Tool steel selection for cold forming of high strength steels based on the stress distribution in tools

Abstract

The excellent combination of high mechanical strength, high elongation and strain hardening of Advanced High Strength Steels (AHSS) has allowed their increasing use in the automobile industry to reduce vehicle weight and thereby fuel consumption while improving crash performance. However, the implementation of such high strength materials has generated difficulties related to wear acceleration and premature failure of forming tools. High loading during cold forming of AHSS increases to a great extent the tool requirements in terms of toughness and hardness properties. The main alternative to overcome these difficulties involves an optimized selection tool material through a proper evaluation of the stress state in the tools themselves. In this work, stress states on tooling during cold forming of AHSS have been evaluated by means of finite element simulation. The calculated results allow selecting the most suitable tool steel in terms of microstructure and mechanical properties.