Me 286 19
19.2 Production of pipes and tubes is associated with which of the following bulk deformation processes (three correct answers): (a) extrusion, (b) ring rolling, (c) roll forging, (d) upsetting?
Answer. (a)
19.3 Which of the following are classified as forging operations (four correct answers): (a) coining, (b) impact extrusion (c) thread rolling, (d) trimming, and (e) upsetting?
Answer. (a), (d), (e),
19.1 The starting workpiece in steel hot rolling of plate and sheet stock is which of the following (one best answer): (a) bar stock, (b) billet, (c) bloom, (d) slab, or (e) wire stock?
Answer. (d).
19.4 In rolling of steel, what are the differences between a bloom, a slab, and a billet?
Answer. A bloom is a rolled steel workpiece with a square cross section of about 150 mm by 150 mm. The starting work unit for a bloom is an ingot heated in a soaking pit. A slab is rolled from an ingot or a bloom and has a rectangular cross section of about 250 mm by 40 mm. A billet is rolled from a bloom and has a square cross section of about 40 mm by 40 mm.
19.13 Although the workpiece in a wire drawing operation is obviously subjected to tensile stresses, how do compressive stresses also play a role in the process?
Answer. Compressive stresses are present in wire drawing because the starting metal is compressed as it is forced through the approach of the die opening.
19.6 What is draft in a rolling operation?
Answer. Draft is the difference between the starting thickness and the final thickness as the workpiece passes between the two opposing rolls.
19.10 What is extrusion?
Answer. Extrusion is a compression forming operation in which a workpiece is forced to flow through a die opening, thus taking the cross-sectional shape of the die opening.
19.8 What is forging?
Answer. Forging is a deformation process in which the workpiece is compressed between two dies, using impact or gradual pressure to form the part.
19.11 Name some products that are produced by extrusion.
Answer. Products produced by continuous extrusion include structural shapes (window frames, shower stalls, channels), tubes and pipes, and rods of various cross sections. Products made by discrete extrusion include toothpaste tubes, aluminum beverage cans, and battery cases.
19.1 What are the reasons why the bulk deformation processes are important commercially and technologically?
Answer. Reasons why the bulk deformation processes are important include the following: (1) they are capable of significant shape change when hot working is used, (2) they have a positive effect on part strength when cold working is used, and (3) most of the processes produce little material waste; some are net shape processes.
19.5 List some of the products produced on a rolling mill.
Answer. Rolled products include flat sheet and plate stock, round bar and rod stock, rails, structural shapes such as I beams and channels.
19.3 What is rolling in the context of the bulk deformation processes?
Answer. Rolling is a deformation process in which the thickness of the workpiece is reduced by compressive forces exerted by two opposing rolls. The rolls rotate, thus pulling and simultaneously squeezing the workpiece between them.
19.7 Besides flat rolling and shape rolling, identify some additional bulk forming processes that use rolls to effect the deformation.
Answer. Some other processes that use rolls are ring rolling, thread rolling, gear rolling, roll piercing, and roll forging.
19.2 Name the four basic bulk deformation processes.
Answer. The four basic bulk deformation processes are (a) rolling, (2) forging, (3) extrusion, and (4) wire and bar drawing.
19.9 What are the two basic types of forging equipment?
Answer. The two types of forging machines are hammers, which impact the workpart, and presses, which apply a gradual pressure to the work.
19.12 What is wire drawing and bar drawing?
Answer. Wire and bar drawing are bulk deformation processes in which the cross section of a wire or bar is reduced by pulling (drawing) it through a die opening.
19.26 In forming, what is the primary factor that makes the mechanical performance of forged parts better than cast parts in many situations?
Answer: The mechanical performance of forged or wrought parts is usually better because of the microstructure changes and the directional grain flow imparted during the forging process.