Product Code: ICAL07_510

Enhancing Dual Phase Steel Formability by Diode Laser Heat Treatment
Authors:
Barbara Previtali, Politecnico Di Milano; Milano Italy
Edorado Capello, Politecnico di Milano; Milan Italy
Presented at ICALEO 2007

In the automotive world, increasing demands regarding weight, safety, and cost have led to the introduction of the so-called advanced high-strength steels (AHSS) . During forming processes, compared to conventional steels, AHSS steel usually has higher yield strengths and much higher ultimate tensile strengths, which require higher press loads and produce greater springback and die wear.
Heat treating just the areas which are mainly involved in high deformation, could be a potential solution to the difficulties encountered in forming AHSS steel. Indeed, by locally changing the AHSS microstructure and/or by tempering the martensite phase, the formability properties could increase only where needed.
In the paper, the diode laser heat treatment was applied to locally heat treat Dual Phase 800 steel, in order to study the effect of different process parameters on the material local formability. A finite element thermal model allowed the temperature and cooling rate curves to be forecast and to be used to explain the micro-hardness measurements and microstructure observations. Then, the mechanical tensile test and Erichsen cup test allowed the positive effect of the heat treatment on the DP steel formability to be quantified.