Manufacturing Processes Quiz
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Questions and Answers

What is one of the key advantages of mechanical working processes over casting?

  • Lower energy consumption
  • Reduced production time
  • Better control over fiber orientation (correct)
  • Higher metal yield rates
  • Why is mechanical working considered more suitable for mass production compared to other methods?

  • It requires less skilled labor.
  • It generally has higher productivity. (correct)
  • It allows for greater design flexibility.
  • It produces more complex geometries.
  • What happens to fiber lines in the material during casting?

  • They are reinforced.
  • They remain unchanged.
  • They follow the contour of the mold.
  • They get destroyed during melting. (correct)
  • Which manufacturing process often results in material loss in the form of chips?

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

    What is a disadvantage of machined components compared to those created by mechanical working?

    <p>Increased exposure to corrosion</p> Signup and view all the answers

    What is the expected yield percentage range for casting processes?

    <p>60 to 70%</p> Signup and view all the answers

    How does the strength of a component relate to the direction of fiber lines in mechanical working?

    <p>Maximum strength is parallel to the fiber lines.</p> Signup and view all the answers

    What is a key limitation of the two high reversing rolling mill design?

    <p>It consumes more power with each reversal of rolls.</p> Signup and view all the answers

    In which scenario are two high reversing mills typically utilized?

    <p>For roughing stands of structural mills.</p> Signup and view all the answers

    What advantage does a three-high rolling mill have over a two high reversing mill?

    <p>It has a constant direction of roll rotation.</p> Signup and view all the answers

    What role do support rolls play in a rolling mill?

    <p>They facilitate the movement of the job through the mill.</p> Signup and view all the answers

    Why are two high non-reversing mills often preferred in production?

    <p>They are the least expensive option.</p> Signup and view all the answers

    What is the typical size range for a bloom?

    <p>150 mm × 150 mm to 250 mm × 300 mm</p> Signup and view all the answers

    Which product is obtained from a reduction of bloom through hot rolling?

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

    What distinguishes a sheet from a plate?

    <p>Thickness less than 6.35 mm</p> Signup and view all the answers

    What is the term for a rolled product with a rectangular cross-section and a thickness of 50 to 150 mm?

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

    What is the maximum width of a strip?

    <p>600 mm</p> Signup and view all the answers

    What is a common use for billets?

    <p>To make rounds, wires, and bars</p> Signup and view all the answers

    What differentiates a foil from other rolled products?

    <p>Foils have very thin dimensions</p> Signup and view all the answers

    Which statement accurately describes plates?

    <p>Plates have a width equal to the width of the roll.</p> Signup and view all the answers

    Which rolled product is typically processed into coils?

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

    What is the primary distinction between a narrow sheet and a standard sheet?

    <p>Thickness less than 6.35 mm and B/t less than 3</p> Signup and view all the answers

    What is the best temperature range for working the specified steel effectively?

    <p>400°C to 700°C</p> Signup and view all the answers

    At what percentage of the melting point (Tm) is warm working generally performed?

    <p>0.3 Tm to 0.5 Tm</p> Signup and view all the answers

    Which of the following processes primarily involves compressive stress?

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

    In which type of metalworking process are bending moments primarily applied?

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

    What characterizes steady state forming processes?

    <p>The deformation zone remains fixed in shape and size.</p> Signup and view all the answers

    Which of the following processes is classified as a combined stress type process?

    <p>Wire drawing</p> Signup and view all the answers

    Which method is commonly associated with shear stress in metal forming?

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

    At what temperature do scaling and oxidation losses start to increase rapidly?

    <p>700°C</p> Signup and view all the answers

    Which process involves the application of tensile stresses?

    <p>Creep forming</p> Signup and view all the answers

    What is the purpose of the angle of contact or bite in the rolling process?

    <p>To control the friction between the metal and the rolls</p> Signup and view all the answers

    In the context of rolling, what happens if the angle of bite is greater than $tan^{-1} μ$?

    <p>The metal will not enter the space between the rolls</p> Signup and view all the answers

    What is the primary role of lubrication in hot rolling?

    <p>Lubrication is generally not necessary</p> Signup and view all the answers

    What does ragging refer to in the context of primary reduction rolling mills?

    <p>Creating fine grooves on the roll surfaces</p> Signup and view all the answers

    What factors influence the maximum permissible angle of bite in the rolling process?

    <p>The surface roughness, temperature, and speed</p> Signup and view all the answers

    What is the relationship between the normal force (P) and the tangential force ($μP$) at the moment of bite?

    <p>Their relationship can be defined as $P sin α = μ P cos α$</p> Signup and view all the answers

    Why are rolling loads high in cold rolling processes?

