Process for washing, pre-desulfurizing and refining tapping steel slag of converter

Abstract

The invention relates to a process for washing, pre-desulfurizing and refining tapping steel slag of a converter, which belongs to the technical field of steel making. The process is characterized in that the steel-tapping temperature of the converter is 1,650-1,720DEG C; strongly deoxidizing by adopting ferro-aluminium the addition of which is 3-5kg / t of steel when the steel is tapped for 1.5min; adding synthetic slag the addition of which is 5-8kg / t of steel at the bottom of a steel ladle before tapping steel; lime the addition of which is 4-6kg / t of steel is continuously added along steel stream when the steel is tapped for 2 min; the flow rate of argon gas bottom blowing from the ladle in the steel tapping process is controlled to be 3-5NL / (min.t); aluminum particles the addition of which is 0.5-0.8kg / t of steel are added into a slag surface after finishing tapping for deoxidizing the slag surface; and after finishing slag washing, the oxidability of steel slag is expressed by the following relationship: the total contents of FeO and MnO is les than or equal to 3.5 percent and the performance index of converter slag (in percentage by weight) is the weight ratio of CaO to (SiO2.Al2O3) being 0.4-0.5. The invention has the advantages that the sulfur content in the steel is desorbed from 90ppm-110ppm to within 60ppm by using a slag-washing control process, the desulfurization rate for slag washing can reach 30-45.45 percent and the sulfur content of end steel in an LF converter is reduced; the invention creates favorable preconditions for rapid deep desulfurization and relieves the pressure of the refining station; and in addition, the method has simple operation and is convenient to achieve the requirement of scale production.

Description

technical field [0001] The invention belongs to the technical field of steelmaking, and in particular relates to a refining process for washing and pre-desulfurization of slag from a converter, especially when smelting low-sulfur steel, creating a good precondition for rapid and deep desulfurization in LF furnace refining, so as to realize the stability of sulfur content in steel control. Background technique [0002] In high-quality steel, sulfur is a harmful element except for special steel types. In addition to causing hot embrittlement of steel, it can also affect the mechanical properties of steel by forming sulfide inclusions; when the sulfur content in steel is controlled to be high, The ductility and toughness of steel are reduced, especially the impact toughness of steel; sulfur has a great influence on the hot deformation processability and weldability of steel; when the sulfur content is high, it will damage the corrosion resistance of steel and cause corrosion on...

AI Technical Summary

Problems solved by technology

[0003] Chinese patent 200710158648.1 discloses a non-refining steel slag washing process. The invention adopts continuous feeding of slag washing material into the molten steel, and then sends the molten steel to the line feeding station for calcium treatment. It does not need to go through the refining equipment and then send it to the variety production line. This method deoxidizes the molten steel, removes the inclusions in the steel, and improves the quality of the slab. The characteristic of this method is that only the deoxidation and inclusion removal analysis of the slag washing process is carried out, and the desulfurization process of the slag washing process is not studied.

[0004] Chinese patent 200810054589.8 discloses a rapid desulfurization method of converter tapping slag washing and refining furnace. The invention includes two steps of tapping slag washing and LF refining. Tapping adopts weak deoxidation, slag washing is added with pre-melted slag and lime, and then refined in LF furnace The sulfur content in steel can be controlled within 0.015%. This method is characterized by the desulfurization process of weakly deoxidized steel for tapping. The slag washing only uses special pre-melted slag, and the slag washing process and desulfurization are not affected during the slag washing process. effect research

[0005] The current status of the process: the sulfur content in steel is generally desulfurized by the LF furnace refining process. For high-quality steel grades with a sulfur content of ≤0.002%, due to the high sulfur content in the LF furnace to the station steel, refining The task is heavy, the production organization is difficult, and there is no patented technology related to tapping slag washing to reduce the sulfur content of the LF furnace to the station for the tapped strong deoxidized steel