EXPERIMENTAL INVESTIGATIONS INTO ENHANCING THE MACHINABILITY OF EN-36C

Abstract

In this thesis the effect of different stages of tempering on EN-36C alloy steel has been carried out to check the mechanical behavioural, microstructural properties and residual stresses. The main objective behind this to enhancing the machinablity during CNC turning with preserving their properties. It would help the researchers to understand the technique how to increase the machinablity of any hard metal by this method. The contents of the thesis are as follows: Chapter 1 In this chapter, conventional machining processes have been described along with its different types of classification. Merits and demerits of CNC machining over other conventional machining have been discussed. Various parts and their uses are included in this section. Later in this chapter, about material EN-36C, tempering process and their different stages has been discussed. Chapter 2 A comprehensive review of the literature has been discussed on machinability of EN-36C alloy steel with and without tempered on CNC turning. In this section, the effect of various process parameters such as feed rate, depth of cut, cutting speed on output responses like material removal rate, surface finish, residual stress, tool tip temperature are reviewed. Effect of tempering on mechanical properties and microstructural behaviour of hard metals is also reviewed. Chapter 3 In this chapter, the sample preparation of EN-36C alloy steel, chemical composition, tempering of prepared samples, testing of samples for mechanical and microstructural properties were carried out. A brief discussion was made on sequence of experimental processes. Chapter 4 In this chapter, the discussion is made on Machinability and related factors which affect on it. Apart from this, a comparative study on mechanical properties of EN-36C alloy steel tempered and untempered has been carried out. The comparative study on surface roughness has also been carried out after conducting v the experiments on CNC lathe at same process parameters using cylindrical bar of tempered and untempered EN-36C alloy steel. Chapter 5 This chapter discusses the design of experiments using Response Surface Methodology (RSM), utilizing statistical analysis and ANOVA to understand the process. The optimum process parameters were selected for minimum surface roughness, residual stress and tool wear and maximum material removal rate for demonstrating the effectiveness of the method in achieving desired results. Chapter 6 This chapter elaborates scanning electron micrographs (SEM) and optical microscope obtained with CNC turned surfaces of tempered and non-tempered work piece of EN-36C alloy steel at optimum process parameters have been studied Chapter 7 This chapter explains the residual stress of CNC turned surfaces of tempered and untempered EN-36C alloy steel using an X-ray residual stress analyzer. The process is analyzed using response surface methodology and ANOVA. The optimal process parameters are obtained for the response percentage reduction in residual stress.The regression analysis investigates the significance of process parameters like cutting speed (V), feed rate (f) and depth of cut (d) and tempering temperature on the output response percentage reduction in residual stress (%∆RS). Chapter 8 This chapter describes the results and discussion part of the investigations in this thesis. The effect of tempering on mechanical properties and behavioral of microstructure as well as the various process parameters such as cutting speed (V), Chapter 9 This chapter contains the conclusions obtained from experimental investigations on EN-36C alloy steel with and without tempered during CNC turning. The process is thoroughly analyzed mechanical properties such as tensile strength, feed rate (f) and depth of cut (d) on their responses like residual stress, surface roughnes, tool wear, material removal rate (MRR) are studied. vi hardness, toughness and percentage elongation, microstructural properties, surface roughness and residual stress by statistical analysis using response surface methodology. The results have been explained in brief and scope of future work is discussed.