Q500q钢的连续冷却转变行为及生产试制

Continuous cooling transformation behavior and trial production of Q500q steel

利用热模拟实验机Gleeble-2000,对Q500q钢连续冷却转变行为以及在650～300℃温度区间的相变行为进行了研究及生产试制.结果表明:当冷速为1～4℃/s时,试验钢的微观组织由铁素体和珠光体组成.当冷速增至4～16℃/s时,发生贝氏体相变;随着冷却速度的增加,贝氏体组织更为细化且体积分数增加.当冷却速度大于4℃/s后,试验钢在650～300℃冷却速度减半时,贝氏体相变的终了温度升高,贝氏体相变区间缩小,与连续冷却转变相比组织差距不大.采用两种不同的冷却方式生产试制后,两组试验钢的力学性能和金相显微组织一致,说明650℃以下可以采用缓冷坑堆冷的方式来提高钢板的探伤合格率.

Using Gleeble 2000 thermo-mechanical simulator,the phase transformation behavior of Q500 bridge steels was studied after cooling with constant and cooling with variable rate 650~300 ℃,and a trial production of Q500q was also carried out.Results showed that:the final microstructure is ferrite and pearlite when the cooling rate is 1 ~ 4 ℃/s,and bainite transformation occurred when the cooling rate increased from 4 ℃/s to 16 ℃/s.The microstructure is refined and the volume fraction of bainite is increased when the cooling rate continues to increase.After cooling to 650℃ with the cooling rate more than 4 ℃/s and the cooling rate variable is reduced to a half between 650 ℃ to 300 ℃,the final microstructure is similar to that achieved with continuous cooling,but bainite transformation end temperature increased and the transformation region was reduced.After trial production by two different cooling methods,the mechanical properties and microstructures of the tested steel are similar,thus the method of stacking cooling in slow cooling pit under 650 ℃ can improve the qualified rate in flaw detection of steel plates.