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Influence of Process Parameters on the Machining Characteristics of Austensite Stainless Steel (AISI 304)
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 13321–13333
www.materialstoday.com/proceedings
ICMMM - 2017
Influence of Process Parameters on the Machining Characteristics of Austensite Stainless Steel (AISI 304) A.P.Junaidha, G.Yuvaraj b*, Josephine Peterc, V Bhuvaneshwarid, Kanagasabapathie, K. Karthikf a,b*,c,d,e,f
KPR Institute of Engineering and Technology,Coimbatore and 641047, India
Abstract Generally Austensite stainless steel are used as most common stainless steel used in various applications because of easily formable and weldable. But the machining properties of Austensite steel is poor due to inherent properties of low thermal conductivity and high work hardening. In the present work focused on the machining characteristics such as cutting force analysis, surface roughness analysis and chip morphology of Austensite stainless steel investigated with the help of turning operation using uncoated carbide tool, which is processed by four different cutting speeds and three different feeds. Based upon cutting force, chip morphology and the surface roughness, it is finally concluded that the proper selection and control of process variables can significantly improve the machining characteristics of AISI 304 austenitic stainless 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: Austensite steel; machining properties; surface roughness; cutting force; Chip morphology 1. Introduction Stainless steel was generally attributed as being an expensive, high-technology alloy. This made stainless steel more cost-effective and affordable. H. Chandrasekaran et.al. [1] investigated the notch wear through step turning which have four austensite steel with cemented carbide material. A.K. Chakrabarti. et.al [2] investigated the properties of added and unadded austensite steel with acknowledged to the cutting force analysis and chip flow characteristics and their morphology, the composition influences the machinability. D.O’Sullivan.et.al. [3] investigate the properties of austenitic alloys with chromium improved the corrosion resitance properties and by adding nickel increase the hardness. C.J. Novak et.al [4] studied the fabrication of stainless steel through laser engineering net shaping method and prove the high percentage of chromium increasing the strength in cutting tool. K.H. Lo.et.al [5] analysed about the characteristics of hardening and ductility of austensite structure, which it is suitable for machining tool. D. San Martin.et.al [6]studied the austenitic phase transforms into martensite upon deformation. Martensite so produced offers higher strength as well as toughness owing to the presence of retained austenite. M. Hattestrand et.al.[7] investigated the change in properties of stainless steel by additional heat *
Corresponding Author: Tel; +918870207350 Email 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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treatment (hardening and tempering). J. Post.et.al. [8, 9] analysed the approach which improves the ductile strength and fatigue failure in different proportions of carbide with austensite structure. H. Dong et.al. [10] studied the unique properties and advantages give raise to wide range of applications for austenitic stainless steels including Automotive parts, Cookware, Food and beverage equipment, Industrial equipment. Shreemoy Kumar Nayak.et.al.[11] analysed the ISO P30 grade uncoated cemented carbide cutting tool of cutting force, surface roughness characteristics. Groover MP [12] investigated the buildup edge formation on the tool when it made to contact on workpiece at small running speed of 140 rpm. Chromium, molybdenum and other alloying metals added also decrease machinability of austenitic stainless steels. Agrawal et al.[13] reviewed the cast duplex austensite steels which influences the cutting speed, surface roughness characteristics. Korkut et al. [14] investigated the properties of AISI 304 steel having high strength, able to withstand the thermal heat distribution which increases the cutting force and feed rate. Ibrahim Ciftci [15] studied the single point tool machining characteristics of turning operations made by AISI 304 and AISI 316 grade austenitic stainless steel specimens by using TiC/TiCN/TiN and TiCN/TiC. Swapnagandha et al. [16] studied the effect of chip – tool interface by adding titanium with aluminium alloy operated at the speed of 1270 rpm in drilling operation, which results in improvement of surface finish. FernándezAbia et al. [17] studied about the Behaviour of PVD coatings in the turning of austenitic stainless steels (AlTiSiN, AlCrSiN, AlTiN and TiAlCrN) and measured tool wear, cutting forces. Jianxin et al. [18] investigated the fatigue strength and by adding Cr12Mn5Ni4Mo3Al it improves the hardening and corrosion withstand capacity. Hence the present study is focused on understanding the characteristics of austenitic stainless steel under the dry turning operation using the uncoated carbide tools. The machining experiments were carried out under the finishing conditions using four speed variations and three feed variations in external longitudinal turning of AISI 304 austenitic steel bars in terms of cutting forces, surface roughness, tool wear and chip morphology. 2. Experimental plan DOE process can be divided into three main stages such as shown in figure 1 and the experimental setup shown in figure 2. a. Planning stage
b. Conducting stage
Fig 1.Methodology followed to find the effect of process parameters on the machining.
c. Analyzing stage
Fig 2. Experimental set up.
