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Forming and Shaping ISAT 430 Module 7

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Page 1: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Forming and Shaping

ISAT 430

Module 7

Page 2: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 2Module 7

Forming and Shaping Meanings blend Forming means changing the shape of an existing

solid body. Shaping usually involves molding or casting

The resulting product is usually near net shape.

Page 3: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 3Module 7

Forming and Shaping Processes Rolling -- Flat

Production of flat plate, sheet and foil Long lengths, high speeds Good surface finish Requires

High capital investment Incurs low to moderate labor cost.

Page 4: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 4Module 7

Forming and Shaping Processes2

Rolling – Shaped Production of various structural shapes

Bars I-beams

High speeds Requires

shaped rolls, expensive equipment Low to moderate labor costs Moderate operator skill

Page 5: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 5Module 7

Forming and Shaping Processes3

Forging Production of discrete parts with a set of dies. Some finishing operations usually necessary Usually performed at elevated temperatures Die and equipment costs are high Requires

Moderate to high labor cost Moderate to high operator skill

Similar parts can be made by casting and powder-metallurgy techniques

Page 6: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 6Module 7

Forming and Shaping Processes4

Extrusion Production of long lengths of solid or hollow

products with constant cross section Product is cut into desired lengths Cold extrusion has similarities to forging and is used

to make discrete products. Requires

Moderate to high die and equipment costs Low to moderate labor costs Low to moderate labor skill

Page 7: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 7Module 7

Forming and Shaping Processes5

Drawing Production of long rod and wire with round or

various cross sections. Smaller cross section than extrusion Good surface finish Requires

Low to Moderate die and equipment costs Low to moderate labor costs Low to moderate labor skill

Page 8: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 8Module 7

Forming and Shaping Processes6

Sheet metal forming Production of a wide variety of shapes with thin

walls Simple or complex geometries Requires

Moderate to high die and equipment costs Low to moderate labor costs Low to moderate labor skill

Page 9: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 9Module 7

Forming and Shaping Processes7

Powder Metallurgy Production of simple or complex shapes by

compacting and sintering metal powders Competitive with casting, forging, and machining

processes Requires

Moderate to high die and equipment costs Low labor costs Low labor skill

Page 10: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 10Module 7

Forming and Shaping Processes8

Processing of plastics and composite materials Production of a variety of continuous or discrete

products Extrusion, spinning, molding, casting

Can be competitive with metal parts Requires

Moderate to high die and equipment costs High operator skill in composite fabrication

Page 11: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 11Module 7

Forming and Shaping Processes9

Forming and shaping of ceramics Production of discrete ceramic products by a variety

of ways Shaping, drying , firing processes

Requires Moderate to high die and equipment costs Low to moderate labor costs Moderate to high labor skill

Page 12: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 12Module 7

Rolling Rolling is a process to reduce the thickness of a long

workpiece by compressive forces applied through a set of rolls.

First developed in the late 1500’s

Page 13: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 13Module 7

Sequence of events A steel ingot is cast into a rectangular mold Placed in a furnace while just solidified and held for

many hours (36) until the temperature is uniform. This process is called soaking

Furnaces are called soaking pits. Implies that properties will be uniform throughout

the ingot and process that way. The rolling temperature for steel is about 1200°C From here the ingot goes to the rolling mill.

Page 14: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 14Module 7

Rolling Starting material depends upon what you are

producing. Bloom

Square cross section 6 x 6 in or larger Slab

Rolled from an ingot or a bloom Rectangular cross section 10 x 1.5 in or more

Billet Rolled from a bloom Square cross section 1.5 x 1.5 in or larger.

Page 15: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 15Module 7

Page 16: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 16Module 7

Page 17: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Metal behavior in forming

An aside

Page 18: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 18Module 7

Stress -- strain Elasticity below the elastic

limit Strain hardening above it. In the plastic region, the

metal’s behavior is expressed as:

0

, P

StressA

0

0

, l l

Strainl

Elastic Plastic

Fracture

YieldStress

Ultimate TensileStress

E

nK

Where K = strength coefficient psi (MPa)

n is the strain hardening exponent.

