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研究了正火处理对FAS390Q桥壳钢显微组织、强度、冲击韧性和韧脆转变温度的影响。结果表明,随着正火温度的升高,FAS390Q钢控轧控冷(TMCP)形成的显微畸变组织逐渐消失,800℃以下正火,保持11级晶粒度不变,800℃以上正火,晶粒开始长大。在600~700℃正火,对钢的屈服强度和断面收缩率影响不大,超过700℃以后,随着温度的提高,屈服强度明显下降,断面收缩率上升。FAS390Q钢的冲击韧性随正火温度的提高先增加后降低,800℃正火时的冲击韧度值最高。FAS390Q钢的冲击韧度值-温度曲线近似呈直线而非通常的S型,不能用能量判据法而应用断口形貌判据法确定其韧脆转变温度。FAS390Q钢未经正火后的韧脆转变温度为-50℃,经800℃正火后其韧脆转变温度下降了10℃。
The effect of normalizing treatment on the microstructure, strength, impact toughness and ductile-brittle transition temperature of FAS390Q axle-case shell steel was studied. The results show that with the increase of normalizing temperature, the microstructure of FAS390Q steel controlled by TMCP gradually disappears and normalized below 800 ℃, the grain size of 11 remains unchanged and the normalized temperature above 800 ℃ , The grain begins to grow. Normalizing at 600-700 ℃ has little effect on the yield strength and reduction of area of the steel. When the temperature is over 700 ℃, the yield strength decreases obviously with the increase of temperature, and the reduction of area decreases. The impact toughness of FAS390Q steel first increases and then decreases with the increase of normalizing temperature, and the impact toughness value of normal temperature at 800 ℃ is the highest. The impact toughness value-temperature curve of FAS390Q steel is approximately linear instead of the usual S-shape. The fracture criterion can not be used to determine the ductile-brittle transition temperature. FAS390Q steel after normalizing the ductile-brittle transition temperature of -50 ℃, after normalizing at 800 ℃ ductile-brittle transition temperature decreased by 10 ℃.