Research On The Formability Of High Strength Sheet For Ultralight Automobile

Automotive industry is facing great challenge from energy problem, environmental problem and safety problem today. The decrease of vehicle fuel consumption and the reduction of noxious emissions become main thrust to auto industry in order to meet rigid requirement about energy and environmental problem. Moreover, lightening vehicle's body weight is the first available and effective measure to reduce fuel consumption and emission. Consequently, ultralight automobile contributes to conservation of energy, emission reduction and the achievement of the sustainable development strategy.The forming property of six typical kinds (DC04,DC06,DP450,DP600,B180H1,MS6000) of automobile high strength steel is researched in this paper. The mechanical property's performance parameter (σ_s,σ_b,n,r,δ_gt, yield ratio and so on) are obtained by uniaxial tensile testing. In addition, the IE value that evaluates high strength steel's expanding property is obtained by cup drawing test. The result shows that the advanced high strength steel has preferable mechanical property and better forming property compared with the traditional mild steel. Moreover, the forming limit of high strength steel is predicted by the empirical models, and the established mathematic model for relativity is of practical usefulness. This paper also analyzed the strengthening mechanisms of high strength steel, by which the formability could be predicted. Furthermore, the work hardening capacity, bake-hardening properties and anti-hollow capacity of high strength steel are researched as well. The results have some significant effects on high strength steel forming process, and the high strength steel is applied to auto-body panel to achieve the goal of lightening the vehicle's body weight.More particular knowledge of strengthening mechanism and fracture mechanics is gained by researching the metallographic structure and fracture appearance. The results reveal that the excellent mechanical property and formability of high strength steel due to its specific microscopic structure. The macro-feature of trial sample should be considered when assess the formability of high strength steel.At last, this research also made finite element modeling for cup drawing test of high strength by Dynaform. Results showed that the test result is equal to the simulated result. And then, high strength dual phase steel (DP450) is applied to the car outdoor. The simulation analysis for forming process is performed and the content result is obtained by correcting the technological parameters.