    <p>The deformation required is more substantial</p> Signup and view all the answers

    What does the coefficient of friction ($μ$) between the metal and the rolls depend upon?

    <p>Materials of the rolls and surface roughness</p> Signup and view all the answers

    What is the central angle $eta$ associated with in the rolling process?

    <p>The arc of contact between the rolls and the metal</p> Signup and view all the answers

    What is the likely reason for increasing friction in raw rolling mills?

    <p>To prevent slippage between the roll and metal</p> Signup and view all the answers

    Which manufacturing process is more competitive as the size and complexity of a part increase?

    <p>Metal Spinning</p> Signup and view all the answers

    What primarily differentiates flow turning from power spinning?

    <p>Change in thickness of the work material</p> Signup and view all the answers

    In hot spinning, what is the role of the rounded stick or roller?

    <p>It applies consistent pressure to the metal.</p> Signup and view all the answers

    What is a common application for hot spinning of metals?

    <p>Forming thick circular plates and pressure vessels</p> Signup and view all the answers

    What is the expected maximum thickness that can routinely be hot spun into shapes?

    <p>150 mm</p> Signup and view all the answers

    Which method primarily uses compressive forces for shaping metal into various forms?

    <p>Flow Turning</p> Signup and view all the answers

    What characterizes a hot spinning machine?

    <p>It combines vertical press functions with spinning lathe capabilities.</p> Signup and view all the answers

    How does increasing temperature affect the time required for recrystallization given a constant amount of prior deformation by cold working?

    <p>It decreases the time required for recrystallization.</p> Signup and view all the answers

    What effect does the presence of second phase particles have on the recrystallization temperature?

    <p>It decreases the recrystallization temperature.</p> Signup and view all the answers

    What characterizes the portion BC of the load deformation curve during cold working?

    <p>It marks the beginning of local necking and post necking deformation.</p> Signup and view all the answers

    How does the amount of deformation prior to recrystallization influence grain size during the process?

    <p>Higher deformation results in smaller grain size.</p> Signup and view all the answers

    What does the curve OAD of the load deformation curve for hot working indicate?

    <p>Deformation occurs with almost constant applied force after yield point.</p> Signup and view all the answers

    What is the primary purpose of using pneumatic hammers in metal working?

    <p>To create surface indents that prepare areas for cold working</p> Signup and view all the answers

    In terms of efficiency, which metal forming process provides the lowest production rate?

    <p>Open die-forging</p> Signup and view all the answers

    Which of the following characteristics has the greatest metal utilization factor?

    <p>4th method</p> Signup and view all the answers

    What typically happens to the microstructure of metal when it experiences cold working?

    <p>Grain shape and orientation change significantly</p> Signup and view all the answers

    Why is a four-high rolling mill often preferred for cold rolling processes?

    <p>It provides better control of the reduction process</p> Signup and view all the answers

    What is a significant drawback of cold working metals compared to hot working?

    <p>Increased risk of microcracking</p> Signup and view all the answers

    Which statement best explains the function of the angle of bite in the rolling process?

    <p>It affects the friction between metal and rolls</p> Signup and view all the answers

    During the die-forging process, what is the maximum number of parts typically achievable per hour using forging hammers?

    <p>1000 parts</p> Signup and view all the answers

    What is the main consequence of cold working a metal, in terms of its mechanical properties?

    <p>Enhanced strength and hardness</p> Signup and view all the answers

    What is the primary difference between hammer forging and drop forging?

    <p>Hammer forging relies on impact force applied by a hammer.</p> Signup and view all the answers

    Which of the following best defines press forging?

    <p>A process using gradual pressure to shape metal.</p> Signup and view all the answers

    What governs the flow of metals during the upset forging process?

    <p>The shape and design of the dies used.</p> Signup and view all the answers

    What is upset forging primarily used for?

    <p>Increasing the diameter of a material at its end.</p> Signup and view all the answers

    How is roll forging distinct from other types of forging processes?

    <p>It integrates a continuous mechanism for forming metal.</p> Signup and view all the answers

    Which method would be best suited for producing thin-walled parts from a metal alloy?

    <p>Tubular extrusion.</p> Signup and view all the answers

    What characterizes the process of rotary forging?

    <p>It imparts rotational motion to the workpiece during forging.</p> Signup and view all the answers

    What is one of the advantages of liquid forging?

    <p>It allows for very complex shapes to be forged.</p> Signup and view all the answers

    What does the degree of drawing refer to in metal drawing processes?

    <p>The percentage reduction in cross-sectional area.</p> Signup and view all the answers

    What differentiates direct extrusion from indirect extrusion?

    <p>Direct extrusion forces metal through a die without any sleeve.</p> Signup and view all the answers

    What is the main consequence of forging steel at too high a temperature?

