Technological method for improving equiaxed crystal ratio of bistable ferrite stainless steel continuous casting billets

Abstract

The invention provides a technological method for improving the equiaxed crystal ratio of bistable ferrite stainless steel continuous casting billets. The technological method comprises the steps of aprimary melting furnace, AOD, VOD, LF and continuous casting. According to the technological method provided by the invention, the equiaxed crystal ratio of the bistable ferrite stainless steel continuous casting billets is improved largely, and the cold machining and molding performances of ferrite stainless steel as well as the surface quality of products are improved; and the problems of nozzle clogging and blockage caused by TiN and TiOx generated by adding excessive Ti in the continuous casting technological process are solved effectively.

Description

technical field [0001] The invention belongs to the field of stainless steel smelting and casting, and in particular relates to a process method for increasing the equiaxed crystal ratio of bistable ferritic stainless steel continuous casting slabs. Background technique [0002] The carbon and nitrogen elements in ferritic stainless steel will have a great adverse effect on its corrosion resistance, weldability and formability. Therefore, reducing the carbon and nitrogen elements in steel as much as possible has always been the constant pursuit of smelters Ferritic stainless steel with carbon and nitrogen content less than 150ppm has gradually occupied the mainstream of the market. It is not economical or even difficult to obtain excellent material properties by means of content. Moreover, even if the W(C+N) content in the steel is reduced to below 150ppm, some properties (such as intergranular corrosion resistance in high temperature sensitized state) are difficult to achi...

AI Technical Summary

Problems solved by technology

However, the higher content of Ti and Zr required (the mass percentage of Ti is greater than 0.2%, and the mass percentage of Zr is greater than 0.1%) will lead to the formation of a large amount of TiN and Ti and Zr oxides in the smelting process, resulting in the failure of the continuous casting process. The occurrence of nozzle blockage will affect the surface quality of the product in severe cases

Chinese patent CN101845603A "A ferritic stainless steel for high-temperature end parts of automobile exhaust system and its manufacturing method", the equiaxed grain rate of ferritic continuous casting slab is improved by adding Ti, and the ferritic stainless steel is improved by adding Nb and W The high-temperature performance of the product, however, the continuous casting slab obtained under the required Ti content combined with the addition of electromagnetic stirring has an equiaxed crystal ratio of 40%, and its equiaxed crystal ratio is not high, so it cannot be completely guaranteed to be excellent in the later cold forming process. Excellent surface quality, while the application of electromagnetic stirring and post-grinding processes will increase the difficulty and cost of the process

[0009] At present, most of the relevant information on niobium-containing ferritic stainless steel focuses on material properties, but the influence of stabilizing elements Ti and Nb on the solidification structure of ultra-pure ferritic stainless steel continuous casting slabs, double-stabilized ultra-pure ferritic stainless steel Reasonable control of solidification structure, reasonable range of alloying elements, and reasonable control of smelting process conditions are rarely reported. At the same time, the optimized ratio of Nb and Ti bistable elements, the influence of C and N element content in steel on the solidification structure, and the stabilization The segregation behavior of elements (especially Nb), the influence of oxygen content in steel, and the influence of cooling rate and casting temperature have not been systematically reported so far.

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