performance evaluation in turning of aisi 316 stainless steel using

Proceedings of the National Conference on Innovative Design and Effective Analysis (IDEA) 18 March 2010 Department of Mechanical Engineering, Government College of Engineering, Tirunelveli-627007. Tamil Nadu, India

PERFORMANCE EVALUATION IN TURNING OF AISI 316 STAINLESS STEEL USING CRYOGENIC CARBON DIOXIDE AS CUTTING FLUID Vinoth Kumar.S 1, Dilip Jerold.B.2, Dhananchezian.M 2 , Pradeep Kumar. M 3 1

PG Student, Department of Mechanical Engineering, CEG, Anna University Chennai. Research Scholar, Department of Mechanical Engineering, CEG, Anna University Chennai. 3 Asst.Professor, Department of Mechanical Engineering, CEG, Anna University Chennai. [email protected], [email protected], [email protected], [email protected] ABSTRACT 2

Machining of stainless steel inherently generates high cutting temperature, which not only reduces tool life but also impairs the product quality. Conventional cutting fluids are ineffective in controlling the high cutting temperature and rapid tool wear. Further, they also deteriorate the working environment and lead to general environmental pollution. The present work deals with experimentally investigating the role of cryogenic CO 2 as cutting fluid in turning of AISI 316 stainless steel using PVD - TiAlN coated carbide tool. The results of cutting force, cutting temperature, chip thickness, shear angle and surface roughness in cryogenic conditions have been compared with that of dry and wet machining. Keywords: Turning, Cryogenic cooling, Cutting temperature, Cutting force. liquid nitrogen, has been known since the early 1950’s. Earlier literature contains some examples of the application of CO2 as coolant in machining while the use of liquid nitrogen has been described extensively in more recent literature. Although carbon dioxide, generally speaking, is considered to have an adverse impact with respect to the greenhouse effect, it can be produced as waste material from power plant combustion and thus provide an environmentally neutral product. Purpose of this investigation is to produce up-to-date experimental data concerning the performance of CO2, as cutting fluid in turning operations

1. INTRODUCTION Metal cutting is one of the most common manufacturing processes for producing parts of desirable dimension. It is used to remove unwanted material from a workpiece and to obtain specified geometrical dimension and surface finish. Understanding of the material removal process in metal cutting is important in selecting tool material and design and in assuring consistent dimensional accuracy and surface integrity of the finished product, especially in automated production and precision parts manufacturing. In the present days the industries looking for the higher material removal rate and thereby improving the productivity. But this will increase the cutting temperature and reduce the product quality and tool life. The ways to control high temperatures are the optimum selection of machining parameters, proper cutting fluid application, and using heat resistant cutting tools. The chip tool-interface penetration of cutting fluid can be achieved by the high-pressure jet and could achieve the temperature reduction to some extent. The conventional coolants fail to achieve the temperature reduction at higher cutting speed of hard to cut materials. An increasing concern for the adverse environmental impact of using metalworking fluids pushes modern manufacturing towards dry or minimum quantity lubrication machining. Among potential alternative solutions, the use of cryogenic gases as cutting and grinding fluids, e.g. carbon dioxide or

2. LITRATURE SURVEY De Chiffre et al. (2007) [1] carried out experimental investigations in which the efficiency of cryogenic CO 2 is compared to that of a commercial water based product with respect to tool life, cutting forces, chip disposal and work piece surface finish, and found improvement in the tool life and cryogenic CO 2 proved to be an efficient coolant for threading operation. Dhar et al. (2007) [2] conducted an experiment on cryogenic cooling and stated that the benefits of cryogenic cooling are mainly by substantially reducing the cutting temperature, which improves the chip–tool interaction and maintains sharpness of the cutting edges and also shows better surface finish and higher dimensional accuracy as compared to dry and wet machining. Chattopadhyay et al. (2007) [3] investigated the cryogenic cooling systems and 87

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found that the reduction in average chip–tool interface temperature was up to 34% depending upon the work materials. The most significant contribution of application of liquid nitrogen jets in machining the steels by the carbide inserts reduced the flank wear and remarkable improvement in the tool life was observed. K. Weinert et al. (2004) [4] did a detailed analysis and adaptation of cutting parameters, cutting tools, machine tools and the production environment is mandatory to ensure an efficient process and successfully enable dry machining and observed MQL (Minimum Quantity Lubricant) has led to significant advancements in machining technology. Dhar et al [5] involved experimental investigation of cryogenic cooling on tool wear, surface roughness and dimensional deviation in turning of AISI 4140 steel by two different geometries of carbide inserts. Substantial benefit of cryogenic cooling on tool wear, surface roughness and dimensional deviation was reported. Kalyan kumar and Choudhury [6] studied the effect of cryogenic cooling on tool wear and high frequency dynamic cutting forces generated during high speed machining of stainless steel. It showed that cryogenic cooling was effective in bringing down the cutting temperatures that attributed for the substantial reduction of the flank wear. The objective of the present work is to experimentally investigate the role of cryogenic cooling by CO 2 jet turning of AISI 316 Stainless steel. The effectiveness of cryogenic cooling in the turning of AISI 316 Stainless steel has been compared with dry and wet machining.