3. EXPERIMENTAL PROCEDURE The procedure used to find the influence of process parameters on machining characteristics of AISI 304 austenitic stainless steel. With the help of machining parameters namely cutting speed, feed rate and depth-of-cut, it is easy to find the cutting force analysis, tool wear analysis and surface roughness of work piece and tool.
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3.1. Cutting Tool: Uncoated tungsten carbide inserts are used for the turning process shown in figure 3. With an ISO designation of SPUN 12 03 08. Specifications of these inserts are given in Table 1.
Fig. 3. Uncoated tungsten carbide inserts used for the turning process
Single insert tool holder used in the experiments manufactured by WIDIA based upon ISO designation CSBPR 25 25 M12 shown in figure 4. Specifications are given in Table 2.
Fig 4. CSBPR 25 25 M12 single insert tool holder used in the machining experiments Table 1. Specifications of cutting tool S.No.
Table 2. Specifications of tool holder
PARAMETER
VALUE
1
Weight
0.0075 kg
1
Weight
0.707 kg
2
Cutting Edge Effective Length (LE)
11.9 mm
2
Head Length
30 mm
3
Insert Thickness (S)
3.175 mm
4
Inscribed Circle Diameter (IC)
12.7 mm
3
Inclination Angle
0 deg
5
Corner Radius (RE)
0.8 mm
4
OrthogonalRake Angle
5 deg
6
Clearance Angle
11 deg
5
Shank Height
25 mm
7
Coating
Uncoated
6
Shank Width
25 mm
8
Insert Included Angle
90 deg
7
Tool Length
150 mm
9
Cutting Edge Count
4
S.No.
PARAMETER
VALUE
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3.2. Manufacturing of workpiece AISI 304 austenitic stainless steel workpiece material has been used. Properties of the material are shown in Table 3. and Table 4. Respectively. Table 3. Properties of AISI 304 Austenitic Stainless Steel S.No.
PROPERTIES
1
Density (g/cc)
2
Tensile Strength (Mpa)
RANGE 8 505
3
Yield Strength (Mpa)
215
4
Hardness, brinell (BHN)
123
5
Young's Modulus (Gpa)
193 - 200
6
Poisson’s ratio
7
Shear Modulus (Gpa)
8
Melting point
9
Specific Heat Capacity (J/g-0C)
1400 – 14550C 0.5
10
Thermal Conductivity (W/m-K)
16.2
0.29 86
Table 4. Typical composition of AISI 304 samples (Wt. %) C
Cr
Silicon
Mn
Ni
P
S
Fe
Maximum 0.08
18-20
Maximum 3
Maximum 2.5
7-9.5
Maximum 0.5
Maximum 0.03
Rest
Cylindrical bars of length 300 mm and diameter 32 mm used as workpiece for the machining experiment. A workpiece sample is shown in figure 5.
Fig 5. Sample work piece used for machining experiment
4. TESTS AND RESULTS 4.1. Cutting Force Analysis In turning operation, Tangential force and axial force plays major role in determining the machinability. Hence, these are discussed in Table 5. These values are obtained by taking average value of an appropriate region of the output data obtained from Labview software. Using these values axial cutting forces (Fx) and tangential cutting forces (Fz) are plotted as a function of cutting speed for different feeds as in figure 6 and figure 7 respectively.
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Table 5. Axial and tangential cutting force values obtained from machining process
Experiment No.
Cutting Speed (m/min)
1
50
2 3
Feed
Depth of Cut (mm)
Axial Cutting Force, Fx (N) 543.18
Tangential Cutting Force, Fz (N) 377.60
(mm/rev) 0.05
0.5
50
0.1
0.5
856.17
562.80
50
0.15
0.5
1220.60
644.91
4
100
0.05
0.5
449.17
264.1
5
100
0.1
0.5
777.51
445.13
6
100
0.15
0.5
1147.3
498.90
7
150
0.05
0.5
331.2
191.99
8
150
0.1
0.5
689.26
354.23
9
150
0.15
0.5
1042.74
421.77
10
200
0.05
0.5
243.82
152.18
11
200
0.1
0.5
641.63
256.77
12
200
0.15
0.5
959.22
392.04
Axial Cutting Force, Fx (N)
1400 1200 1000 800 600 400 200 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 6. Axial cutting forces of TnC tools in dry turning of AISI 304 at different cutting speeds and feeds (test conditions: depth of cut=0.5mm,
Tangential Cutting Force, Fz (N)
machining length=30mm.)
