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利用材料万能试验机、金相显微镜和透射电镜研究了热成形钢WHT1300HF在850、900和950℃分别保温5 min,以及在900℃分别保温2、10和15 min奥氏体化处理并模拟热冲压淬火后的组织和性能变化规律。结果表明,随着奥氏体化温度从850℃升高到950℃,试验钢的屈服强度先下降后有所升高,抗拉强度和伸长率均呈明显的下降趋势,显微硬度则迅速升高;而试验钢的强度、伸长率和显微硬度均随奥氏体化时间的延长呈明显的下降趋势。另外,在850℃和900℃保温2 min奥氏体化处理,试验钢的微观组织中均存在铁素体,而在900℃及以上的温度或在900℃保温5 min及更长时间奥氏体化处理后均为全马氏体组织;奥氏体晶粒大小随加热温度的升高和保温时间的延长逐渐增大,但加热温度对奥氏体晶粒的长大作用更显著。
The WHT1300HF thermoformed steel was heat-retained at 850, 900 and 950 ℃ for 5 min respectively by universal testing machine, metallographic microscope and transmission electron microscope. The microstructures of the hot-formed steel WHT1300HF after austenitizing at 900 ℃ for 2, 10 and 15 min The rule of microstructure and properties after press hardening. The results show that as the austenitizing temperature increases from 850 ℃ to 950 ℃, the yield strength of the test steel first decreases and then increases, the tensile strength and elongation decrease obviously, and the microhardness rapidly Increased; while the strength, elongation and microhardness of the test steel decreased obviously with the prolonging of austenitizing time. In addition, austenitizing treatment at 850 ℃ and 900 ℃ for 2 min showed that ferrite was present in the microstructure of the test steel, while austenite was retained at 900 ℃ and above or at 900 ℃ for 5 min and longer All of them were all martensite after austenite treatment. The austenite grain size increased with the increase of heating temperature and holding time, but the heating temperature had more significant effect on the growth of austenite grains.