Q355D热轧H型钢的CCT曲线及冲击性能

利用膨胀法结合金相-显微硬度法，在Glebble-3500热模拟试验机对Q355D热轧H型钢的连续冷却转变规律进行研究，并绘制了静态连续冷却转变曲线(CCT曲线)。结果表明，从CCT曲线可以看出，在冷速小于1℃/s时，组织是铁素体和珠光体，冷速在1～10℃/s时，组织为铁素体+珠光体+贝氏体，冷速在20～50℃/s时，组织为针状铁素体+贝氏体+马氏体；随着冷却速率的增大，Q355D热轧H型钢的硬度增大，硬度由171 HV0.2增大至301 HV0.2。依据CCT曲线来制定不同轧制试验方案，当总压下量为75%、应变速率0.3 s^-1、变形温度1150℃时，试验钢铁素体晶粒尺寸为8.13μm,-20℃冲击吸收能量为146 J,性能最优。

CCT curves and impact property of Q355D hot rolled H-steel

Continuous cooling transformation rule of Q355D hot-rolled H-steel was investigated on Glebble-3500 thermal simulation test machine by means of expansion method and metallography hardness method. In addition, static CCT curves were obtained. The results show that from the CCT curves, the microstructure of the steel is composed of ferrite and pearlite when the cooling rate is less than 1 ℃/s, ferrite, pearlite and bainite when the cooling rate is 1-10 ℃/s, and ferrite, bainite and martensite when the cooling rate is 20-50 ℃/s. With the increase of cooling rate, the hardness of the Q355D hot-rolled H-steel increases, and the hardness increases from 171 HV0.2 to 301 HV0.2. According to CCT curves, different rolling experiment schemes are worked out. When the total reduction is 75%, the strain rate is 0.3 s^-1 and the deformation temperature is 1150 ℃, the ferrite grain size of the tested steel is 8.13 μm, and the impact absorbed energy at -20 ℃ is 146 J, with the best performance.