1 000 MPa级高强钢焊接件的氢脆敏感性研究

利用氢渗透试验、慢应变速率拉伸试验(SSRT)研究了1 000MPa级高强钢(HSS)焊接件在海水中的氢渗透行为及其应力腐蚀敏感性,结合SEM观察了试样的断口特征,并利用电化学试验和显微组织观察分析了焊接件不同区域的氢脆特征。结果表明:相对于焊缝区(WM)和母材区(BM),热影响区(HAZ)的自腐蚀电位最负、析氢电位最正,更容易发生腐蚀和析氢行为。热影响区的氢扩散系数最大,具有较强的吸氢倾向。动态电化学充氢对高强钢焊接件的影响主要体现在对塑性的损减方面;随着极化电位的负移,高强钢焊接件的强度没有明显变化,但断面收缩率、断后延伸率均减小,断裂方式逐渐由韧性断裂变为解理断裂;当极化电位约为-930mV(vs SCE)时,高强钢焊接件的氢脆系数达25%;在不同充氢极化电位下,焊接件试样的断裂位置多在热影响区。

Hydrogen Embrittlement Susceptibility of 1 000 MPa Grade High Strength Steel Weldment

Hydrogen permeation behavior and stress corrosion sensitivity of 1 000 MPa grade high strength steel (HSS) weldment in sea water were studied by hydrogen permeation test and slow strain rate test (SSRT). The fracture characteristics were observed by SEM. Electrochemical test and microstructure observation were also applied to research the hydrogen embrittlement (HE) of the weldment. The results showed that heat affected zone (HAZ) compared with the weld material (WM) and the base metal(BM) had the most negative open circuit potential(OCP) and most positive hydrogen evolution potential, which meant hydrogen evolution and corrosion would be easier to take place in the HAZ. The HAZ of high strength steel weldment had a maximum hydrogen diffusion coefficient and strong tendency to absorb hydrogen. The effect of dynamic electrochemical hydrogen charging on the weldment of high strength steel mainly reflected in the reduction of its plasticity. The strength of the high strength steel weldment showed slight differences under various polarization potentials. While with polarization potential negative shifted, the shrinkage and the elongation decreased and the fracture mode gradually changed from ductile to cleavage. The hydrogen embrittlement coefficient of high strength steel weldment reached the threshold of 25% while the cathodic potential was about -930 mV (vs SCE). The fracture locations of the specimen were mostly in the HAZ under different cathodic potentials.