En24钢在海水中的应力腐蚀

用恒位移弯曲试验,慢应变速率试验、动电位扫描和浸蚀试验研究了En24钢在海水中的应力腐蚀特性。结果表明,En24钢的环境敏感断裂倾向随强度降低而降低;强度低于临界值,则不出现应力腐蚀裂缝。外加电位对En24钢的环境敏感特性有重要影响,裂缝扩展平台速度于-900mV处出现极小值。依据裂缝扩展动力学、断口形貌、物理冶金参数和电化学等方面的判据,认为En24钢在海水中的应力腐蚀与电位密切相关。低于-900mV,属氢致开裂;高于-900mV,则由阳极溶解过程所制约;在一定电位范围内,不排除两种机理共同作用的可能性。

STRESS CORROSION CRACKING OF En 24 STEEL IN SEA WATER

Stress corrosion cracking of En 24 steel has been systematically investigated using constant displacement cantilever beam tests, slow strain rate tests,potentiodynamic polarization and etching technique. The experiments were performed in natural sea water at various applied potentials and a range of heat treatments was used to obtain hardness from 250 to 550 kgfmm~(-2). The results show that the trend of environment sensitive fracture of En 24 steel decreases with the decrease of strength level. There is a critical strength level, below which no SCC is observed. The stress corrosion susceptibility is dependent upon applied potential, being least at an applied potential of-900 mV(SCE). The experimental data, including crack growth rates, fractographs, physico-metallurgical and electrochemical parameters etc, suggest that the mechanism of SCC of En 24 steel is closely related to the applied potential. At potentials more negative than-900 mV, hydrogen induced cracking occurs. From-570 to-900 mV, environmentally assisted cracking results from an anodic dissolution mechanism while both mechanisms may be operative at potentials near to-900 mV.