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运用TEM和EDS等测试方法,对高铌X80管线钢连铸过程微合金元素的析出行为进行研究。结果表明:铸坯凝固冷却至1 100℃时,存在片层状以及棒状析出物,此类析出物为Nb(C,N)碳氮化物,同时存在一些TiN析出物。当铸坯冷却至900℃时,开始出现中心富钛、边部富铌的(Nb,Ti)(C,N)星形和枝晶形碳氮化物。当铸坯冷却至750℃时,枝晶状析出物增多,同时也存在部分富铌的枝晶状Nb(C,N)碳氮化物。冷却至室温的铸坯晶界上存在大量的枝晶状析出物。由热力学计算和试验结果得出,对于高铌X80管线钢,枝晶状复合析出物开始析出温度介于1 000~1 100℃之间。
The precipitation behavior of microalloyed elements in continuous casting process of high niobium X80 pipeline steel was studied by TEM and EDS. The results show that when the billet is solidified and cooled to 1 100 ℃, there are lamellar and rod-like precipitates. These precipitates are Nb (C, N) carbonitrides and some TiN precipitates exist at the same time. When the billet cooled to 900 ° C, the center of the rich titanium, niobium edge of the (Nb, Ti) (C, N) star and dendritic carbonitride began to appear. When the billet is cooled to 750 ° C, dendritic precipitates increase, and some niobium-rich dendritic Nb (C, N) carbonitrides are also present. There is a large amount of dendritic precipitates on the grain boundary of the slab cooled to room temperature. From the thermodynamic calculation and experimental results, it is concluded that for the high niobium X80 pipeline steel, the dendritic composite precipitates begin to precipitate at a temperature of between 1000 and 1 100 ° C.