion Brazing with Carbide Synthesis for the Production of Heat-Resistant Joints............................. 402 Strength of Brazed Joints.......................................................................................................................... 403 Troubleshooting........................................................................................................................................ 405 Bibliography............................................................................................................................................. 406 CHAPTER 22—CEMENTED CARBIDES AND CERMETS.......................................................... 409 Introduction............................................................................................................................................. 410 Base Materials.......................................................................................................................................... 410 Brazing Filler Metals................................................................................................................................. 418 Joint Design.............................................................................................................................................. 423 Fluxes and Atmospheres........................................................................................................................... 426 Precleaning and Surface Preparation......................................................................................................... 427 Brazing Techniques and Equipment.......................................................................................................... 428 Postbrazing Operations.............................................................................................................................. 434 Strength of Brazed Joints............................................................................................................................ 435 Examination and Testing.......................................................................................................................... 437 Brazing of Superhard Materials to Cemented Carbides............................................................................. 439 Applications............................................................................................................................................. 440 Wear-Resistant Hardfacing Produced by Brazing Carbide Particles............................................................. 441 Troubleshooting........................................................................................................................................ 444 Bibliography............................................................................................................................................. 447 CHAPTER 23—CAST IRON.............................................................................................................. 449 Introduction............................................................................................................................................. 450 Applicable Brazing Processes.................................................................................................................... 450 Preparation of Cast Iron for Brazing......................................................................................................... 450 Metallurgical Considerations.................................................................................................................... 451 Brazing Filler Metals................................................................................................................................. 451 Preheating................................................................................................................................................. 452 Joint Clearance......................................................................................................................................... 452 Surface Plating.......................................................................................................................................... 453 Heating and Cooling................................................................................................................................ 453 Brazing of Dissimilar Metals..................................................................................................................... 453 Other Applications................................................................................................................................... 454 CHAPTER 24—CERAMICS............................................................................................................... 457 Introduction............................................................................................................................................. 458 Ceramic Materials.................................................................................................................................... 458 Brazing Processes...................................................................................................................................... 462 Joint Design.............................................................................................................................................. 464 xix  Page No. Joint Functionality and Process Development........................................................................................... 467 Processes and Equipment.......................................................................................................................... 467 Surface Preparation and Cleaning............................................................................................................. 469 Bibliography............................................................................................................................................. 469 Suggested Reading List.............................................................................................................................. 469 CHAPTER 25—COPPER AND COPPER ALLOYS........................................................................ 471 Introduction.............................................................................................................................................. 472 Base Metals............................................................................................................................................... 