piezoelectric three-component dynamometer (Kistler, type 9257B), charge amplifiers and a PC based data acquisition system. Cutting temperature was measured by non contact type infra red pyrometer. Chip thicknesses are measured by using micrometer. The surface roughness on the job was also monitored by a surface roughness tester (Surtronic 3+ Roughness checker). Piezoelectric three component dynamometer (Kistler, type 9257B)

Cryogenic CO2 Nozzle

316 Stainless steel W/P

Fig 1. Work material and Experimental set-up of the study Table 1: Specification of Material, And Tool Used For The Experimental Work

3. EXPERIMENTAL WORK Machining is a very complex process it requires systematic and quantitative study on all the major influencing parameters on machining performance in order to frame the rule base under wide range of work conditions. Fig. 1 shows the AISI 316 stainless steel bar and experimental setup using a NAGMATI175 All geared lathe with maximum power of 2.25 kW and maximum spindle speed of 1500rpm. Series of experiments were conducted by changing the cutting conditions. The cutting conditions used, tool used and their geometries are presented in Table 1. The machining performance was assessed by monitoring the parameters such as cutting temperature, cutting force, chip thickness, shear angle and surface roughness. The cutting force components were measured using

Machine tool Workpiece

NAGMATI-175 Lathe

Composition

0.065 C; 1.498 Mn; 0.349 Si; 0.013 S; 0.025 K; 16.51 Cr; 10.110 Ni; 0.222 Mo; 81 HRB

Hardness Tool material

88

AISI 316 Stainless steel

PVD - TiAlN coated carbide insert (KC5010) Rake angle 5o (-ve) Clearance angle 0o Lead angle 95o Side cutting edge 5o angle End cutting edge 5o angle Nose radius 0.4mm Insert style CNMG Tool holder PCLNR

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3.2 Process Parameters In this present investigation, the selected cutting conditions of the input parameters are as follows. Speed (V) 145 m/min Feed (f) 0.051, 0.096,0.143 mm/rev Depth of cut 1mm Environment Dry, wet, cryogenic The secondary parameters like tool geometry, the tool height, the tool overhang and hardness of the material kept constant during the machining process.

wet and cryogenic machining are shown in Figure 3. It is very clear from the curves that the cutting force in cryogenic cutting is less than that of dry and wet cutting. This is because application of cryogenic fluid reduces the co-efficient of friction at the interface of the tool and chip. The cutting force increase with increasing feed rate. It was observed that cryogenic CO 2 reduces the cutting force 3551% when compared with wet machining and 42-55% when compared to dry machining .

Wet

Cutting force (N)

150

100

0 0.051

0.096

0.143

Feed rate (m m /rev)

Figure.3 Comparison of cutting forces 4.3 Chip Thickness Figure 4 shows the variation in chip thickness of AISI 316 stainless steel with different feed rates for a constant cutting velocity under dry, wet and cryogenic environments. On analysis of the chip thickness, it is observed that as the feed rate increases, the chip thickness considerably increases. It was observed that reduction in chip thickness is about 14-18% on cryogenic machining when compared with wet machining and 14-28 % when compared with wet machining. In cryogenic machining, the chip breakability is good when compared with dry and wet machining. As the cutting temperature gets reduced on application of CO 2 gas it reduces the adhesion between the tool and the chip, resulting in the reduction of the chip thickness.

Cryo

160 140 Temperature (0 C)

Cryo

50

4.1 Cutting Temperature The reduction in cutting temperature of AISI 316 stainless steel under dry, wet and cryogenic cooling is shown in Figure 2. It was observed that cryogenic CO 2 jet reduces the cutting temperature by 7-15% when compared with wet machining and 34-36% when compared to dry machining depending upon the levels of the cutting parameters (feed rate). It was observed that cryogenic CO 2 effect reduces the cutting zone temperature. The result shows that, the cryogenic cooling effect decreases due to increase in the cutting temperature there by changing the chip-tool nature of contact. Dry

Wet

200

4. RESULT AND DISCUSSION The experiments on Turning of AISI 316 Stainless steel using PVD -TiAlN coated carbide inserts under dry, wet and cryogenic environments was carried out .The results obtained are compared for different cutting conditions.

