Influence Of Machining Parameter On Cutting Force And Surface Roughness While Turning Alloy Steel

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ScienceDirect Materials Today: Proceedings 5 (2018) 11794–11801

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ICMMM - 2017

Influence Of Machining Parameter On Cutting Force And Surface Roughness While Turning Alloy Steel Poorna Chandraa,*C R Prakash Raob, Kiran Rc, V. Ravi kumard a-d

Dept. of Mechanical Engineering, Global Academy of Technology, Bengaluru –560098, Karnataka, INDIA. a-d Affiliation to Visvesvaraya Technological University, Belagavi

Abstract Alloy steels are preferred for manufacturing of machine parts owing to their physical and mechanical properties. However, these parts require turning operation to be carried out in order to obtain desired quality product. Components can be machined at minimum lead time, with higher machining parameters such as cutting speed, feed/revolution and depth of cut, which leads to increase in cutting force and surface roughness. Thus, the main objective of present research work is to study the influence of machining parameters on cutting force and surface roughness while machining alloy steels following ISO3685 standards. The experimental results revealed that the surface roughness was low at 350m/min cutting speed and 0.15mm/revolution feed. The cutting forces measured around 35% greater while machining HCHCr alloy steel when compared to EN24 grade alloy steel. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).

Keywords: Alloy steel; coated carbide insert; turning; cutting force;surface roughness;

1. Introduction Materials of grade EN24 is used in the manufacturing of gears, shafts, Tool holders, Boring bars, Gauges etc., and High Carbon High Chromium ( HCHCr ) alloy steel is used in the manufacturing of swaging dies, ball and roller bearings, forming dies, Chipper knives, Punches, shear blades, stamping tools by machine tool industries which requires turning operation. While turning these components, surplus materials are to be removed in the form of chips is the most important aspects which decide the surface roughness and cutting force. The angle made by the plane of the shear with the direction of tool travel is known as shear angle. At smaller shear angle, the chip produced will be thicker, which results in higher cutting forces and vice versa [1-3]. At higher

* Corresponding author. Tel.: 080 2860 3158; fax: 080 2860 3157. E-mail address:[email protected] 2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).

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machining parameters increase of cutting speeds, feeds and depth of cut results in increase of cutting force and surface roughness [4-8]. The machining parameters that influence cutting force and surface roughness of the component are the cutting speed, feed per revolution, radial depth of cut, nomenclature of the cutting tool, work material, machining conditions and cutting tool over hang. During assembly of component the surface roughness is one of the main parameter considered to determine the quality of the product [9-16]. The response surface analysis showed that the cutting forces increase with increase in cutting parameters during turning operation. These parameters have significant effect on every machining operation. During finish turning of the hardened alloy steels using standard geometry radial force component was more significant than tangential force component. Prediction of forces ‘or’ power requirement for a given machining parameters may become detrimental due to the higher tool force generation which leads to deterioration of surface finish. [17-19]. Thus the main objective of present research work is to study the influence of cutting speed, feed per revolution on the cutting force and surface roughness while machining EN24 & HCHCr alloy steels of diameter 100mm and300mm length.

Figure 1: Various Forces on Cutting Tool and shear plane

2. Experimental details 2.1 Materials The work material for the present studies was EN24 & HCHCr alloy steels. EN24 is one of the most commonly used materials for manufacturing of gears, shafts, carrier bodies in machine tools and metal cutting industries due to its excellent machinability and can be through hardened to around 280-330 BHN and tempered in order to obtain desired quality of the product. The chemical composition of the work materials are presented in Table 1 and 2. The specimen diameter of 100mm and length 300mm was used to conduct experimentation. Table 1: Chemical composition of EN24 alloy steel Chemical composition

C

Si

Mn

Cr

Mo

Ni

% wt

0.446

0.188

0.515

1.457

0.259

1.522

Table 2: Chemical composition of HCHCr alloy steel Parameter

C

Si

Mn

Cr

Mo

Ni

%Wt

1.416

0.56

0.8

10.92

0.84

0.22

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2.2 Hardness measurement of work material The Brinell hardness tests were conducted in accordance with the ASTM E10 standard on KB3000H model Krystal Elmec make Brinell Hardness Tester. The hardness of the EN24 & HCHCr alloy steels were measured using 10mm diameter steel ball indenter at standard load of 3000Kgf.The hardness measurement on the specimen is as shown in Figure 2 and corresponding hardness values are tabulated in Table 3.

Figure 2: Hardness measurement on EN24 & HCHCr

Table 3: Hardness of the work material Material Load P Hardness in BHN (kgf) EN24

3000

208.7

HCHCr

3000

281.4

2.3 Machine tool & Cutting tool 2.3.1 Machine tool The machine tool used for the experiments was ACE designers make, JOBBER XL CNC lathe shown in Figure 3. The specifications of the lathe are presented in Table 4.

Figure 3: CNC Lathe used for the experiment

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Table 4: Specifications of lathe used for the experiments Maximum diameter can be turned

270 mm

Maximum length can be turned

400 mm

Range of Spindle speed

50 – 4000 RPM

Clamping system

Hydraulic

Bar can be used

36 mm maximum

Dimension in mm

2200X1750X1750

2.3.2 Cutting tool Turning tool holder of style PCLNL 2525 M12 was the cutting tool used for the experiment. The multilayer coated carbide inserts of grade M15 and M20 and style CNMG120408 inserts were mounted on the tool holder during the experiments. The nomenclature of cutting tool used for the experiment is shown in Table 5. Table 5: Nomenclature of cutting tool used for the experiment Description

3

M15 & M20

Back rake angle

-6º

Side rake angle

-6º

End cutting edge angle

95º

Side cutting edge angle

95º

End clearance angle

5º

Side clearance angle

5º

Results & Discussion 3.1 Hardness test

The Brinell hardness tests were conducted following ASTM E10 standard and average of five to eight locations from core to case was considered to determine hardness of the work material. From the experiment, it is also observed that hardness of High carbon high chromium steel was found higher when compared to EN24 alloy steel, and shown in Figure 4.

