Manufacturing Processes EG 4391 A Fall 2024 PDF

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 2 - Structure and properties Chapter 5 Casting Process and Heat Treatment Copyright © 2017, 2008 Pearson Education, Inc. All R...

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 2 - Structure and properties Chapter 5 Casting Process and Heat Treatment Copyright © 2017, 2008 Pearson Education, Inc. All Rights Reserved  Lesson # 3- Casting and Heat Treatment History of Casting Image Courtesy: https://i0.wp.com/www.mechdaily.com/wp-content/uploads/2023/12/What-Is-Casting.webp?fit=1280%2C720&ssl=1  Lesson # 3- Casting and Heat Treatment Casting: a) conventionally cast b) directionally solidified with columnar grains c) Single crystal  Lesson # 3- Casting and Heat Treatment Casting: Important Factors – Solidification – Flow – Heat Transfer – Mold material  Lesson # 3- Casting and Heat Treatment Casting: Solidification – Pure metals vs. Alloys Differing melting/freezing points Liquidus and Solidus (Highest temp at which an alloy is solid, temp at which the alloy is completely melted)  Lesson # 3- Casting and Heat Treatment Casting: Solidification – Pure metals  Lesson # 3- Casting and Heat Treatment Casting: Solidification – Alloys Solute – minor element Solvent – major element – Substitutional solid solutions (e.g. brass - zinc + copper) – Interstitial solid solutions (solute atoms much smaller than solvent, e.g. carbon and iron)  Lesson # 3- Casting and Heat Treatment Casting: Intermetallic Compounds – Structures of solute atoms among solvent atoms in specific proportions Strong hard and brittle (e.g. CuAL2)  Lesson # 3- Casting and Heat Treatment Two Phase Alloys: – A solid solution where two or more elements are soluble in a a solid state, forming a single homogeneous material in which the alloy elements are uniformly distributed throughout the solid. a) lead in copper b) two sets of grains  Lesson # 3- Casting and Heat Treatment Two Phase Alloys: – Phase Diagrams  Lesson # 3- Casting and Heat Treatment Two – Phase Alloys: – The lever rule, and the composition of various phases S C O −C L Weight Fraction of solids = S+ L C S −C L L C S −C O Weight Fraction of liquids = S + L C S−C L  Lesson # 3- Casting and Heat Treatment The Iron-Carbon System (iron-carbon binary system)  Lesson # 3- Casting and Heat Treatment The Iron-Carbon System (iron-carbon binary system) – Ferrite – Alpha and delta, BCC, soft and ductile, magnetic – Austenite – Allotropic transformation (the appearance of more than one type of crystal), FCC, ductile at elevated temps, non magnetic, good formability – Cementite (Fe3C)– also called carbide (not tool carbides), hard and brittle α −ferrite γ − Austenite  Lesson # 3- Casting and Heat Treatment The Iron-Carbon System (iron-carbon binary system) – Eutectoids (eutecticlike) – a single solid phase transforms into two solid phases – Alloying elements always lower the eutectoid composition in steel, thus lowering the eutectoid temperature  Lesson # 3- Casting and Heat Treatment Cast Structures – Pure Metals:  Lesson # 3- Casting and Heat Treatment Cast Structures – Solid-solution alloys:  Lesson # 3- Casting and Heat Treatment Cast Structures – Structure obtained by heterogeneous nucleation of grains:  Lesson # 3- Casting and Heat Treatment Cast Structures – Structure obtained by heterogeneous nucleation of grains:  Lesson # 3- Casting and Heat Treatment Cast Structures – Structure obtained by heterogeneous nucleation of grains: And the formation of dendrites  Lesson # 3- Casting and Heat Treatment Cast Structures – Structure obtained by heterogeneous nucleation of grains: And the formation of dendrites  Lesson # 3- Casting and Heat Treatment Cast Structures – Structure obtained by heterogeneous nucleation of grains: And the formation of dendrites Freezing range =T L −T S  Lesson # 3- Casting and Heat Treatment Cast Structures a) Columnar dendritic b) Equiaxed dendritic c) Equiaxed nondendritic  Lesson # 3- Casting and Heat Treatment Effects of cooling rates – Slow cooling rates: coarse dendtritic structures – High cooling rates: smaller dendrite arm spacing – Higher cooling rates: amorphous structures(without any ordered crystalline structure)  Lesson # 3- Casting and Heat Treatment Structure-Property Relationships – Formation of dendrites: Cored and uniform composition – Cored: concentration gradient, differing material composition at surface vs. center due to solute rejection from the core toward the surface (microsegregation)  Lesson # 3- Casting and Heat Treatment Structure-Property Relationships – Formation of dendrites: Cored and uniform composition – Macrosegregation: differences in the composition throughout the casting – Normal segregation: low melting point constituents are driven towards the center – Inverse segregation: occurs in dendritic structures in solid-solution alloys – the center has a lower concentration of alloying