Evaluation of Mechanical Properties of Medium Carbon Low Alloy Steels

Chandan BR1, Ramesha CM2*

1Professor & Head, Department of Mechanical Engineering, G Madegowda Institute of Technology, Bharathinagara, Mandya Dist, chandanbrmech@gmail.com, 8904489596

2Associate professor, Department of Mechanical Engineering, M.S.R.I.T, Bangalore.

*Corresponding author: Ramesha CM, Associate professor, Department of Mechanical Engineering, M.S.R.I.T, Bangalore. E-mail: cmramesha@gmail.com

Citation: Chandan BR, Ramesha CM (2020) Evaluation of Mechanical Properties of Medium Carbon Low Alloy Steels. Int J Mater Res Sci Tech 1(1): 21-24.

https://dx.doi.org/10.47890/IJMRST/2020/CMRamesha/14205433

Received Date:May 21, 2020; Accepted Date: June 19, 2020; Published Date: July 10, 2020

Abstract

Medium carbon low alloy steel is being used in the forged condition in the automobile, aerospace and transport industry. Reliability of critical components made of EN Series is directly based on the fatigue strength of this steel, which in turn is dependent on forging process. A review of literature shows that substantial information is available relating to structure and mechanical properties of medium carbon low alloys forged steels. Some information is available regarding the evaluation of mechanical properties of steels. In the light of the above, the present investigation was taken up to study the effect of variables on the chemical composition of EN Steels. Mechanical properties such as UTS, percentage of elongation, Percentage of reduction (%RA) and hardness,of the alloy was assessed. The aim of the study is to evaluate the possibility of replacement of this steel with lower Ni content.

Keywords: EN series; elongation; Hardness; Medium carbon steel; reduction; Ultimate Tensile strength (UTS);

Introduction

Medium-carbon steels are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65% [1]. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium carbon steels to be used in the quenched and tempered condition. The uses of medium carbon steels include shafts, axles, gears, crankshafts, couplings and forgings. Steels in the 0.40 to 0.60% C range are also used for rails, railway wheels and rail axles.EN18 (AISI 4140) EN19 (AISI 4142) EN24 (AISI 4340) are medium carbon low alloy steels under High strength Low alloy [HSLA] categories. EN 19 is nickel free steel and EN 24(low nickel) steels. The mechanical strength of medium carbon low alloy steels can be improved by forging and heat treatment. The primary source of information for heat treatment of steels is ASM Metals Handbook Vol-4 [2]. Various other textbooks and standards are available for determining the temperatures of homogenization, quench media, tempering temperatures and procedures thereof.

Materials and Methods

Chemical composition Test

The chemical composition test of medium carbon low alloy steel samples for this investigation is given in (Table 1).

Table 1: Chemical Compositions of selected Steels

Steel

Element

Wt %

C

Mn

P

S

Si

Ni

Cr

Mo

EN18

Min

0.35

0.65

0.040

0.040

0.10

--

0.85

--

Max

0.45

0.95

0.040

0.040

0.35

--

1.15

--

EN19

Max

0.43

1.10

0.035

0.040

0.30

--

1.10

0.25

Max

0.43

1.10

0.035

0.040

0.30

--

1.10

0.25

EN24

Min

0.37

0.60

0

0

0.15

1.65

0.70

0.20

Max

0.43

8.80

0.035

0.040

0.30

2.00

0.90

0.30

EN25

Min

0.27

0.45

0

0

0.10

2.30

0.50

0.45

Max

0.35

0.70

0.04

0.04

0.40

2.80

0.80

0.65

Heat Treatment

Heat treatment of steels is based on three diagrams (i) the Iron Carbon Diagram for the specific composition, (ii) The Time-Temperature-Transformation (TTT) diagram and (iii) the Continuous Cooling Transformation (CCT) Diagram. These are well explained in ASM Metals Handbook and various other handbooks [3].

The prepared tensile test samples and other samples were heated to different tempering temperatures and soaked for 45 minutes using muffle furnace. Taken Test samples were quickly taken out of the furnace after each of the heat treatment temperatures. Surface morphologies of the heat-treated samples the hardness and tensile test were carried out

Mechanical Test

Tensile Testing

The tensile strengths of the steels under various heat-treated conditions were determined using a Hounsfield Tensometer (shown in Figure 2.1), according to ASTM E8 standard.

Figure 2.1: Tensile Test Specimen as per ASTM E8 Standard

Hardness Test

Vickers pyramid method was used for the determination of the hardness of the heat-treated samples. Each of the test specimens was flatten after heating and then mounted on the anvil. The specimens were brought in contact with the pyramid indenter and allowed to rest for a dwell time. The hardness of the specimen is indicated by the penetration of the indenter on the test specimen and average values are recorded after repeating the test for each of the test specimens.

Results and Discussion

Mechanical tests were carried out as a part of quality confirmation of forging and heat treatment process as per customer specifications. Tension, hardness was carried out for each batch of components.

