Investigation of the influence of tool material and lubricant onto the process parameters and quality of work piece surface at ironing

Abstract

At cold plastic forming, the size of contact surface changes during the process, which means that parts of material which were not in contact in the previous phase now get in contact with the tool. This condition, as well as many others, create a series of specific problems, such as: change of friction coefficient in conditions of plastic forming, significance of tool roughness and its interaction with initial and then variable roughness of material being formed, and also prominently large differences in their mechanical properties, development of the wearing process and potential local welding (appearance of “galling”), possibility and quality of lubrication, etc. If it is necessary to achieve the larger strain ratio during the ironing process, which would be possible without interoperation glowing, then the drawing is performed through many dies in succession. Thereat, due to the change of contact conditions (dislodging of lubricant, change of surface roughness, formation of diffusion and adhesion junctions), the friction condition change as well. The aim of the experimental researches carried out in this paper was to indicate the changes which occur at multiphase drawing and to consider the influence of some factors (tool material, lubricant on die and punch) onto the process development.