Page 19: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 19Module 7

Flow Stress

As the metal deforms its strength increases (strain hardening)

Thus the stress required to deform must be increased

Flow stress Instantaneous value of

the stress needed to keep the metal “flowing”

fYfY

Y

Shear Rate

Tru

e St

ress

nfY K

Yf = flow stress MPa

Page 20: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 20Module 7

Average Flow Stress

The average flow stress is the average stress needed over entire strain region.

Just integrate the flow stress over the strain region of interest:

fYfY

Y

Shear Rate

Tru

e St

ress

nfY dY K d

1

n

f

KY

n

Page 21: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 21Module 7

Effect of Strain Rate In theory, a metal in hot working should be perfectly

plastic with n = 0. The rate of metal deformation is directly related to

the speed of deformation v.

v

h

v is the velocity of the roll or ram

h is the instantaneous height of the piece being deformed.

Page 22: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 22Module 7

Effect of Strain Rate

Note that if v is constant, the strain rate will increase with decreasing h.

v

h

Page 23: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 23Module 7

Effect of strain rate

0.1 1.0 10.0 100.0

Strain rate (sec-1)

Flo

w S

tres

s (M

Pa

)

Similar

C is strength constant m is the slope, called the

strain rate sensitivity exponent.

The effect of temperature is pronounced.

mfY C

Page 24: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 24Module 7

Effect of temperature on stress

0.1 1.0 10.0 100.0

Strain rate (sec-1)

Flo

w S

tres

s (M

Pa

)room temperature

400°C

800°C

1200°C

Page 25: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 25Module 7

Temperature Cold working (~room temperature)

Advantages accuracy Surface finish Strain hardening increases strength Grain flow can provide directional properties No heating required

Page 26: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 26Module 7

Temperature Cold working (~room temperature)

Disadvantages Higher forces and power needed Part must be dirt and scale free (stress risers) Ductility and strain hardening limit the amount

forming that can be done without part fracture or cracking.

Page 27: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 27Module 7

Temperature Warm Working (0.3Tm – 0.5Tm)

Working above room temperature but below recrystallization temperatures.

Advantages Low forces and power More intricate work geometries possible Need for annealing may by reduced

Tm = melting T.

Page 28: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 28Module 7

Temperature Hot working (0.5Tm – 0.75Tm)

The recrystallization temperature is about one half the melting point. So hot working is above these temperature

Disadvantages Deformation process causes localized heating which can

cause localized melting (bad Ju Ju) Scale formation increases as the temperature increases. Lower dimensional accuracy Poorer surface finish Shorter tool life.

Tm = melting T.

Page 29: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 29Module 7

Temperature Hot working (0.5Tm – 0.75Tm)

Advantages Can produce SIGNIFICANT PLASTIC

DEFORMATION of the metal. Lower forces and power Brittle metals can be hot worked. Strength properties are usually isotropic No work hardening

Tm = melting T.

Page 30: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Back to Flat Rolling

Page 31: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 31Module 7

Flat Rolling A strip of thickness h0

enters the roll gap and leaves at a thickness of hf.

The initial velocity V0 increases to Vf at the exit.

Note that because the surface speed of the roll is constant, there must be relative sliding between the roll and the strip

Page 32: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 32Module 7

Flat Rolling At one point (no slip point),

Vstrip = Vmill.

To the left, the roll moves faster than the strip

To the right the roll moves slower than the strip

Friction is necessary Too much ruins the

surface and costs power Too little and nothing

happens.

Page 33: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 33Module 7

Flat Rolling The draft is (h0 –hf) The maximum draft is a

function of the coefficient of friction and the big roll radius R

20 fh h R

Higher friction and bigger roll, the greater draft.

Compare Large tires and rough

treads on tractors and off road vehicles.

