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以工业含铌X80管线钢为对象,研究了不同Nb含量条件下,焊接热影响区粗晶区中的原奥氏体晶粒和析出的状态;通过对焊接热影响区中粗晶区的热模拟实验,研究了不同热输入下,高Nb管线钢焊接粗晶区的晶粒粗化、显微组织演变、及大角晶界分布等情况。结果表明,高Nb钢的粗晶区范围更窄,粗晶区内的晶粒尺寸更小;经过双道焊的热循环后,高Nb钢粗晶区的析出尺寸更小,没有对韧性有害的大尺寸析出。此外,原奥氏体晶粒的粗化,以及显微组织中大角晶界密度的下降,明显降低了高Nb管线钢焊接粗晶区的韧性。
The industrial austenite X80 pipeline steel was used as the research object to study the original austenite grain size and precipitation state in the heat affected zone (HAZ) under the condition of different Nb content. The heat affected zone Simulation experiments were carried out to investigate the grain coarsening, microstructure evolution and distribution of the large-angle grain boundaries in the coarsening zone of high Nb steel with different heat input. The results show that the coarse grain region of the high Nb steel is narrower and the grain size in the coarse grain region is smaller. After the double pass welding thermal cycle, the precipitation size of the coarse grain region of the high Nb steel is smaller and has no detrimental effect on the toughness Large size precipitation. In addition, the coarsening of the original austenite grains and the decrease of the density of large-angle grain boundaries in the microstructure significantly reduce the toughness of the coarser grain boundaries of the high Nb line steel.