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研究了不同工艺热处理后对440C钢轴向尺寸的变化规律,分析了尺寸变化机理,并提出了轴向尺寸变化率最小的热处理工艺参数。试验结果表明,退火和回火后试样轴向尺寸收缩,且随着退火和回火温度的升高,轴向尺寸的收缩量增大。淬火和冷处理后试样轴向尺寸增大,随着淬火温度的升高和冷处理前存放时间的延长,轴向尺寸伸长量减小。轴向尺寸伸长是马氏体相变引起的组织应力大于热应力所致;而热应力单独作用时导致轴向尺寸减小。推荐热处理工艺为163℃×2h去应力退火+850℃×1.5h退火+1050℃×15min淬火+16h后-75℃×2h冷处理+190℃×2h回火。
The change rule of the axial size of 440C steel after different heat treatment was studied. The mechanism of size change was analyzed, and the parameters of heat treatment with the smallest axial dimension change rate were proposed. The experimental results show that the axial size of the sample shrinks after annealing and tempering, and as the annealing and tempering temperatures increase, the axial shrinkage increases. After quenching and cold treatment, the axial size of the sample increases. With the increase of quenching temperature and storage time before cold treatment, the axial size elongation decreases. Axial dimensional elongation is caused by martensitic transformation of the tissue stress is greater than the thermal stress; and thermal stress alone when the axial size decreases. Recommended heat treatment process is 163 ℃ × 2h stress relief annealing + 850 ℃ × 1.5h annealing + 1050 ℃ × 15min quenching + 16h after -75 ℃ × 2h cold treatment + 190 ℃ × 2h tempering.