472 Processes and Equipment.......................................................................................................................... 477 Joint Design.............................................................................................................................................. 477 Precleaning and Surface Preparation......................................................................................................... 477 Brazing Filler Metals................................................................................................................................. 478 Fluxes....................................................................................................................................................... 478 Atmospheres............................................................................................................................................. 479 Assembly................................................................................................................................................... 480 Brazing Considerations............................................................................................................................. 480 Postbrazing Operations............................................................................................................................. 486 Inspection................................................................................................................................................. 486 Safety Considerations................................................................................................................................ 487 Bibliography............................................................................................................................................. 487 CHAPTER 26—LOW-CARBON, LOW-ALLOY, AND TOOL STEELS........................................ 489 Introduction.............................................................................................................................................. 490 Low-Carbon and Low-Alloy Steels........................................................................................................... 490 Tool Steels................................................................................................................................................. 493 Bibliography............................................................................................................................................. 496 CHAPTER 27—MAGNESIUM AND MAGNESIUM ALLOYS...................................................... 497 Introduction.............................................................................................................................................. 498 Characterization and Brazeability of Base Metals..................................................................................... 498 Joint Design.............................................................................................................................................. 502 Brazing Filler Metals................................................................................................................................. 502 Fluxes....................................................................................................................................................... 503 Brazing Processes...................................................................................................................................... 503 Precleaning and Surface Preparation......................................................................................................... 505 Assembly and Fixturing............................................................................................................................ 506 Selection of the Brazing Temperature........................................................................................................ 506 Postbraze Cleaning.................................................................................................................................... 506 Corrosion Resistance................................................................................................................................ 506 Inspection................................................................................................................................................. 506 Typical Applications.................................................................................................................................. 507 Safe Practices............................................................................................................................................ 508 Bibliography............................................................................................................................................. 509 Suggested Reading List.............................................................................................................................. 510 CHAPTER 28—NICKEL-BASED AND COBALT-CONTAINING ALLOYS................................ 511 Introduction.............................................................................................................................................. 512 Nickel and Nickel-Based Alloys................................................................................................................ 512 Cobalt-Containing Alloys......................................................................................................................... 518 Bibliography............................................................................................................................................. 519 Suggested Reading List.............................................................................................................................. 519 xx  Page No. CHAPTER 29—PRECIOUS METALS.............................................................................................. 521 Introduction............................................................................................................................................. 522 Gold and Gold Alloys............................................................................................................................... 522 Platinum Group Metals............................................................................................................................ 522 Silver and Silver Alloys............................................................................................................................... 523 Plated Materials........................................................................................................................................ 