MEC 322 > Rolling, forging & extrusion > Flashcards

Rolling, forging & extrusion Flashcards

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1
Q

What is rolling

A

it is a bulk deformation processes, where there is plastic deformation

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2
Q

How much waste does bulk deformation make?

A

no wastage of material

generally cold is net shape
hot is near net shape

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3
Q

what are bulk deformations performed as

A

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

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4
Q

How do u choose which operation is best

A

bigger the deformation higher the heat

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5
Q

what are the pros and cons of hot working

A

PROS
less force required, fill the micro cracks, and makes more ductile

CONS
accuracy, tolerence and surface finish is poor

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6
Q

what are the pros and cons of cold working

A

PROS
better finish and accuracy, much stronger final product

CON
requires ALOT of force

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7
Q

what happens in a rolling processes

A

length increases significantly and width mildly increases

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8
Q

what happens to the initial and final velocity in a rolling processes

A

output velocity is much higher than input velocity

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9
Q

what are the 5 rolling mill configurations

A
  1. two-high (two opposing rolls)
  2. three high (work passes in both directions)
  3. four high (backing rolls support smaller work rolls)
  4. cluster-mill (multiple backing rolls on smaller rolls)
  5. tandem rolling mill (sequence of two high mills, velocity is synchronized and increases)
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10
Q

what are the two types of two-high rolling mills

A
  1. non reversing mill
  2. reversing mill (reduces times required)
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11
Q

what does a backup roll do

A

supports the work roll and saves it from deformation,
(goes in the opposite direction)
also reduces contact area so less force required

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12
Q

what are the 2 roles of rolls

A
  1. pull the work into the gap between by friction
  2. squeeze the work to reduce its cross section (shrinks it)
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13
Q

what is the 2 rolling processes divided to

A
  1. flat rolling
  2. shape rolling
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14
Q

what are defects in flat rolling

A
  1. roll and material stick (hot)
  2. bending of rolls (deformed material)
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15
Q

the thicker the material… (velocity)

A

lower the velocity

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16
Q

how is bending of rolls compensated for

A

by applying camber (deforming the roll to give the shape u want)

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17
Q

what are the two types of camber

A
  1. insufficient camber (not enough roundness)
  2. over cambered (too much roundness
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18
Q

grain structure of hot and colds role

A

hot role is smaller and more random
cold role is bigger and more aligned

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19
Q

What is the roll called for thread rolling

A

a die

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20
Q

do you use cold or hot rolling for thread rolling

A

cold rolling because the deformation is small and because it needs to be strong

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21
Q

machined thread vs. roll thread

A

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

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22
Q

what condition is ring rolling generally done in

A

hot rolling

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23
Q

what is a cavity in rolling

A

the void when creating tubes in rolling

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24
Q

what is a mandrel used for

A

to shape the cavity

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25
the higher the forces (work), the _____ material hardening
more
26
what types of forging of metals are there
cold and hot forging
27
what are the advantages/ disadvantages of hot and cold forging
same as cold and hot rolling
28
is forging used for high or low volume
used for high volume production because it is expensive
29
grain shapes between casting, machining, and forging
casting - random dots machining - straight line dots forging - clean and follow shape of product
30
what size shape is forging used for
big and small!!
31
is forging expensive or cheap
expensive $$$$ and high quality (high volume manufacturing)
32
what are the 3 groups of forging
1. open die forging 2. impression die forging 3. closed die forging
33
1. open die forging
used for simple shapes, material can flow around, any type of force application
34
what does friction do in open die forging
allows for easy flow at center and restricted flow at the edges -> causing "barelling or "pankacking" (more deformation at center)
35
friction in cold vs hot forging
coefficient of friction is much higher in hot forging (so barrelling effect is more in hot forging)
36
when height to diameter ratio is high what happens to the barrelling effect
the barreling effect is more
37
2. impression die forging
die contains cavity or impression that is imparted to workpart (Metal flow is constrained so that flash is created)
38
is impression die forging one step process?
no, it cant be done in one step (many processes)
39
what is flush in forging
the excesses material only in impression forging
40
what is the 2 purposes of the flush
1. constrains material to fill die cavity 2. holds in excesses material
41
too much flush requires...
more force
42
3. closed die forging
amount of material needed need to be known because there's no place for extra (or adding more) material can be used for complex shapes (no excesses material)
43
used for big or small deformation (closed die forging?)
generally small deformations, but can be complex i.e coins
44
what is upsetting and heading
a forging process used to make heads of nails and bolts (form of open die forging)
45
how is swaging done
rotating dies that hammer the workpiece radially inward as the work piece is fed into the die
46
Two main types of forging materials/tools
1. press 2. hammer
47
Main things that can go wrong during forging process
1. improper shapes due to little material 2. too much extra material
48
3 types of presses
1. hydraulic press (high force low speed) 2. mechanical press (crank & knuckle joint) 3. screw press
49
3 types of hammers (more vibration)
1. gravity drop hammer 2. power drop hammer 3. counterblow hammer
50
What is extrusion of metals
pushing through die opening to make the shape u want
51
what is drawing of metals
pulling though die opening to make the shape u want
52
can you use hot and cold working for extrusion
yes done in cold and hot
53
what is relief angle
the angle needed so the die doesn't touch the work piece
54
what is butt
the small porion of billet (workpiece) that can never be romved ~ gets stuck in die (lol it’s in the butt crack)
55
what is a mandrel and why is it needed
its attached to the ram (thing that pushes) and is needed to make a hallow object
56
what is hot and cold extrusion further classified as
1. direct (forward) 2. indirect (reverse/backward)
57
what are the 2 limits of indirect extrusion (backwards)
1. lower rigidity of hollow ram 2. difficulty in supporting extruded product as it exits
58
what is dead zone controlled by
controlled by friction (changes by changing the geometry of die and whether it is hot or cold working) hot working gives more dead zone
59
is dead zone good or bad?
bad, we dont want it
60
what are dead zones?
dead zones are areas in the container where material flow is zerp
61
relationship between complexity of shape and force
simple chape = less force, complex shape = more force
62
can you use hot and cold working for drawing
no. generally done in cold
63
what is cold drawing further classified as
1. bar (large diameter, single step) 2. wire (small diameter, multi step)
64
area reduction in drawing formula
r = (Ao - Af)/Ao r = area reduction in drawing Ao = original area of work Af = final area of work
65
what is a wire drawing process
many drawing machines with multiple draw dies (4 - 12) separated by accumulating drums
66
what do the drums (capstan) do
they provide proper force to draw wire stock through up stream die
67
what is annealing
it is used between dies to relieve work hardening
68
Pros and Cons of Wire Drawing
PROS - length - surface finish CONS - multiple dies and take up roles
69
What are the 3 preparations of work for drawing
1. annealing (increase ductility ~ stretch not crack) 2. cleaning (clean to avoid damage to work surface and die) 3. pointing (reduce diameter of starting end to allow insertion through draw die)
70
what do lubricants do
reduce friction during drawing and reduces temperature
71
what are the three lubricants
1. wet drawing (completely in oil) 2. dry drawing (coated, passing through box with oil) 3. coating (wire/bar is coated with soft metal that acts like lubricant)
72
what type of metal can be used as a lubricant
copper or tin
73
what is the rule for max reduction per pass
max draw stress has to be less than yield strength of existing metal
74
as reduction increases, the draw stress ________
increases (draw stress is required to draw aka force)
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