Molten steel continuous pouring method for extremely-low phosphorus-sulfur high alloy steel through single LF furnace and multiple tanks

Abstract

The invention provides a molten steel continuous pouring method for extremely-low phosphorus-sulfur high alloy steel through a single LF furnace and multiple tanks. Before production is conduced, to-be-used molten steel tanks and a to-be-used molten vacuum chamber which are used for low silicon-aluminum killed steel rinsing for a time are arranged, and after molten iron is desulfurized, sulfur is equal to or less than 0.0010%; after a converter starts blowing, active lime, light roasting dolomite and two-thirds ores are added, blowing is conducted for 4-5 min, deslagging is conducted in the molten iron, and then slagging is conducted again; blowing is conducted for 8.5-9.5min, when the temperature reaches 1400-1450 DEG C, steel tapping is conducted, steel tapping C is ensured to be 2.00-2.30%, and P is ensured to be less than 0.025%; before a decarburization furnace starts blowing, a carburant used for raising the temperature is added, when a terminal point C is 0.03-0.05%, steel tapping is conducted, and in the process of steel tapping, slag tapping is strictly prohibited; top slag Als of the LF furnace needs to be accurately controlled to be 0.015-0.020%; and the RH vacuum degree is equal to or less than 200 Pa, circulation is conducted for 30 min or more, and after vacuum is broken, argon bottom blowing is conducted for 15-20 min. Through the method, steel tapping P can be controlled to be 10-20 ppm, rephosphoration is within 15 ppm, and finished product P is within 35 ppm. The LF treatment period is shortened to 70 min, the number of continuous pouring tanks is increased to be four, and steel-iron materials are reduced 52 kg / t steel.

Description

technical field [0001] The invention belongs to the technical field of smelting technology, and in particular relates to a method for cleaning and continuous pouring of molten steel in multiple tanks in a single LF furnace for ultra-low phosphorus and sulfur high alloy steel. Background technique [0002] Very low-phosphorus, high-sulfur alloy steel, such as ultra-low temperature pressure vessel steel 9Ni, composition: nickel 9%, phosphorus less than 0.005%, sulfur less than 0.002%. About 20ppm. In order to control the phosphorus content of the finished product to meet the quality requirements, the tapping slag + molten steel slag removal process is adopted to control the phosphorus return of molten steel. After adopting this process, the LF treatment is forced to be divided into three steps: 1. Raise the temperature first when entering the station, but do not modify the steel slag to prevent phosphorus return after modification; 2. Remove slag from molten steel after heatin...

AI Technical Summary

Problems solved by technology

The problems in the above method: one is that the molten steel is seriously polluted due to the long processing time of the molten steel, and the quality of the steel is deteriorated

Second, because the number of single pouring tanks is too small, there are many waste products, and the consumption of various materials is large, resulting in high production costs per ton of steel