Figure 4: Comparison of Hardness test results of EN24 & HCHCr alloy steels

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3.2 Measurement of Cutting force The experiments were carried out on Jobber XL CNC Lathe following ISO3685 standards. Multi layer coated Tungsten carbide inserts of two different grades, M15 & M20 and CNMG120408 style inserts were mounted on PCLNL 2525 M12 turning tool holder during experiment. The cutting speed of 150m/min to 350m/min in steps of 50m/min, and feed of 0.15mm/rev, 0.25mm/rev and 0.35mm/rev, and constant radial depth of 1.5mm was selected for the experimentation. The cutting force measured using Kistler make, model 9265B dynamometer. The results of the experiments are presented in Table 6 and analyses of the results are presented in Figure 5. Table 6: Influence of machining parameters on Cutting force Work material

Cutting force in N M15 Cutting speed in m/min

EN24

HCHCr

0.15mm/ rev

M20

0.25 mm/rev

0.35 mm/rev

0.15 mm/rev

0.25 mm/rev

0.35 mm/rev

150

950

1126

1415

956

1138

1446

200

912

1080

1364

922

1094

1412

250

883

1047

1323

905

1077

1351

300

836

994

1249

854

1023

1278

350

778

921

1162

794

950

1094

150

1294

1523

1906

1322

1561

1953

200

1236

1469

1839

1265

1505

1885

250

1189

1416

1766

1224

1460

1824

300

1128

1339

1660

1169

1386

1719

350

1044

1246

1542

1086

1296

1603

3.3 Measurement of Surface Roughness Table7: Influence of machining parameters on Surface Roughness Work material

Surface Roughness, Ra in microns M15 Cutting speed in m/min

EN24

HCHCr

0.15mm/ rev

M20

0.25 mm/rev

0.35 mm/rev

0.15 mm/rev

0.25 mm/rev

0.35 mm/rev

150

1.56

3.6

4.98

1.44

3.42

4.80

200

1.46

3.34

4.63

1.37

3.22

4.49

250

1.31

3.12

4.33

1.27

3.04

4.23

300

1.23

2.84

3.99

1.15

2.91

4.09

350

1.03

2.57

3.76

0.94

2.65

3.88

150

1.28

3.03

4.18

1.24

2.96

4.15

200

1.22

2.92

3.98

1.18

2.84

3.98

250

1.15

2.72

3.75

1.09

2.63

3.70

300

0.93

2.36

3.31

0.93

2.31

3.26

350

0.78

2.01

2.82

0.82

2.09

2.97

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The Surface Roughness measurement as a result of varied cutting speed, feed per revolution and the cutting tool is presented in Table 7 and shown in Figure 6. The apparatus used for the measurement of surface roughness was SJ201P portable surface roughness tester. As per the recommendation of international standard there are three parameters for any machined surface that has to be specified. That is Centre line average - Ra, Ten point average height – Rz, Height difference between highest crest and lowest valley – Rmax, which is expressed in microns. However in the present research paper the centre line average - Ra is considered to assess the quality of the surface roughness. 4

Analysis of Results and Discussion 4.1 Analysis of Cutting force Cutting force measured while machining EN24 material using M15 grade insert

Cutting force measured while machining HCHCr material using M15 grade insert

Cutting force measured while machining EN24 material using M20 grade insert

Cutting force measured while machining HCHCr material using M20 grade insert

Figure 5(A - D): Analysis of machining parameters on Cutting force

Figure 5 (A-D) analyses, it can be inferred that as cutting speed increases the Cutting force decreases. Increase of feed rate results in increase of cutting force. Marginal Increase of cutting force observed while machining HCHCr alloy steel when compared to EN24 alloy steel. The reason for higher cutting force might be the presence of high alloying elements in HCHCr steel and Higher hardness of the material. 4.2 Analysis of Surface roughness Figure 6 (A-D) analyses, it can be inferred that surface roughness increases as feed per revolution increases. It can be inferred that as cutting speed increases the surface roughness decreases. The surface roughness on HCHCr alloy steel found better than EN24 alloy steel material irrespective of machining parameter. The reason for lower surface roughness on HCHCr alloy steel machined parts might be the presence of high alloying elements in HCHCr steel and Higher hardness of the material.

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Surface Roughness measured on EN24 material, machined using M15 grade insert

Surface Roughness measured on HCHCr material, machined using M15 grade insert

Surface Roughness measured on EN24 material, machined using M20 grade insert

Surface Roughness measured on HCHCr material, machined using M20 grade insert

Figure 6(A - D): Analysis of machining parameters on Surface Roughness

5

Conclusion 1. 2. 3. 4. 5. 6. 7. 8.

Hardness of the HCHCr material found higher when compared to EN24 alloy steel. Increase of cutting speed leads to the decrease of surface roughness. Increase of feed rate results in increase of surface roughness. The surface roughness on HCHCr alloy steel found better than EN24 alloy steel material irrespective of machining parameter. As the cutting speed increases the cutting force decreases. Increase of feed rate results in increase of cutting force. The cutting force measured while machining HCHCr grade alloy steel found higher when compared to EN24. The reason for higher cutting force while machining HCHCr grade alloy steel might be the presence of high alloying elements in HCHCr alloy steel and Higher hardness of the material.

Acknowledgements The author acknowledges the management of Global Academy of Technology for their constant encouragement and support. Further the author is grateful to MrP. Chandan Chavan and Mr B.L.Girija Shankar for the financial assistance for the project.

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