elements – Gravity segregation: due to density differences Inoculants: a nucleating agent that induces nucleation of grains throughout the liquid metal (e.g. Titanium Diboride (TiB2)  Lesson # 3- Casting and Heat Treatment Structure-Property Relationships – Formation of dendrites: Cored and uniform composition – Macrosegregation: differences in the composition throughout the casting – Normal segregation: low melting point constituents are driven towards the center – Inverse segregation: occurs in dendritic structures in solid-solution alloys – the center has a lower concentration of alloying elements – Gravity segregation: due to density differences Inoculants: a nucleating agent that induces nucleation of grains throughout the liquid metal (e.g. Titanium Diboride (TiB2)  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – https://www.youtube.com/watch?v=HSOtZj2Y8is  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – Gate design, and the limiting of exposure of molten metal to the environment Bernoulli’s theorem p v2 h+ + =Constant ρg 2g Mass Continuity Q= A 1 V 1= A 2 V 2  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – Sprue Profile: traditionally tapered A1 A2 h = 2 √ h1 – Mold filling: v =c √ 2 gh – Turbulent vs. Laminar flow: vD ρ R e= n  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – Fluidity of Molten Metal Characteristics of the molten metal – Viscosity – Surface Tension – Inclusions – Solidification pattern of the alloy Casting Parameters – Mold design – Mold material and its surface characteristics – Degree of superheat – the increment of temperature above an alloy’s melting point – Rate of pouring – Heat transfer  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – Fluidity of Molten Metal Tests for fluidity Image courtesy:https://thelibraryofmanufacturing.com/metalcasting_operation.html :  Lesson # 3- Casting and Heat Treatment Fluid Flow and Heat Transfer – Solidification time: n Volume (Chvorinov ' s rule)Solidificatoin time=C ( ) Surface area  Lesson # 3- Casting and Heat Treatment Shrinkage: – Can sometimes cause cracking in a casting Contraction of the molten metal Contraction of the metal during phase change from L to S (largest temp change and why risers/pressure feeding are needed) Contraction of the solidified metal as it cools to ambient temp  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Fluxes: inorganic compounds that refine the molten metal by removing dissolved gases and various impurities – Primary Metals: include remelted or recycled scrap, pure alloying elements are added as necessary – Master Alloys (hardeners): are used where melting points are too high and the alloying elements do not readily mix with the low-melting point metals  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Furnaces Electric-arc (primarily steel) Induction Crucible Cupolas Levitation melting  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Furnaces Electric-arc (primarily steel) Induction Crucible Cupolas Levitation melting  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Furnaces Electric-arc (primarily steel) Induction Crucible  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Furnaces Electric-arc (primarily steel) Induction Crucible Cupolas Levitation Melting  Lesson # 3- Casting and Heat Treatment Melting practices and furnaces – Furnaces Electric-arc (primarily steel) Induction Crucible Cupolas Levitation Melting Image Courtesy: https://www.researchgate.net/figure/a-Photograph-of-levitation-melting-system-b-The-schematic-drawing-of-levitation_fig1_319592793  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Casting Alloys:  Lesson # 3- Casting and Heat Treatment Ingot Casting and Continuous Casting: – I-beams, and channels  Lesson # 3- Casting and Heat Treatment Ingot Casting and Continuous Casting: – Strip Casting Thin slabs/srips produced from molten metal Thes are rolled to form the final shape Compressive stresses help to reduce porosity Image Courtesy: https://ars.els-cdn.com/content/image/3-s2.0-B9781845699680500107-f10-08-9781845699680.jpg  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting (most common method by total weight) Place a pattern in sand to make an imprint Incorporate a gating system Fill the cavity with molten metal Allow the metal to solidify Break away the sand mold Remove the casting and finish it Image Courtesy: https://ars.els-cdn.com/content/image/3-s2.0-B9781845699680500107-f10-08-9781845699680.jpg  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting (most common method by total weight) Place a pattern in sand to make an imprint Incorporate a gating system Fill the cavity with molten metal Allow the metal to solidify Break away the sand mold Remove the casting and finish it Image Courtesy: https://ars.els-cdn.com/content/image/3-s2.0-B9781845699680500107-f10-08-9781845699680.jpg  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, sand types (mostly