700 600 500 400 300 200 100 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 7. Tangential cutting forces of uncoated tungsten carbide tools in dry turning of AISI 304 at different cutting speeds and feeds (test conditions: depth of cut=0.5mm, machining length=30mm.)
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4.2. Surface Roughness Analysis Surface texture is an important factor to determine the machinability of a material. In post-machining stage, the lower surface roughness (Ra) for a machined surface means the material is having better machinability. Depends upon cutting conditions, surface quality is obtained. 4.2.1. Test Procedure of Surface Roughness: The test procedure to measure surface roughness is explained. By this method, Ra, Rq, Rz and Rmax values are obtained for each case. Ra - The Mean Roughnes Table 6. shows the different ranges in surface roughness values with cutting speed for the machined AISI 304 austenitic steel workpieces. It is clear that cutting speed has the major effect on surface roughness. Observed maximum roughness value is at the cutting speed of 50 m/min. As the speed increases surface roughness reduces to certain value and then it increases. Minimum values of surface roughness values are obtained at the cutting speed 150 m/min and feed rates of 0.05 and 0.1 mm/rev. It can be also noted that surface roughness increases with an increase in feed.
Surface Roughness, Ra (µm)
1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 8. Variation in surface roughness values with cutting speed for the machined AISI 304 workpieces for different feeds (test conditions: depth of cut=0.5mm, machining length=30mm.)
From the figure 8, it is clearly seen that surface roughness increases with increase in feed which is in line with the cutting speed. Also, increase in feed, friction between work piece and tool interface increases. Table 6. Surface roughness (Ra) values of workpieces obtained. Experiment
Cutting Speed
Feed
Depth of Cut
No.
(m/min)
(mm/rev)
(mm)
Surface Roughness,Ra (µm)
1
50
0.05
0.5
2
50
0.1
0.5
1.172 1.3
3
50
0.15
0.5
1.552
4
100
0.05
0.5
1.002
5
100
0.1
0.5
1.14
6
100
0.15
0.5
1.46
7
150
0.05
0.5
0.794
8
150
0.1
0.5
0.827
9
150
0.15
0.5
1.439
10
200
0.05
0.5
0.866
11
200
0.1
0.5
0.99
12
200
0.15
0.5
1.5
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4.3. Tool Wear Analysis Flank wear is most common in machining of hard and difficult to machine materials. So, the present study mainly focuses on flank wear even though crater wear images are also shown in figure 9.
a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 9. Flank wear and crater wear at cutting speed 50 m/min.
Both flank wear and crater wear are noted in the experiment. Figures 9, 10, 11, 12 shows microscopic images of flank wear and crater wear on the cutting tool formed at the cutting speed of 50 m/min, 100m/min, 150 m/min and 200m/min respectively (maximum and minimum flank wear values are shown).
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a) wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e)
Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 10. Flank wear and crater wear at cutting speed 100 m/min.
It is observed from the images rake surface was not affected as the turning operation. But flank surface have notable wear. Figure 11 shows the ranges of maximum flank wear with cutting speeds for different feeds.
A.P.Junaidh et al. / Materials Today: Proceedings 5 (2018) 13321–13333
a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig 11. Flank wear and crater wear at cutting speed 150 m/min.
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a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 12. Flank wear and crater wear at cutting speed 200 m/min.
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4.3. CHIPS ANALYSIS: The results from the chip morphology analysis corroborate the trends observed in other machinability evaluations such as tool wear and surface texture analysis. Morphology of chips obtained at different cutting speeds and feeds are presented in Table 7. Table 7. Morphology of chips obtained at different cutting speeds and feeds
For the cutting speed of 50 m/mim & feed of 0.05mm
For the cutting speed of 50 m/mim & feed of 0.1mm
For the cutting speed of 50 m/mim & feed of 0.15 mm
For the cutting speed of 100 m/mim & feed of 0.05mm
For the cutting speed of 100 m/mim & feed of 0.1mm
For the cutting speed of 100 m/mim & feed of 0.15mm
For the cutting speed of 150 m/mim & feed of 0.05mm
For the cutting speed of 150 m/mim & feed of 0.1mm
For the cutting speed of 150 m/mim & feed of 0.15mm
For the cutting speed of 200 m/mim & feed of 0.05mm
For the cutting speed of 200 m/mim & feed of 0.1mm
For the cutting speed of 150 m/mim & feed of 0.15mm
It can be seen that continuous chips are obtained at all cutting conditions. This is due to the high ductility of the material. Two different kind of chips obtained are coiled and uncoiled. Figure 13 shows a graphical representation of images of chips obtained with cutting speed along X axis and feed along Y axis.
