Effects of manufacturing processes and in-service mperature variations on the properties of TRIP steels

This paper examines some key aspects of the manufacturing process that "Transformation Induced Plasticity" (TRIP) steels would be exposed to, and systematically evaluate how the forming and thermal histories affect final strength and ductility of the material. We evaluate the effects of in-service temperature variations, such as under hood and hot/cold cyclic conditions, to determine whether these conditions influence final strength, ductility and energy absorption characteristics of several available TRIP steel grades. As part of the manufacturing thermal environment evaluations, stamping process thermal histories are included in the studies. As part of the in-service conditions, different pre-straining levels are included. Materials from four steel suppliers are examined. The thermal/straining history versus material property relationship is established over a full range of expected thermal histories and selected loading modes. Establishing these relationships will allow OEM designers to select TRIP steels for proper vehicle applications, and to specify manufacturing process conditions that yield reliable final material property levels.