钼、铬对低碳铌钛微合金钢连续冷却转变行为的影响

Effect of Mo and Cr on the Behaviour of Continuous Cooling Transformation of Nb-Ti Bearing Low Carbon Microalloyed Steels

为研究合金元素钼、铬对低碳铌钛微合金钢连续冷却转变行为的影响,采用Gleeble-3800热模拟试验机和热膨胀试验方法,测定了钼、铬含量不同的3种低碳铌钛成分微合金钢在不同冷却速度下的相变点,采用光学显微镜及扫描电子显微镜观察了其转变产物的微观组织,同时结合维氏硬度测试,绘制了动态CCT曲线。结果表明,钼和铬均降低奥氏体向针状铁素体转变的相变温度,并且在冷速大于1℃/s时,钼比铬的作用效果更加明显。钼、铬均能抑制先共析铁素体和珠光体的转变,扩大针状铁素体形成冷速范围,并能够显著细化组织。

The effect of molybdenum （Mo） and chromium （Cr） on the behaviour of continuous cooling transforma tion （CCT） of low carbon microalloyed steels containing niobium （Nb） and titanium （Ti） was investigated by using a Gleeble 3800 thermomechanical simulator and heat expansion method. The phase transformation temperature of three low carbon microalloyed steels at various cooling rates with different content of Mo and Cr was detected, the microstructure was observed by optical microscopy and scanning electron microscopy, and vickers hardness was also tested, then the dynamic continuous cooling transformation curves were determined. As a result, the transformation temperature from deformed austenite to acicular ferrite is decreased with adding Mo and Cr in the steels, and the effect of Mo is more significant than that of Cr when the cooling rate is above 1 ℃/s, and the formation of proeutecid ferrite and pearlite is inhabited or postponed. Mo and Cr element also can enlarge the range of cooling rate for form ing acicular ferrite, and can refine the microstructure effectively.