180

Dry

250

120 100 80 60 40 20 0 0.051

0.096

0.143


Figure.2 Variation in cutting temperature 4.2 Cutting Forces The comparison of cutting force for AISI 316 stainless steel with different feed rates for a constant cutting velocity under dry, 89

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0.3

Dry

Wet

after turning process under wet and cryogenic conditions. It is observed that the surface finish is increased to a nominal amount in the finished part, which is turned under cryogenic conditions. It was observed that the surface finish gets better and there is an increase in surface roughness values when the feed is increased. The surface finish gets better by 3851% in cryogenic conditions when compared to wet condition and 45 -56 % better surface finish in cryogenic condition when compared to dry machining .

Cryo

Chip thickness (mm)

0.25 0.2 0.15

0.1 0.05 0 0.051

0.096

0.143


Dry

Surface roughnes Ra (µ m)

4

Figure .4 Comparison of chip thickness 4.4 Shear Angle The comparison of shear angle for AISI 316 stainless steel with different feed rates for a constant cutting velocity under dry and cryogenic machining is shown in Figure 5. On comparing the shear angle under dry, wet and cryogenic machining it is noticed that there is an increase in shear angle in cryogenic machining as there is reduction in the cutting temperature at the cutting zone by the application of cryogenic coolant. The increase in shear angle will reduce the plane of shear thereby reducing the chip thickness. Increase shear angle is 10-13% on cryogenic machining.

Dry

Wet

Shear angle (degree)

3.5 3 2.5 2 1.5 1 0.5

0.051

0.096

0.143

Feed rate (mm/rev)

Figure .6 Comparison of Surface roughnesses 5. CONCLUSION Experiments were carried out in AISI 316 stainless steel under dry, wet and cryogenic conditions. The major conclusions are 1. Cryogenic cooling system provides the benefits mainly by substantially reducing the cutting temperature by 751% when compared with wet machining and 34-36% when compared with wet machining. 2. Cryogenic cooling by CO 2 reduced the cutting force to a maximum of 51% over wet machining and 55% over dry machining. 3. Cryogenic machining with CO 2 jet reduced the chip thickness up to 12% and increased the shear angle by 810% when compared with wet machining. 4. The surface finish gets better by 415% in cryogenic conditions when compared to wet condition.

Cryo

40 35 30 25 20 15 10 5 0 0.096

Cryo

0

45

0.051

Wet

0.143


Figure .5 Comparison of Shear angle 4.5 Surface Roughness Figure 6 shows the comparison of surface roughness of AISI 316 stainless steel with different feed rates for a constant cutting velocity under dry, wet and cryogenic environments .Surface finish is an important index of machinability because their surfaces finish, extent of residual stresses and presence of surface or sub surface micro cracks often affect the performance and service life of the machined part. Surface roughness is measured 90

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6. REFERENCES [1]. L.De Chiffre,J.L. Andreasen, S. Lagerberg, Thesken, (2007) ,”Performance Testing of Cryogenic CO2 as Cutting Fluid in Parting/Grooving and Threading Austenitic Stainless Steel”.Vol.56,pp.101-104. [2]. Dhar N.R, Kamruzzaman.M (2007), “Cutting temperature, tool wear, surface roughness and dimensional deviation in turning AISI-4037 steel under cryogenic condition” International journal of machine tools manufacturer. Vol. 47, pp. 754-759.

[5]. N.R. Dhar, S. Paul and A.B. Chattopadhyay, “Machining of AISI 4140 steel under cryogenic cooling – tool wear, surface roughness and dimensional deviation,” Journal of Materials Processing technology, Vol. 123, pp. 483-489, 2002. [6]. K. V. B. S. Kalyan kumar and S. K. Choudhury, “Investigation of tool wear and cutting force in cryogenic machining using Design of Experiments,” Journal of Materials Processing technology, Vol. 203, pp. 95-101, 2008.

[3]. Chattopadhyay.A.B, Venugopal.K.A , Paul.S(2007), “Growth of tool wear in turning of Ti-6Al-4V alloy under cryogenic cooling” Wear, Vol. 262, pp. 1071–1078. [4]. K. Weinert, I. Inasaki, J. W. Sutherland, T. Wakabayashi, (2004), Dry Machining and Minimum Quantity Lubrication.

7. NOMENCLATURE

91

Symbol

Meaning

Unit

v

Cutting speed

m/min

f

Feed rate

mm/rev

Ra

Surface roughness

µm

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