Method for producing steel for low-nitrogen stranded wire by use of non-vacuum process of converter

Abstract

The invention discloses a method for producing steel for a low-nitrogen stranded wire by use of the non-vacuum process of a converter, belonging to the technical field of steel for prestressed steel strand. The method comprises the steps of molten iron desulphurization and slagging off, converter smelting, slag blocking and tapping, steel ladle deoxidization and alloying, steel ladle slag modification, LF steel ladle refining, Si-Ca wire feeding, steel ladle bottom soft argon blowing, full-protection casting of 160mm*160mm small square billet and terminal electromagnetic stirring matched with a crystallizer; the technical parameters of control are as follows: the converter adopts double-slag operation, the end point carbon is under 0.20-0.30% control, the tapping temperature is 1,600-1,630 DEG C, and the thickness of roughing slag is 0-50mm; a micro-nitrogen carburant (N: 0.005-0.025%) is matched with 5kg of carbon per ton of steel, 1.5kg of Si-Ca-Ba per ton of steel is added for deoxidization, and 4kg of synthetic slag per ton of steel is added; the oxygen activity outside the LF refining station is controlled to be less than or equal to 10ppm, and the content of FeO and MnO in final slag is less than or equal to 3%; and 1m Ca-Si wire per ton of steel is fed, and the soft argon blowing time is 12-30 minutes. The method disclosed by the invention remarkably lowers the production cost and reaches the nitrogen quality control level of steel for producing a stranded wire in a vacuum degassing process.

Description

technical field [0001] The invention belongs to the technical field of steel for prestressed steel strands, and in particular relates to a method for producing steel for low nitrogen strands using a converter non-vacuum process, which is suitable for producing nitrogen content in converters, LF furnaces, and billet continuous casting processes. The production method of steel for steel strands (0.78-0.90% carbon content in steel) less than 40ppm is applied to high-grade building prestressed concrete. Background technique [0002] Under certain circumstances, the nitrogen in the steel will reduce the performance of the material, and its presence will reduce the toughness and plasticity of the steel; cause the steel to produce strain aging, age precipitation hardening or age brittleness; cause the steel to be blue brittle, red hot brittle, cold Brittle; make the center loose or form microscopic pores; produce hairlines and bubbles; affect the deep drawing performance, welding p...

AI Technical Summary

Problems solved by technology

This results in a large fluctuation range of product strength, toughness and other indicators after drawing by the product enterprise, and a low qualified rate of finished products; on the other hand, it is easy to cause brittle fracture during drawing, and in severe cases, it cannot be processed

[0004] The nitrogen content of high-carbon steel (carbon content greater than 0.77%) produced by Japanese companies is generally controlled below 40ppm. The main difference lies in the control of different processes. Japanese companies generally use molten iron three-stranding process, converter or electric furnace, and LF furnace to produce high-carbon steel. Refining+vacuum degassing, bloom opening, two-fire process, stable product quality, high process production cost