钙处理对AH36船体钢耐点蚀性能的影响

为提高AH36钢的耐海水腐蚀性能,炼钢时引入了钢水钙处理工艺.本文通过室内间浸挂片试验、交流阻抗试验、动电位极化试验及极化试验后的SEM分析,研究了钙处理对AH36钢中的夹杂物及耐点蚀性能的影响.结果表明:变性夹杂物中的CaS对钙处理钢的耐点蚀性能有明显的影响.通过钙处理把钢中氧化铝夹杂、硅铝酸盐夹杂等球化变性成无CaS或低CaS的球状CaO-Al2O3复合夹杂,可有效提高钢的耐点蚀性能;变性球状复合夹杂中含较多的CaS会促进诱发夹杂物周围基体腐蚀,提高点蚀诱发敏感性;含硫量较高的AH36钢在钙处理不充分时,形成CaS夹杂或以CaS为主的复合夹杂,会使AH36钢的耐点蚀性能恶化.

Effect of calcium-treatment on resistance against pitting corrosion of AH36 hull structural steel

In order to improve the corrosion resistance of AH36 hull structural steel in seawater, calcium-treatment of molted steel was introduced into its steelmaking procedure. The effect of calcium-treatment on inclusions and resistance against pitting corrosion of AH36 steel was studied by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and other test methods such as indoor interval immersion tests, AC impedance tests, and potentiodynamic polarization tests combined with SEM analysis after polarization tests were also included. The results show that the content of CaS in the modified inclusions after calcium-treatment influences the resistance against pitting corrosion significantly. The resistance against pitting corrosion of AH36 steel enhance significantly after calcium-treatment while Al₂O₃ and aluminosilicate inclusions are transformed into CaO-Al₂O₃ spherical complex inclusions without CaS or containing few CaS. The pitting susceptibility of calcium-treated steel will be enhanced with the increase of the content of CaS in the modified spherical complex inclusions, because the corrosion of substrate around the modified inclusions containing more CaS can be induced more easily. When calcium-treatment of the AH36 steel containing higher level of S is not carried out sufficiently, CaS inclusions or complex inclusions mainly composed of CaS may be formed, which results in a deterioration in the resistance against pitting corrosion.