Smelting method for controlling content of nitrogen in low-carbon steel

Abstract

The invention relates to a smelting method for controlling the content of nitrogen in low-carbon steel, which belongs to the technical field of steelmaking. The process characteristics are as follows: the smelting slag of a converter is controlled to be 60kg / t steel-120kg / t steel, and the alkalinity is 5 to 7; the circular flow is tapped and strongly deoxidized, and slag is added into the bottom of a ladle before tapping; the arrival temperature of an LF furnace is ensured, the LF furnace refines and the primary heating time is controlled to be 1min to 15min, so as to reduce nitrogen increase; through RH vacuum treatment, the flow of argon is controlled and increased, the vacuum treatment time is more than or equal to 10min and the vacuum degree, and heat insulation agent is uniformly spread on the surface of the ladle after the vacuum treatment; a double-loop suture sleeve and a 3mm-7mm washer are adopted in the casting process and are sealed and protected by argon; and covering agent is added onto the molten steel surface, and the covering effect of the molten steel surface is ensured in the whole casting process. The smelting method for controlling the content of nitrogen in low-carbon steel has the advantages of successfully controlling the nitrogen content of high-grade low carbon steel to be within 30ppm, and providing technical guarantee for the development of high-grade steel, so that the performance of continuous cast ingots and steel sheets is greatly improved.

Description

technical field [0001] The invention belongs to the technical field of steelmaking, and in particular relates to a smelting process for controlling nitrogen content in low-carbon steel, in particular to smelting high-grade steel grades to realize stable control of nitrogen content in steel. Background technique [0002] Nitrogen is generally regarded as an impurity element in steel, except for special steel types. When the nitrogen content in steel is high, it can cause aging embrittlement of steel, reduce the impact toughness of steel, and also cause adverse effects such as cold brittleness of steel; The precipitation of nitrides in the steel has a very significant effect on improving the yield strength of the steel. When heated to a certain temperature range, the strength of the steel increases, the impact toughness decreases, and the phenomenon of "blue embrittlement" occurs. Reducing the nitrogen content in the steel can improve the yield strength of the steel. In additi...

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Problems solved by technology

[0003] Chinese patent 200710704833.7 discloses a steelmaking method using weak deoxidation of converter tapping to reduce nitrogen content in steel. This invention uses weak deoxidation of converter tapping to make steel have a high oxygen content to prevent molten steel from absorbing nitrogen from the air After adopting this method, the nitrogen content in the steel can be controlled within 30ppm. The disadvantage of this method is that only a single control measure is used to control the nitrogen content in the tapping process, and it is only suitable for the control of the nitrogen content in weakly deoxidized steel.

[0004] Chinese patent 200910300110.9 discloses a method of controlling the nitrogen content of aluminum deoxidized steel produced by converter process. The invention adopts the control of converter smelting and casting process to control the nitrogen content in steel, and realizes the production of P210L and 20CrMoH steel, LD-LF-SCC process The nitrogen content of the slab is ≤35ppm, and the nitrogen content of the LD-LF-RH-BCC process slab is ≤30ppm. The disadvantage of this method is that it only takes measures to control the nitrogen content in the tapping and casting process, and it is only suitable for high carbon and strong deoxidation. Control of Nitrogen Content in Steel

[0005] Current status of process technology: the smelting process of "converter smelting-LF furnace refining-RH vacuum refining-continuous casting" is generally used in the production of high-grade steel grades, and high-grade steel grades require low carbon, low phosphorus, low sulfur and low nitrogen content , the steel adopts strong deoxidation, the nitrogen content control in the steel is unstable, and there are no technological measures for the nitrogen content control of high-grade low-carbon steel smelting