Huzhou Nanxun Yintuo Special Material Technology Co., Ltd. specializes in the development and production of high-quality ferritic stainless steel seamless pipe and tube and nickel-nickel alloys. The following introduces ferritic stainless steel.
Atmospheric corrosion resistance of ferritic stainless steel
Since ferritic stainless steel has good resistance to atmospheric corrosion, it has been recently used as the roof and curtain wall of buildings. However, the atmospheric environment in areas close to the sea is particularly harsh, especially the suspended particles in the sea and air are quite corrosive substances. Therefore, the high-chromium ferritic stainless steel used in these environments has been developed. Stainless steel resistant to atmospheric corrosion contains high chromium and high molybdenum, and a small amount of niobium and titanium are added. The steel actually contains 22% chromium and 1.2% molybdenum. Sufficient chromium and molybdenum are essential to improve the pitting resistance of stainless steel. With the increase of the number of cyclic corrosion test cycles, the rusted area of Type 304 and Type 316 austenitic stainless steel increases significantly. In contrast, for ferritic stainless steels such as 444 and RD steel grades, the rusted area increased slightly during the first 600 test cycles, and after a longer test cycle, the rusted area was saturated.
Intergranular corrosion resistance of ferritic stainless steel
410L or 409 stainless steel is used as a material for automobile exhaust emission control system due to its good corrosion resistance, formability and heat resistance. In recent years, the design temperature of automobile exhaust has increased. This is because the increase in automobile exhaust temperature can improve the conversion efficiency of catalytic converters and reduce harmful gases such as NOx, SOx, and hydrocarbon (HC) emissions. However, the increase in temperature may lead to worse corrosion conditions of the material. For example, chromium carbide will produce deposits on the muffler at the exhaust temperature, that is, at a temperature of 400~500C, it will lead to chromium depletion at the grain boundary and intergranular corrosion. Since the weld area is particularly sensitive to intergranular corrosion, it is necessary to improve the corrosion resistance of ferritic stainless steel containing 12% Cr. Another way to solve this problem is to develop new ferritic stainless steels.
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