Electric arc furnace's non-slag tapping technology

Electric arc furnace slag-free tapping technology

The electric arc furnace slag-free tapping technology is a tapping technology in which the steel slag is separated when the steel is tapped in the electric arc furnace, the slag is left in the furnace, and the molten steel flows into the ladle. Common methods include siphon tapping method, center bottom tapping method, eccentric furnace bottom tapping method, etc.

With the continuous development of metallurgical technology, the electric arc furnace steelmaking method has gradually developed from electric furnace independent smelting to a two-step steelmaking process of electric arc furnace-external refining furnace. In the electric arc furnace, melting, oxidation, and even melting and heating are completed, that is, the initial molten steel is poured into the refining furnace (ladle), and the refining furnace completes the tasks of deoxidation, desulfurization and alloying. Here, tapping is an intermediate link of two-step steelmaking, and oxidizing slag should not be brought into the refining furnace with molten steel. That is to say, the traditional tapping method of mixing steel slag can not meet the requirements of the refining technology outside the furnace, which has triggered the development and application of a variety of slag-free tapping technologies for electric arc furnaces. The more important ones are the siphon tapping method, the center bottom tapping method and the eccentric bottom tapping method. Among them, the eccentric bottom tapping method is the most widely used.

Arc furnace steelmaking

A steelmaking method that uses the thermal effect of an electric arc to heat the charge for smelting. Alternating current is fed into the furnace through three graphite electrodes, and an electric arc is generated between the lower end of the electrode and the metal material. The high temperature of the electric arc is used to directly heat the furnace material, so that the steelmaking process can be carried out. Electric arc furnace steelmaking uses scrap steel as the main raw material. Depending on the lining material and slagging material, there are alkaline methods and acidic methods. The most commonly used is the alkaline method. Electric arc furnace steelmaking uses electric energy as the heat source, avoiding the pollution of the steel by the sulfur contained in the gas heat source; the operation process is flexible, and the slag and furnace gas can be adjusted to oxidizing or reducing; strong reducibility can make the charge contained in the charge. The precious elements chromium, nickel, tungsten, molybdenum, vanadium, titanium, etc. are rarely burned; the furnace temperature is high and easy to control; the product quality is high.

The basic process of electric arc furnace steelmaking includes slagging and repairing the furnace, loading metal charge, power transmission, melting, oxidation, reduction refining and steel tapping. According to the characteristics of the steel to be smelted, there can be different operation methods. The traditional process mainly has three phases of melting, oxidation, and reduction. The reduction phase uses diffusion deoxidation and precipitation deoxidation, and white slag or calcium carbide slag is required. Each furnace requires 3 to 4 hours for smelting, and the power consumption is as high as 600 to 700 kWh/t. With the continuous development of technology, the electric arc furnace steelmaking process has also undergone great changes. During the melting period, auxiliary energy sources are used to accelerate the melting, such as injection of oil-oxygen, natural gas-oxygen or pulverized coal-oxygen, and the melting time per furnace is shortened by 15 ～20min, the power consumption can be reduced by 50～60kWh/t; in the oxidation period, measures such as early dephosphorization, enhanced oxygen use, powder spraying to create foam slag, and rapid temperature rise can reduce the amount of oxidative decarburization from 0.3% of the traditional process to 0.1 %～0.15%, so the oxidation period can be shortened by more than 50%. In the reduction period, the diffusion deoxidation in the traditional process is mainly changed to precipitation deoxidation, and the diffusion deoxidation is supplemented. Not only can the expected refining effect be achieved, the steel quality is guaranteed and the reduction time is shortened by more than 60%. With the improvement of the process, while the quality of molten steel is guaranteed, the productivity is also increased by about 20%, the power consumption is reduced by 10% to 15%, and the electrode consumption is reduced by about 8%, achieving considerable economic benefits.