Abstract

The features of the chemical composition and structural-phase state of the metal samples of 18Cr–10Ni steel (AISI 304) are investigated which could promote the appearance of general corrosion damage and formation of pittings on parts made of this steel under the action of an aggressive environment. It is established that the sulfur content in steel exceeds the level established by the standard for this steel (<0.03% S) almost tenfold. Therefore, it contains about 3 vol % manganese sulfides with a size of 1–~50 μm which form stitches and accumulations along the direction of rolling. According to the published data, manganese sulfide particles (MnS) in particular are the most corrosive in corrosion-resistant steels and alloys. They manyfold decrease the ability of Fe–Cr–Ni steels to passivate in a corrosive environment. The formation of FeSH⁺ ions requires a high concentration of S^2– ions. The larger is the inclusions of sulfide particles, the higher is their ability to decrease the corrosion resistance of steel. Therefore, the large size of the MnS particles found in the steel plays an important negative role. It is shown that an additional factor promoting the decrease in the corrosion resistance of the steel under study is the presence of deformation martensite in the surface layer of the studied steel which is formed in the machining process during manufacturing by cutting and grinding parts from a billet. The appearance of this martensite is due to the low concentration of austenite-forming elements (0.01–0.04% C, 7.96–8.23% Ni). In the modified Scheffler–Delong diagram, steel is in the region, where the formation of martensite is possible, the calculated value of M_d(30/50) for it was 28°C. According to the published data, deformation martensite in steels of the 18–10 type causes a decrease in their resistance to pitting corrosion in solutions of acids and salts. It is shown that the presence of an electric potential activates the corrosive action on the samples of 18Cr–10Ni steel in an acidic environment. It is concluded that the corrosion damage of the parts made of the studied steel is facilitated by the presence of accumulations of sulfide particles in the individual areas of the metal combined with the presence of deformation martensite in these areas.

中文翻译：

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决定 18Cr-10Ni 钢零件耐腐蚀性能的化学成分和结构相状态的特征

摘要

研究了 18Cr-10Ni 钢 (AISI 304) 金属样品的化学成分和结构相状态的特征，这些特征可以促进由该钢制成的零件在腐蚀作用下出现全面腐蚀损伤和点蚀的形成。侵略性的环境。已确定钢中的硫含量几乎超过该钢标准规定的水平 (<0.03% S) 近十倍。因此，它含有大约 3 vol% 的硫化锰，尺寸为 1-~50 μm，沿轧制方向形成针迹和堆积物。根据已公布的数据，硫化锰颗粒 (MnS) 在耐腐蚀钢和合金中的腐蚀性最强。它们会成倍地降低 Fe-Cr-Ni 钢在腐蚀环境中的钝化能力。FeSH的形成⁺离子需要高浓度的 S ^2–离子。硫化物颗粒夹杂物越大，其降低钢的耐蚀性的能力越高。因此，钢中发现的大尺寸 MnS 颗粒起着重要的负面作用。结果表明，促进所研究钢的耐腐蚀性能下降的另一个因素是所研究钢的表层存在变形马氏体，该变形马氏体是在制造过程中通过切削和磨削钢坯零件的加工过程中形成的。 . 这种马氏体的出现是由于形成奥氏体的元素浓度低（0.01-0.04% C，7.96-8.23% Ni）。在修正的Scheffler-Delong图中，钢处于可能形成马氏体的区域，M _d(30/50)的计算值因为当时是 28°C。根据已发表的数据，18-10 型钢中的变形马氏体会导致其在酸和盐溶液中的抗点蚀能力下降。结果表明，在酸性环境中，电位的存在会激活对 18Cr-10Ni 钢样品的腐蚀作用。得出的结论是，由研究钢制成的零件的腐蚀损坏是由硫化物颗粒在金属的各个区域中的积累以及这些区域中变形马氏体的存在促进的。