1.1) ABSTRACT

The hardness test was conducted with three specimens which is low, medium and high

carbon steel to test hardness value of three different materials. It is necessary to know the

hardness value of materials for design and safety factors. Hardness testing is also one of

the most common quality control checks performed. Through this experiment, students

are able to understand the importance of hardness test in engineering, to study the

hardness of different material, and also to understand the principle of Rockwell hardness

testing. The same material that were used for optical microscope experiment are used

here. The specimens were first grinded and cleant using grinding machine. Then, the

diamond indenter was then inserted and the specimen was placed on the anvil to obtain

the hardness value. The rusty part of the specimens should to be tested since it would

affect the hardness value. Other than that, students were also advised not to take the

reading from the same place of the specimens where they took the values earlier. Type

C(steel and metal) was used for Rockwell hardness tester and the load used was 150 kg.

There is no unit for hardness because many many other units such as area,volume and etc.

are involved.From the results obtained, the hardness of the high carbon steel is the

highest followed by the medium carbon steel and low carbon steel. The average hardness

of the high carbon steel is 19.1,medium carbon steel,16.16 and low carbon steel,7.5.

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1.2 OBJECTIVES

The objectives of this laboratory session are that the student must achieve:-

I. Understand the importance of hardness test in engineering,

II. To study the hardness of different material,

III. Understand the principle of Rockwell hardness testing.

1.3) INTRODUCTION

Hardness is a material quality with many definitions and application. In this lab, we

define hardness as resistance to indentation under an applied load, which corresponds

with deformation of the material under a load. Other definitions of hardness include

resistance to scratching, resistance to abrasion, resistance to cutting or drilling, or

energy absorption under impact loads.

Hardness is related to ductility, tensile strength, and many other material properties,

but does not have a define relationship with any of them. As such, the hardness test is

by and large used to computer the hardness values of different material and not in

calculations to determine other properties. Still, there are multiple applications of

hardness tests. Hardness test result can sometimes differentiate between materials, and

material may be graded according to hardness.

Many different hardness test exist; Brinell, Rockwell, Knoop, Monotron, and Shore

sclerescope tests. All of these test use an indenter, whether a ball, cone, or pyramid

made out of a hard substance such as hard steel, diamond, or, more modernly,

tungsten carbide. Each hardness test has its own limitations.

For the purpose of this lab, we will use the Rockwell test method (fig. 1). The

Rockwell test is particularly quick and convenient, leading to its popularity in

production and manufacturing uses. The test makes use fifteen different scales,

according to the hardness range of the material being tested and determined by the

type of indenter and the load applied. It can, as a result, be used to find hardness

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values that fall outside of other test method’s scales, for instance those higher than the

Brinell scale reaches. The Rockwell B and C scales will be used for this experiment.

The Rockwell Bscale is suitable for soft engineering metals, and the Rockwell C scale

is appropriate for hard engineering metals.

1.4) EQUIPMENT/APPARATUS

I. 1) Digital Rockwell type hardness tester 2) Standard specimen

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1.5) PROCEDURE

1) The specimen was grinded and cleant using grinder machine.

2) The Rockwell hardness tester first examined, to ensuring that the operating lever

was in the position closets to the operator and that the correct major load was in

position been applied.

3) The proper indenter was inserted into the testing machine and the test specimen

was placed on the anvil.

4) Next, the elevating screw was turned , the specimen was raised into contact with

the indenter. The specimen was continued to elevate until the initial load was fully

applied, until “tik” sound was produced.

5) The operating lever was released in a smooth motion after the specimen was

checked that it was held firmly in place by the initial load. Then, the handle was

leaved to move without any disturbance until the major load was applied and

waited until the handle and pointer came to rest.

6) The operating load was returned to its original position with a smooth, gentle

motion.

7) Finally the results of the test of the apppropiate dial was recorded.

8) The step 3 to 7 was repeated for a total five tests on each specimen.