524 Brazing Filler Metals................................................................................................................................. 524 Joint Design.............................................................................................................................................. 525 Processes and Equipment.......................................................................................................................... 525 Precleaning and Surface Preparation......................................................................................................... 525 Fluxes and Atmospheres........................................................................................................................... 525 Assembly Procedures and Techniques....................................................................................................... 526 Postbrazing Operations............................................................................................................................. 526 Inspection................................................................................................................................................. 527 Bibliography............................................................................................................................................. 527 Suggested Reading List............................................................................................................................. 527 CHAPTER 30—REACTIVE METALS: TITANIUM, ZIRCONIUM, AND BERYLLIUM........... 529 Introduction............................................................................................................................................. 530 Applicable Brazing Processes.................................................................................................................... 530 Atmospheres and Fluxes........................................................................................................................... 532 Titanium and Titanium Alloys.................................................................................................................. 533 Zirconium and Zirconium Alloys............................................................................................................. 541 Beryllium.................................................................................................................................................. 543 Safe Practices............................................................................................................................................ 545 Bibliography............................................................................................................................................. 549 Suggested Reading List............................................................................................................................. 550 CHAPTER 31—REFRACTORY METALS: NIOBIUM, MOLYBDENUM, TANTALUM, AND TUNGSTEN........................................................................................................................................... 551 Introduction............................................................................................................................................. 552 Fundamentals........................................................................................................................................... 552 Niobium and Its Alloys............................................................................................................................. 557 Molybdenum and Its Alloys...................................................................................................................... 559 Tantalum and Its Alloys............................................................................................................................ 561 Tungsten................................................................................................................................................... 562 Joining of Refractory Metals to Other Materials and Dissimilar Metals................................................... 564 Suggested Reading List............................................................................................................................. 565 CHAPTER 32—STAINLESS STEELS............................................................................................. 567 Introduction............................................................................................................................................. 568 Categorization of Stainless Steels.............................................................................................................. 568 Processes and Equipment.......................................................................................................................... 571 Precleaning and Surface Preparation......................................................................................................... 571 Brazing Filler Metals................................................................................................................................. 571 Fluxes and Atmospheres........................................................................................................................... 573 Postbrazing Operations............................................................................................................................ 574 Repair Methods........................................................................................................................................ 574 Applications............................................................................................................................................. 574 Bibliography............................................................................................................................................. 575 Supplementary Reading List..................................................................................................................... 575 xxi  Page No. CHAPTER 33—ELECTRON TUBES AND VACUUM EQUIPMENT.......................................... 577 Introduction.............................................................................................................................................. 578 Base Materials........................................................................................................................................... 578 Brazing Filler Metals................................................................................................................................. 