Machining of Austenitic Stainless Steel Under Various Cooling-Lubrication Strategies Smita Padhan, Ajay Kumar Behera, and Sudhansu Ranjan Das Abstract


Fig. 2 Machinability study under various turning environments at v= 111 m/min, f = 0.24 mm/rev,d= 0.4 mm a



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Fig. 2 Machinability study under various turning environments at v
= 111 m/min, f = 0.24 mm/rev,
d
= 0.4 mm a Crater wear, b Flank wear, c & d Cutting temperature, e Surface finish

S. Padhan et al.
between chip and tool is reduced. Figure
2
e depicts the optical images and D images of machined surfaces in precited turning environments. Out of the four precited cutting conditions, the surface topography of machined surface (D image profile)
clearly reflects that turning with MQL presents a lower peak compared to other machining environments. Also, Fig.
2
e shows reasonably low feed marks and feed mark area expansion to ridges under MQL. As the absence of cutting fluid in dry turning, high friction is generated at tool- work interface resulting wear at the cutting edge followed by increasing in cutting force. This increase in the principal cutting force consequently enhance the roughness value of the machined surface. In flooded condition, due to the presence of abundant cutting fluid which provide desired cooling and lubrication effect, which leads to reduction in cutting edge wear followed by improving surface quality. In case of MQL turning, as cutting fluid is supplied in spray form, due to aerosolization of cutting fluid effective cooling is obtained at the cutting zone. Thus, it subsequently protects the tool from the thermal stress and able to uphold the effectiveness of the cutting insert. In addition, cutting forces also increase comparatively less to other cooling methods.
By taking into consideration of control criterion of flank wear (i.e., VB till mm, one more experiment was performed for each precited CL condition by setting cutting speed and feed at their higher limit (i.e., v
= 111 m/min and f =
0.24 mm/rev) and doc at 0.4 mm for estimating tool life of SiAlON ceramic cutting insert. Effective cooling-lubrication capability by MQL technique results in improvement of tool life. Machining under above four precited CL conditions experience the tool life of 34, 47, 73 and 81 min, respectively. These obtained results show that the tool life in turning in MQL are 138, 72 and 11% greater than dry, compressed air,
flooded condition, respectively. To study the economic feasibility, Gilbert’s approach was employed to estimate overall machining cost per component considering both direct and indirect cost associated with machining, as shown in Table. Results
Table 2 Cost analysis in turning Nitronic 60 with SiAlON ceramic toolunder various environments
Sl. no
Type of costs
Dry
Compressed air
Flooded
MQL
1
Machine and labor cost (per min
Rs. 5
Rs.5.17
Rs. Rs. 5.42 Cutting cost per component
(xT
m
)
Rs. Rs. Rs. Rs. 13.82 Tool changing cost per component [xT
d
(T
m
/T )]
Rs. Rs. Rs. Rs. 0.85 Cost of each tool
Rs. Rs. Rs. Rs. 650 Average cost of each cutting tool edge (y)
Rs. Rs. Rs. Rs. 162.5 Tooling cost per piece [y
(T
m
/T )]
Rs. Rs. Rs. Rs. 5.12 Overall cutting cost per piece, (2
+ 3 + Rs. Rs. Rs. Rs. 19.79

Machining of Austenitic Stainless Steel obtained from cost analysis reveals that the utilization of SiAlON ceramic tool is more economically feasible under MQL environment as the overall machining cost per component is lower (Rs. 19.79) as compared to dry (Rs. 26.81), compressed air (Rs. 23.4), flooded (Rs. 21.76) machining conditions. Thus, cost saving can be attained when using SiAlON ceramic tool in MQL condition.

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