Method for producing ultra-low phosphoretic steel by molten steel dephosphorising outside furnace

Abstract

The invention provides a method to produce ultra low phosphorus steel by out-of-furnace dephosphorization, in particular to a controlling method to control phosphorus in steel during ultra low phosphorus steel production process. The invention is done according to the following steps: (1) when converter tapping, the weight percent of end phosphorus content is less than 0.013 percent and dephosphorization flux is added along with steel flow stream to ladle at the same time; (2) slag-stopping and non-deoxidation tapping is adopted; (3) after tapping, remove dephosphorization flux in the ladle; (4) after flux removal, refining treatment such as heating, deoxidation alloying and desulphurization; (5) continuous casting is done. The invention is convenient for operation, high efficiency of dephosphorization, short time consumption, and stable dephosphorization effect which can satisfy dephosphorization requirement of different content ultra low phosphorus molten steel by dephosphorization during the tapping without increase treatment time.

Description

Technical field [0001] The invention relates to a method for smelting steel grades, in particular to a method for controlling phosphorus in steel when producing ultra-low phosphorous steel. Background technique [0002] Phosphorus in steel is generally considered to be a harmful element. Phosphorus segregates more severely during the solidification of molten steel, which significantly reduces the toughness of steel. Especially under low temperature conditions, the deterioration of toughness is more significant, leading to the "cold brittleness" of steel. The segregation of steel is also easy to make the local structure of the steel abnormal, causing anisotropy, and it is also detrimental to the welding performance, causing welding cracks. For this reason, some low-temperature steels, marine steels, hydrogen-induced cracking steels and some thick steel plates require the phosphorus content of the steel to be less than 0.01% or even 0.005%. Therefore, many metallurgical workers hav...

AI Technical Summary

Problems solved by technology

This method has strict requirements on the phosphorus content of the tapping water and the tapping temperature, the dephosphorization treatment takes a long time, and the process control is complicated

Low-phosphorus steels often have lower requirements for sulfur in steel. According to this method, the molten steel is dephosphorized and slag removed, then deoxidized and alloyed, and new slag is refined and desulfurized, which undoubtedly prolongs the production cycle.