采用Gleeble-3500型热模拟试验机,测定了6种X70钢的焊接CCT曲线,分析了不同冷却条件下的组织与性能的关系,讨论了合金元素对组织和性能的影响.结果表明:当冷却速度小于1℃/s时,组织中出现多边形铁素体；冷却速度在1～7 ℃/s时,组织以针状铁素体或粒状贝氏体组织为主；当冷却速度大于10C/s时,组织以细小的贝氏体为主.C具有抑制相变的作用,适当降低C含量,能扩大获得高韧性的冷却速度范围,并降低焊接热影响粗晶区的硬度,有利于提高钢管焊接质量.%The welding CCT curves of six kinds of X70 pipeline steel were tested on a Glccble-3500 thermo-mechanical simulator, the relationship between structure and property was analyzed under different cooling conditions, and the effect of alloying elements on structure and properly was discussed. The results showed that the polygonal ferrite appears in the microstructure when cooling rate is below 1 ℃/s; as cooling rate is in the range of 1～7 ℃/s, the microstructure is main as acicular ferrite or granular bainite; as cooling rate is over 10 ℃/s, the microstructure is dominated by fine bainite. C can inhibit phase transition; properly reducing C content can expand cooling rate range, and decrease hardness of HAZ coarse grain zone, it is favorable to increase welding quality of steel pipe.
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