Manufactring method for smelting stainless steel containing N biphase

Abstract

A method for smelting double-phase with N stain less steel characterizes 1. carrying out the primary smelting according to the return oxygen blowing wethod 2. smelting qualified double stainless steel with N in composition and purity (1) blown temperature is higher than or equal to 1540deg,c (2) carbon elimination: blowing N2, O2 mixed gas for decarbonization and increasing N2 and process the increased temperature O2 / N2=4, sampling to regulated the components: when c=0.10%, stop blowing O2 but Ar instead, adding prerecovered stags for 7min, total sample analysis including all stags and adding recovery stags (3) recovery: blowing Ar and forcing to eliminate O, blowing N to increase N, sample analysis, fine adjustment to the composition to get the cast ingot.

Description

technical field [0001] The invention relates to a method for smelting and casting stainless steel in the metallurgical industry, in particular to a method for smelting duplex stainless steel. Background technique [0002] Stainless steel is a common alloy steel, which can be generally divided into austenitic stainless steel, ferritic stainless steel, martensitic stainless steel and duplex stainless steel. The so-called duplex stainless steel is that in its solid solution structure, the austenite phase and the ferrite phase each account for about 50%, and generally the content of the lesser phase needs to reach at least 30%. Duplex stainless steel not only has the excellent toughness and weldability of ferritic stainless steel, but also has the high strength and chloride stress corrosion resistance of austenitic stainless steel. Medium, especially in high chloride ion environment and high stress corrosion conditions for long-term use, widely used in petroleum, marine and che...

AI Technical Summary

Problems solved by technology

Relatively speaking, the N-containing duplex stainless steel started earlier in European, American, Japanese and Korean steel mills, the production process is more mature, and there are many grades; while my country started late, not only the production scale is small, the grades are also relatively single, and the smelting process It is still in the stage of exploration, especially the control of the composition of C and N is difficult, so the metallurgical quality is not stable enough, and there are no literature reports on detailed production methods at home and abroad.

[0005] Theoretically, there are two ways to add nitrogen (N) to molten stainless steel: one is to add N-containing alloys, but due to the low N content in N-containing alloys (such as manganese nitride, chromium nitride, etc.) The composition is unstable (that is, the composition fluctuates greatly), causing the extremely unstable N recovery rate, making it difficult to control the N content of the duplex stainless steel product, and causing the product to be scrapped in severe cases. In addition, N-containing alloys such as manganese nitride and chromium nitride The price is relatively high, which is also a restrictive factor for normal production; the other is to blow nitrogen into the molten steel (in actual production, the AOD furnace is mainly a mixed gas containing nitrogen and oxygen in the early stage of refining, on the one hand for decarburization, on the other hand Nitrogen increase

), this method is more economical and practical, and the favorable condition is that N has a certain solubility in the stainless steel liquid, and the price of nitrogen is relatively cheap; The partial pressure of nitrogen in the atmosphere, the temperature of molten steel, and the sulfur and oxygen content in steel are affected by many factors, and the upper and lower limits of N content in molten steel are very narrow. For relatively high-grade N-containing duplex stainless steel, the N content The upper and lower limits are only 0.05% (that is, 500ppm, for a specific N-containing duplex stainless steel, if the N content is too high or too low, it will affect the phase balance in the steel and affect the performance of the steel

), so it is very difficult to control nitrogen in steel, and it is very difficult to produce and smelt