Identification of Optimum Heating Temperature in Thermal Assisted Turning of Stainless Steel Using Three Different Approaches

Thermal or heat assisted machining is used to machine hard and difficult-to-machine materials such as Inconel and Titanium alloys. The main concept is that localized surface heating of the work-piece reduces the yield strength of the material significantly, making it amenable to plastic deformation and machining. Thus, heat assisted machining has been used for over a century. However, the heating technique and temperature are very much dependent on the type of working material. Therefore, a multitude of heating techniques has been applied over the years including Laser Assisted Machining (LAM) and Plasma Enhanced Machining (PEM) in the industry. But such processes are very expensive and have not been found in wide scale applications. The authors of the current research have therefore looked into the application of a simple Tungsten Inert Gas (TIG) welding setup to perform heat assisted turning of AISI 304 Stainless Steel. Such welding equipment is relatively cheap and available. Also, stainless steel is perennially used in the industry for high strength applications. Hence, it is very important to determine with optimal cutting temperature when applying a TIG setup for heat assisted machining of stainless steel. This paper describes three separate techniques for determining the optimum temperature. All three processes applied the same experimental setup but used different variables for evaluating the best temperature. The first process used vibration amplitude reduction with increment in temperature to identify the desired temperature. The second process used chip shrinkage coefficient to locate the same temperature. And finally, the third process investigated tool wear as a criterion for determining the optimum temperature. In all three cases the three primary cutting parameters: cutting speed, feed, and depth of cut, were varied in the same pattern. The results obtained from all three approaches showed that 450oC was undoubtedly the best temperature for heat assisted machining of stainless steel.