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采用Gleeble-3500热模拟试验机模拟研究了两种典型的焊接热输入条件下高铌高强管线钢焊接热影响区的组织和性能分布,结果表明:高铌高强管线钢焊接热影响区的硬度高于母材的硬度,没有明显的软化现象;但临界两相区及焊接粗晶区的韧性显著恶化。临界两相区韧性降低是原奥氏体晶界处形成尺寸较大的链状M/A岛所致;而焊接粗晶区则是由于原奥氏体晶粒粗化及混晶,以及冷却后形成粗大的贝氏体及贝氏体边界处尺寸较大的M/A岛所致。在高铌钢中,高的合金含量所引起碳当量的升高是导致韧性降低的主要原因。
The microstructure and property distribution of HAZ of high niobium high strength pipeline steel under two typical welding heat input conditions were simulated by Gleeble-3500 thermal simulation test machine. The results show that the hardness of HAZ of high niobium high strength pipeline steel is high The hardness of the base metal, there is no obvious softening phenomenon; but the critical two-phase region and the toughness of the welding area significantly worsened. The reduction of the toughness in the critical two-phase region is caused by the formation of large-sized chain M / A islands at the original austenite grain boundaries. The welding of the coarse-grained region is due to the coarsening and mixed austenite grain growth and cooling After the formation of coarse bainite and bainite boundaries M / A Island due to the larger size. In high-niobium steels, the increase of carbon equivalent caused by high alloy content is the main reason for the decrease of toughness.