组织状态对X120管线钢力学性能的影响

在实验室条件下对热轧X120管线钢进行两种不同工艺淬火,研究了回火温度对不同淬火态试验钢组织力学性能的影响。试验结果表明:直接快冷工艺下,显微组织以板条铁素体+马氏体为主;缓冷+直接快冷工艺下以粒状贝氏体+板条铁素体+马氏体为主。随回火温度升高,两种试验钢强度均出现起伏,在400~500℃范围内回火后,冲击功和伸长率均得到改善;采用直接快冷工艺在350℃和600℃回火后出现断口分离现象,从而导致力学性能波动,而缓冷+快冷工艺在回火过程中力学性能稳定性较好。因此,采用缓冷+快冷工艺+(450~500℃)回火,其力学性能达到X120级管线钢性能要求。

Effects of Microstructure Status on Mechanical Property of X120 Pipeline Steel

The influence of tempering temperature on microstructures and mechanical properties of X120 pipeline steels with two different quenching processes,which can be classified as direct quenching process（DQP） and indirect quenching process（IDQP）,was studied.The results showed that,the microstructures of two different quenching processes were BF and M and GB,BF and M,respectively.With tempering temperature increasing,the strength of the steels fluctuated,the impact toughness and elongation improved remarkably in tempering temperature range from 400℃ to 500℃.In DQP,the mechanical properties were fluctuating because it led to fracture separation when tempered at 350℃ and 600℃.However,for IDQP,the stability of mechanical properties was comparatively high during tempering process.Therefore,it is suggested that the process tempering from 450℃ to 500℃ in IDQP could help obtain a pipeline steel with an excellent mechanical properties,which met the demand of X120 pipeline steel.