    <p>Possibility of grain growth and resulting brittleness</p> Signup and view all the answers

    What is a primary difference between cold working and hot working?

    <p>Hot working occurs above the recrystallization temperature of metals</p> Signup and view all the answers

    How does annealing relate to cold working?

    <p>Annealing reduces the residual stresses induced by cold working</p> Signup and view all the answers

    What effect does hot working have on the microstructure of metals?

    <p>It results in a more uniform crystal structure</p> Signup and view all the answers

    What is the estimated blanking force required to cut a 25 mm by 30 mm blank from a 1.5 mm thick metal strip with a shear stress of 450 N/mm²?

    <p>74.25 kN</p> Signup and view all the answers

    What lubricant is often suggested for hot forging processes?

    <p>Graphite or some form of MOS2</p> Signup and view all the answers

    Which lubricant is appropriate for cold rolling processes?

    <p>Water-soluble oils</p> Signup and view all the answers

    What role does lubrication play in the forging process?

    <p>It reduces friction and wear, improving metal flow</p> Signup and view all the answers

    What is an important consideration regarding the penetration percentage in blanking operations?

    <p>It affects the total force during blanking</p> Signup and view all the answers

    What is a common lubricant used in hot extrusion processes?

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

    Study Notes

    Mechanical Working of Metals

    • Mechanical working processes involve permanent changes in material shape due to external forces.
    • Processes include rolling, forging, extrusion, drawing, and sheet metal working.
    • Stresses induced are generally greater than the yield strength but less than the fracture strength of the material, except for shearing, piercing, and blanking. These processes exceed the material's fracture strength.
    • Starting materials for mechanical working processes vary, and may include cast ingots, billets, cast preforms, powdered-metal bars, bar stock, powdered-metal preforms, or blanks, depending on the specific process.

    Extrusion

    • Extrusion: Shaping a metal block into a desired shape by forcing it through a die opening.
    • Two types: Direct and Indirect.
    • Direct extrusion: Metal flows in the same direction of the force application.
    • Indirect extrusion: Metal flows in the opposite direction of the force application.
    • Hot extrusion is frequently used for non-ferrous metals (e.g., aluminum, magnesium, copper alloys).
    • Cold extrusion is more commonly used when higher tolerances are required for metals such as steel, to maximize strength and reduce waste.

    Forging

    • Forging: Shaping a metal by applying compressive force, can be done either hot or cold, although hot forging is more common.
    • Two types: Open die forging and Closed die forging
    • Open die forging: Uses two flat dies, less expensive, suitable for simpler shapes and lower production volumes.
    • Closed die forging: Uses two dies with cavities, suitable for more complex shapes, high accuracy, and higher production volumes.
    • Common forging operations: Upsetting, heading, fullering, edging, drawing down, blocking, cutting off, and piercing.
    • Hammer forging (or open die) and Press forging (or closed die)

    Rolling

    • Rolling: Shaping metal by passing it between rotating rollers, the main aim is to reduce thickness.
    • Rolling methods: Two-high, three-high, and four-high rolling mills. Different types are suited to different products and production volumes.
    • Key terms: Bloom, billet, slab, plate, sheet, strip, and foil (different shapes with differing dimensions).
    • Rolling is a crucial step in many manufacturing processes, particularly for ferrous metals to produce plates, sheets and coils.

    Other Processes

    • Coining: A closed die forging operation that produces very high pressures, used for making coins, medals, badges, etc., produces high accuracy, precise shapes.

    • Embossing: Creates raised or depressed designs on a metal surface, commonly used for decorative or functional purposes, unlike the squeezing of coining.

    • Hobbing: Creating a die cavity by pressing a hardened punch into a softer metal block, creating smooth, complex shaped dies.

    • Riveting: Permanently joining two metal parts using a rivet.

    • Staking: A fastening method using a shaped punch to deform a projection of one part so it grips the second, often used as a replacement for more conventional methods.

    • Shot Peening: Impacts of shots (steel, aluminum, or glass) on a metal surface to increase fatigue strength and to prevent cracking under corrosive conditions.

    • Hot/Cold Forming, Warm-forming

    • HIP (Hot Isostatic Pressing): High pressure, high temperature forming process for intricate shapes and high temperature alloys.

    • Super-plastic Forging: Forging at elevated temperatures (near the melting point), allowing large deformations and producing more complex shapes.

    • Metal Spinning: Used to produce hollow, axisymmetrical shapes.

    • Various other manufacturing techniques discussed further for various metals.

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    Description

    Test your knowledge on mechanical working and casting processes in manufacturing. This quiz covers advantages, disadvantages, and specific scenarios related to mechanical working, rolling mills, and material yield. Perfect for students studying manufacturing engineering or material science.

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