The influence of the surface defects concerning upsetting and extrusion processes of the micro-alloyed steel

摘要

This paper investigates behaviour of bolts' defects (cracks) of varying magnitude that may occur in bolt production processes (compression, upsetting). The objective has been to determine whether surface micro-cracks in the bolt semi-products can be a source of macro-cracks that might occur during the further processing stages leading to a serious damage of the material utilised [1]. Principal attention was paid to determining of the extreme limit deformation as a result of the upsetting and compression stages of the bolt semiproduct forming; at which point propagation of cracks - causing the material brittleness - may start. Note that it concerns production of high-strength bolts for automobile industries that demand extreme strength and finest surface qualities of components utilised.