Rockwell hardness test lab report conclusion

Lab Report

ABSTRACT
The article describes the correlation between heat treatment process and Jominy test. Steel is an alloy of iron and carbon whose properties are better than either of them. To further improve its properties, heat treatment is applied to steel variants such as steel 1045 and steel 4140. To determine how effective, the process is, an experiment was conducted and the results analyzed. The concept on cooling rate affecting steel’s hardness was tested and the results were positive. Jominy test is used to determine the hardenability of steel exposed to elevated temperatures. The data from all these experiments were analyzed with known mathematical relations and graphs drawn to aid visually represent the data.

INTRODUCTION:
Steel is an alloy of iron and carbon. Steel is a critical material in the development and assembling industry. Steel is an alloy of iron and carbon which are blended in different extents to create a few steel variations, for example, steel 4140 and steel 1045. Every one of these variations of steel has fluctuating properties which are valuable in development of structures and manufactures of auxiliary parts. These properties include: hardness, sturdiness, elasticity, malleability, electrical conductivity and thermal conductivity.

With a specific end goal to figure out which steel variation to utilize, one needs to know the applicable methods for determination of steel properties and methods for enhancing each. Normally utilized technique for enhancing hardness as a part of steel is the heat treatment method. It is a technique that has experienced enormous changes throughout the years because of headway in innovation yet it depends on chemistry ideas on heating and cooling. Steps in heat treatment are: austenitize, cooling, quenching, and tempering. Heat treatment alters both the full scale structure and the small scale structure of steel where the last is influenced by both temperature and weight.

Hardness of steel in various stages in the heat treatment method is resolved utilizing the Jominy test. An austenitized steel bar is quenched at one end then hardness is measured length-wise at consistent interims. The steel's hardness is measured utilizing the Hardness Rockwell A scale and the Brinell hardness number. This strategy goes for deciding hardness in steel under fluctuating cooling rate. The goal of the Experiment was to study the process of heat treatment of steal as well as hardness of the material and examination of micro structure. Concepts of steal treatment and hardness were used in the experiment and data utilized as follows.

THEORETICAL
Data collected during the experiment does not make much sense until it is analyzed using mathematical relations. After analysis, one is able to extract useful information regarding the properties of steel. This is true in the case of steel’s hardness and its tensile strength which are related by following formulae:

Where:

Where:

Where:

Materials
1. Thongs.

2. A furnace.

3. TTT table.

4. Hammer.

5. Letter punch.

6. Water.

7. Steel 4140.

8. Steel 1045.

9. Rockwell hardness tester machine.

10. Brinell hardness tester

PROCEDURE
1. Rockwell A scale was used to obtain hardness measurements for the six samples.

2. The six samples were heated in a furnace at 1600 F for thirty minutes.

3. Four samples were quenched in water, one sample air cooled, and one sample furnace cooled for one hour before quenching.

4. One steel 1045 and one steel 4140 were heated at 1600 F for forty five minutes after determining hardness using Rockwell A scale.

5. The two samples were clamped with one side quenched then hardness was determined length-wise.

6. Three of the six specimens were tempered at 600 F, 800 F, and 1000 F for thirty minutes.

7. The three specimens were quenched in water after tempering and their hardness measured using Rockwell A scale.

8. Brinell hardness number was used on the six samples to obtain their hardness.

RESULTS
Hardness test results:

Specimens

Rockwell

A scale

measurements

RHA Conversion to BHN

Dimple Diameters (mm)

BHN from Dimple Diameters

S instant quench

72

363

2.50

601

H Tempered @540 0C

67

207

3.20

363

D Tempered @ 430 0C

73

388

2.90

444

K Tempered @ 315 0C

73.5

321

2.81

417

M (air cooled)

56

111

4.29

197

E (Furnace cooled)

51

121

4.51

179

Table 1 Comparison between performed Brinell hardness numbers measurements with Brinell hardness numbers obtained by conversion of Rockwell A scale measurements.

Jominy test results for steel 4140 and steel 1045.
Distance from quenched end (in)

4140 Steel hardness (HRA)

1045Steel hardness (HRA)

0.0000

47.5

44.5

0.0625

47.4

58.6

0.1250

58.9

68.9

0.1875

64.4

68.3

0.2500

64.6

57.6

0.3125

66.4

54.2

0.3750

66.7

53.2

0.4375

66.0

53.3

0.5000

65.3

53.2

0.5625

62.0

52.2

0.6250

61.9

53.0

0.6875

60.8

52.5

0.7500

59.8

52.5

0.8125

59.0

52.3

0.8750

59.1

51.6

0.9375

58.4

52.2

1.0000

57.2

51.8

1.1250

57.0

50.9

1.2500

56.3

50.7

1.3750

55.9

50.1

1.5000

49.5

49.7

1.6250

50.6

49.1

1.7500

55.2

50.0

1.8750

54.4

49.4

2.0000

54.0

48.6

2.2500

52.9

47.1

2.5000

46.5

46.2

2.7500

32.1

45.5

3.0000

46.4

41.5

3.5000

43.1

33.6

4.0000

41.9

35.0

DISCUSSION
An experiment was conducted in the lab and the results analyzed with an objective to check the heat treatment effectiveness. The concept on cooling rate affecting steel’s hardness was tested and the results were positive. Jominy test is used to determine the hardenability of steel exposed to elevated temperatures. The data from all these experiments were analyzed with known mathematical relations and graphs drawn to aid visually represent the data.

With a specific end goal to decide the validity of the methodology, steel tests must be subjected to heat treatment hence they were heated to1600 0F utilizing a heater for a time of 60 minutes. Since the temperature almost melting of steel thus the miniaturized scale structure is totally disturbed. At this temperature the particles shaping the miniaturized scale structure are energized and versatile because of extra vitality acquired from warming. This marvel causes a change in the miniaturized scale structure of steel. The specimens were left to cool and quenched.

The heat treatment method from the experiment done was discovered to alter the hardness and tensile strength of steel 4140 and steel 1045. The results of the experiment proved the theoretical concepts of heat treatment. The steel samples cooled swiftly indicated higher hardness than those cooled at lower rate. The goals of the experiment was met with very least experimental errors incurred.

CONCLUSION
In conclusion, heat treatment method was found to alter the hardness and tensile strength of steel 4140 and steel 1045. The experimental results were consistent with concepts learnt about heat treatment. The steel samples that were cooled rapidly exhibited higher hardness than those cooled at a lower rate. However, the higher the hardness the lower the toughness and ductility. During tempering, the material heated at 315 0C falls under martensite microstructure. It is brittle and hard hence useful in carrying heavy loads in structures. The one tempered at 430 0C and 540 0C falls under bainite and pearlite respectively. They are ductile and tough but less hard. They can be used to fabricate structural components that do not experience high tensile stress
References
Rajan, T. V., Sharma, C. P., & Sharma, A. (2011). Heat treatment: principles and techniques. PHI Learning Pvt. Ltd..
Thelning, K. E. (2013). Steel and its heat treatment. Butterworth-Heinemann.
Totten, G. E. (Ed.). (2006). Steel heat treatment: metallurgy and technologies. CRC press.
APPENDIX:
A graph of distance from the quenched end against hardness
A graph of harness against tempering temperature

TTT (Time, Temperature, Transformation) chart.

Iron-cementite metastable diagram