Cold Working a Copper Alloy

STANDARD VS EXPERIMENTAL PLOTS FOR COPPER ALLOY

KYLE HOSSLI, MIKE RANIS, MOHAMMAD ALI

SRJC, ENGR45, SPRING 2014

What is Cold Working?

Cold working, also known as Work hardening, is the process of

strengthening a metal by plastic deformation. Plastic deformation

occurs when a material is altered past its region of elasticity. This

can be done by several methods such as: rolling, drawing, pressing,

spinning and etc. On the microscopic level, the dislocations within

the material are moving.

Importance of Cold Working

Cold Working is important because it allows a user to alter the

mechanical properties of the material into properties that the user

needs. Cold Working does not just affect hardness of material but

also: the yield strength, tensile strength, and ductility. This process is

also very helpful because it does not require any heating, it

decreases the cost of hardening.

Our Semester Project?

For our semester project, we are taking 4 samples of Wrought

Copper alloy (Cartridge Brass), 70 Cu- 30-Zn, and cold working them

to 10%, 20%, 30%, and 40%. We will take all the point from each

hardness and plot them on a hardness vs % Cold work graph. We

will create to plots, one that calculates the %Cold work using area,

and the other using thickness. Finally, we will compare each plot to

a standard plot provided by L.H. Van Vlack, Elements of Materials

Science and Engineering, 4th edition.

The Experiment-Equipment

1. Calipers

2. Rollers

3. Rockwell Hardness Tester

4. Furnace

1.Calipers

2. Rollers

3. Rockwell Hardness Tester

4. Furnace

The Experiment- Procedure

1. First, we took all 4 samples of 70 Cu- 30 Zn and put them in the furnace at 600 °C. The samples were annealed for one hour.

2. The samples were allowed to thoroughly furnace cool for 1 week.

3. Initial hardness measurements were taken for each of the 4

samples

4. We rolled each piece to slowly reach our desired % cold work

5. The desired % cold work was determined by measuring the

thickness of each sample after each time through the roller.

6. Upon reaching the desired % cold work we measured the new

hardness of each sample twice, and took the average as the final

measurement.

Our Samples: Cold work Progression

Our Samples: Cold work Progression

continued

Data Analysis

Data Analysis Continued

The Experiment-Results

Comparison Standard Experimental Results

The experimental hardness curve is shifted up from the standard curves. This suggests our copper

alloy had a higher Zn concentration because this follows the trend of the standard curves.

Potential Sources of Error

Our main sources of error were due to issues with the equipment used

during the experiment.

Rollers & the resulting shapes of the metal… (issues with our area analysis)

The Rockwell Hardness Testers have not been calibrated in years…

Industry standards recommend calibrations once every three months… “ensuring that the scope is reading accurately, the load being applied is consistent and the steel ball has not been worn or deformed.”

Importance of Results

The importance of our results is that many data points are required

to form a very precise representation of the hardness vs % cold work

graph. Also that the equipment used must be calibrated as well as

maintained. Cold working is a very important form of hardening. It is

a tool that has been used since the beginning of mankind. In this

day in age, the amount of precision has become a very important

factor in manufacturing processes. Cold working is a viable method

as well as inexpensive method to aid in the manufacturing process.

Work Cited

http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts

&NM=266

http://metals.about.com/library/bldef-Cold-Working.htm

http://en.wikipedia.org/wiki/Work_hardening

Materials Science and Engineering: An Introduction, 8th Edition,

William Calister

The Team

Mohammad Ali Mike Ranis Kyle Hossli