Page 34: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 34Module 7

Flat Rolling The roll force F is shown as

perpendicular to the strip (rather than perpendicular to the point of contact) Because R >>> h

The roll force may be estimated as:

avgF LwY

Page 35: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 35Module 7

Flat Rolling

avgF LwY

L = roll strip contact length 0 fL R h h

w = strip width

Yavg = average true stress on the strip in the roll gap

Page 36: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 36Module 7

Flat Rolling Equation assumes no friction The higher , the further off the

formula (low side). The power per roll can be

estimated by assuming F acts in the middle of the arc of contact

The torque/roll is F x a so in S. I. Units (Newton, meters, seconds) the power per roll is:

avgF LwY

260,000

FLNPower

kW

F is in Newtons

L is in meters

N is rpm

Page 37: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 37Module 7

Flat Rolling Equation assumes no friction The higher , the further off the

formula (low side). The power per roll can be

estimated by assuming F acts in the middle of the arc of contact

The torque/roll is F x a so in English Units (Pounds, feet, seconds) the power per roll is:

avgF LwY

233,000

FLNPower

hp

F is in Pounds force

L is in feet

N is rpm

Page 38: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 38Module 7

Example: An annealed copper strip, 9 in (228 mm) wide, and 1 inch (25 mm) thick is rolled to a thickness of 0.8 in (20 mm) in one pass. The roll radius is 12 in (300 mm), and the rolls rotate at 100 rpm. What is the roll force and power required?

avgF LwY

0 12 1.00 0.80 1.55fL R h h in

From Table 3.4 pg 51 Groover, K = 300 MPa, n = .5

1.00ln 0.223

0.80

.5300 0.223 141.7 20,551nfY K MPa psi

Page 39: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 39Module 7

Example: An annealed copper strip, 9 in (228 mm) wide, and 1 inch (25 mm) thick is rolled to a thickness of 0.8 in (20 mm) in one pass. The roll radius is 12 in (300 mm), and the rolls rotate at 100 rpm. What is the roll force and power required?

avgF LwY

.5300 0.223 141.7 20,551nfY K MPa psi

1.55 9 20,551 286,688F lb

2 2 (286,688)(1.5/12)100680

33,000 33,000FLN

Power hp hp

But, there are two rolls so the power is: 1360Power hp

Page 40: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 40Module 7

Effect of rolling on Structure This is a typical ingot

The outer edges have small grains Faster cooling

Note the large interior grains. Slow cooling Plenty of time to grow.

Page 41: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 41Module 7

Effect of rolling on Structure The normal forces elongate

the grains With enough energy new

smaller grains grow Structure becomes much

more uniform Better strength and

ductility

Page 42: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 42Module 7

Shape Rolling

Flat rolling is just the start. Straight and long structural shapes

Bars Channels I – beams

The material cross section is reduced non-uniformly The sequence and type of rolls is quite complex.

Page 43: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 43Module 7

Shape rolling of an H– section part.

Page 44: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 44Module 7

Ring Rolling Ring is placed between two

rolls, of which one is driven Volume of the ring is

constant to the diameter increases during the process

Ring blanks Cut from a plate Cutting a thick walled

pipe.

Page 45: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 45Module 7

Ring Rolling -- shapes Shapes can be quite

complex. Uses

Large rings for rockets and turbines

Gearwheel rims Ball bearing races Flanges.

Page 46: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 46Module 7

Thread Rolling Straight or tapered threads

put in round rods. Most bolts and screws are

made this way. Production rates of up to

80 pieces per second are possible

Page 47: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 47Module 7

Thread Rolling No loss in material Good strength (cold

working) Surface finish is very good Process induces residual

compressive stresses on surface which improves fatigue life.

Page 48: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 48Module 7

Thread Rolling

Page 49: Forming and Shaping ISAT 430 Module 7 Spring 2001ISAT 430 Dr. Ken Lewis 2 Forming and Shaping Meanings blend Forming means changing the shape of an existing

Spring 2001 ISAT 430 Dr. Ken Lewis 49Module 7

Thread properties Machining cuts through the

grains Rolling compresses them