Extrusion & Drawing Processes Quiz
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Questions and Answers

How does the billet temperature impact the extrusion force?

  • Higher temperature leads to increased extrusion force.
  • Higher temperature increases deformation resistance.
  • As temperature increases, deformation resistance decreases. (correct)
  • Higher temperature has no effect on extrusion force.

    • What is the primary role of a stripper plate in impact extrusion?

  • To increase the flow of lubricants into the die.
  • To cool the extruded parts rapidly after extrusion.
  • To remove the extruded parts from the punch during the process. (correct)
  • To change the angle of the die for better efficiency.

    • What effect does increasing the die angle have on lubricant flow during the extrusion process?

  • It restricts lubricant flow into the die. (correct)
  • It eliminates the need for lubricant altogether.
  • It enhances lubricant flow into the die.
  • It has no impact on lubricant flow.

    • Why would glass not be a suitable lubricant for impression-die forging?

    <p>Glass may lead to incomplete filling of die cavities.</p> Signup and view all the answers

    What happens to extrusion force as the extrusion speed increases?

    <p>The extrusion force decreases due to lower yield stress.</p> Signup and view all the answers

    What primarily determines the size and shape of the dead metal zone in square die extrusion?

    <p>Friction and strength</p> Signup and view all the answers

    Why is aluminum commonly used for extruded parts?

    <p>It has good ductility and low extrusion resistance</p> Signup and view all the answers

    What is the primary disadvantage of hot extrusion compared to cold extrusion?

    <p>Increased die wear</p> Signup and view all the answers

    What purpose does the glass serve in steel extrusions?

    <p>Reduces sticking of the hot metal</p> Signup and view all the answers

    In the welding-chamber process, what limitation is faced regarding lubrication?

    <p>It cannot be used at all</p> Signup and view all the answers

    What is a common characteristic of parts produced through cold extrusion?

    <p>They exhibit strain hardening</p> Signup and view all the answers

    Which process is primarily utilized for producing collapsible metal containers like toothpaste tubes?

    <p>Impact-extrusion process</p> Signup and view all the answers

    In drawing processes, what limits the amount of area reduction achievable?

    <p>Strength of the drawing wire</p> Signup and view all the answers

    What is the primary purpose of drawing in manufacturing?

    <p>To reduce or change the cross section of materials.</p> Signup and view all the answers

    Which of the following drawing processes primarily uses elevated temperatures?

    <p>Drawing of larger hollow sections.</p> Signup and view all the answers

    What is the primary characteristic of direct extrusion?

    <p>A hydraulic ram drives the billet through a die at high pressure.</p> Signup and view all the answers

    What equipment is used for cold-drawing operations?

    <p>Draw Bench.</p> Signup and view all the answers

    Which of the following is a limitation of indirect extrusion?

    <p>The ram must be hollow to accommodate the extrusion.</p> Signup and view all the answers

    What does the extrusion ratio (R) describe?

    <p>The reduction from billet size to the size of the extrusion.</p> Signup and view all the answers

    How is the drawing force primarily generated in a Draw Bench?

    <p>Through a chain drive or hydraulic cylinder.</p> Signup and view all the answers

    What limitation is inherent when using a Draw Bench for drawing operations?

    <p>The length of drawn products is usually limited.</p> Signup and view all the answers

    Which condition is NOT relevant to the extrusion force required during the extrusion process?

    <p>Size of the die opening.</p> Signup and view all the answers

    How does hydrostatic extrusion affect the properties of brittle metals?

    <p>Increases ductility by applying pressure from all sides.</p> Signup and view all the answers

    What material characteristic is particularly high in thin steel wire produced for springs?

    <p>Tensile strength.</p> Signup and view all the answers

    In lateral extrusion, how is the ram positioned?

    <p>It operates horizontally to push the billet through the die.</p> Signup and view all the answers

    Which term describes the zone in the extrusion chamber where metal does not flow through the die?

    <p>Dead Metal Zone.</p> Signup and view all the answers

    What is the effect of metal flow during the extrusion process?

    <p>It creates an elongated grain structure affecting the material properties.</p> Signup and view all the answers

    Which type of drawing machine can contain multiple sequential dies?

    <p>Bull Block Machine.</p> Signup and view all the answers

    What does the term 'Shape Factor' (S) refer to in the context of extrusion?

    <p>The complexity of the extruded shape.</p> Signup and view all the answers

    What is the primary difference between extrusion and drawing processes?

    <p>Extrusion reduces the cross-section by forcing the billet through a die, while drawing reduces it by pulling the billet.</p> Signup and view all the answers

    What is the role of a spider die in the extrusion process?

    <p>To support internal mandrels and create hollow cross sections.</p> Signup and view all the answers

    What characterizes a dead-metal zone in the extrusion process?