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Fig 13. Graphical representation of chips obtained when machining AISI 304 workpieces at various cutting speeds and feeds (test conditions: depth of cut=0.5mm, machining length=30mm.).
The temperature variation across the thickness of chip is the main reason why it gets coiled. At lower feed of 0.05 mm/rev coiled chips are obtained at all cutting speeds. This is because, at lower feeds, the chip thickness is low and the temperature variation is high. Therefore uncoiled chips are obtained for the feeds of 0.1 mm/rev and 0.15 mm/rev at all cutting speeds. Since coiled chips are more delicate and easier to handle, this suggests using a lower feed value for machining of AISI 304. 5. CONCLUSIONS In the present study, the effect of process parameters like cutting speed and feed on the machining characteristics of AISI 304 austenitic stainless steel is investigated in terms of cutting forces analysis, surface roughness, tool wear analysis and chip morphology. External longitudinal turning under dry cutting condition using uncoated tungsten carbide tool is carried out as the machining process. Four different cutting speeds (50 m/min, 100 m/min, 150 m/min and 200 m/min) and three feed values (0.05 mm/rev, 0.1 mm/rev and 0.15 mm/rev) under constant depth of cut (0.5 mm) are used in the experiment. Cutting forces measured using dynamometer during the machining process and chips are collected. Surface roughness of the machined workpieces measured and chip morphology is analysed. Following conclusions can be drawn If cutting speed increases, cutting forces decreases where as it increases with feed. With increasing cutting speed, surface roughness values decreased. Tool wear found increasing with an increase in speed but it shows decreasing behaviour with an increase in feed. Coiled chips are obtained at lower feed value, which are easier to handle. From this study, it is concluded that the proper selection and control of process variables can significantly improve the turning operation performance of AISI 304 austenitic stainless steel.
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References [1] H. Chandrasekaran, J.O. Johansson, Chip flow and notch wear mechanisms during the machining of high austenitic stainless steels, Swedish Institute for Metals Research (1994). [2] S. Agrawal, A.K. Chakrabarti, A.B. Chattopadhyay, A study of the machining of cast austenitic stainless-steels with carbide tools, Journal of Materials Processing Technology 52 (1995) 610-620. [3] D. O’Sullivan, M. Cotterell, Machinability of austenitic stainless steel SS303, Journal of Materials Processing Technology 124 (2002) 153– 159. [4] C.J. Novak, D. Peckner, I.M. Bernstein, Handbook of Stainless Steels, McGraw-Hill, New York. [5] K.H. Lo, C.H. Shek, J.K.L. Lai, Recent developments in stainless steels, Material Science and Engineering R65 (4–6) (2009) 39–104. [6] D. San Martin, P.E.J. Rivera Diaz del Castillo, E. Peekstok, S. Van der Zwaag, A new etching route for revealing the austenite grain boundaries in an 11.4% Cr precipitation hardening semi-austenitic stainless steel, Material Characteristics 58 (2007) 455–460. [7] M. Hattestrand, J.O. Nilsson, S. Krystyna, P. Liu, M. Andersson, Precipitation hardening in 12%Cr–9%Ni–4%Mo–2%Cu stainless steel, Acta Materilia 52 (2004) 1023–1037. [8] J. Post, H. Nolles, K. Datta, H.J.M. Geijselaers, Experimental determination of the constitutive behaviour of a metastable austenitic stainless steel, Material Science and Engineering A 498 (1–2) (2008) 179–190. [9] S.S.M. Tavares, J.M. Pardal, L. Menezes, C.A.B. Menezes, C. D’Ávila, Failure analysis of PSV springs of 17-4PH stainless steel, Engineering Failure Analysis 16 (5) (2009) 1757–1764. [10] H. Dong, M. Esfandiari, X.Y. Li, On the microstructure and phase identification of plasma nitrided 17-4PH precipitation hardening stainless steel, Surface Coating Technoogy 202 (13) (2008) 2969–2975. [11] Shreemoy Kumar Nayak, Jatin Kumar Patro, Shailesh Dewangan, Soumya Gangopadhyay, Multi-objective optimization of machining parameters during dry turning of aisi 304 austenitic stainless steel using grey relational analysis, Procedia Materials Science 6 ( 2014 ) 701 – 708. [12] Groover MP, Fundamentals of modern manufacturing – materials, process and