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利用Gleeble3500热模拟试验机,建立了X80管线钢焊接热影响区的连续冷却转变曲线(SH-CCT曲线),采用金相分析、显微硬度测试和夏比冲击试验,分析了X80管线钢焊接粗晶区在不同冷却速度下的组织转变和性能变化规律。结果表明:当冷却速度低于0.3℃/s时,粗晶区组织为多边形铁素体和少量珠光体或粒状贝氏体的混合物,具有较好的冲击性能,但硬度较低;当冷却速度为0.3～2℃/s时,粗晶区中的粒状贝氏体和MA岛状组织增多,且晶界模糊,其冲击性能较差;当冷却速度在2～30℃/s时,热影响区组织以粒状贝氏体为主,MA岛状组织的形状和分布均匀,具有优良的冲击性能;当冷却速度大于30℃/s时,随着冷却速度的增加,粒状贝氏体的含量逐渐减小,而贝氏体铁素体的含量逐渐增多,硬度升高,冲击性能下降。
Using the Gleeble3500 thermal simulation testing machine, the continuous cooling transformation curve (SH-CCT curve) of the heat affected zone (HAZ) of X80 pipeline steel was established. The metallographic analysis, microhardness test and Charpy impact test were used to analyze the welded coarse Crystal structure at different cooling rates of the organizational change and performance changes. The results show that when the cooling rate is lower than 0.3 ℃ / s, the coarse grain structure is a mixture of polygonal ferrite and a small amount of pearlite or granular bainite, which has better impact properties but lower hardness. When the cooling rate Is 0.3 ~ 2 ℃ / s, the granular bainite and MA island structure in the coarse grain zone increase, and the grain boundary is fuzzy, and the impact performance is poor. When the cooling rate is 2 ~ 30 ℃ / s, the thermal effect The granular bainite is dominant in the zone organization, and the shape and distribution of MA island is uniform with excellent impact performance. When the cooling rate is more than 30 ℃ / s, the content of granular bainite gradually increases with the cooling rate increasing Decrease, while the content of bainitic ferrite increases gradually, the hardness increases, the impact performance decreases.