Method for controlling nitrogen content during smelting process of LF (Ladle Furnace)

Abstract

The invention discloses a method for controlling nitrogen content during a smelting process of an LF (Ladle Furnace). The method comprises the following steps: (1), oxygen in molten steel and top slags in the molten steel in the LF is removed, the flow of argon is adjusted to be 250-300 L / min; mixing and desulfurizing is performed for 3-5 min; a slag surface is blown off for a diameter of 400-500mm; (2), practical argon bottom-blowing control is performed during an electrifying and temperature-raising process; a slag blowing diameter D is greater than or equal to 170 mm and is smaller than orequal to 220 mm; (3), during an electrifying and temperature-raising and slag melting process, a molten steel deoxidant is added in for 0.2-0.3 kg per ton of steel every 2-3 min; the content of CaC2in the molten steel deoxidant is above 60%; (4), the contents of carbon, silicon, manganese and aluminum in the steel are reduced; adjustment is performed for 1-2 times, so that the times for large-area exposure of the molten steel are reduced to one; (5), the top slag blowing-off diameter is adjusted to 1-50 mm before pure calcium line feeding; and line feeding is performed for 30 S, stopped for10 S, performed for 30 S and stopped for 10 S until line feeding is finished. According to the method, reinforced molten steel and top slag deoxidation is adopted, large argon flow mixing and desulfurizing time is shortened; the argon consumption amount per ton of steel is lowered; aluminum loss in the molten steel is reduced; a nitrogen increasing amount in a smelting process is controlled; and therefore the nitrogen content of the molten steel product meets requirement of the nitrogen content of high-quality steel.

Description

technical field [0001] The invention belongs to the technical field of steelmaking, in particular to a method for controlling nitrogen content in the smelting process of an LF refining furnace. Background technique [0002] The control of nitrogen in 120t molten steel has always been a difficult problem. Not only has many furnaces been downgraded and changed due to excessive nitrogen content, but also excessive nitrogen content in the molten steel will also affect the quality of the steel. Therefore, how to effectively control the steel To reduce the nitrogen content in the liquid so that the nitrogen content in the steel meets the nitrogen content requirements of high-quality steel, an effective method must be found. The original nitrogen control method is: (1) the deoxidation of the top slag is not complete, and the desulfurization of the large argon flow is carried out; (2) the actual bottom blowing argon control during the power transmission and temperature raising proce...

AI Technical Summary

Problems solved by technology

[0002] The control of nitrogen in 120t molten steel has always been a difficult problem. Not only has many furnaces been downgraded and changed due to excessive nitrogen content, but also excessive nitrogen content in the molten steel will also affect the quality of the steel. Therefore, how to effectively control the steel Nitrogen content in the liquid, so that the nitrogen content in the steel meets the nitrogen content requirements of high-quality steel, an effective method must be found

The original nitrogen control method is: (1) the deoxidation of the top slag is not complete, and the desulfurization of the large argon flow is carried out; (2) the actual bottom blowing argon control during the power transmission and temperature raising process: the diameter of the exposed surface of the molten steel is 300mm≤D≤450mm; (3 ) The submerged arc effect is poor during power transmission; (4) The number of component adjustments is 3 to 5 times; (5) The area of ​​the slag surface is large by argon blowing during the wire feeding process, and the diameter of the exposed surface is about 200mm; according to the original nitrogen control method, The effect is as follows: (1) Because the top slag deoxidation is not complete, the stirring desulfurization time of large argon gas flow is long, an average of 6 minutes. Although the sulfur can be desulfurized to the required level, the argon consumption is relatively high, and the argon gas consumption per unit is 0.078 Nm 3 / t, and the loss of aluminum components in molten steel is serious, with an aluminum loss of 0.008% per minute, and the risk of nodulation is also increased; (2) Due to the large flow control of argon gas during the power transmission and temperature raising process, the molten steel is in contact with air, resulting in steel (3) Due to the poor gas permeability of the top slag and the poor submerged arc effect, the transfer of nitrogen in the air to the molten steel is accelerated; (4) The frequent adjustment of the composition leads to an increase in the exposure of the molten steel, which increases the The risk of nitrogen absorption; (5) Feeding pure calcium wire, the flow of argon gas is relatively large during the wire feeding process, which leads to intensified splashing and aggravates the increase of nitrogen in molten steel