systems. Prentice-Hall (1996). [13] S. Agrawal, A.K. Chakrabarti, A.B. Chattopadhyay, A study of the machining of cast austenitic stainless-steels with carbide tools, Journal of Materials Processing Technology 52 (1995) 610 -620. [14] Ihsan Korkut a, Mustafa Kasap, Ibrahim Ciftci, Ulvi Seker, Determination of optimum cutting parameters during machining of AISI 304 austenitic stainless steel, Materials and Design 25 (2004) 303–305. [15] Ibrahim Ciftci, Machining of austenitic stainless steels using CVD multi-layer coated cemented carbide tools, Tribology International 39 (2006) 565–569. [16] Swapnagandha, S. Wagha, Atul P. Kulkarni, Vikas G, Sargade, Machinability studies of austenitic stainless steel (AISI 304) using PVD cathodic arc evaporation (CAE) system deposited AlCrN/TiAlN coated carbide inserts, Procedia Engineering 64 (2013) 907–914. [17] A.I. Fernández-Abia, J. Barreiro, J. Fernández-Larrinoa, L.N. López de Lacalle, A.Fernández-Valdivielso, O.M. Pereira, Behaviour of PVD coatings in the turning of austenitic stainless Steels, Procedia Engineering 63 (2013) 133–141. [18] Deng Jianxin, Zhou Jiantou, Zhang Hui, Yan Pei, Wear mechanisms of cemented carbide tools in dry cutting of precipitation hardening semi-austenitic stainless steels, Wear 270 (2011) 520–527.
ScienceDirect Materials Today: Proceedings 5 (2018) 13321–13333
www.materialstoday.com/proceedings
ICMMM - 2017
Influence of Process Parameters on the Machining Characteristics of Austensite Stainless Steel (AISI 304) A.P.Junaidha, G.Yuvaraj b*, Josephine Peterc, V Bhuvaneshwarid, Kanagasabapathie, K. Karthikf a,b*,c,d,e,f
KPR Institute of Engineering and Technology,Coimbatore and 641047, India
Abstract Generally Austensite stainless steel are used as most common stainless steel used in various applications because of easily formable and weldable. But the machining properties of Austensite steel is poor due to inherent properties of low thermal conductivity and high work hardening. In the present work focused on the machining characteristics such as cutting force analysis, surface roughness analysis and chip morphology of Austensite stainless steel investigated with the help of turning operation using uncoated carbide tool, which is processed by four different cutting speeds and three different feeds. Based upon cutting force, chip morphology and the surface roughness, it is finally concluded that the proper selection and control of process variables can significantly improve the machining characteristics of AISI 304 austenitic stainless 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: Austensite steel; machining properties; surface roughness; cutting force; Chip morphology 1. Introduction Stainless steel was generally attributed as being an expensive, high-technology alloy. This made stainless steel more cost-effective and affordable. H. Chandrasekaran et.al. [1] investigated the notch wear through step turning which have four austensite steel with cemented carbide material. A.K. Chakrabarti. et.al [2] investigated the properties of added and unadded austensite steel with acknowledged to the cutting force analysis and chip flow characteristics and their morphology, the composition influences the machinability. D.O’Sullivan.et.al. [3] investigate the properties of austenitic alloys with chromium improved the corrosion resitance properties and by adding nickel increase the hardness. C.J. Novak et.al [4] studied the fabrication of stainless steel through laser engineering net shaping method and prove the high percentage of chromium increasing the strength in cutting tool. K.H. Lo.et.al [5] analysed about the characteristics of hardening and ductility of austensite structure, which it is suitable for machining tool. D. San Martin.et.al [6]studied the austenitic phase transforms into martensite upon deformation. Martensite so produced offers higher strength as well as toughness owing to the presence of retained austenite. M. Hattestrand et.al.[7] investigated the change in properties of stainless steel by additional heat *
