Effect of temperature, strain rate and stress state on the strain hardening behaviour of modern low and high alloyed high-strength sheet steels

摘要

With regard to energy conservation and emission reduction, the lightweight construction is the center of attention in the production of passenger car bodies with complex requirements. The development of innovative vehicle concepts requires therefore a substantial weight reduction of all assigned components, in particular also due to a significant weight increase of modern vehicles by additional construction units (safety and electronic components). The fact, that automobile lightweight construction with steel is possible, was demonstrated in two international research projects; in addition it is meanwhile occupied by many examples. In order to fulfill the future requirement profile of the automotive industry regarding the lightweight construction with steel and the corrosion protection, new high-strength steels and stainless steel grades for the automotive manufactures have been developed within the last years. The development in this sector led to the multiphase steels, like DP (Dual Phase) and PM (Partly Martensitic), FB (Ferritic Bainitic), TRIP (Transformation Induced Plasticity), CP (Complex Phase) and MS (Martensite Phase) steels. Current developments represent also the austenitic stainless steels X8CrMnNi19-6-3 (1.4376) and X13CrMnNi 19-7-2 (1.4377) as well as TWIP (Twinning Induced Plasticity) steels, which have a very high alloying content and a microstructure of austenite. This austenite can be plastically deformed by dislocation glide and by mechanical twinning. Figure 1 reflects the short term (2004) and long term (2010) expectations for the materials usage in the car body with regard to technology importance and urgency. It can be concluded that dual phase steels and bainitic or complex phase steels are considered to be of highest relevance for the next car generation.