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应用光滑拉伸试样,弯曲试样以及预裂纹WQL型试样具有对广泛拉伸强度的多种低碳及低合金钢研究了电解充氧对表观屈服强度的影响,并对氢致滞后塑性变形进行了金相观察。结果表明:氢对光滑拉伸试样屈服强度的影响不明显。随钢种不同,充氢后屈服强度可能没有变化,也可能升高或降低,但其差值小于10％。对存在应力梯度的无裂纹弯曲试样以及预裂纹WOL试样,当钢的强度和进入的氢量超过临界值后氢能使表观屈服强度明显降低,从而引起氢致滞后塑性交形,最终导致氢致滞后裂纹的产生和扩展。随钢的强度升高,进入的氢量增加,氢致表观屈服强度下降也愈明显。另外,具有更大应力梯度和三向应力的裂纹试样,下降效应比无裂纹弯曲试样更为明显。氢致表观屈服强度下降作用是扩散控制过程,明显依赖变形速度和试验温度。另外,它具有可逆性,随着氢的逐渐消除,表观屈服应力也逐渐回到未充氢状态的数值。氢致表观屈服强度下降和原始变形量及是否存在加工硬化关系不大。根据上述实验事实,本文对屈服强度下降的原因作了探讨。
Applications Smooth Tensile Specimens, Bent Specimens, and Pre-Cracked WQL Specimens have been investigated for their effect on apparent yield strength for a wide range of low carbon and low alloy steels with a wide range of tensile strengths. Hydrogen-induced hysteresis Plastic deformation of the metallographic observations. The results show that hydrogen has no obvious effect on the yield strength of smooth and tensile specimens. Depending on the type of steel, the yield strength after hydrogen charging may not change, may increase or decrease, but the difference is less than 10%. For crack-free bent specimens with pre-cracked stress and pre-cracked WOL specimens, the apparent yield strength was significantly reduced by hydrogen when the strength of the steel and the amount of hydrogen entering exceeded the critical value, causing hydrogen-induced delayed plastic deformation, eventually Lead to hydrogen induced hysteresis cracks generation and expansion. As the strength of the steel increases, the amount of hydrogen entering increases, and the more pronounced the decrease in the apparent yield strength due to hydrogen. In addition, the cracked specimens with larger stress gradient and three-direction stress have more obvious descending effect than those without cracked specimens. Hydrogen induced apparent yield strength decline is the diffusion control process, obviously dependent on the deformation speed and the test temperature. In addition, it is reversible, and as hydrogen gradually disappears, apparent yield stress gradually returns to the value of the uncharged state. Hydrogen induced apparent yield strength decline and the original amount of deformation and the existence of work hardening has little to do. Based on the above experimental facts, this paper discusses the reasons for the decrease of yield strength.