【摘要】 通过热膨胀实验和显微组织观察分析了SA508 Gr.3钢连续冷却和等温冷却过程中的相变行为，并绘制了连续冷却转变曲线(CCT曲线)和等温冷却转变曲线(TTT曲线)。结果表明：SA508 Gr.3钢避免出现铁素体的临界冷速为0.5℃/s,冷速在0.5～2℃/s之间时，可获得贝氏体组织；当冷速≥20℃/s时，可获得完全的马氏体组织；在100℃/s的冷速下测得的M_s和M_f分别为424和198℃;在700～580℃之间等温时，SA508 Gr.3钢以较缓慢的速率发生铁素体转变；在560～380℃之间等温时，SA508 Gr.3钢以较快的速率发生贝氏体转变；等温铁素体转变的C曲线鼻尖温度约为640℃,等温贝氏体转变的C曲线鼻尖温度约为440℃;等温温度高于480℃时，贝氏体相变存在明显的不完全转变现象。更多还原

【Abstract】 The phase transformation behavior of SA508 Gr.3 steel during continuous cooling and isothermal cooling was analyzed by thermal dilatation experiment and microstructure observation, and the continuous cooling transformation curves(CCT curve) and isothermal cooling transformation curves(TTT curve) were drawn. The results show that the critical cooling rate for avoiding ferrite in the SA508 Gr.3 steel is 0.5 ℃/s, and bainite structure can be obtained when the cooling rate is between 0.5-2 ℃/s. When the cooling rate is ≥ 20 ℃/s, the fully martensite structure can be obtained. The M_s and M_f temperatures detected at a cooling rate of 100 ℃/s are 424 ℃ and 198 ℃, respectively. For the isothermal cooling process, ferrite transformation occurs at a relatively low rate when the isothermal temperature is in the range of 700-580 ℃. Furthermore, bainite transformation occurs at a relatively high rate when the isothermal temperature is in the range of 560-380 ℃. The nose temperatures of C-curves for isothermal ferrite and bainite transformation are 640 ℃ and 440 ℃, respectively. It is also worth noting that the incomplete character of bainite transformation can be obviously observed at an isothermal temperature higher than 480 ℃.更多还原