Corresponding Author: Tel; +918870207350 Email 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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treatment (hardening and tempering). J. Post.et.al. [8, 9] analysed the approach which improves the ductile strength and fatigue failure in different proportions of carbide with austensite structure. H. Dong et.al. [10] studied the unique properties and advantages give raise to wide range of applications for austenitic stainless steels including Automotive parts, Cookware, Food and beverage equipment, Industrial equipment. Shreemoy Kumar Nayak.et.al.[11] analysed the ISO P30 grade uncoated cemented carbide cutting tool of cutting force, surface roughness characteristics. Groover MP [12] investigated the buildup edge formation on the tool when it made to contact on workpiece at small running speed of 140 rpm. Chromium, molybdenum and other alloying metals added also decrease machinability of austenitic stainless steels. Agrawal et al.[13] reviewed the cast duplex austensite steels which influences the cutting speed, surface roughness characteristics. Korkut et al. [14] investigated the properties of AISI 304 steel having high strength, able to withstand the thermal heat distribution which increases the cutting force and feed rate. Ibrahim Ciftci [15] studied the single point tool machining characteristics of turning operations made by AISI 304 and AISI 316 grade austenitic stainless steel specimens by using TiC/TiCN/TiN and TiCN/TiC. Swapnagandha et al. [16] studied the effect of chip – tool interface by adding titanium with aluminium alloy operated at the speed of 1270 rpm in drilling operation, which results in improvement of surface finish. FernándezAbia et al. [17] studied about the Behaviour of PVD coatings in the turning of austenitic stainless steels (AlTiSiN, AlCrSiN, AlTiN and TiAlCrN) and measured tool wear, cutting forces. Jianxin et al. [18] investigated the fatigue strength and by adding Cr12Mn5Ni4Mo3Al it improves the hardening and corrosion withstand capacity. Hence the present study is focused on understanding the characteristics of austenitic stainless steel under the dry turning operation using the uncoated carbide tools. The machining experiments were carried out under the finishing conditions using four speed variations and three feed variations in external longitudinal turning of AISI 304 austenitic steel bars in terms of cutting forces, surface roughness, tool wear and chip morphology. 2. Experimental plan DOE process can be divided into three main stages such as shown in figure 1 and the experimental setup shown in figure 2. a. Planning stage
b. Conducting stage
Fig 1.Methodology followed to find the effect of process parameters on the machining.
c. Analyzing stage
Fig 2. Experimental set up.
3. EXPERIMENTAL PROCEDURE The procedure used to find the influence of process parameters on machining characteristics of AISI 304 austenitic stainless steel. With the help of machining parameters namely cutting speed, feed rate and depth-of-cut, it is easy to find the cutting force analysis, tool wear analysis and surface roughness of work piece and tool.
A.P.Junaidh et al. / Materials Today: Proceedings 5 (2018) 13321–13333
13323
3.1. Cutting Tool: Uncoated tungsten carbide inserts are used for the turning process shown in figure 3. With an ISO designation of SPUN 12 03 08. Specifications of these inserts are given in Table 1.
Fig. 3. Uncoated tungsten carbide inserts used for the turning process
Single insert tool holder used in the experiments manufactured by WIDIA based upon ISO designation CSBPR 25 25 M12 shown in figure 4. Specifications are given in Table 2.
Fig 4. CSBPR 25 25 M12 single insert tool holder used in the machining experiments Table 1. Specifications of cutting tool S.No.
Table 2. Specifications of tool holder
PARAMETER
VALUE
1
Weight
0.0075 kg
1
Weight
0.707 kg
2
Cutting Edge Effective Length (LE)
11.9 mm
2
Head Length
30 mm
3
Insert Thickness (S)
3.175 mm
4
Inscribed Circle Diameter (IC)
12.7 mm
3
Inclination Angle
0 deg
5
Corner Radius (RE)
0.8 mm
4
OrthogonalRake Angle
5 deg
6
Clearance Angle
11 deg
5
Shank Height
25 mm
7
Coating
Uncoated
6
Shank Width
25 mm
8
Insert Included Angle
90 deg
7
Tool Length
150 mm
9
Cutting Edge Count
4
S.No.
PARAMETER
VALUE
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3.2. Manufacturing of workpiece AISI 304 austenitic stainless steel workpiece material has been used. Properties of the material are shown in Table 3. and Table 4. Respectively. Table 3. Properties of AISI 304 Austenitic Stainless Steel S.No.
