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本文研究了3Cr2W8V 钢的热疲劳特性。试验结果表明,热疲劳裂纹优先萌生于热应力最大和弱化最严重的局部地区。在一定尺寸范围内,裂纹的亚稳扩展速率近似是常数。裂纹扩展方式除条带模型外,还有不连续突进。长期冷热循环引起钢软化,软化机理是累积回火,热应力对循环软化有加速作用。热疲劳抗力随热处理温度改变呈非单调变化,分别有一个最佳淬火温度和最佳回火温度。随着循环上限温度的升高,热疲劳抗力显著下降,最佳回火温度向高温方向移动,最佳淬火温度基本不变。热疲劳抗力主要取决于材料的高温屈服强度,在强度、塑性及循环热稳定性取得适当配合时最大。
This article studies the thermal fatigue properties of 3Cr2W8V steel. The experimental results show that the thermal fatigue crack initiation preferentially occurs in the areas with the largest thermal stress and the weakest. In a certain size range, the crack metastable expansion rate is approximately constant. Crack propagation mode in addition to the band model, there are discontinuous sudden. Long-term hot and cold cycle caused by steel softening, softening mechanism is cumulative tempering, thermal stress on the accelerated cycle of softening effect. The thermal fatigue resistance changes non-monotonically with the heat treatment temperature, and there is an optimum quenching temperature and the optimal tempering temperature respectively. With the increase of the upper limit temperature of the cycle, the thermal fatigue resistance decreases significantly, and the optimum tempering temperature moves to the high temperature. The optimum quenching temperature is basically unchanged. The thermal fatigue resistance depends mainly on the high temperature yield strength of the material and is maximized when the appropriate combination of strength, ductility and thermal cycle stability is obtained.