Cold forming of bolts without thermal treatment

In this paper, we describe the experience with cold forming of bolts, made of micro-alloyed steel, specially designed to enable elimination of thermal treatment. First, the flow stress curve and hardening of material are evaluated by compression testing. Next, cold forming of various geometrical versions of the bolts is numerically simulated to obtain and compare their strain distribution and formability exhaustion. The results are verified by hardness measurement of produced specimens. Final products are then subjected to tensile testing to evaluate basic mechanical characteristics of the bolts—yield and tensile strength and elongation at rupture.