Repot Lab Asb 1

8/8/2019 Repot Lab Asb 1

http://slidepdf.com/reader/full/repot-lab-asb-1 1/12

Title:

The hardness tests and the Charpy test

Objective:

1. To analysis the hardness number of the material

2. To test the resistance of the material towards an impact load

Apparatus:

I. Vickers Hardness Test instrument, a rod of mild steel and a rod of carbonate steel.

II. Rockwell Hardness Test instrument, a rod of round shaped ASSAB steel with a center

hole and a rod of carbonate steel without a center hole.

III. Brinell Hardness Test instrument, a rod of mild steel and a rod of carbonate steel.

IV. Charpy Test instrument, a rod of mild steel and a rod of carbonate steel.

Introduction:

The Hardness Test is a measurement of the resistance of the material to indentation,

which indicates its strength. The indenter can be either rounded or pointed and is made of

a material much harder than the test piece, for example hardened steel and diamond.

There are 3 methods to test the hardness of the materials:

PART A

Vickers Hardness Test

· Two techniques to test the hardness of a material are Knoop Test (called nup) and

Vickers Test (also known as diamond pyramid). For each test, small diamond with

pyramid geometry is used to indent the material surface.

·The force used is much lighter than the force used in Rockwell and Brinell test.

· The preparation of the specimen must be correct, to insure the measurement of the

indent is exact.

· Knoop and Vickers Hardness Number are fixed which is HK and HV and the

scale of both techniques are almost alike.



· Both techniques refer to the micro hardness methods based on the force and the

measurement of the indent.

· Both are suitable to measure small value hardness of the selected specimen,

especially Knoop, which is used to measure brittle materials such as ceramic.

Brinell Hardness Test

· Brinell test uses the force of a sphere shaped indenter on the specimen surface,

just like the Rockwell Test.

· To test the hardness of a steel (or carbide tungsten), the diameter of the

indentation used is 10.00mm(0.394 in.).

· Harder material requires more force.

·Brinell Hardness Number, HB serves as both function, as the diameter and the

magnitude, which is the final result of an indentation.

· The force for each magnitude produced with the standard force between 500 and

3000 kg where the incensement of 500 kg in the test, follows a specified time

(between 10 and 30 seconds).

Rockwell Hardness Test

· The most routinely used technique to measure the hardness of a material because

of its simplicity and doesnt require specific skills.

· A few scales can be used from few possibility different techniques that are used

widely for many types of steel and alloy, from the soft materials to a more hard

material.

· The Rockwell scale is known as HR, and its followed by a suitable identity.

Example, 80HRB refers to the B scale of the Rockwell Hardness with the value of

80 and 60HR30W refers to the Rockwell Hardness of the value of 60 in the 30W

scale.



The table below shows the values of the steel sphere used :

Steel sphere

center point

(mm)

Load (kgf)

Cast irons and

steel

Copper and

Cu-Al alloys

Aluminum Titanium and

other alloys

P/D2 =30 D/D2 =10 P/D2 =5 P/D2 =1

1 30 10 5 1

2 120 40 20 4

5 750 250 125 25

10 3000 1000 500 100

PART B

Charpy Test

Figure 1



· One of the impact energy tests used to determine the resistance towards load

impulse, which directly changes the plastic shape that is known to be brittle.

· The elasticity state refers to the difficulty of the impact to change the plastic shape

of the materials.

· Brittle fracture leads to a clear, shinny and surfaces results while elastically

fracture results with a typical cleavage texture.

· Charpy test is a test to measure the resistance of the material towards the load

impulse.

· The impacted specimen with small fracture or no even change in the plasti c shape

of the material is known as brittle.

· Fracture of plastic deformation mechanisms involved, is said to be in elasticity.

The elasticity fracture results with the typical cleavage texture while the brittle

fracture leads to a clear, shinny and surfaces.



Method:

PART A

a) Vickers Hardness Test (BS 427:1961)

1) The specimen (carbonate steel) is correctly place on anvil of the Vickers

Hardness instrument.

2) The specimen is being focused and changed it below the indenter exactly.

3) The START button is pressed and the machine will shine with the sound

showed that the machine is readily operated.

4) When the START light goes off, the indenter is assured that it doesnt

touches the specimens surface.

5) Change the indenter with the lens.

6) The width of the corner is measured and noted.

7) Step 1-6 is repeated for the other area of the steel and for the mild steel.

b) Rockwell Hardness Test

1) The specimen is correctly placed on the anvil of the R ockwell Hardness

instrument.

2) The base of the instrument is slowly rotated the LED will started to move

until it reaches SET.

