Chapter 19 Manufacturing

Which of the following stress or strength parameters is used in the computation of the force in an extrusion operation (one best answer): (a) average flow stress, (b) compression strength, (c) final flow stress, (d) tensile strength, or (e) yield strength?

(a) average flow stress

Production of pipes and tubes is associated with which of the following bulk deformation processes (three correct answers): (a) extrusion, (b) hobbing, (c) ring rolling, (d) roll forging, (e) roll piercing, (f) tube sinking, and (g) upsetting?

(a) extrusion, (e) roll piercing, (f) tube sinking

Theoretically, the maximum reduction possible in a wire drawing operation, under the assumptions of a perfectly plastic metal, no friction, and no redundant work, is which of the following (one answer): (a) zero, (b) 0.63, (c) 1.0, or (d) 2.72?

(b) 0.63

In wire drawing, why must drawing stress NEVER exceed yield strength of work metal?

Because instead of forcing the metal through the opening we would be stretching it through the opening.

What does the centerburst defect in extrusion have in common with the roll piercing process?

They are both examples of how compressive stresses applied to the outside surface of a solid cylindrical cross section can create high tensile stresses in the interior of the cylinder.

What is rolling in the context of bulk deformation process?

When slab's or plate's thickness is reduce by compression in between opposing rolls.

What is wire drawing and bar drawing?

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.

Why are bulk deformation processes important commercially and technologically?

1. Capable of significant shape change when hot working is used. 2. Positive effect on part strength when cold working is used. 3. Most processes include little material waste and they are net shape processes

Flash in impression die forging serves no useful purpose and is undesirable because it must be trimmed from the part after forming: (a) true or (b) false?

(b). Flash causes build-up of pressure inside the die, which forces the work metal to fill the die cavity.

The production of tubing is possible in indirect extrusion but not in direct extrusion: (a) true or (b) false?

(b). Tube and pipe cross sections can be produced by either direct or indirect extrusion.

Which of the following stress or strength parameters is used in the computation of the maximum force in a forging operation (one best answer): (a) average flow stress, (b) compression strength, (c) final flow stress, (d) tensile strength, or (e) yield strength?

(c) final flow stress

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?

(d) slab,

Why is friction a factor in determining ram force in direct extrusion but not a factor in indirect extrusion?

Because in direct extrusion the metal workpiece can have friction with container. In indirect metal work piece does not touch the container.

Identify ways in which force in flat rolling can be reduced?

Different configuration of rolling mills to reducing diameter of rolls, use hot rolling and reduce draft in each pass.

Distinguish between direct and indirect extrusion.

Direct has a flow in direction of ram. Indirect has metal flow in opposite direction of ram.

What is draft in a rolling operation?

Draft is the difference between the starting thickness and the final thickness as the workpiece passes between the two opposing rolls.

Besides flat rolling and shape rolling, identify some additional bulk forming processes that use rolls to effect the deformation.

Some other processes that use rolls are ring rolling, thread rolling, gear rolling, roll piercing, and roll forging.

What is sticking in a hot rolling operation?

Sticking is a condition in hot rolling in which the surface of the workpiece adheres to the rolls as the piece passes between the rolls, causing severe deformation of the metal below the surface in order to allow passage through the roll gap.

List the accessory tools that can be used during open die forging according to the video on forging.

Accessory tools that can be used during open-die forging are (1) saddles, (2) blocks, (3) rings, (4) mandrels, and (5) punches

Which of the following are alternative names for indirect extrusion (two correct answers): (a) backward extrusion, (b) direct extrusion, (c) forward extrusion, (d) impact extrusion, and (e) reverse extrusion?

(a) backward extrusion, (e) reverse extrusion

Which of the following stress or strength parameters is used in the computation of rolling force (one best answer): (a) average flow stress, (b) compression strength, (c) final flow stress, (d) tensile strength, or (e) yield strength?

(a) average flow stress

Which of the following bulk deformation processes are involved in the production of nails for lumber construction (three best answers): (a) bar and wire drawing, (b) extrusion, (c) flashless forging, (d) impression die forging, (e) rolling, and (f) upsetting?

(a) bar and wire drawing, (c) flashless forging, (d) impression die forging; Bar stock is rolled, and then drawn into wire stock. Upset forged is used to form the nail head.

Which of the following rolling mill types are associated with relatively small diameter rolls in contact with the work (two correct answers): (a) cluster mill, (b) continuous rolling mill, (c) four-high mill, (d) reversing mill, and (e) three-high configuration?

(a) cluster mill, (c) four-high mill

The maximum possible draft in a rolling operation depends on which of the following parameters (two correct answers): (a) coefficient of friction between roll and work, (b) roll diameter, (c) roll velocity, (d) stock thickness, (e) strain, and (f) strength coefficient of the work metal?

(a) coefficient of friction between roll and work, (b) roll diameter

Which of the following are classified as forging operations (four correct answers): (a) coining, (b) fullering, (c) impact extrusion, (d) roll piercing, (e) swaging, (f) thread rolling, (g) trimming, and (h) upsetting?

(a) coining, (b) fullering, (e) swaging, (h) upsetting

In which of the following extrusion operations is friction a factor in determining the extrusion force (one best answer): (a) direct extrusion or (b) indirect extrusion?

(a) direct extrusion

Johnson's formula is associated with which one of the four bulk deformation processes: (a) bar and wire drawing, (b) extrusion, (c) forging, and (d) rolling?

(b) extrusion

In rolling of steel, what are the differences between a bloom, a slab, and a billet?

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.

What is extrusion?

A deformation process where a ram pushes the metal workpiece through an open die to get a desired cross section.

What is trimming operation in context of impression die forging?

A trimming operation where the flash is removed by shearing.

What is reversing mill in rolling?

A two high rolling mill where the direction of rotation of rolls can be reversed to allow for work to pass through from either side.

What is a two-high rolling mill?

A two-high rolling mill consists of two opposing rolls between which the work is compressed.

How do compressive stresses play a role in wire drawing?

Compressive forces are present as metal workpiece is compressed as it is forced the approach of the die opening.

Why is flash desirable in impression die forging?

Flash acts as a constrain for the metal to properly flow through cavity.

Two basic types forging equipment?

Forging hammers, which impact the workpart, and forging presses, which apply a gradual pressure to the work

What is forging?

Forging is a deformation process in which the workpiece is compressed between two dies, using impact or gradual pressure to form the part.

What is isothermal forging?

Isothermal forging is a hot forging operation in which the die surfaces are heated to reduce heat transfer from the work into the tooling

Name the three basic types of dies in forging.

Open die Impression die Flashless die

Name the four bulk deformation processes.

Rolling, forging, extrusion and wire and bar drawing

List some products produced on a rolling mill?

Sheet stock, I-beam, U-beam, rails for railroad tracks and round and bar stock

Name some products produced by extrusion?

Slide door railings, door and window frames, door handles, aluminum beverage cans.

According to the video on forming, what is the primary factor that makes the mechanical performance of forged parts better than cast parts in many situations?

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.

List the preforming operations discussed in the forming video

The preforming operations discussed in the forming video are (1) edging - to increase the cross section of the work and (2) blocking - to refine the shape. Then, (3) finish forging is used to complete the shape.

Which of the following operations are closely related to open-die forging (three best answers): (a) cogging, (b) flashless forging, (c) fullering, (d) impression-die forging, (e) Mannesmann process, (f) precision forging, (g) soaking, and (h) upsetting

a) cogging, (c) fullering, and (h) upsetting