Smelting method for accurately controlling nitrogen content in steel

Abstract

The invention discloses a smelting method for accurately controlling the nitrogen content in steel, which comprises the procedures of converter smelting, LF furnace refining and VD furnace refining, wherein the vacuumizing process time of the VD furnace refining procedure is less than or equal to 10 min, bottom blowing stirring is forbidden in the vacuumizing process, bottom blowing nitrogen stirring is started when the vacuum degree is less than or equal to 67 Pa, the nitrogen flow is controlled to be 30-80 NL / min, and the vacuum time is controlled to be 6-7 min. The technology that a small amount of manganese nitride alloy is added in the stokehole tapping process to increase nitrogen, nitrogen blowing is carried out in the refining process and nitrogen blowing is carried out in the VD high-vacuum process is adopted, the requirement that the nitrogen content hits the target range at a time after VD vacuum treatment is achieved, the quality stability of nitrogen-containing steel is improved, the denitrification rate in the VD furnace refining process is less than or equal to 45%, and the loss rate is 5-6 ppm / min.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a smelting method for precisely controlling the nitrogen content in steel. Background technique [0002] Nitrogen is a harmful element for most steel types, but it is a beneficial alloying element in some stainless steels, non-quenched and tempered steels, and some high-toughness structural steels. The nature of nitrogen is similar to that of carbon, and it is the main element as an interstitial atom, which is determined by its small atomic size and electronic layer structure. His role in steel is mainly to precipitate fine alloy nitrides in the cooling process after rolling or heading to achieve the purpose of dispersion strengthening. [0003] Nitrogen increase is a difficult problem for the steelmaking process, especially for steel types that have a narrow range of nitrogen content requirements. Different smelting equipment and conditions require matching nitro...

AI Technical Summary

Problems solved by technology

The vast majority of iron and steel enterprises use nitrogen-containing alloys in appropriate processes or feed nitrogen-containing alloy wires and bottom-blown nitrogen gas stirring in the refining process to achieve nitrogen increase. These methods of nitrogen increase are more effective methods, but there are also disadvantages : 1) Nitrogen-increasing of nitrogen-containing alloy is stable, but the price is relatively expensive. 2) Nitrogen-increasing of nitrogen-containing alloy wire is also relatively stable, but the molten steel is violently tumbling during the wire feeding process, which easily causes secondary pollution of molten steel. 3) Refining Too long nitrogen blowing time will affect the refining effect and the nitrogen increase will be unstable