X80与X100管线钢粗晶区SHCCT曲线的比较研究

采用相变仪DIL805A/D将X80、X100管线钢空心微缩管状试样,以200℃/s加热至1 350℃,保温10 s后以1~200℃/s的不同速度冷却至室温,在分析显微组织、硬度和相变温度的基础上获得两种管线钢的粗晶区SHCCT曲线。对比发现,随着冷却速度的增加,X80与X100的相变温度均降低,而硬度都增加;在相同冷却速度下,X100的相变温度明显低于X80,硬度却更高。对于X100管线钢,当v10℃/s时,粗晶区为GB、QF和M-A组元的混合组织;当10℃/s≤v≤50℃/s时,组织由GB、BF和M-A组元组成;当v50℃/s时,出现LM组织,当v100℃/s后转变为LM和M-A组元的混合组织。而X80管线钢只有当v≥25℃/s时才出现BF,v100℃/s时开始出现LM组织。

Comparison of SHCCT curves of coarse grained heat affected zone between X80 and X100 pipeline steel

The DIL805A/D quenching dilatometer was adopted to simulate thermal cycles of miniature and X80 and X100 pipeline steel hollow cylinder specimens.By using a heating rate of 200 ℃/s and a peak temperature of 1 350 ℃ with 10 s holding time,then cooled down to room temperature with a cooling rate of 1～200 ℃/s.The SHCCT curves of coarse grained heat affected zone of two kinds of pipeline steels were obtained on the basis of the microstructure,hardness and phase change temperature.The results show that,as the cooling rate increases,the phase transition temperature of X80 and X100 decreases,but the hardness increases.The phase change temperature of X100 is obviously lower than that of X80 with the same cooling rate,but the hardness is higher than that of X80.The microstructure of coarse grained heat affected zone of X100 is a mixed structure when the cooling rate is lower than 10 ℃/s,including of GB,a small amount of QF and M-A constituents.GB,BF and M-A components prevail in the Xl00 with a cooling rate of 10～50 ℃/s.The LM forms in the X100 when the cooling rate is higher than 50 ℃/s.The microstructure is made entirely of LM and M-A components until the cooling rate is over 100 ℃/s.The BF and LM forms in the X80 with the cooling rate are higher than 25 ℃/s and 100 ℃/s,respectively.