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利用Gleeble热模拟试验机模拟研究了X80钢焊接热影响区粗晶区组织在不同冷却速度下的变化规律,研究了冷却时间、组织和性能之间的关系。结果表明,X80钢焊接热影响区粗晶区组织主要由板条贝氏体和粒状贝氏体组成。随冷却时间t8/5时间增加,板条贝氏体含量逐渐减少,由细长状转变成粗大片状、并趋于平行;粒状贝氏体含量逐渐增加,其间的马氏体M/奥氏体A组元数量增加,间距缩短,面积增大。随冷却时间t8/5时间增加,焊接热影响区粗晶区冲击韧性先增加后减小;当t8/5=7 s时,X80钢焊接热影响区粗晶区组织为少量的粒状贝氏体,且弥散分布于大量板条贝氏体之间,细化板条贝氏体,增加有效晶界,起到细化和强化作用,冲击断口分布着大量的细小韧窝,为明显的韧性断裂。
The Gleeble thermal simulation test machine was used to simulate the variation of coarse-grained microstructure in heat affected zone of X80 steel at different cooling rates. The relationship between cooling time, microstructure and properties was studied. The results show that the coarsening zone of the heat affected zone of X80 steel consists mainly of lath bainite and granular bainite. With the cooling time t8 / 5 time increases, the slab bainite content decreased gradually from slender to coarse flakes, and tends to parallel; granular bainite content gradually increased, during which the martensite M / austenitic Body A group increased the number of components, spacing shortened, the area increases. With the increase of the cooling time t8 / 5, the impact toughness of the coarse heat-treated zone first increases and then decreases; when t8 / 5 = 7 s, the coarse grain zone of the weld heat affected zone of X80 steel is a small amount of granular bainite , And dispersed in a large number of lath bainite between the refinement of bainite lath, increasing the effective grain boundaries, play the role of thinning and strengthening, the impact fracture distribution of a large number of small dimples, for the obvious ductile fracture .