Hardness Of Cold Rolling Copper Biology Essay

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Rockwell hardness test is used, for determining the hardness of a material using a steel ball or diamond point depending on the letter prefix of the material. These experiments involve pressing a hard indenter into a specimen whose hardness is to be measured by the depth of the indenter. In the investigation reported here a letter prefix of B scale with a 1.6mm diameter hardened steel ball is been used to carry out the experiment due to the softness of the specimen.

Observing the hardness of a cold rolling copper of deferent percentage of reduction can be explained using the concept which proves that the higher the cold rolling percentage reduction of a copper, the higher the hardness of the Rockwell.

In the second experiment which involved annealing copper, a different concept was obtained as the result obtained showed that the higher the annealing temperature of a copper the lower the Rockwell hardness.

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The experiment offers strong evidence that a cold rolling copper gets harder with increment to the percentage reduction while annealing copper tends to get softer with increment to the annealing temperature.

Introduction

The Rockwell hardness test is a standardized method of testing the hardness of a material. This method was first introduced in the year 1 1908 by Paul ladwik, and was later co-invented on the 15th of July 1914 by Hugh M. Rockwell (1890-1957) and Stanley P. Rockwell (1886-1940) . The first Rockwell hardness machine was invented for the purpose of testing the effect of a heat treatment which may affect steel bearing races.

Today, it is used in many industries and companies to determine the durability, strength of the grain boundaries and hardness of a material to establish whether the material actually suits or meet the requirement or purpose.

The main purpose for the experiment is to show the hardness of a copper in relation to the change in percentage reduction of a copper as well as the change in the annealing temperature of a copper.

The report focuses particularly on the methodology of how the hardness of a material can be determined before the material can be made fully viable.

Materials

1. 1.6mm diameter hardened steel ball

2. 6 annealed copper slabs of different temperature (100,150,200,250,400 and 500)0C

3. 9 cold rolled copper slabs of different percentage reduction (0, 10,20,30,40,50,60,70 and 80) %

4. Rockwell hardness test machine

Methods

For a 0% rolling reduction of a copper slab which may have a thickness of 2mm, the following experimental procedure are being listed below

1. At first the correct scale of the indenter that suit the hardness of the specimen. For a copper the best indenter or penetrator that can be used is a 1.6mm diameter of hardened steel.

2. The crank was ensured that it is in the horizontal position facing user.

3. The specimen was the placed on the anvil.

CAUTION: we avoid using any part of the copper which has a pointed hole so as to get accurate reading.

4. After placing the specimen on the anvil, the wheel spokes was turned to clockwise direction, in these process the anvil and the sample are been pushed upward to the indenter or penetrator. After contact is gradually made, the next process was to turn the wheel spokes until the metre gives a reading from 100 to 130.

5. The pass light in the machine was allowed to signal before proceeding to the nest stage.

6. After getting the pass light signal on the Rockwell machine, the crank is being turn to its clockwise direction on 1800 and back to his original 0 at the horizontal axis to force the indenter into the material.

Fig1.12

7. The reading been displayed in the machine which shows the hardness of the material is then recorded

8. Finally the specimen was removed by turning the wheel spoke to an anti clockwise direction which helps to lower the anvil. These same process is been used to carry out the other experiments which involve cold rolled copper and annealing copper.

Fig 1.23 Rockwell hardness tester fig1.34 specimen before fig1.45 specimen after

Hardness test hardness test

Fig1.55 A picture showing the basic component of a Rockwell hardness test

Problem analysis

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Problems encountered during the course of the experiment involved getting the accurate Rockwell hardness readings. This was actually due to a difference in the grain structure of each part of the specimen.

Problem solution

In order to get the accurate reading, the experiment had to be done three times, after which the average was taken, thereby enhancing the chances of getting an accurate result.

Results

Table 1. Variation of hardness with % rolling reduction for copper

%ROLLING REDUCTION ROCKWELL B HARDNESS

0.00 (117.3 + 120.1 + 120.4)/3 = 119.2

10.00 (123.5 + 125.3 + 127.8)/3 = 125.5

20.00 (128.6 + 125.4 + 126.9)/3 = 126.6

30.00 (128.5 + 120.1 + 128.9)/3=128.8

40.00 (128.8 + 127.6 + 128.3)/3=128.2

50.00 (129.9 + 128.3 + 127.8)/3=129.7

60.00 (128.2 + 130.3 + 129.7)/3=129.4

70.00 (130.7 + 130.3 + 129.5)/3=130.0

80.00 (129.7 + 129.2 + 129.3)/3=129.4

NOTE: Experiment was carried out three times and the average of the three readings was taken. The reason for using the average is because we tend to have more accurate result with the average than with one reading.

Chart 1: Variation of hardness with % rolling reduction for copper

Table 2. Variation hardness with annealing temperature for copper

ANNEALING TEMPERATURE(0C) ROCKWELL B HARDNESS

100 (130.9 + 130.8 + 131.4)/3 = 131.0

150 (130.3 + 128.5 + 127.6)/3 = 128.8

200 (129.4 + 128.5 + 129.5)/3 = 129.1

250 (128.5 + 129.0 + 128.1)/3 = 128.5

400 (121.4 + 122.7 + 123.2)/3 = 122.4

500 (121.8 + 120.6 + 119.1)/3 = 120.8

NOTE: Experiment was carried out three times and the average of the three readings was taken. The reason for using the average is because we tend to have more accurate result with the average than with one reading.

Chart 2. Variation hardness with annealing temperature for copper.

Discussion of results

After carrying out our result on the test, it was fully proved that the higher the rolling reduction percentage of a copper, the harder it becomes, reason for our conclusion.

In table 1 showed above, a copper which had a rolling reduction of 0.00% was tested in a Rockwell machine. After taking the average of 3 reading it was observed that the Rockwell hardness were 119.2 as show in table 1, the same experiment was carried out on 8 other coppers which had a rolling reduction of 10% to 80% with an increment of 10% as showed in table 1.

When plotting Rockwell B hardness against percentage rolling reduction in graph 1, it was observed that at 0.00% rolling reduction the Rockwell hardness was 119.2(low) and at 10% rolling reduction the Rockwell hardness was 125.5(higher than 0.00% etc).

In table 2, it was observed that the result obtain is showing the opposite proved of table 1, in theses case, it was proved that higher the annealing temperature (0C) of a copper the lower the Rockwell B hardness, reason for our conclusion.

In table 2 as showed above, a copper which had an annealing temperature of 100 (0C) was tested, after taking the average of 3 readings it was observed that Rockwell hardness was 131.0 as written tables 2. The same procedure was used to carry out experiment on 5 other coppers which had an annealing temperature of (150,200,250,400 and 500)0C as listed in table 2.

In plotting Rockwell B hardness against annealing temperature (0C) as showed in graph 2, it was observed that at 100(0C) annealing temperature the Rockwell hardness was 131.0(high) and also at 150(0C) annealing temperature the Rockwell hardness was 128.8 [lower than 100(0C) etc].

Conclusion

In conclusion, this report has discussed how Rockwell hardness can be carried out using a copper of different annealing temperature (0c) and different rolling reduction percentage. By keeping estimated reading of the experiment, the report was able to prove that the higher the rolling reduction percentage of a material the harder the material becomes and also the higher the annealing temperature (0C) of a material the less hard the material becomes.

However, I am very happy to say that my group was able to manage and achieve all the aims and objectives of the experiment, the main purpose of these experiment is that we have broadened our knowledge about green technologies and mechanical principles that can be used to determine the hardness of a material. The Skills that we developed working in this experiment will definitely help us in future experiment and studies.