PROPERTIES
1
Density (g/cc)
2
Tensile Strength (Mpa)
RANGE 8 505
3
Yield Strength (Mpa)
215
4
Hardness, brinell (BHN)
123
5
Young's Modulus (Gpa)
193 - 200
6
Poisson’s ratio
7
Shear Modulus (Gpa)
8
Melting point
9
Specific Heat Capacity (J/g-0C)
1400 – 14550C 0.5
10
Thermal Conductivity (W/m-K)
16.2
0.29 86
Table 4. Typical composition of AISI 304 samples (Wt. %) C
Cr
Silicon
Mn
Ni
P
S
Fe
Maximum 0.08
18-20
Maximum 3
Maximum 2.5
7-9.5
Maximum 0.5
Maximum 0.03
Rest
Cylindrical bars of length 300 mm and diameter 32 mm used as workpiece for the machining experiment. A workpiece sample is shown in figure 5.
Fig 5. Sample work piece used for machining experiment
4. TESTS AND RESULTS 4.1. Cutting Force Analysis In turning operation, Tangential force and axial force plays major role in determining the machinability. Hence, these are discussed in Table 5. These values are obtained by taking average value of an appropriate region of the output data obtained from Labview software. Using these values axial cutting forces (Fx) and tangential cutting forces (Fz) are plotted as a function of cutting speed for different feeds as in figure 6 and figure 7 respectively.
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Table 5. Axial and tangential cutting force values obtained from machining process
Experiment No.
Cutting Speed (m/min)
1
50
2 3
Feed
Depth of Cut (mm)
Axial Cutting Force, Fx (N) 543.18
Tangential Cutting Force, Fz (N) 377.60
(mm/rev) 0.05
0.5
50
0.1
0.5
856.17
562.80
50
0.15
0.5
1220.60
644.91
4
100
0.05
0.5
449.17
264.1
5
100
0.1
0.5
777.51
445.13
6
100
0.15
0.5
1147.3
498.90
7
150
0.05
0.5
331.2
191.99
8
150
0.1
0.5
689.26
354.23
9
150
0.15
0.5
1042.74
421.77
10
200
0.05
0.5
243.82
152.18
11
200
0.1
0.5
641.63
256.77
12
200
0.15
0.5
959.22
392.04
Axial Cutting Force, Fx (N)
1400 1200 1000 800 600 400 200 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 6. Axial cutting forces of TnC tools in dry turning of AISI 304 at different cutting speeds and feeds (test conditions: depth of cut=0.5mm,
Tangential Cutting Force, Fz (N)
machining length=30mm.)
700 600 500 400 300 200 100 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 7. Tangential cutting forces of uncoated tungsten carbide tools in dry turning of AISI 304 at different cutting speeds and feeds (test conditions: depth of cut=0.5mm, machining length=30mm.)
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4.2. Surface Roughness Analysis Surface texture is an important factor to determine the machinability of a material. In post-machining stage, the lower surface roughness (Ra) for a machined surface means the material is having better machinability. Depends upon cutting conditions, surface quality is obtained. 4.2.1. Test Procedure of Surface Roughness: The test procedure to measure surface roughness is explained. By this method, Ra, Rq, Rz and Rmax values are obtained for each case. Ra - The Mean Roughnes Table 6. shows the different ranges in surface roughness values with cutting speed for the machined AISI 304 austenitic steel workpieces. It is clear that cutting speed has the major effect on surface roughness. Observed maximum roughness value is at the cutting speed of 50 m/min. As the speed increases surface roughness reduces to certain value and then it increases. Minimum values of surface roughness values are obtained at the cutting speed 150 m/min and feed rates of 0.05 and 0.1 mm/rev. It can be also noted that surface roughness increases with an increase in feed.
Surface Roughness, Ra (µm)
1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 50
100
150
200
Cutting Speed, Vc (m/min) Fig 8. Variation in surface roughness values with cutting speed for the machined AISI 304 workpieces for different feeds (test conditions: depth of cut=0.5mm, machining length=30mm.)
From the figure 8, it is clearly seen that surface roughness increases with increase in feed which is in line with the cutting speed. Also, increase in feed, friction between work piece and tool interface increases. Table 6. Surface roughness (Ra) values of workpieces obtained. Experiment
Cutting Speed
Feed
Depth of Cut
No.
(m/min)
(mm/rev)
(mm)
Surface Roughness,Ra (µm)
1
50
0.05
0.5
2
50
0.1
0.5
1.172 1.3
3
50
0.15
0.5
1.552
4
100
0.05
0.5
1.002
5
100
0.1
0.5
1.14
6
100
0.15
0.5
1.46
7
150
0.05
0.5
0.794
8
150
0.1
0.5
0.827
9
150
0.15
0.5
1.439
10
200
0.05
0.5
0.866
11
200
0.1
0.5
0.99
12
200
0.15
0.5
1.5
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4.3. Tool Wear Analysis Flank wear is most common in machining of hard and difficult to machine materials. So, the present study mainly focuses on flank wear even though crater wear images are also shown in figure 9.
a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 9. Flank wear and crater wear at cutting speed 50 m/min.
