High Temperature Corrosive Environment in a Sintering Plant for Pig Iron Production and Its Effect on Different Steel Grades
The harsh environment in a sintering plant for pig iron production leads to high temperature corrosion of the sinter grates. In the present study, a detailed analysis of the corrosives in such applications is given to understand materials failure. Various steels are tested, revealing effects of various alloying concepts, the resulting phases and their corrosive behavior in this complex corrosive environment at ≈900 °C. In order to understand the underlying corrosion mechanisms, detailed analyses are performed. Results indicate mainly chlorine, sulfur, and oxidation based corrosive decay at elevated temperature and a high relevance of protecting alloying elements within the steels.
Formation of Si diffusion layer on stainless steels and their high temperature corrosion resistance in molten salt
Abstract The surface alloying of Si into SUS430 and SUS304 stainless steels was achieved by a pack-cementation method. A high-temperature corrosion test was undertaken under a corrosive ash in a high-temperature gas, which simulated the environment of a waste incinerator. The effect of the surface alloying of Si on the high temperature corrosion resistance of these stainless steels was examined. The result of the corrosion test showed that the corrosion mass loss of the siliconized stainless steel was lower than that of non-treated stainless steel. It was thought that the high temperature corrosion resistance in the corrosive ash containing large amounts of molten salt was improved by the surface alloying of Si. The change in corrosion loss with test time in the corrosive ash was also examined. The corrosion loss of the non-treated stainless steels rapidly increased. On the other hand, the corrosion rate of the siliconized stainless steels was small. It was found from the observation and EPMA analysis of a cross-section of the specimen after the corrosion test that, for the non-treated stainless steels, the metallic elements were dissolved into the molten salt. On the other hand, for the siliconized stainless steels, a scale consisting of silicon oxide was formed on the steels. As a result, the dissolved metallic elements were small. The electrochemical studies indicated that there was an effect of the surface alloying of Si on the hot corrosion resistance of the stainless steels. Hence, the corrosion potentials of the siliconized steels were higher than those of the non-treated steels. The increase in the anodic current densities for the siliconized steels was smaller than that for the non-treated steels. It was thought that the electrochemical corrosion reaction was difficult to occur due to the surface alloying of Si into the stainless steels.
High temperature corrosion behavior of siliconized 310 stainless steel
Abstract Surface alloying of Si into AISI 310 austenitic stainless steel (SS) to increase its high temperature corrosion resistance was attempted by employing pack cementation process. High temperature corrosion resistances of AISI 310 SS with or without siliconization treatment were evaluated in air and in CO/CO2 gas mixtures at 700, 750 and 800°C. The experimental results showed that the weight losses for both 310 SS and siliconized 310 SS in CO/CO2=10/1 reducing gas environment were less than those in air atmosphere at the temperatures tested. Furthermore, siliconization treatment provided better high temperature corrosion resistance for 310 SS both in air and in reducing gas environment. Compositional and structural analyses showed that the oxides formed on 310 stainless steel were composed of an outer spinel of Cr/Mn/Fe oxide and an inner layer of chromium oxide in air and reducing gas environments. For siliconized stainless steel, SiO2 was found in the oxide layer after high temperature exposure in the gas environments tested.