微合金化钢热送热装过程组织演变研究

Study on Microstructure Evolution of Micro-alloyed Steel During Hot Delivery and Hot Charging

通过实验室模拟微合金化含Ti钢连铸坯热送热装过程,并利用光学显微镜观察了室温条件下不同热履历试样的显微组织,分析了热送热装连铸坯组织演变的规律和特点。结果表明,700℃左右是不同热送温度的一个分界线,700℃以下热送试样均会发生奥氏体分解相变;700℃以上试样的高温组织为奥氏体,且奥氏体晶粒的大小基本相同;700℃以上热送热装试样的晶粒度较700℃以下粗大;不同的热送温度导致热处理室温显微组织有极大的差别,热送温度越高,二次奥氏体化过程越容易;热送温度越低,相变过程比较复杂;在700℃热送是较为合理的,可以尝试在750℃进行热送实践。

Hot delivery and hot charging of a Ti micro-alloyed steel slab at different delivery temperature were simulated in laboratory. The microstructure morphologies of specimens at room temperature in different thermal histories were observed by optical microscope （OM）. The law and specialty of the microstrucatre evolution of the specimen was also analyzed. The results show that, a demarcation line of hot charging at different temperature is about 700℃, the austenite decomposition of specimen occurs below 700 ℃, the high temperature microstructure of the specimen is austenite and the size of the austenite grain is similar above 700 ℃. The size ofaustenite grain above 700 ℃ is coarser than that below 700 ℃. The microstructure of thermal treatment at room temperature is very different at different hot charging temperature. The re-austenitization becomes easier as the hot charging temperature increases; the phase transformation becomes more complicated as the hot charging temperature decreases. Hot charging at 700℃ is reasonable, and hot charging at 750 ℃ can also be implemented.