581 Inspection................................................................................................................................................. 584 Bibliography............................................................................................................................................. 586 Suggested Reading List.............................................................................................................................. 586 CHAPTER 34—HONEYCOMB STRUCTURES.............................................................................. 587 Introduction.............................................................................................................................................. 588 Brazing Processes and Equipment............................................................................................................. 589 Base Metals............................................................................................................................................... 591 Brazing Filler Metals................................................................................................................................. 592 Assembly for the Fabrication of Honeycomb............................................................................................ 594 Quality Control and Inspection................................................................................................................. 595 Applications.............................................................................................................................................. 597 Bibliography............................................................................................................................................. 607 Suggested Reading List.............................................................................................................................. 607 CHAPTER 35—PIPE AND TUBING................................................................................................. 609 Introduction.............................................................................................................................................. 610 Copper and Copper Alloys........................................................................................................................ 610 Cutting and Sizing Pipe and Tubing.......................................................................................................... 612 Surface Preparation and Cleaning............................................................................................................. 616 Fluxes and Fluxing Operations................................................................................................................. 618 Assembly................................................................................................................................................... 619 Application of Heat and Brazing Filler Metals.......................................................................................... 619 Postbraze Cleaning.................................................................................................................................... 620 Inspection................................................................................................................................................. 620 Bibliography............................................................................................................................................. 621 CHAPTER 36—DIAMOND................................................................................................................. 623 Introduction.............................................................................................................................................. 624 Base Materials........................................................................................................................................... 624 Interaction of Diamond with Liquid Metals and Alloys............................................................................ 626 Brazing Filler Metals and Brazing Processes.............................................................................................. 628 Applications.............................................................................................................................................. 634 Bibliography............................................................................................................................................. 635 Suggested Reading List.............................................................................................................................. 636 APPENDIX A—BRAZING TERMS AND DEFINITIONS.............................................................. 637 APPENDIX B—PROPERTIES OF BRAZEABLE METALS AND ALLOYS............................... 645 APPENDIX C—THERMAL EXPANSION DATA............................................................................. 665 INDEX..................................................................................................................................................... 679 xxii AWS BRAZING HANDBOOK 1 CHAPTER 1 BASICS OF BRAZING Prepared by: C. A. Paponetti Expert Brazing & Heat Treating, Incorporated M. Sapp NAVAIR—Cherry Point Contents Introduction 2 Historical Perspective 3 Physics of Brazing 6 Factors Controlling the Properties of the Brazement 9 The Five Elements of Brazing 12 Bibliography 20 Suggested Reading List 20 Photograph courtesy of The Gold Bulletin 2 CHAPTER 1—BASICS OF BRAZING AWS BRAZING HANDBOOK CHAPTER 1 BASICS OF BRAZING INTRODUCTION The process of brazing that we know today joint by capillary action.1, 2 The term brazing temper- began as an ancient art. Through our increased ature refers to the temperature to which a material is understanding of the nature and behavior of mate- heated to enable the brazing filler metal to spread rials, this art evolved into technology and science. and adhere to, or wet, the base metal and form a In a very general sense, brazing is a joining process brazed joint.3 that relies on the melting, flow, and solidification of This definition serves to distinguish brazing from a brazing filler metal to form a leak-tight seal, a the other joining processes of soldering and welding. strong structural bond, or both between materials. Brazing and soldering share many important fea- The process is unique in that this metallurgical tures, but the term brazing is used to refer to the bond is formed by melting the brazing filler metal joining processes performed