管线钢氢致附加应力与氢致门槛应力的相关性

RELATIONSHIP BETWEEN HYDROGEN-INDUCED ADDITIVE STRESS AND THRESHOLD CRACKING STRESS FOR A PIPELINE STEEL

X80钢在空气中拉伸至塑性变形大于1％后卸载,充氢至饱和再空拉,其屈服应力小于卸载前的流变应力,其差值即氢引起的附加应力.它协助外应力促进塑性变形,引起应力集中,进而导致低应力下的脆断（即氢脆）,或在低的恒定外应力下就发生氢致滞后断裂.实验表明,氢致附加应力σad随氢浓度C0升高而线性升高;即σad=-14.1+3.89C0;动态充氢慢应变速率拉伸时断裂应力随氢浓度升高而线性下降,即σF（H）= 675-6.1C0;恒载荷下氢致滞后断裂门槛应力随氢浓度对数升高而线性下降,即σHIC=669-124lnC0.

Tensile specimen of X-80 pipeline steel was strained to over 1% plastic deformation in air. The strained specimen was charged with hydrogen, and the charged specimen was strained in air. The flow stress and yield stress of the charged specimens are different from the uncharged. The difference is the hydrogen-induced additive stress, which can help the external stress to enhance the plastic deformation. The hydrogen-induced additive stress, sigma(ad), increases linearly with the hydrogen concentration, i.e, sigma(ad) = -14.1 + 3.89C(0). On the other hand, fracture stress during dynamically charging with hydrogen decreases linearly with hydrogen concentration in slow stain rate tests, i.e, sigma(F)(H) = 675 - 6.1C(0). The threshold stress decreases linearly with the logarithm of hydrogen concentration for the samples in constant load tests, i.e, sigma(HIC) = 669 - 124 ln C-0.