    <p>An area where the metal remains stationary and does not flow.</p> Signup and view all the answers

    Why is glass used as a lubricant in hot extrusion?

    <p>It melts and coats the die, protecting it during the process.</p> Signup and view all the answers

    In direct extrusion, how is the billet processed in relation to the die?

    <p>The billet is placed in the chamber and forced through the die.</p> Signup and view all the answers

    What is the function of the land in a drawing die?

    <p>To ensure the drawn wire is of exact size.</p> Signup and view all the answers

    Which factors can affect the extrusion pressure during the process?

    <p>Extrusion temperature, speed, and die design.</p> Signup and view all the answers

    What distinguishes reverse extrusion from direct extrusion?

    <p>The die moves towards a stationary billet in reverse extrusion.</p> Signup and view all the answers

    Study Notes

    Extrusion & Drawing Processes

    • Direct Extrusion (Forward Extrusion): A common process where a cylindrical billet is loaded, and then a powerful hydraulic ram forces it through a small die at high pressure. The die opening can be round or shaped.

    • Indirect Extrusion: The chamber and billet remain stationary, and the ram is driven back into the chamber against the billet. This reduces friction requiring less ram force.

    • Lateral Extrusion: The ram is vertical and drives the billet horizontally through a die. Less common than direct or reverse extrusion.

    • Hydrostatic Extrusion: Uses a billet smaller than the chamber ID. Hydraulic pressure squeezes the billet from all sides through the die. Improves ductility of some brittle metals.

    • Extrusion Ratio (R): A measure of reduction from billet size to extrusion size (typically 10 < R < 100). Billet must be larger than the circumscribing circle diameter (CCD) of the extrusion.

    • Shape Factor (S): Measures the complexity of an extruded shape.

    • Extrusion Force: Depends on material strength, temperature, extrusion ratio, friction between the billet/chamber and metal/die surfaces, and die angle.

    Extrusion Force Formula

    • Fextrusion=Ao×k×ln(AoAf)F_{extrusion} = A_o \times k \times ln(\frac{A_o}{A_f})Fextrusion​=Ao​×k×ln(Af​Ao​​)

      • AoA_oAo​ = original billet area
      • AfA_fAf​ = area of the extruded shape
      • kkk = extrusion constant (affected by die angle, friction, and strength)

    Metal Flow in Extrusions

    • The flow of metal during extrusion affects final properties & quality.
    • Similar to incompressible fluid flow in pipes, but at high pressure.
    • An elongated grain structure may result; recrystallization may occur (depending on temperature).
    • Dead metal zones may form during extrusion through square dies.

    Extrusion Practicalities

    • Common alloys include aluminum, copper, magnesium, and steel.
    • Aluminum is commonly used and has high maximum CCD.
    • Steel is hard to extrude and requires lubrication (glass).
    • Maximum extruded lengths are limited.

    Extrusion Temperature Ranges

    • Extrusion can be done hot or cold, but hot extrusion is more versatile with lower forces & less die wear.
    • Temperature ranges vary for different metals and alloys.

    Die Design for Shapes

    • Dies with thin sections & no cavities are easier.
    • Complex shapes with internal cavities require special dies and processes (like spider-dies).

    Welding-Chamber Process

    • Metal flows around the supports and is re-welded downstream.
    • Suitable for aluminum and other materials.

    Drawing

    • Similar to extrusion, but metal is pulled through a die.
    • Area reduction is limited by the strength of the drawing wire.
    • The available drawing force is limited to the breaking strength of the wire already drawn.
    • Used to make wire, springs, cables, etc.

    Drawing Force

    • Formula for drawing force without friction: F=YavgAo ln(Ao/Af)

    • F=YavgAo(1+(1/2)ln(Ao/Af) + (α/3)) (with friction)

      • AoA_oAo​ = original billet area
      • AfA_fAf​= area of the extruded shape
      • YavgY_{avg}Yavg​ = average true stress in the die gap
      • µµµ = the co-efficient of friction
      • ααα = the die angle (in radians)

    Draw Bench

    • Used for a single die or multiple dies.
    • Gripping mechanism is pulled by chains to provide drawing forces.
    • Used for heavy sections & shapes.
    • Lengths of drawn items are usually limited.

    Cold Extrusion

    • Similar to cold forging, creating good grain flow patterns and toughness.

    • Increased strength from strain hardening.

    Extrusion vs. Rolling vs. Forging

    • All involve compression, but extrusion forces metal through a die, rolling reduces thickness, and forging shapes the object in a die.

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    Extrusion & Drawing PDF

    Description

    Test your knowledge on various extrusion and drawing processes, including direct, indirect, lateral, and hydrostatic extrusion. Explore concepts like extrusion ratio and shape factor, and discover how these methods impact the manufacturing of metals. Perfect for students and professionals in materials science and engineering.

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