above 840ºF (450ºC), only; the components being joined undergo no while soldering refers to the joining processes per- melting. formed below this temperature. Brazing differs from Brazing is a well-established commercial process welding in that in brazing the intention is to melt the capable of producing strong joints. It is widely used brazing filler metal, not the base materials. In weld- in industry because, in large part, it is capable of ing, both the brazing filler metals and the base metals joining most metallic and ceramic materials. It is are melted to effect the coalescence of materials. a versatile process that can be performed using Several factors influence the quality of the brazed manual techniques as well as automated production joint. To achieve a good joint using any of the braz- modes. Brazing lends itself to the production of large ing processes, the components to be joined must be assemblies and assemblies composed of dissimilar properly cleaned and protected from excessive oxi- metals. Brazing produces a tiny, clean fillet in con- dation by fluxing or the use of a controlled atmo- trast to the irregular bead made by welding, an sphere. The assembly must be designed so that when advantage when appearance is critical. One of the the components are properly aligned a capillary is main advantages of brazing is usually associated with cost savings. High production processes adapt 1. American Welding Society (AWS) Committee on Definitions, well to today’s improved processes. Brazing espe- 2001, Standard Welding Terms and Definitions, Including Terms cially adapts to large production quantities as well as for Adhesive Bonding, Brazing, Soldering, and Thermal Spraying, AWS A3.0:2001, Miami: American Welding Society, p. 5. single individual quantities. 2. At the time of the preparation of this chapter, the referenced The term brazing refers, in fact, to a group of pro- standards were valid. If a standard is cited without a date of publi- cesses. The American Welding Society (AWS) defines cation, it is understood that the latest edition of the document referred to applies. If a standard is cited with the date of publica- brazing (B) as a group of joining processes that pro- tion, the citation refers to that edition only, and it is understood duce the coalescence of materials by heating them to that any future revisions or amendments to the code or standard the brazing temperature in the presence of a brazing are not included; however, as standards undergo frequent revision, filler metal that has a liquidus temperature above the reader is encouraged to consult the most recent edition. 3. American Welding Society (AWS) Committee on Definitions, 840ºF (450ºC) and below the solidus temperature of 2001, Standard Welding Terms and Definitions, Including Terms the base materials. The brazing filler metal is distrib- for Adhesive Bonding, Brazing, Soldering, and Thermal Spraying, uted between the closely fitted faying surfaces of the AWS A3.0:2001, Miami: American Welding Society, p. 6. AWS BRAZING HANDBOOK CHAPTER 1—BASICS OF BRAZING 3 formed, permitting the molten brazing filler metal to flow. It is imperative that the heating process that produces the proper brazing temperature and heat distribution be selected. To provide a basic understanding of brazing, this chapter presents a brief history and an overview of the factors that are fundamental to the brazing pro- cesses. To assist the reader with unfamiliar terms, a glossary of common brazing terms is provided in Appendix A of this volume. HISTORICAL PERSPECTIVE Other than mechanical fastening, brazing is per- haps the oldest known technique used for the joining of metals. Gold, silver, and copper metals found in the natural state were identified and collected by Source: Photograph reprinted with permission from Hunt, L., 1977, The Origin of humans as early as 5000 B.C. The peoples of Sumer, Brazing, Gold Bulletin 10(1), pp. 27–28, based on a review of Wolters, J., 1977, Zur Geschichte der Loettechnik, Germany: Dedussa AG. in the area lying between the Tigris and the Euph- rates in modern-day Iraq, were the first to discover Figure 1.1—Wall Painting Dated 1475 B.C. the melting of metals in their furnaces. The birth- from the Tomb of Rekh-Mi-Re at Thebes, Egypt place of civilization was also the beginning of metal- lurgy. The melting of simple ores is usually associated with the period beginning with 4400 B.C., and by 3400 B.C. silver and gold brazing were being used extensively by the Sumerians.4 depending on the color of the liquid metal (indicat- Artifacts found by the archaeologists in tombs in ing temperature) and the metal’s ease of melting in the Middle East, Egypt, and even in Ireland prove the furnace. Among other changes to the ancient that brazing was being widely used by this time. brazing procedure was the concoction of new fluxes Images from an ancient Egyptian tomb depict a that would react at the brazing temperature. This smith blowing through a reed into a fire. Wall paint- experimentation depended on minute observations ings from the Fifth Dynasty, 2500 B.C. in tombs at Ti that could only result from trial and error. at Saqqara, Egypt portray the use of mouth blow- As early as 3000 B.C., the smiths, who knew of the pipes. Figure 1.1 presents an image of a wall painting varying changes in brazing filler metal melting tem- dated approximately 1475 B.C. from the tomb of peratures, developed step brazing, a method for Rekh-mi-Re at Thebes in Egypt. It depicts a metal- brazing complex components in sequential steps. worker brazing gold with a charcoal fire in a clay This allowed the smiths to employ many different bowl, a reed a blowpipe, and tongs. The reed may brazing filler metals at different temperatures. The have had a clay mouthpiece to assist the brazing placement of the brazing filler metal involved a small process. Clearly, this was a two-hand operation— bead or strips on the braze joint between the two with one hand directing the blowpipe while the other metals to be joined. By raising the temperature of the manipulated the part in the fire.5 brazing filler metal with localized heat and air, the The development of brazing continued during the brazing filler metal would flow into the joint. next 3000 years, with metal smiths experimenting Whether flux was used at this time is unknown. with different ratios of gold (Au), silver (Ag), and Early furnaces were augmented with bellows to raise copper (Cu) brazing filler metals and identifying the temperature, replacing the blowpipe to some fluxes to facilitate the brazing operation. The black- degree. smiths would select brazing filler metal mixtures In 2500 B.C, various brazed joints containing a brazing filler metal of 25Ag-Au