Papers by Keyword: Automobile Steel

Abstract: The advantages and disadvantages of the conventional hot stamping steel and the hot tamping technology were shortly reviewed. It was proposed that new type steel with relative low austenization temperature and air hardening ability should be designed and produced to overcome the surface oxidation and avoid the complexity of cooling system of the stamping dies. In this study, it was shown that the 3rd generation sheet steel with medium-Mn composition could be austenized and pressed at 700-750°C and air cooled into automobile parts with strength no less than 1.5GPa and ductility larger than 12%. This new steel and corresponding forming technology were called warm stamping technology, which overcomes the disadvantages of the conventional hot stamping steel. The fabrication trials of the automobile parts in the automobile industries were demonstrated with high strength and relative good ductility. It was concluded that the 3rd generation sheet steel and the warm stamping technology could be applied to replace the conventional hot stamping steel and conventional hot stamping technology in near future.

Abstract: Cold rolled TRIP-600 steels has been developed on a laboratory scale. Composition of the steels is 0.12wt%C-0.30wt%Si-1.6wt%Mn-1.2wt%Al. Effects of Al concentration on phase diagram, TTT curves and T0 line of bainite formation in the steels were calculated and discussed.Cold rolled sheets of 1.7mm thick were annealed between 830 °C and 870 °C followed by austempering at 420 oC. UTS of 660~700MPa, YS 390~420MPa and total elongation 30.5~37.5% is obtained.Volume fraction of the retained austenite is 9~11% and carbon content in the retained austenite is 0.9% ~1.3wt% in the steels. The chemical composition and processing parameters of the experimental steels could be referred for trial-manufacture of TRIP 600 steels.

Abstract: The recrystallization behavior of high strength automobile steel sheets (ZJ590L) developed by CSP technology is studied in this paper. The effect of the deformation temperature, reduction on the austenite grain size and the recrystallized fraction of ZJ590L steel during hot deformation has been investigated. Technique of test and analysis includes preparing stepped test piece and quantitative metallograph. The mechanism of austenite microstructure refinement has been discussed, which provides valuable references to set parameters of controlled rolling and controlled cooling process. The analysis shows that the austenite grain size fines with the increase of deformation temperature and reduction, and the recrystallized fraction increases. When the deformation temperature is above 1000°C and reduction exceeds 40%, complete recrystallization can be obtained.