1.4 RESULTS

Material Rockwell Hardness Number (HR) Average (HR)

Low-

carbon- steel7.3 8.5 7.3 7.1 7.3 7.5

Medium-

carbon-steel16.8 16.9 16.9 14.9 15.3 16.16

High-

carbon-steel20.1 19.7 18.5 17.6 19.6 19.1

Table 1 : Data for Hardness Test

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CALCULATIONS

LCS MCS

Average HR = Total reading Average HR = Total reading

5 5

= 7.3+8.5+7.3+7.1+7.3 = 16.8+16.9+16.9+14.9+15.3

5 5

=7.5 =16.16

HCS

Average HR = Total reading

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= 20.1+19.7+18.5+17.6+19.6

5

= 19.1

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1.6)DISCUSSION AND QUESTION

1) Summarize, in words, the results of the testing.

From the results obtained, the hardness of the high carbon steel is the highest followed

by the medium carbon steel and low carbon steel. The average hardness of the high

carbon steel is 19.1,medium carbon steel,16.16 and low carbon steel,7.5.

2) Why is it necessary to know the hardness value of the materials?

It is necessary to know the hardness value of materials for design and safety factors.

Hardness testing is also one of the most common quality control checks performed. It

is often used to determine the success or failure of a particular heat treatment

operation or to understand the material’s current condition . Besides, it is also used to

determine whether or not they meet the specifications required. Lastly, it is also used

extensively to characterize materials and to determine if they are suitable for their

intended use.

3) What are the advantages of using hardness test machine?

Firstly, the main advantage is that the value of hardness can be obtained directly from

the machine without involving any calculations. In addition, it is easy to perform, we

can obtain the results in a few seconds besides being inexpensive, any size and shape

or specimen can be tested, and most commonly used is to verify the heat treatment of

a part and to determine if a material has the properties necessary for its intended use.

4) Which hardness test and scales would you use for very thin strips of materials, such

as aluminium foil? Why?

The micro hardness tests such as Knop or Vickers would be suitable because since

thin strips such as aluminium foil is very thin, the indentations on the surface must be very

small The Vickers test is often easier to use than other hardness tests since the required

calculations are independent of the size of the indenter, and the indenter can be used for all

materials irrespective of hardness. The basic principle, as with all common measures of

hardness, is to observe the questioned material's ability to resist plastic deformation from a

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standard source. The Vickers test can be used for all metals and has one of the widest scales

among hardness tests. Knop Hardness test for mechanical hardness used particularly for very

brittle materials or thin sheets, where only a small indentation may be made for testing

purposes.

1.7 CONCLUSION

In conclusion, the aims of the hardness test conducted have been achieved whereby the

students finally understood the importance of hardness test in engineering besides studying

the hardness of different material and understanding the principle of Rockwell hardness

testing. We obtained an opportunity to do hands-on practical work without having the

theoretical knowledge only. We learned the right techniques used to acquire the hardness

value from the Rockwell hardness tester, by not letting the rusty part of the specimens to be

tested which would affect the hardness value. Other than that, we were also advised not to

take the reading from the same place of the specimens where we took the values earlier. After

conducting the experiment, we came to know that the hardness of the high carbon steel is the

highest followed by the medium carbon steel and low carbon steel. The average hardness of

the high carbon steel is 19.1,medium carbon steel,16.16 and low carbon steel,7.5. It is called

low carbon steel if the carbon content is around 0.1% ,low-carbon steels are good choices

because they are easy to handle (draw, bend, punch, swage, etc.) and fairly inexpensive. High

carbon steel has more than 1.0% carbon, and is thus harder and less formable and machinable

than low-carbon steel. Used mainly for cutting EDGEs, compression springs, farming and

gardening equipment, and other high-wear applications. Medium carbon steel contains 0.4%

carbon content. It can be heat treated to have a good balance of ductility and strength. These

steels are typically used in large parts, forgings, and machined components.

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1.8) REFERENCE

1) http://www.instron.us/wa/applications/test_types/hardness/default.aspx

2) http://www.ndt-edu.org/EducationResources/Materials/Mechanical/Hardness.htm

3) http://userwww.sfsu.edu/~ozer/Lab%202-Hardness.pdf

4) http://mee-inc.com/rockhar.html

5) http://www.materials.co.uk/rockwell.htm

6) http://www.substech.com/dokuwiki/doku.php?id=hardness_test_methods

7) http://en.wikipedia.org/wiki/Rockwell_scale

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