Rolling, forging & extrusion

Question 1

What is rolling?

Answer 1

bulk deformation process where a material is passed through a gap between two rollers

Question 2

How much waste does bulk deformation make?

Answer 2

NONE!

• cold is net shape
• hot is near net shape

Question 3

What are bulk deformations performed as?

Answer 3

cold (room temp), warm (heated), hot (very high heat)

Question 4

How to choose which operation is best:

Answer 4

the bigger the deformation, the higher the heat

Question 5

Pros and cons of cold working:

Answer 5

Pros
- better finish and accuracy
- stronger product
Cons
- needs LOTS of force

Question 6

What happens in a rolling process?

Answer 6

length significantly increases, width mildly increases

Question 7

What happens to the initial and final velocity in a rolling process?

Answer 7

output velocity is much greater than input velocity

Question 8

What are the 5 rolling mill configurations?

Answer 8

• 2 high
• 3 high
• 4 high
• cluster-mill
• tandem rolling mill

Question 9

What are the two types of 2 high rolling mills?

Answer 9

1. non-reversing mill
2. reversing mill

Question 10

What does a backup (*support) roll do?

Answer 10

supports the work roll and saves it from deformation, reduces contact area so less force is required

Question 11

What are the two roles of rolls?

Answer 11

1. pull the work into the gap by friction
2. squeeze the work to reduce its cross section

Question 12

What are the pros and cons of hot working?

Answer 12

Pros
- less force required
- fills micro cracks
- more ductile
Cons
- accuracy
- tolerance
- poor surface finish

Question 13

What are the two rolling processes?

Answer 13

1. flat rolling
2. shape rolling

Question 14

Defects of flat rolling

Answer 14

1. roll and material stick
2. bending of rolls (deformed material)

Question 15

The thicker the material… (*velocity)

Answer 15

the lower the velocity

Question 16

How is bending of rolls compensated for?

Answer 16

by applying camber (deforming the roll to get desired shape)

Question 17

The two types of camber

Answer 17

1. insufficient camber (not enough roundness)
2. over cambered (too much roundness)

Question 18

Grain structure of hot and cold roll

Answer 18

• hot roll is smaller and more random
• cold roll is bigger and more aligned

Question 19

Die

Answer 19

roll used for thread rolling

Question 20

Cold or hot rolling for thread rolling?

Answer 20

Cold because the deformation is small and needs to be strong

Question 21

Machined thread vs roll thread

Answer 21

• machine thread is straight and not for mass production
• roll thread is more curved, better for mass production

Question 22

What condition is ring rolling generally done in?

Answer 22

hot rolling

Question 23

What is a cavity in rolling?

Answer 23

the hole when creating tubes in rolling

Question 24

What is a mandrel used for?

Answer 24

shaping the cavity

Question 25

The higher the forces, the ____ material hardening

Answer 25

more

Question 26

What types of forging of metals are there?

Answer 26

cold and hot forging

Question 27

Advantages/Disadvantages of hot and cold forging

Answer 27

same as hot and cold rolling

Question 28

Is forging used for high or low volume production? (a lot or a little)

Answer 28

high volume production because it's expensive

Question 29

Grain shapes between casting, machining, and forging

Answer 29

casting: random dots (*gas) machining: straight line dots (*liquid) forging: clean and follow shape of product (*solid)

Question 30

What shape size is forging used for?

Answer 30

big and small

Question 31

Is forging expensive or cheap?

Answer 31

EXPENSIVE and high quality (high volume manufacturing)

Question 32

The 3 groups of forging:

Answer 32

1. open die forging 2. impression die forging 3. closed die forging

Question 33

Open die forging

Answer 33

used for simple shapes, material can flow around, any type of force application

Question 34

What does friction do in open die forging?

Answer 34

allows for easy flow at center and restricted flow at edges (causes barreling/pancaking - more deformation at center)

Question 35

Friction in cold vs hot forging

Answer 35

coefficient of friction is much higher in hot friction (barreling is greater in hot forging)

Question 36

When height to diameter ratio is high, what happens to barreling effect?

Answer 36

increases

Question 37

2. Impression die forging

Answer 37

die contains cavity or impression that is imparted to workpart (metal flow constrained)

Question 38

Is impression die forging a one step process?