The measured values of ultimate strength, yield strength, % elongation and % reduction in area, and BHN for selected steel tempered at different temperatures are tabulated in Table 2 to 4.

Table 2: Mechanical Properties of EN19 steel for various Tempering Temperatures

Sl. NO

Temp

YS

UTS

% EL

%RA

BHN

1

670

679

849

29.4

68

232

2

650

647

824

19.6

58.6

232

3

640

590

913

28.8

59

258

4

620

596

736

26.80

62

258

Table 3: Mechanical Properties of EN24 steel

Sl. NO

Temp

YS

UTS

% EL

%RA

BHN

1

600

755

925

16

60

290

2

600

960

1140

24

56

330

3

640

796

990

28

58

309

4

670

818

964

29

60

298

Table 4: Mechanical Properties of EN25 steel forVarious Tem-pering Temperatures

Sl. NO

Temp

YS

UTS

% EL

%RA

BHN

1

620

945

1099

19.8

60.15

318

2

600

803

1003

14

56.4

316

3

600

878

1088

26

59

333

4

620

893

1084

19.6

61.5

320

  1. Ultimate strength and yield strength of the EN19 steel decrease with increase in tempering temperature.
  2. % Elongation and % reduction in area increase with increasing tempering temperature.
  3. Hardness decreases with increasing tempering temperature.
  4. The following observations can be made from the Figure 3.1 to 3.6.

    Figure 3.1: Variation in UTS & YS with Tempering Temperature for EN19

    % Elongation and % reduction in area increase with increasing tempering temperature.

    Figure 3.2: Variation in %EL and %RA with Tempering Temperature for EN19

    Hardness decreases with increasing tempering temperature

    Figure 3.3: Variation in BHN with Tempering Temperature for EN19

    Ultimate tensile strength and yield strength of the EN24 steel decrease with increase in tempering temperature.

    Figure 3.4: Variation in UTS & YS with Tempering Temperature for EN24

    % Elongation and % reduction in area increase with increasing tempering temperature.

    Figure 3.5: Variation in UTS and YS with Tempering Temperature for EN24

    Hardness decreases with increasing tempering temperature

    Figure 3.6: Variation in %El and %RA with Tempering Temperature for EN24

  5. Ultimate tensile strength and yield strength of the EN24 steel decrease with increase in tempering temperature.
  6. % Elongation and % reduction in area increase with increasing tempering temperature.
  7. Hardness decreases with increasing tempering temperature

The behavior of EN24 almost duplicates that of EN19.

Since the industrial test values are compared with the values specified by customers and not with standard values, no correlation is attempted for the mechanical properties of EN25 steel.

Conclusions

From the different heat treatment results we can conclude EN 24 steel have good mechanical properties than EN 19 steel, so we can recommend EN 24 steel for some critical and semi critical applications. Mechanical test revealed that EN19 and EN24 can be used in place of EN25 for some critical and sub critical applications.

Acknowledgement

The authors express heartfelt thanks to Management of Gokula Education Foundation (GEF) and Department of Mechanical Engineering, MSRIT Bangalore-560054 to provide all facility to carry out this research work.

References

  1. Philip TV, Thomas J and Cafffery. “Properties and selection - Iron, Steels and high-Performance Alloys”, ASM Hand Book Vol-1, ASM International. 1961:1119 – 1127.
  2. Homer Research Labs. Bethlehem Steel Co.reprinted in “Source Book on Industrial Alloy and Engineering Data”, ASM, Metals Park. 1978;125.
  3. Sharma Ramesh C.  Principles of Heat treatment of steels, New age International. 2008.
  4. Callister WD. Materials Science and Engineering, 8th Ed., John Wiley & Sons. 2007.
  5. The Mechanical and Physical Properties of British Standard En Steels”, Woolman J. and Mottram R.A. (comp.), British iron and Steel Research Association”, Pergramon Press. 1964.
  6. Ranjan TV, Sharma CPand Sharma A. Heat Treatment Principles andTechniques, McGraw Hill. 2002;175-181.
  7. Brooks CR. Heat treatment of Ferrous Alloys, McGraw-Hill, ISBN-10: 0070080763. 1979.
  8. Funatani K. Heat Treatment of Automotive Components: Current Status and Future Trends, Trans. Ind. Inst. Metals. 2004;57:381-396.
  9. Park M. Failure analysis of an accessory bevel gear installed on a J69 turbojet engine, Engineering Failure Analysis, 2003;10:371-382.
  10. Shamasundar S. Computer simulation-based design and optimization of die forging operations, forging. 2006;65.
  11. Shamasundar S.Prediction of defects and analysis of grain flow in crank shaft forging by process modeling”, National Forging Seminar, ProSIM. 2004;1-12.
  12. Homer Research Labs. Bethlehem Steel Co. reprinted in “Source Book on Industrial Alloy and Engineering Data, ASM, Metals Park. 1978;125.
  13. www.engineer.tamuk.edu/…./iecn/…./me3344_call-Ch11_short.pdf.
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