SiO2) Naturally bonded (bank sand) Synthetic (lake sand) – prefered due to it’s controlled composition – Clay used to cohesively bond sand particles, and sand is typically mulled before use (conditioned/mixed) Image Courtesy: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcR_gizS4ANpUUeEQ5aiGuwcooGBob97vgeXBg&s  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, types of sand molds: Green Sand (most common, least expensive) – moist or damp sand used Cold-box – inorganic and organic binders blended into the sand for greater mold strength No-bake – synthetic liquid resin mixed with the sand  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, patterns:  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, cores: (Typically made of sand aggregates)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, operation:  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, operation:  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, operation: -Almost all commercially used alloys can be sand cast. Lower dimensional accuracy than other casting processes. Low equipment costs.  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, operation: Mold ablation: used to improve the mechanical properties and production rates in sand casting. – Sand molds filled with molten metal – Mold sprayed with a liquid and/or gas solvent to erode the sand – As the mold is removed the liquid steams causes rapid and directional solidification of the metal, lowering the porosity (higher strength and ductility)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Sand Casting, operation: Mold ablation: Image Courtesy: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcR_gizS4ANpUUeEQ5aiGuwcooGBob97vgeXBg&s  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Shell-Mold Casting:  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Shell-Mold Casting: -Sometimes more economical than other casting processes* High quality finished casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Ceramic Mold: -Good for ferrous and high temp alloys (stainless, tool steel). More expensive, good dimensional accuracy and surface finish  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Vacuum Casting -Suitable for thin walled complex shapes with uniform properties, used in gas turbine manufacturing  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Expendable Pattern Casting -Relatively simple, minimal casting cleaning/finishing  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Expendable Pattern Casting -Costly labor and material, can produce intricate shapes, good surface finish and tolerance  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Expendable Pattern Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Metal molds used – Higher rate of cooling (effects microstructure and grain size within casting)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: (1) Mold is preheated and coated for lubrication and heat dissipation  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: (2) Cores (if any are used) are inserted and mold is closed; (3) molten metal is poured into the mold, where it solidifies  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: (4) Mold is opened to remove part  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Slush Casting Image Courtesy:https://i.ytimg.com/vi/1Y5miK44_Kk/maxresdefault.jpg  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Pressure Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Die Casting (Hot Chamber)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Die Casting (Cold Chamber)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Die Casting (Cold Chamber)  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Centrifugal Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Centrifugal Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Squeeze Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Squeeze Casting  Lesson # 3- Casting and Heat Treatment Expendable-Mold, Permanent-Pattern Casting Processes: – Permanent-Mold Casting: Semisolid Metal Forming (Thixocasting) and Rheocasting – Takes advantage of thixotropic (decreased viscosity when agitated) behavior of alloys) – “Mushy state” metals used during extrusion, forging, rolling  Lesson # 3- Casting and Heat Treatment Casting techniques for single-crystal components  Lesson # 3- Casting and Heat Treatment Heat Treatment:  Lesson # 3- Casting and Heat Treatment Heat Treatment: – Tempering – heating process to reduce the hardness and improve elasticity (toughness) – Quenching - Rapid cooling, may be done in water, bring, oils, molten salts, air, caustic solutions, polymer solutions, various gases – Annealing – restoration of a cold work or heat treated part to it’s original properties – Carburization – the loss of carbon through heat treatment  This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License. It makes use of the works of Mateus Machado Luna.