当试样中存在拉应力梯度时,氢能使表观屈服应力明显下降,从而能引起氢致滞后塑性变形和氢致滞后裂纹,对Ⅲ型裂纹,由于不存在流体静压力,故一般认为它不能产生氢致裂纹。但我们的工作表明,对充氢的Ⅲ型试样,在扭矩大于临界值后保持一定时间就能在和原裂纹面成-45°的诸平面上产生氢致滞后裂纹,它导致典型的沿晶断口。对三个钢种都有类似结果。如充氢试样直接扭断,则 When tensile stress gradient exists in the sample, hydrogen can significantly reduce the apparent yield stress, which can cause hydrogen induced hysteresis plastic deformation and hydrogen induced hysteresis cracks. For type Ⅲ cracks, hydrostatic pressure is not considered, so it is generally considered as Hydrogen-induced cracking can not occur. However, our work shows that for hydrogenated type III specimens, hydrogen induced hysteresis cracks can be produced on planes that form a -45 ° angle with the original crack surface for a certain time after the torque is greater than the critical value, resulting in a typical along Crystal fracture. Similar results for all three grades. If hydrogen charging sample is directly broken, then