Pipe specially designed for harsh corrosive environment – super austenitic 904L stainless steel pipe

Super austenitic 904L stainless steel pipe is specially designed for harsh corrosive environment. Through reasonable optimization of chemical composition, the super austenitic 904L stainless steel pipe is a high alloyed super austenitic stainless steel with low C content. The 904L super austenitic stainless steel tube blank was successfully developed through a specific production process. In the process of research and development, A single slag refining process (CaO-SiO2-MgO-Al2O3) suitable for four-component slag system of ultra-low carbon stainless steel has been developed, which not only solves the problem of carbon recovery during smelting, but also can deeply desulfurize. The smelting operation effect of single slag method can reach the desulfurization and deoxidation effect equivalent to that of double slag method. Through experimental research, a scientific and reasonable addition process of rare earth, boron and other trace elements has been obtained, improving the processing performance of steel, and a suitable hot working technology has been developed.

Super-austenitic 904L stainless steel pipe, high-molybdenum corrosion-resistant super-austenitic stainless steel, is equivalent to the original stainless steel N08904 in the American standard ASTM with 20% chromium content and 25% nickel content, and the molybdenum content is increased to 4%~5%, and the copper element is added to further improve its pitting corrosion resistance and corrosion resistance. It is often used in strong corrosive environment, and the service life of conventional stainless steel is many times. Although this steel has excellent service performance, the effect of rare earth on the thermoplasticity of multi-element super austenitic stainless steel pipe was studied by high-temperature impact method, thermal torsion method and wedge rolling method, and the formation of rolling crack, the morphology of impact fracture and the segregation of alloy were also observed by metallographic and scanning electron microscope.

The experiment shows that the impact energy at 950~1200 ℃ can be increased by 20%, the critical reduction rate at 900~1200 ℃ can be increased by 15%, and the number of hot torsion at 950~1200 ℃ can be increased by 20-30%. The main reason for the improvement of thermoplasticity is that rare earth can improve the solidification process, refine the as-cast structure, reduce alloy segregation, and strengthen the grain boundary. The thermoplasticity of stainless steel is very important, which largely determines the qualification rate and the range of use of stainless steel products. Because the super austenitic 904L stainless steel pipe contains more and higher alloy elements, such as CrNiMoCu51, etc., the high temperature deformation resistance of steel is large, the as-cast structure is generally coarse, and sometimes there is a small amount of ferrite, resulting in poor thermoplasticity of the super austenitic 904L stainless steel pipe and difficult hot processing.