Effect of lubrication technique in tube drawing

Abstract

Cold drawing process is widely used in steel tube manufacturing industry as it offers advantages like close dimensional tolerances, superior surface finish, flexibility in achieving different sizes and manipulated mechanical properties. This process needs to control friction parameters and lubrication extensively in order to obtain acceptable quality tubes and generally a phosphate and stearate coating has been the conventional approach to achieve this objective. Off late, some alternatives have emerged and a recently developed alternative lubrication system based on micro-porous lubricant carrierlayer generated on steel tube substrate by electroplating an alloy and selectively etching out one component of the alloy has been specifically taken up for detailed study. The porous layer is to trap the lubricant and act as lubricant reservoir in the metal deformation zone under the extreme pressures of cold drawing process. The attempt has been made to practically investigate the effectiveness of this alternative lubrication system for cold drawing process in tube manufacturing from an industrial perspective. Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscope (SEM) has been used in the analysis to verify that the aimed chemical composition and uniform distribution and to visualize the generated porous layer. Experimental investigations were carried out by subjecting the tube specimens (with lubricated porous layer) to the cold drawing process carried through a special drawing die attachment mounted on Universal Testing Machine (UTM). Comparison of the results with the conventional phosphate and stearate film based lubrication method has been made. The results show 10% of reduction in draw load and about 40% of improvement in surface roughness.