Abstract: Dilatation curves of C-Mn-Si series low carbon （/% : 0.11C , 1.15Si, 1.85Mn, 0.032A1, 0.003Ti, 0.002 4N） and medium carbon （/% ： 0.35C, 1.1 ISi, 1.82Mn, 0.041 Al, 0.002Ti, 0.004 2N） bainite steel continuous cooling with cooling rate 0.5 ~ 30 ℃/s have been measured by using thermal dilation method and metallographic examination with the Gleeble-1500 hot simulation machine to define the phase transformation points, and combined with microstructure observation, the continuous cooling transformation （ CCT） curves of two steels are respectively plotted by Origin software. Results show that with cooling rate ≤ 1 °C/s, the structure of 0. 11% C steel is ferrite + bainite + martensite, as cooling rate ≥ 2 °C , its structure is bainite + martensite, and with cooling rate ≥ 0.5 °C/s the 0.35% C steel has bainite 4- martensite structure ； with increasing carbon content, the transformation temperature of bainite and martensite all decreases.

摘要： 采用热膨胀法和金相法,通过Gleeble-1500热模拟试验机测定C-Mn-Si系低碳(/%:0.11C、1.15Si、1.85Mn、0.032Al、0.003 Ti、0.002 4N)和中碳(/%:0.35C、1.11Si、1.82Mn、0.041Al、0.002 Ti、0.004 2N)贝氏体钢在0.5～30℃/s的冷却速度下连续冷却时的膨胀曲线,确定相变点,并结合显微组织,借助Origin软件分别绘制出两种钢的连续冷却转变(CCT)曲线。结果表明,0.11%C钢当冷却速度≤1℃/s时获得铁素体+贝氏体+马氏体组织,冷却速度≥2℃/s时为贝氏体+马氏体组织,0.35%C钢冷却速度≥0.5℃/s即可获得贝氏体+马氏体组织;随碳含量增加,贝氏体和马氏体转变温度均降低。

关键词: C-Mn-Si系贝氏体钢, C含量, CCT曲线, 相变点, 组织