Forging and Extrusion Processes Quiz
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Questions and Answers

What is the primary function of rotating rolls in the manufacturing process?

  • To pull the work into the gap and reduce its cross section (correct)
  • To create a smooth surface finish on the work piece
  • To heat the metal for better malleability
  • To cut the work piece into specific lengths
  • What is the primary purpose of the hot rolling process?

  • To increase the thickness of materials
  • To create brittle materials
  • To produce round rods directly
  • To convert cast structures to wrought structures (correct)
  • Which of the following best describes flat rolling?

  • Creating complex shapes like I-beams
  • Forming a circular cross section from a rectangle
  • Increasing the length of a work piece without changing its cross section
  • Reducing the thickness of a rectangular cross section (correct)
  • What is the typical shape and size of a bloom after the first hot rolling operation?

    <p>Square cross-section, at least 150 mm on the side</p> Signup and view all the answers

    What type of rolling process is commonly used for producing finished sheet and plate stock?

    <p>Cold rolling</p> Signup and view all the answers

    What is a key advantage of thread rolling over thread cutting?

    <p>Higher production rates</p> Signup and view all the answers

    Which of the following statements correctly describes a billet?

    <p>It can have a square or round cross-section</p> Signup and view all the answers

    In shape rolling, how is the desired shape achieved?

    <p>By passing work through rolls with the reverse of the desired shape</p> Signup and view all the answers

    What transformation occurs to internal defects during the hot rolling process?

    <p>Brittle grain boundaries break up</p> Signup and view all the answers

    Which of the following is NOT a product of the rolling process?

    <p>Ingot caps</p> Signup and view all the answers

    Which type of rolling mill configuration supports smaller work rolls with backing rolls?

    <p>Four-high mill</p> Signup and view all the answers

    What form of rolling is specifically a bulk deformation process to create threads?

    <p>Thread rolling</p> Signup and view all the answers

    How is a slab typically defined in terms of its cross-section?

    <p>Rectangular, width greater than twice the thickness</p> Signup and view all the answers

    Which rolling process is typically used to form shapes like I‑beams and U‑channels?

    <p>Shape rolling</p> Signup and view all the answers

    What initial form is processed by the rolling mills to create blooms or billets?

    <p>Ingots</p> Signup and view all the answers

    What characteristic of the wrought structure is improved by the hot rolling process?

    <p>Finer grain structure</p> Signup and view all the answers

    What is the purpose of the accumulating drums in wire drawing machines?

    <p>To apply a constant force to draw wire stock through the dies</p> Signup and view all the answers

    What does the area reduction formula in wire drawing measure?

    <p>The change in size of the work in terms of area</p> Signup and view all the answers

    Which of the following materials is used for die production to provide improved wear resistance?

    <p>Chromium plating for steel dies</p> Signup and view all the answers

    In bar or rod drawing, what characterizes the stock used?

    <p>It is a straight cylinder with large diameter</p> Signup and view all the answers

    How is tube drawing accomplished?

    <p>By pulling the stock through the sides of a mandrel placed between dies</p> Signup and view all the answers

    What is a characteristic feature of the hydraulic press?

    <p>It uses hydraulic piston to actuate the ram.</p> Signup and view all the answers

    Which defect in forging is specifically attributed to exhausted ductility?

    <p>Fracture</p> Signup and view all the answers

    What process is comparable to squeezing toothpaste out of a tube?

    <p>Extrusion</p> Signup and view all the answers

    Which of the following types of extrusion involves lower force due to the billet moving relative to the container wall?

    <p>Indirect Extrusion</p> Signup and view all the answers

    What is the purpose of process annealing between steps in forging?

    <p>To improve material ductility after deformation.</p> Signup and view all the answers

    What is the primary factor that influences the extrusion force?

    <p>Material properties</p> Signup and view all the answers

    How is the extrusion ratio (ER) defined?

    <p>The ratio of the cross-sectional area of the billet to the area of the extruded product.</p> Signup and view all the answers

    What role does friction play in direct extrusion?

    <p>It increases the extrusion force required.</p> Signup and view all the answers

    What is the primary characteristic of shallow drawing?

    <p>The depth of the formed cup is equal to $D/2$ or less.</p> Signup and view all the answers

    In the process of ironing, what is the result of reducing the thickness of the sheet?

    <p>It produces a cup with constant wall thickness.</p> Signup and view all the answers

    What is a characteristic of reverse redrawing when compared to direct redrawing?

    <p>It allows for better ductility of the material.</p> Signup and view all the answers

    Which of the following describes the primary function of the stripper ring in the deep drawing process?

    <p>To facilitate the removal of the formed cup from the punch.</p> Signup and view all the answers

    What type of can is produced by using the ironing process followed by deep drawing?

    <p>Two-piece cans</p> Signup and view all the answers

    How does the clearance between the punch and die affect the ironing process?

    <p>Smaller clearance allows for a greater amount of ironing.</p> Signup and view all the answers

    What challenges are typically addressed by redrawing operations?

    <p>Drawing containers that are difficult in one operation.</p> Signup and view all the answers

    What is a common issue that can occur during drawing operations?

