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采用高频真空感应炉在1 550℃的Ar气氛中冶炼不同钛含量的钛、铌微合金化钢并对其进行热处理。分析了钛加入量对钢的成分、组织结构、钢中典型夹杂物及宏观力学性能的影响。研究结果表明:采用Al脱氧后的钛、铌微合金化钢氧含量降低到0.002 0%左右,合金元素的利用率超过80%。钢中的夹杂物主要有球形或近似球形的Al2O3、SiO2、TiOx及其复合夹杂。(Ti,Nb)(C,N)、NbC、TiC夹杂以氧化物夹杂为核心析出。随着钛合金加入量的增加,钢样中的部分夹杂物形貌由球形发展成长方形。经共聚焦激光扫描高温显微镜热处理过的钢样中析出较多细小的(Ti,Nb)(C,N)夹杂物。随着钛含量的增加,热处理后的钢中小于1μm夹杂物数量急剧增加,尺寸大于1μm的夹杂物的数量呈现减少的趋势。高温在线金相组织分析表明:钢中钛加入量增加,高温奥氏体晶粒变小,钢的组织细化,从而钢的宏观硬度增高。
The high-frequency vacuum induction furnace was used to smelt titanium and niobium micro-alloyed steels with different titanium contents in an Ar atmosphere at 1 550 ℃ and heat-treat them. The effects of titanium addition on the composition, microstructure, typical inclusions in steel and macroscopic mechanical properties were analyzed. The results show that the content of oxygen in the niobium microalloyed steel decreases to about 0.002 0% after using Al deoxidized titanium, and the alloying element utilization rate exceeds 80%. The inclusions in steel are mainly spherical or nearly spherical Al 2 O 3, SiO 2, TiO x and their composite inclusions. (Ti, Nb) (C, N), NbC, TiC inclusions with oxide inclusions as the core precipitation. With the increase of the amount of titanium alloy, part of the inclusions in the steel samples developed from spheres to rectangles. The more (Ti, Nb) (C, N) inclusions were precipitated in the heat-treated steel samples by confocal laser scanning microscope. With the increase of titanium content, the number of inclusions less than 1μm increased sharply in the heat-treated steel, and the number of inclusions larger than 1μm tended to decrease. High temperature on-line metallographic analysis shows that the amount of titanium in the steel increases, the high temperature austenite grains become smaller and the microstructure of the steel is refined, so that the macroscopic hardness of the steel increases.