3) The test is automatically started.

4) The reading is taken after TI

5) Step 1-4 is repeated for the other area of the steel



c) Brinell Hardness Test

1) The mild steel was placed correctly on the anvil of the instrument.

2) The base of the instrument is slowly rotated until the specimen touches the

indenter.

3) The right holder of the machine is adjusted until it reaches the 1000kgf

load and wait until 15 minutes.

4) The holder is moved forward again.

5) The base is anti-clockwise rotated.

6) The specimen is removed, and the reading is taken by using the

microscope.

7) Step 1-4 is repeated for carbonate steel.

PART B

Charpy Test

1) The indenter specimen is positioned at the maximum heights and at the

stress-concentrating notch.

2) The pendulum is swing from the initial height to the final heights towards

the piece.

3) The necessary to fracture the test piece is directly calculated from

difference heights.



RESULTS :

PART A :

a) Vickers Hardness Test (BS 427:1961)

CARBON STEEL

Readings D1 (mm) D2 (mm) VHN

1 334.6 342.6 162.0

2 303.3 304.3 201.0

3 267.8 260.0 266.0

4 317.9 317.9 183.0

5 277.2 268.4 249.0

MILD STEEL

Readings D1 (mm) D2 (mm) VHN

1 408.3 414.0 110

2 413.9 419.7 107


ASSAB STEEL

Readings Rockwell Hardness Number

1 57.4

2 57.1

3 57.4

Average 57.3



HIGH QUALITY CARBON

Readings Rockwell Hardness Number

1 27.7

2 28.1

3 27.2

Average 27.7


( load = 1000kgf )

MILD STEEL

Readings Center line for the notch

part d (mm)

Brinnel Hardness Test

number (BHN)

1 3.8 84.9

2 3.9 80.4

3 3.7 89.7

Average 3.8 85.5

CARBON STEEL

Readings Center line for the notch

part d (mm)

Brinnel Hardness Test

number (BHN)

1 2.8 159

2 2.9 148

3 3.0 138

Average 2.9 148.3



PART B :

Charpy Test

Carbon Steel 26 J

Mild Steel 299 J



CALCULATIONS:

a) Vickers Hardness Test





DISCUSSION:

PART A

1) Knowing that the Vickers Hardness test and the Brinell Hardness test were using

both mild steel and carbonate steel while the Rockwell Hardness test used both

ASSAB steel and high quality of carbonate steel.

2) The values of the BHN and VHN are much higher for carbonate steel compared to

the values of mild steel.

3) The value of Rockwell Hardness Number is higher for the ASSAB steel than the

value of the high quality of carbonate steel.

4) However, the value of the center line of the indenter for mild steel are much

higher compared to the carbonate steel in the Vickers and Brinell hardness test.

PART B

1) From the results, based on the shape of the test piece after the pendulum swing was;

a) The mild steel was not fully break that is the end of the specimen is still

connected with each other.

b) The carbonate steel is fully broken.

2) All this happened is because of (a) has higher plasticity properties compared to the

(b) The carbonate steel has high carbon that caused it more ductile.

3) The carbonate steel is much harder and brittle while the mild steel is ductile and

elastic. This caused the carbonate steel cannot absorb the impact energy. Thus, it

made the test piece break into two. While, for the mild steel, which is softer and more

elastic can absorb the energy.

4) The high carbon carbonate steel reduced the ability to absorb the impac t energy.

5) As the assumption, the carbonate steel can change the shape easily when there is

impacted energy put on it. The surface of this steel is shinny and smooth. While the

surface of the mild steel is results with typical cleavage on it.

6) There is 0.2% carbon in the mild steel. The carbonate steel has almost 85% carbon.

The amount of carbon affected the mechanical properties of the materials.



ERRATUM:

PART A

1) The imperfect surfaces of each steel such as rusty surface.

2) Steels surfaces have lots of small indentation that result in only small area left

for new indentation.

3) Position of the specimen not exactly localize as wanted.

CONCLUSION:

PART A

The ASSAB steel is the hardest steel, followed by carbonate steel and lastly the mild

steel.

PART B

From the aspect of strength ness of steels, the mild steel have the most strength

followed by the carbonate steel. Where as, the ASSAB steel is the hardest, followed

by carbonate steel and lastly the mild steel.

REFFENCES

1) Cliffe Technical Metallurgy page 150 154

2) Sergal Material, Their Nature, Fabrication and Properties page 143 145, 71

72

3) Rollesan Metallurgy for Engineers page 15

Documents

Repot Lab Asb 1