Method for protecting steel tapping electric furnace

What is electric arc furnace？

An electric arc furnace is an electric furnace that uses the high temperature generated by an electrode arc to smelt ores and metals, so it is also called an electric furnace. When the gas discharge in the electric furnace forms an arc, the energy is very concentrated, and the arc zone temperature is above 3000 ℃. The electric furnace has greater flexibility than other steelmaking furnaces in the smelting process, and can effectively remove impurities such as sulfur and phosphorus; and the furnace temperature of the electric arc furnace is easy to control during the smelting process, which is suitable for smelting high-quality alloy steel.

After the molten steel is smelted and tapped by the electric furnace, the outside refining and continuous casting process controls the oxygen, nitrogen, hydrogen and temperature in the steel very strictly. However, it is almost impossible to protect the molten steel during the tapping process. The molten steel directly contacts the air during the tapping process of the electric furnace, which causes a large amount of harmful gases such as nitrogen and hydrogen to enter the molten steel, which deteriorates the performance of the steel and contributes to subsequent refining and refining outside the furnace. Continuous casting brings pressure, greatly increases production costs, and reduces product quality.

Protecting steel tapping electric furnace

Nitrogen is a harmful element in general steel grades. During the tapping process, the exposed molten steel is in direct contact with the air, thereby increasing the nitrogen content in the molten steel, generally increasing by 10-20ppm. Because the air contains a certain amount of humidity, it will also cause the molten steel to increase hydrogen. Hydrogen is likely to produce white spots in the steel, causing hydrogen-induced cracks in the steel, which reduces the quality of the product. There is an urgent need to develop an electric furnace that protects the molten steel during the tapping process based on the existing tapping process of the electric furnace, so as to protect the molten steel during the tapping process and prevent the molten steel from absorbing harmful impurities in the air during the tapping process.

The impact on temperature is very large. This process lasts about 4-6 minutes. During the tapping process, the temperature of the molten steel decreases due to heat radiation, convection heat dissipation, deoxidation alloying, and heat absorption of the ladle lining. For this reason, alloy heating, ladle baking and optimized scheduling are used in production to reduce the temperature drop during the tapping process. However, no measures have been taken to radiate heat and convection heat generated between the molten steel and the air, resulting in serious heat dissipation of the molten steel, which makes it difficult to effectively control the temperature drop of the molten steel.

After searching, it was found that in the continuous casting process, the protection tube has been used to protect the molten steel. For example, the name of the invention is: composite molten steel protection sleeve, and the name of the invention is: a kind of anti-growth used for molten steel pouring Nitrogen protection tube. However, this kind of protection tube is difficult to protect the molten steel during the tapping process.

In addition, the name of the invention is: a method to prevent the increase of nitrogen in the molten steel during the converter tapping process. The argon blowing time and the argon flow rate are controlled before and during the converter tapping process, divided into two stages or continuous discontinuity. Blow argon into the ladle intermittently until the end of tapping. In this way, the air in the ladle is discharged by the blown argon, preventing the molten steel from tapping into the ladle from contacting the air, so that the molten steel in the ladle is always protected by argon, which not only prevents the nitrogen increase caused by the contact between the molten steel and the air, but also, which makes the molten steel easily adsorbed on the surface of the bubbles, can be removed as the argon bubbles rise and discharge. Although this method can prevent the molten steel from increasing nitrogen to a certain extent, it is difficult to protect the molten steel during the tapping process.