X90?????SHCCT???????????

为了弄清t8/5对X90管线钢焊接热影响区组织和硬度的影响,利用Gleeble-3500热模拟试验机对该钢焊接热影响区在t8/5=10~300s下的热循环过程进行了模拟;结合热膨胀法和金相法建立了SHCCT曲线;针对各模拟样品,采用光学显微镜和透射电镜观察了显微组织,测定了维氏硬度HV0.3。结果表明:随着t8/5的减小,试验钢焊接热影响区相变开始和结束的温度降低,粒状贝氏体数量减少,板条贝氏体数量增多,原奥氏体晶粒和贝氏体铁素体细化,使该区域的硬度值升高。该钢环焊的t8/5宜控制在10~20s。

Measurement and Analysis of SHCCT Curve for X90 Pipeline Steel

For revealing the effect of t8/5 on microstructure and hardness of X90 pipeline steel in welding heat affected zone (HAZ) , the thermal cycles process at different t8/5 (10～300 s) were simulated by a Gleeble-3500 simulator. The SHCCT curve was established through analysis of thermal expansion curve and microstructure. For each sample, the microstructure was observed by optical microscopy (OM) and transmission electron microscope (TEM), and the vickers hardness was measured. The results show that with the t8/5 decreasing, the starting and finishing temperatures for phase transition in HAZ of experimental steel decreased. The dominated microstructure changed gradually from the granular bainite (GB) to the lath bainite (LB). The prior austenite grain and bainitic ferrite were obviously refined. The variation in the microstructure of HAZ caused an increasing hardness value. The t8/5 of 10～20 s is recommended for the girth welding of this steel.