Both flank wear and crater wear are noted in the experiment. Figures 9, 10, 11, 12 shows microscopic images of flank wear and crater wear on the cutting tool formed at the cutting speed of 50 m/min, 100m/min, 150 m/min and 200m/min respectively (maximum and minimum flank wear values are shown).
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a) wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e)
Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 10. Flank wear and crater wear at cutting speed 100 m/min.
It is observed from the images rake surface was not affected as the turning operation. But flank surface have notable wear. Figure 11 shows the ranges of maximum flank wear with cutting speeds for different feeds.
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a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig 11. Flank wear and crater wear at cutting speed 150 m/min.
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a)
Flank wear at feed = 0.05 mm/rev.
c) Flank wear at feed = 0.1 mm/rev.
e) Flank wear at feed = 0.15 mm/rev.
b) Crater wear at feed = 0.05 mm/rev
d) Crater wear at feed = 0.1 mm/rev
f) Crater wear at feed = 0.15 mm/rev
Fig. 12. Flank wear and crater wear at cutting speed 200 m/min.
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4.3. CHIPS ANALYSIS: The results from the chip morphology analysis corroborate the trends observed in other machinability evaluations such as tool wear and surface texture analysis. Morphology of chips obtained at different cutting speeds and feeds are presented in Table 7. Table 7. Morphology of chips obtained at different cutting speeds and feeds
For the cutting speed of 50 m/mim & feed of 0.05mm
For the cutting speed of 50 m/mim & feed of 0.1mm
For the cutting speed of 50 m/mim & feed of 0.15 mm
For the cutting speed of 100 m/mim & feed of 0.05mm
For the cutting speed of 100 m/mim & feed of 0.1mm
For the cutting speed of 100 m/mim & feed of 0.15mm
For the cutting speed of 150 m/mim & feed of 0.05mm
For the cutting speed of 150 m/mim & feed of 0.1mm
For the cutting speed of 150 m/mim & feed of 0.15mm
For the cutting speed of 200 m/mim & feed of 0.05mm
For the cutting speed of 200 m/mim & feed of 0.1mm
For the cutting speed of 150 m/mim & feed of 0.15mm
It can be seen that continuous chips are obtained at all cutting conditions. This is due to the high ductility of the material. Two different kind of chips obtained are coiled and uncoiled. Figure 13 shows a graphical representation of images of chips obtained with cutting speed along X axis and feed along Y axis.
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Fig 13. Graphical representation of chips obtained when machining AISI 304 workpieces at various cutting speeds and feeds (test conditions: depth of cut=0.5mm, machining length=30mm.).
The temperature variation across the thickness of chip is the main reason why it gets coiled. At lower feed of 0.05 mm/rev coiled chips are obtained at all cutting speeds. This is because, at lower feeds, the chip thickness is low and the temperature variation is high. Therefore uncoiled chips are obtained for the feeds of 0.1 mm/rev and 0.15 mm/rev at all cutting speeds. Since coiled chips are more delicate and easier to handle, this suggests using a lower feed value for machining of AISI 304. 5. CONCLUSIONS In the present study, the effect of process parameters like cutting speed and feed on the machining characteristics of AISI 304 austenitic stainless steel is investigated in terms of cutting forces analysis, surface roughness, tool wear analysis and chip morphology. External longitudinal turning under dry cutting condition using uncoated tungsten carbide tool is carried out as the machining process. Four different cutting speeds (50 m/min, 100 m/min, 150 m/min and 200 m/min) and three feed values (0.05 mm/rev, 0.1 mm/rev and 0.15 mm/rev) under constant depth of cut (0.5 mm) are used in the experiment. Cutting forces measured using dynamometer during the machining process and chips are collected. Surface roughness of the machined workpieces measured and chip morphology is analysed. Following conclusions can be drawn If cutting speed increases, cutting forces decreases where as it increases with feed. With increasing cutting speed, surface roughness values decreased. Tool wear found increasing with an increase in speed but it shows decreasing behaviour with an increase in feed. Coiled chips are obtained at lower feed value, which are easier to handle. From this study, it is concluded that the proper selection and control of process variables can significantly improve the turning operation performance of AISI 304 austenitic stainless steel.
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