    <p>Wrinkling in unsupported regions of the sheet.</p> Signup and view all the answers

    Study Notes

    Forging Presses

    • Apply gradual pressure to accomplish compression operation
    • Mechanical press - Converts rotation of drive motor into linear motion of ram
    • Hydraulic press - Hydraulic piston actuates ram
    • Screw press - Screw mechanism drives ram

    Forging Defects

    • Fracture - Exhausted ductility or intergranular fracture
    • Barreling - Friction

    Extrusion Process

    • A plastic deformation process in which metal is forced under pressure through a die to produce the desired shape
    • Similar to squeezing toothpaste out of a tube
    • Used to produce long parts with uniform cross sections
    • Typical products include railings, tubing, structural and architectural shapes, doors, and window frames
    • Extrusion Ratio - Ratio of the cross-sectional area of the billet to the cross-sectional area of the extruded product (A o / A f)
    • Extrusion Force - Force required to extrude the metal, calculated using the formula F = A o K Ln (A o/A f)
    • Types of Extrusion:
      • Direct Extrusion (Forward Extrusion) - Billet is placed in a chamber and forced through a die opening by a hydraulically-driven ram
      • Indirect Extrusion (Backward Extrusion) - Metal is forced to flow through the die in the opposite direction of the ram's motion
      • Hydrostatic Extrusion - Extrusion is performed under high pressure using a fluid
      • Impact Extrusion - Extrusion is performed using a high-velocity impact
    • Extrusion Force Factors:
      • Friction
      • Material Properties
      • Reduction in Area
      • Speed
      • Temperature
      • Geometry of the Die

    Rolling Process

    • Metal deformation process used to reduce work thickness by compressive forces exerted by two opposing rolls
    • Initial breaking down of an ingot or continuously cast slab is done by hot rolling
      • Cast structure includes coarse and non-uniform grains, which are usually brittle and may contain porosities
      • Hot rolling converts the cast structure to a wrought structure, which has finer grains and enhanced ductility, both resulting from breaking up the brittle grain boundaries and closing up of internal defects.
    • Products of hot rolling operations are called bloom, slab, or billet.
      • Bloom - square or rectangular cross-section with a thickness greater than 6" and a width no greater than 2x the thickness, further processed into structural shapes
      • Slab - rectangular cross-section with a width greater than 2x the thickness, rolled into plates, sheets, and strips
      • Billets - square or circular cross-section smaller than a bloom, rolled into various shapes like round rods and bars
    • Types of Rolling:
      • Flat Rolling - used to reduce the thickness of a rectangular cross-section
      • Shape Rolling - square cross-section is formed into a shape such as I‑beam
      • Hot Rolling - most common due to the large amount of deformation required
      • Cold Rolling - Produces finished sheet and plate stock

    Thread Rolling

    • A bulk deformation process used to form threads on cylindrical parts
    • Important industrial process for mass producing bolts and screws
    • Performed by cold working in thread rolling machines
    • Advantages over thread cutting:
      • Higher production rates
      • Better material utilization
      • Stronger threads and better fatigue resistance due to work hardening

    Rolling Mills

    • Heavy and expensive equipment
    • Configurations:
      • Two-high - Two opposing rolls
      • Three-high - Work passes through rolls in both directions
      • Four-high - Backing rolls support smaller work rolls
      • Cluster mill - Multiple backing rolls on smaller rolls
      • Tandem rolling mill - Sequence of two-high mills

    Wire Drawing

    • A metal forming process used to reduce the diameter of wire
    • Consists of multiple draw dies (typically 4 to 12) separated by accumulating drums
    • Each drum provides proper force to draw wire stock through upstream die
    • Each die provides a small reduction, so the desired total reduction is achieved by the series
    • Annealing is sometimes required between dies to relieve work hardening
    • Area Reduction in wire Drawing - Change in size of work is usually given by area reduction, calculated by: (Ao - A f) / Ao where 'r' is the area reduction in drawing, 'Ao' is the original area of work, and 'Af' is the final work.

    Die Materials

    • Tool steels and carbides are commonly used materials
    • Diamond dies are used for fine wire
    • To improve wear resistance, steel dies may be chromium plated, and carbide dies may be coated with titanium nitride
    • Cast-steel dies are used for hot drawing

    Bar or Rod Drawing

    • A metal forming process where stock is pulled through one die opening
    • Accomplished as a single draft operation
    • Beginning stock has a large diameter and is a straight cylinder
    • Requires a batch type operation

    Tube Drawing

    • Metal is pulled through the sides of the mandrel, which is placed between dies

    Deep Drawing

    • A sheet metal forming process to produce cups or shells from flat sheet metal
    • Shallow drawing - depth of formed cup  D/2
    • Deep or moderate drawing - depth of formed cup > D/2

    Ironing Process

    • Process to reduce the thickness of the sheet metal as it enters the die cavity, resulting in a cup with a constant wall thickness
    • A cup is forced through the die with a punch having a smaller diameter than the die opening.
    • Smaller clearance between the punch and the die, results in a greater amount of ironing.

    Redrawing Operations

    • Containers or shells that are too difficult to draw in one operation are generally redrawn.
    • Reverse redrawing is a process in which the metal is subjected to bending in the direction opposite to its original bending configuration. It results in lower forces and a more ductile material.

    Aluminum Two-Piece Beverage Can

    • Aluminum beverage cans are made using a metal-forming process involving a number of steps:
      • Blanking - Sheet metal is cut into the desired shape.
      • Deep drawing - The blank is formed into a cup.
      • Ironing - The walls of the cup are thinned to the desired thickness.
      • Beading - A bead is formed around the top edge of the cup to ensure a good seal.
      • Bottoming - The bottom of the can is formed.
      • Necking - The top of the can is necked down to fit the lid.

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    Description

    Test your knowledge of forging presses, defects, and the extrusion process. This quiz covers mechanical, hydraulic, and screw presses, as well as common forging issues like fractures and barreling. Additionally, explore the principles and applications of metal extrusion.

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