MSE 201 LAB II: Part aMSE 201 LAB II: Part a

Cold Rolling Copper AlloysCold Rolling Copper Alloys

What is Cold Rolling?What is Cold Rolling?

• Deformation below the “recrystallization Deformation below the “recrystallization temperature”temperature”

COLD ROLLING HOT ROLLING

Lab OverviewLab Overview

• 4 Alloys Rolled Today:4 Alloys Rolled Today:– Pure CopperPure Copper– 5% Zinc5% Zinc– 10% Zinc10% Zinc– 20% Zinc20% Zinc

• This is called “Alpha Brass”This is called “Alpha Brass”– Solid solution of one phase (the alpha Solid solution of one phase (the alpha

phase)phase)

Why Add Zinc?Why Add Zinc?

• Zinc hardens copper by “Solid Solution Zinc hardens copper by “Solid Solution Hardening”.Hardening”.

(click to play)

Cu: Z=29

Zn: Z=30

Rolling Causes DeformationRolling Causes Deformation

• Deformed microstructure has many more Deformed microstructure has many more defects, thus it is harder.defects, thus it is harder.

(click to play)

Goal: Hardness vs. % CWGoal: Hardness vs. % CW

Hardness, DPH vs. %CW

25

75

125

175

0 20 40 60

%CW

Har

dn

ess,

DP

H

20% Zn DPH

10% Zn DPH

5% Zn DPH

Pure Cu DPH

Solid Solution

Hardening

Increased Dislocation

Density with %CW

How to Measure %CW?How to Measure %CW?

• Percent Cold Work (%CW) is thePercent Cold Work (%CW) is the% Change in Cross-sectional Area.% Change in Cross-sectional Area.

% *100f o

o

A ACW

A

• Area of these samples = Width * Area of these samples = Width * Thickness.Thickness.

Making It EasierMaking It Easier

• Assume width doesn’t change.Assume width doesn’t change.* *

% *100*

f o f f o o

o o o

A A w t w tCW

A w t

**100 *100

*o f o f o

o o o

w t t t t

w t t

%Reduction1

100final initialt t

Using a MicrometerUsing a Micrometer

Using a Micrometer Using a Micrometer (cont.)(cont.)Measuring to 0.001”Measuring to 0.001”

Using a Micrometer Using a Micrometer (cont.)(cont.)The Vernier Scale The Vernier Scale (0.0001”)(0.0001”)

Lab ProcedureLab Procedure

1.1. Measure initial thicknessMeasure initial thickness2.2. Calculate target thickness values for each Calculate target thickness values for each

%CW%CW3.3. Measure initial width, hardnessMeasure initial width, hardness4.4. Roll sample to reach the target thicknessRoll sample to reach the target thickness

(Set micrometer to target thickness for “pass-(Set micrometer to target thickness for “pass-thru test” to save time)thru test” to save time)

5.5. Measure “Actual Thickness”Measure “Actual Thickness”6.6. Measure hardnessMeasure hardness7.7. Reset micrometer and go to step 4Reset micrometer and go to step 4

Notes on Hardness Notes on Hardness MeasurementMeasurement• Start with HRF scale (60kgf load)Start with HRF scale (60kgf load)• If reading is >100 HRF, switch to HRB If reading is >100 HRF, switch to HRB

(100kgf)(100kgf)• If indent is visible on the back side of If indent is visible on the back side of

the sample, use superficial scalethe sample, use superficial scale– HR30T for softer samples, orHR30T for softer samples, or– HR45T for harder samplesHR45T for harder samples

• Use “spot anvil” to negate curvatureUse “spot anvil” to negate curvature

Upon Completion of Upon Completion of Rolling…Rolling…• Average hardness (HRF/HRB) and convert to DPHAverage hardness (HRF/HRB) and convert to DPH• Make sure data sheet is completely filled outMake sure data sheet is completely filled out• Write on your copper strip:Write on your copper strip:

– Alloy (Pure, 5%, 10%, 20%)Alloy (Pure, 5%, 10%, 20%)– Class Time (1:25 or 3:25)Class Time (1:25 or 3:25)– Team members’ namesTeam members’ names

• Turn in to TA the following:Turn in to TA the following:– Data sheetData sheet– Copper stripCopper strip– MicrometerMicrometer

NO REPORT DUE THIS TIME, NO REPORT DUE THIS TIME, BUT LAB MEETS NEXT WEEK TO FINISH THE BUT LAB MEETS NEXT WEEK TO FINISH THE

EXPERIMENT!!!EXPERIMENT!!!

NO REPORT DUE THIS TIME, NO REPORT DUE THIS TIME, BUT LAB MEETS NEXT WEEK TO FINISH THE BUT LAB MEETS NEXT WEEK TO FINISH THE

EXPERIMENT!!!EXPERIMENT!!!

Let’s Roll!Let’s Roll!