Answer 38

NO, it's a multiple step process

Question 39

What's flush in forging?

Answer 39

the excess material only in impression forging

Question 40

What are the two purposes of the flush?

Answer 40

1. constrains material to fill die cavity 2. holds in excess material

Question 41

Too much flush requires...

Answer 41

more force

Question 42

3. closed die forging

Answer 42

the amount of material needs to be known, there's no place for extra material. can be used for complex shapes

Question 43

Used for big or small deformation? (*closed die forging)

Answer 43

generally small deformations, but can be complex (e.g. coins)

Question 44

What is upsetting and heading?

Answer 44

a forging process used to make heads of nails and bolts (form of open die forging)

Question 45

How is swagging done?

Answer 45

rotating dies that hammer the workpiece radially inward as the workpiece is fed into the die

Question 46

Two main types of forging tools

Answer 46

1. press 2. hammer

Question 47

Main things that can go wrong during forging process:

Answer 47

- improper shapes due to little material - too much material

Question 48

3 types of presses:

Answer 48

1. hydraulic press 2. mechanical press 3. screw press

Question 49

3 types of hammers

Answer 49

1. gravity drop hammer 2. power drop hammer 3. counterblow hammer

Question 50

What is extrusion of metals?

Answer 50

PUSHING through die opening to make desired shape

Question 51

What is drawing of metals? (*horse drawn carriage)

Answer 51

PULLING through die opening to make desired shape

Question 52

Can hot and cold working be used for extrusion?

Answer 52

YES, done in both

Question 53

What is relief angle?

Answer 53

the angle needed so the die doesn't touch the workpiece

Question 54

What is butt?

Answer 54

the small portion of billet (workpiece) that can be removed - gets stuck in die (in the butt crack)

Question 55

What is mandrel and why's it needed?

Answer 55

it's attached to the ram (thing that pushes) and is needed to make a hollow object

Question 56

What can hot and cold extrusion be further classed as?

Answer 56

1. direct (forward) 2. indirect (backward/reverse)

Question 57

What are the two limits of indirect (backward) extrusion?

Answer 57

1. lower rigidity of hollow ram 2. difficulty in supporting extruded product as it exits

Question 58

What is dead zone controlled by?

Answer 58

friction, hot working gives more dead zone

Question 59

Is dead zone good or bad?

Answer 59

BAD, we don't want it

Question 60

What are dead (0) zones?

Answer 60

dead zones are areas in the container where material flow is 0

Question 61

Relationship between complexity of shape and force

Answer 61

simple shape = less force complex shape = more force

Question 62

Hot or cold working for drawing?

Answer 62

generally done in COLD

Question 63

What is cold drawing further classified as?

Answer 63

1. bar (large diameter, single step) 2. wire (small diameter, multi-step)

Question 64

Area reduction in drawing eqn

Answer 64

r = (Ao - Af)/Ao r = area reduction in drawing Ao = original area of work Af = final area of work

Question 65

What is a wire drawing process?

Answer 65

many drawing machines with multiple draw dies (4 to 12) separated by accumulating drums

Question 66

What do the drums (capstan) do?

Answer 66

They provide proper force to draw wire stock thru up-stream die

Question 67

What is annealing?

Answer 67

used between dies to relieve work hardening

Question 68

Pros and cons of wire drawing

Answer 68

Pros - length - surface finish Cons - multiple dies and take up rolls

Question 69

What are the 3 preparations of work for drawing?

Answer 69

1. annealing (increase ductility) 2. cleaning (literally) 3. pointing (reduce diameter of starting end to allow insertion through draw die)

Question 70

What doe lubricants do?

Answer 70

reduce friction during drawing and reduce temperature

Question 71

What are the three lubricants?

Answer 71

1. wet drawing (completely in oil) 2. dry drawing (coated, passing thru box with oil) 3. coating (wire/bar coated with soft metal that acts as lubricant)

Question 72

What types of metal can be used as lubricants?

Answer 72

copper or tin

Question 73

What is the rule for max reduction per pass?

Answer 73

max draw stress < yield strength of existing metal

Question 74

As reduction increases, the draw series ____

Answer 74

INCREASES