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研究了不同炉批的ASTM A470叶轮转子钢在蒸汽杂质NaCl溶液中的电化学特性及应力腐蚀开裂敏感性。在pH=10,0.01M和0.613M(3.5wt%)NaCl液液中,这种钢在室温与沸点下均显示有钝化行为。钝化膜的破裂电位随Cl~-浓度与温度增加而降低。慢应变速率拉伸试验表明,在100℃下,每个炉批均有一延伸率极小值出现在接近开路电位的阴极区中。在阴极区,延伸率随温度降低而降低。扫描电镜断口分析表明,仅有少量准解理区分布在断口表面周围,未观察到沿晶破坏。可以认为,这种钢在碱性氯化钠液液中对应力腐蚀稍有敏感,其破坏机理取决于电位条件,既受膜的破裂影响,也与氢助开裂有关。
The electrochemical characteristics and stress corrosion cracking resistance of ASTM A470 impeller rotor steels with different furnace lots in steam impurity NaCl solution were studied. In steel solutions of pH = 10, 0.01 M and 0.613 M (3.5 wt%) NaCl, this steel showed passivation at both room and boiling points. The rupture potential of passivation film decreases with the increase of Cl ~ - concentration and temperature. Slow strain rate tensile tests showed that at 100 ° C, a minimum of elongation in each batch appeared in the cathode region near the open circuit potential. In the cathode zone, the elongation decreases with decreasing temperature. Scanning electron microscopy fracture analysis showed that only a small amount of quasi-cleavage zone located around the fracture surface, no damage observed along the crystal. It can be considered that this kind of steel is slightly sensitive to stress corrosion in alkaline solution of sodium chloride, and its failure mechanism depends on the potential conditions, which are both affected by the rupture of the membrane and also related to hydrogen cracking.