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通过对25MnTiBR钢碳氮共渗疲劳源位置的转移与最佳层深度关系的研究,得到以下主要试验结果:疲劳极限的最佳层深度为0.8～0.94毫米范围;疲劳源位置开始转移的临界深度和临界转移深度与试样半径之比分别为0.8毫米与0.27毫米;疲劳源位置转移的深度范围与最佳层深度范围相当,并随各种条件的变化而有所变化。在接近疲劳极限的低过载应力下,当层深小于转移的临界深度时试样断口上可全部得到“鱼眼”内源的浅层,但当层深大于转移深度范围时,可全部得到深层的表面疲劳裂纹源。碳氮共渗的最佳层深,疲劳源开始转移的临界深度,临界转移比均较渗碳为小.
Through the study of the relation between the transfer position of the fatigue source and the optimal layer depth in 25MnTiBR steel, the following main results are obtained: the optimum depth of the fatigue limit is in the range of 0.8 ~ 0.94mm; the critical depth at which the fatigue source begins to transfer And the ratio of critical transfer depth to sample radius were 0.8 mm and 0.27 mm, respectively; the depth range of the fatigue source transfer was comparable to the optimum depth range and varied with various conditions. Under the low overload stress near the fatigue limit, when the layer depth is less than the critical depth of transfer, all the shallow layers of “fish-eye” can be obtained at the fracture surface of the specimen, but when the layer depth is greater than the transfer depth range, The source of surface fatigue cracks. The best depth of carbonitriding, the critical depth at which the fatigue source starts to migrate, and the critical transfer ratio are all smaller than the carburization.