Effects of Si on ductile-to-brittle transition behavior of a ferritic heat-resistant stainless steel
ZHANG Ying-bo1,2, ZOU De-ning1, LI Yu-nong1, WANG Yong2, XU Ran2, WANG Fan1
1. School of Metallurgical Engineering, Xi′an University of Architecture and Technology, Xi′an 710055, Shaanxi, China; 2. Shaanxi Special Equipment Inspection and Testing Institute, Xi′an 710048, Shaanxi, China
Abstract:The 18Cr-Al-Si ferritic heat-resistant stainless steel has excellent thermal conductivity and good high-temperature resistance for gas corrosion, and compounded addition with Al and Si elements to ensure its excellent resistance to high-temperature oxidation. This steel is a new type of material used for key structural connectors of supercritical and ultra critical power station boilers. In the past, the traditional water-jet forming method was mainly used for the processing of the connector material, but the production efficiency was low and the cost was high. When the room temperature stamping forming method is adopted, because the ferritic heat-resistant stainless steel plate is brittle, it is easy to generate cracks in the center of the thickness of the steel plate. When using warm stamping processing (ie processing in the toughness temperature range), the problem of cracking in the center of the steel plate can be avoided. In order to improve the production efficiency of the connecting parts, it is necessary to optimize and determine the technological parameters of the warm processing of the steel. The effect of ductile-brittle transition behavior of silicon content(mass fraction is 0%-0.9%)18Cr-Al-Si steel was studied by means of a series of Charpy impact test methods and by means of scanning electron microscope (SEM), transmission electron microscope(TEM) and energy dispersive spectrometer(EDS).The results show that with the increase of silicon content,the impact absorption energy at each test temperature gradually decreases,the ductile-brittle transition temperature(DBTT)increases, the proportion of cleavage plane area in the micro fracture gradually increases,and the dimple area gradually decreases.The silicon element has a great influence on the microstructure and precipitates of the annealed 18Cr-Al-Si steel. With the increase of silicon, the ferrite grain size in the steel gradually increases, and the M23C6 carbide gradually changes from small-sized strips or blocks. become long or large. The larger ferrite grain size and the precipitation of elongated or massive M23C6 carbides are the main factors that deteriorate the impact toughness of the steel.
张英波, 邹德宁, 李雨浓, 王勇, 徐冉, 王帆. 硅对铁素体耐热不锈钢韧脆转变行为的影响[J]. 钢铁, 2022, 57(8): 143-151.
ZHANG Ying-bo, ZOU De-ning, LI Yu-nong, WANG Yong, XU Ran, WANG Fan. Effects of Si on ductile-to-brittle transition behavior of a ferritic heat-resistant stainless steel[J]. Iron and Steel, 2022, 57(8): 143-151.
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