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用抛光的WOL型恒位移试样跟踪观察了各种低合金钢在H_2S中应力腐蚀裂纹产生和扩展的规律。结果表明:当钢的强度和K_I均大于临界值之后,在裂纹前端将会发生滞后塑性变形,即裂纹前端塑性区的大小及其变形量将随时间延长而逐渐增加,当这种滞后塑性变形发展到临界状态时就会导致应力腐蚀裂纹的产生和扩展。 对超高强钢来说,当这个滞后塑性区闭合后应力腐蚀裂纹就在其端点形核,随着滞后塑性变形的发展,这些不连续的应力腐蚀裂纹逐渐长大并互相连接。对强度较低的钢,随滞后塑性变形的发展,应力腐蚀裂纹沿着滞后塑性区边界向前扩展。 已经证明这个滞后塑性变形是由氢引起的,称作氢致滞后塑性变形。 利用WOL型试样测量了在H_2S气体以及H_2S饱和水溶液中的K_(ISCC)和da/dt研究了它们随强度变化的规律,以及阴极极化和阳极极化对超高强钢K_(ISCC)和da/dt的影响。
The polished WOL constant displacement specimen was used to track the generation and propagation of stress corrosion cracking of various low alloy steels in H_2S. The results show that when the strength and K_I of steels are both greater than the critical value, the plastic deformation of the crack will occur at the tip of the crack. That is, the plastic zone size at the crack tip and its deformation will gradually increase with time. When this lag plastic deformation To the critical state will lead to the generation and expansion of stress corrosion cracking. For super-high strength steels, the stress corrosion cracking nucleates at its end when the hysteretic plastic zone is closed. As the lag plastic deformation develops, the discontinuous stress corrosion cracking gradually grows and interconnects. For lower strength steels, as the lag plastic deformation develops, the stress corrosion crack propagates forward along the boundary of the hysteretic plastic zone. It has been shown that this hysteresis plastic deformation is caused by hydrogen, referred to as hydrogen induced hysteresis plastic deformation. The changes of K_ (ISCC) and da / dt in H_2S gas and H_2S saturated aqueous solution were investigated by using WOL samples. The effects of cathodic and anodic polarization on the properties of ultra high strength steel K_ (ISCC) and da / dt effect.