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对系列X80管线钢研究表明,该材料组织特征为含有粒状贝氏体的针状铁素体;粒状贝氏体越细小弥散,其强韧性匹配越好。粒状贝氏体中,M-A岛的作用为阻碍裂纹的扩展;晶粒边界和M-A岛边界易萌生裂纹源。管线钢的有效晶粒决定了材料的塑韧性。具体表现为,当有效晶粒减小时,材料韧脆转变温度降低,断面收缩率提高。随着慢拉伸速率的提高,材料的断裂方式将发生改变。当拉伸速率为0.1 mm/s时,管线钢的延性最佳,而对强度的影响不大。这说明在管线钢富气服役状态下,富气压力有一个最佳值。拉伸速率升高后,断裂逐渐向脆性方式转变。
The research of series X80 pipeline steel shows that the material is characterized by acicular ferrite containing granular bainite. The finer the granular bainite, the better the toughness matching. In granular bainite, M-A island acts as a barrier to crack propagation; grain boundary and M-A island boundaries are prone to crack initiation. The effective grain of pipeline steel determines the plasticity and toughness of the material. Specifically, when the effective grain size decreases, the ductile-brittle transition temperature of the material decreases, and the reduction of area decreases. As the rate of slow stretching increases, the way the material breaks will change. When the tensile rate is 0.1 mm / s, the ductility of the pipeline steel is the best, but has little effect on the strength. This shows that in rich gas pipeline service status, rich gas pressure has an optimal value. After the stretching rate increases, the fracture gradually changes to brittle mode.