Microstructure and properties of new stainless steel for corrosion resistant heating pipe
ZHAO Lei1, YAN Hai-tao1,2, MA Deng-de1, SHEN Peng1, LI Jie1, LIANG Cui-feng1
1. Zhenshi Group Eastern Special Steel Co., Ltd., Jiaxing 314005, Zhejiang, China; 2. Zhenshi Group HuaZhi Research Institute (ZheJiang) Co., Ltd., Jiaxing 314505, Zhejiang, China
Abstract:Stainless steel materials for electric water heater mainly include 310S、840 and other materials. During the process of using, the electric heating pipe is easy to scale, resulting in corrosion failure of heating pipe. In order to solve this problem, according to the service environment of heating pipe, Mo element was added on the basis of 310S composition system, other alloy composition systems were also optimized and adjusted, and a new stainless steel material for corrosion-resistant heating pipe was developed. The microstructure, mechanical properties and corrosion properties of a new type heating tube stainless steel in hot rolling solution pickling state were studied and compared with 310S steel. The change law of alloy structure with temperature under equilibrium condition was analyzed by Thermo-Calc thermodynamic software. It is shown that the σ phase precipitation begin at about 900 ℃, but the number is small. Under the same rolling procedure and heat treatment procedure as 310S, the average values of tensile strength (Rm), yield strength (Rp0.2) and elongation of hot-rolled solid solution pickling state of the new material are 611 MPa, 286 MPa, 52.8%, respectively. The overall strength is slightly higher than 310S, but the difference is small, and the elongation is slightly lower than 310S. The grain size of the new material is grade 5.5 and grade 7 in some areas. The grain size is slightly bigger than 310S, and there is little difference in whole. The average corrosion rates of new materials and 310S are 0.49 g/(m2·h) and 1.37 g/(m2·h) respectively. It can be seen that the pitting corrosion resistance of new materials is significantly better than 310S steel.
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ZHAO Lei, YAN Hai-tao, MA Deng-de, SHEN Peng, LI Jie, LIANG Cui-feng. Microstructure and properties of new stainless steel for corrosion resistant heating pipe[J]. China Metallurgy, 2022, 32(6): 117-122.
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