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我厂生产的BC584毛纺机中的大齿轮主轴,批量较大,用45钢制成,需进行调质处理,其硬度要求为HB220～260。过去,我们按45钢传统调质工艺,即盐炉加热840℃,保温8～10min,在5～1％氯化钠水溶液中冷却淬火,然后再经620～640℃× 1.5 h气冷到室温的高温回火。结果,硬度虽符合技术要求,但有50％的零件产生淬火纹裂(见示意图)。
I plant production BC584 wool spinning machine in the large gear spindle, larger, made of 45 steel, to be quenched and tempered, the hardness requirements for the HB220 ~ 260. In the past, according to the traditional quenching and tempering process of 45steel, that is, the salt furnace was heated at 840 ℃ for 8 ~ 10min, cooled and quenched in 5 ~ 1% sodium chloride aqueous solution, then cooled to room temperature by 620 ~ 640 ℃ × 1.5h Tempering at high temperature. As a result, although the hardness meets the technical requirements, 50% of the parts produce quench cracking (see illustration).