利用金相显微镜、X射线衍射等方法研究了0.15C-1.46Si-1.56Mn-0.06Nb冷轧TRIP钢板等温淬火温度对组织和力学性能的影响.结果表明,试验钢最佳的临界热处理工艺:在840℃两相区保温180 B,再快速冷却到420℃并在该温度保温240 S,进行贝氏体等温转变处理.采用这种热处理工艺,试验钢的微观组织为铁素体+贝氏体+残留奥氏体,其中铁素体占72%,贝氏体占20%,残留奥氏体占8%,可获得较佳的相变诱发塑性和较好的强韧性配合,其强塑积可达到2.5×10~4MPa·%,提高或降低贝氏体等温淬火温度都会降低强塑积.结果还表明,在840℃,适当的延长热处理时间可以提高残留奥氏体体积分数及残留奥氏体的碳含量,有助于提高材料的强塑积.
The influence of isothermal transformation temperature on microstructure and mechanical properties of a cold rolled TRIP steel sheet with the composition of Fe-0. 15C-1. 46Si-1. 56Mn-0. 06Nb was investigated by mean of optical microscopy and X-ray diffraction. The results show that the optimum heat treatment process for the steel is aU8tenizing in intercritical region at 840℃ for 180 s and then isothermal at 420℃ for 240 s for bainite transformation. The microstructure of steel sheet under this heat treatment is composed of 72% ferrite,20% bainite and 8% retained austenite,and the maximum product of strength and elongation,which is 2. 5 × 10~4 MPa · % ,is also obtained by this heat treatment process. The product of strength and elongation of the steel can be increased by increasing holding time properly at 840℃ ,due to the increase of volume fraction of retained austenite and carbon content in retained austenite.
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