Annealing (Experiment # 3)

Objective: To study the effect of annealing on the hardness and microstructure of cold-worked brass.

Introduction: Annealing involves the heating of plastically deformed alloys for certain time-temperature combinations that will affect the cold worked properties of these alloys.

Equipment:

 Electric Furnace

 Rockwell Hardness Tester

 Rolling Mill

 Micrometer

 Hacksaw

 Belt Sander

 Polishing and Etching Equipment

 Metallograph

Material: One piece annealed cartridge brass 3/4 " x 4" x 1/8" thick.

Procedure:

    1. Using the rolling mill reduce the thickness of the annealed cartridge brass by 60 %.
    2. Cut the annealed cartridge brass into 10 pieces.
    3. Pre-heat the electric furnace to _____ oF.
    4. Place 9 specimens on a ceramic tray in order that specimen # 2 can be removed first, # 3 next, etc.
    5. Measure the RB or RF (Rockwell B or Rockwell F Scale) of specimen # 1 which is not placed in the oven. This means that specimen # 1 has no annealing. Take three readings and average them.
    6. At the end of one minute, remove specimen #2 and cool rapidly in water.
    7. At the end of two minutes, remove specimen #3 and cool rapidly in water. Remove successively numbered specimens at 3, 4, 6, 8, 15, 30 and 60 minutes and cool them rapidly in water.
    8. Take three hardness readings on upper end of the rolled surface. Average and record the hardness numbers.
    9. Examine the microstucture of specimens # 1 through 10.

Experimental Data: Construct the table shown below and include your experimental results. If you measured the hardness in Rockwell B scale (RB), convert each reading to Rockwell F scale (RF) and include them in the last two columns of the table.

Specimen Number

Time

(Minutes)

Hardness

(RB)

Hardness

(RF)

1

0

   

2

1

   

3

2

   

4

3

   

5

4

   

6

6

   

7

8

   

8

15

   

9

30

   

10

60

   

Table 1

After the construction of the table plot a graph that shows the effect of cold work on the hardness of the material as shown below. Use logarithmic scale for the horizontal axis (Time-axis).

Figure 1

Report:

 Prepare a report with the following format:

 Objective

 Equipment

 Experimental Procedure

 Laboratory Data

 Discussion of Results

 Present your experimental data as shown in Table 1.

 Plot Hardness vs. Annealing Time as shown in Figure 1.

 Label the microstructure photographs of the selected specimens. Discuss the structure differences and their relationship to hardness of the specimen and explain what has happened to the structure after annealing.

 Answer the following questions:

 What is the effect of annealing on the hardness and microstructure of cold worked brass?

 How long a time at the annealing temperature was required for:

(a) recovery

(b) recrystallization

(c) grain growth

(Use the microstructure photographs to answer this question)

 Define recrystallization temperature.

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Last Update: September 21, 1999

By: Serdar Z. Elgun