700 MPa级高强度耐候钢过冷奥氏体连续冷却相变行为

采用热模拟试验机研究了添加Ni、Cr、Cu的车厢用微合金化耐候钢的过冷奥氏体连续冷却相变行为,并建立了试验钢的静态和动态CCT曲线。结果表明,在无变形条件下,试验钢在各冷速下均不能获得全铁素体组织,冷却速率为0.2 ℃/s时,室温组织中的铁素体含量最高,为41%,平均晶粒尺寸为36.9 μm;在施加30%变形量的条件下,试验钢在0.2 ℃/s冷速下可获得全铁素体+极少量珠光体组织,平均晶粒尺寸为17.9 μm,具有较好的耐腐蚀能力。当冷却速率在0.2~0.5 ℃/s之间(铁素体+珠光体相变区间),提高冷却速率可以增加试验钢的硬度,在施加30%变形量和0.2 ℃/s冷却速率条件下,试验钢的宏观硬度值达181 HV30。

Continuous cooling transformation behavior of undercooled austenite of 700 MPa high strength weathering resistance steel

Continuous cooling phase transformation behavior of micro-alloyed weathering resistance steel with addition of Ni, Cr, Cu for carriage was studied by means of thermal simulation test machine, and the static and dynamic CCT curves of the tested steel were established. The results show that under the condition of no deformation, not all ferrite microstructure can be obtained at test cooling rates. When the cooling rate is 0.2 ℃/s, the ferrite content in the room temperature after cooling is the highest, which is 41%, and the average grain size is 36.9 μm. Under the condition of deformation of 30%, all ferrite and mintue quantity of pearlite microstructure can be obtained at the cooling rate of 0.2 ℃/s, and the average grain size is 17.9 μm, at which the tested steel has good corrosion resistance. When the cooling rate is in the range of 0.2-0.5 ℃/s (ferrite and pearlite phase transformation), the hardness of the tested steel increases with the rise of cooling rate. Under the condition of deformation of 30% and cooling rate of 0.2 ℃/s, the macrohardness of the tested steel reaches 181 HV30.