were found on a gold 4. Hunt, L., 1977, The Origin of Brazing, Gold Bulletin 10(1), pp. 27–28, based on a review of Wolters, J., 1976, Zur Geschichte goblet and a bowl in the tomb of Queen Pu-abi at der Loettechnik, Frankfurt: Dedussa AG. Ur in Sumer. The discoverer of the Greek city of 5. See Reference 4. Troy unearthed double-spouted drinking vessels with 4 CHAPTER 1—BASICS OF BRAZING AWS BRAZING HANDBOOK separate handles brazed to a thin sheet of gold dated Another 16 years elapsed before scientists began to 2200 B.C., providing evidence that brazing tech- using the oxyhydrogen blowpipe, the precursor to nology using the same technique had traveled to the the modern welding/brazing torch, developed by west and the south. In Egypt around 1800 B.C., small Robert Hare, professor of chemistry of the Univer- sphinxes were fabricated by brazing. Other known sity of Pennsylvania in 1801.9 The blowpipe was items included brazed buttons using a Cu-Ag brazing used in laboratories to investigate what would hap- filler metal with an Au addition. pen to refractory metal when achieving temperatures Later, in 60 A.D., Pliny described gold brazing of 4468°F (2464°C). Soldering and brazing informa- and the salts needed for a good braze in Historia tion was so well known that an article published in Naturalis.6 Excavations of the city of Pompeii, dev- Manufacturer and Builder in July 1869 apologizes to astated by the eruption of Mount Vesuvius in 79 A.D., its readers with the following, “Soldering and braz- have uncovered wall painting depicting economic ing are such well-known arts that many deem it a activities of the time, including the melting and waste of space on our part to say anything on the working of gold with a melting furnace and a blow- subject.”10 Little did the author know many more pipe. Around 1125, Theophilus, a German monk, years of advances were yet to come. documented recipes for making brazing fluxes in De In 1860, another fuel gas was looming on the Diversis Artibus. He writes of fluxes prepared from horizon when Pierre Eugène Marcelin Berthelot was beechwood ashes, lard, and a mixture of copper able to identify the chemical formula for acetylene as salts. In 1568, the Italian goldsmith and sculptor C2H2. Two years later, a German, Friedrich Wohler, Benventuto Cellini was using gold-copper-silver produced, studied, and characterized acetylene gas brazing filler metals. With respect to the production generated from carbide of calcium and water. Thirty years later, Canadian engineer Thomas Wilson of successive joints, he wrote, “You must introduce a attempted to make calcium from heating slacked fresh alloy of silver and copper so as to prevent the lime mixed with coal tar and ground carbon in an solder of the time before from running.”7 electric oven while working for J. T. Morehead in By 1677, the distinction between brazing and Spray, North Carolina. J. T. Morehead’s son, J. M. welding was firmly established when Joseph Moxon Morehead, a chemist, determined that the solid described in Mechanick Exercises the subtle defini- Wilson had produced was calcium carbide. Fifty-six tion of brazing as “You may have occasion some- years after Edmund Davy first discovered acetylene times to Braze...a piece of work, but it is used by gas, Wilson discovered how to mass produce it. Smiths only, when their work is so thin, or small, Shortly thereafter, in 1898, Union Carbide Com- that it will not endure Welding.” The word weld, pany was formed. In 1895, George Claude and first used in 1599 and later in 1677 by Moxon, M. A. Hess of France proved that acetylene could be described the mixing of metals performed by black- stored up to 25 times its volume when dissolved in smiths: “As so weld, or work in the doubling into acetone. Cylinders were designed and fabricated by one another, and make it become one entire lump.”8 the French Dissolve Acetylene Company to safely The smiths knew the difference between brazing and store and transport acetylene. welding by the method used to work the metal based In 1896, the combustion of oxygen and acetylene on the application. was discovered by Frenchman Henri Louis Le Chate- After centuries of performing brazing with the lier. In the same year, Dr. Carl von Linde of Germany only known source of heat, fire in a furnace, a new designed a process for liquefying air using the source of energy emerged. In 1766, Henry Cavendish Thomson-Joule process. The first U.S. plant using described the chemical and physical properties of the Linde process was built in Buffalo, New York in hydrogen gas. Although hydrogen gas had been known 1907. for thousands of years, scientists in the late 1700s Scientists began mixing acetylene with oxygen to advanced the research to the point of harnessing and produce a flame temperature of 5900ºF (3260ºC), understanding this gas. In 1774, oxygen was dis- which exceeded the 4388ºF (2420ºC) produced by covered, and two years later, a Frenchman, Antoine the oxyhydrogen flame. The laboratory interest in Lavoisier, cut an iron spiral in a flask filled with the gas flames soon gave way to commercial interests oxygen. and prompted the development of the oxyacetylene torch. In France in 1900, Edmond Fouche and 6. Roberts, P. M., 1974, Early Evolution of Welding, Welding and Metal Fabrication 42(11), pp. 412–416. 9. Virtualogy.com, 2001, Virtual American Biographies: Robert 7. See Reference 4. Hare, February 9, 2006,. London: University of Oxford. 10. n.a. Manufacturer and Builder, 1869. AWS BRAZING HANDBOOK CHAPTER 1—BASICS OF BRAZING 5 Charles Picard invented the oxyacetylene torch, and 1934, Littleton received a British patent for this pro- one year later, Picard used the new invention to braze cess, which became known as the Littleton Process. weld a cast iron pump for an acetylene generator. In 1939, Floyd Kelly, of General Electric, published a One small problem that needed to be overcome paper titled “Properties of Brazed 12% Chromium was controlling the detonation of the flame within Steel,”11 describing the strength of brazed joints the early torches. Picard revised the internal structure made with 12% chromium steels. He performed his of the torch to include two separate tubes with a tests using the single-lap tensile specimen, a 45º mixing chamber where the gas would mix at the V-shaped tensile specimen and a butt brazed tensile torch tip. In 1901, Fouche announced the birth of specimen. the oxyacetylene torch at the meeting of the Société The year 1948 marked a major turning point des Anciens Élèves des Arts et Métiers. At this time, in brazing history when a young man, Robert L. an American, Eugene Bournonville, traveled to Peaslee, recognized the potential brazing application France to purchase the Fouc