What is the electric arc furnace?

Electric arc furnace is an electric furnace that uses the high temperature produced by electrode arc to melt ores and metals. The energy is very concentrated when the gas discharge forms the arc, and the temperature of the arc area is above 3000 ℃. For metal smelting, the electric arc furnace is more flexible than other steelmaking furnaces, which can effectively remove sulfur, phosphorus and other impurities. The furnace temperature is easy to control, and the equipment occupies a small area, which is suitable for smelting high-quality alloy steel.

Introduction to electric arc furnace

The industrial furnace that generates electric arc heating through metal electrode or nonmetal electrode is called electric arc furnace. The electric arc furnace can be divided into three-phase electric arc furnace, consumable electric arc furnace, single-phase electric arc furnace and resistance electric arc furnace. The furnace body of electric arc steelmaking furnace is composed of furnace cover, furnace door, tapping trough and furnace stack. The furnace bottom and furnace wall are built with alkaline refractory or acid refractory. Electric arc steelmaking furnace is divided into ordinary power electric arc furnace, high power electric arc furnace and ultra-high power electric arc furnace according to the transformer capacity allocated for each ton of furnace capacity. Electric arc furnace steelmaking is to input electric energy into the electric arc steelmaking furnace through the graphite electrode, and use the electric arc between the electrode end and the furnace charge as the heat source for steelmaking. The electric arc furnace uses electric energy as the heat source, which can adjust the atmosphere in the furnace, and is extremely favorable for smelting steel grades containing more easily oxidized elements. Not long after the invention of electric arc furnace steelmaking, it was used to smelt alloy steel and has been greatly developed.

With the improvement of electric arc furnace equipment and smelting technology, the development of electric power industry, the cost of electric arc furnace steelmaking continues to decline. At present, electric arc furnace steelmaking is not only used to produce alloy steel, but also used to produce a large number of ordinary carbon steel. The proportion of its output in the total steel output of major industrial countries is rising.

Electric arc furnace classification

Electric arc furnaces are classified in many ways.

1. According to the melting form of electrode, it can be divided into non consumable electrode arc furnace and consumable electrode arc furnace. The non consumable electrode type electric arc furnace uses tungsten or graphite as the electrode, and the electrode itself does not consume or consumes little in the smelting process; The consumable electrode type electric arc furnace uses the melted metal as the electrode, and the metal electrode is consumed while melting.

2. According to the control mode of arc length, it can be divided into constant arc voltage automatic control arc furnace, constant arc length automatic control arc furnace and droplet pulse automatic control arc furnace. The constant arc voltage automatic control electric arc furnace relies on the comparison between the voltage between two electrodes and the given voltage, and its difference value drives the consumable electrode to rise and fall through signal amplification to keep the arc length constant; The constant arc length automatic control electric arc furnace approximately controls the constant arc length by the constant arc voltage; The droplet pulse automatic control electric arc furnace automatically controls the constant arc length according to the relationship between the pulse frequency generated in the process of metal droplet formation and dropping and the pulse duration and arc length.

3. According to the operation form, it can be divided into periodic operation electric arc furnace and continuous operation electric arc furnace. Periodic operation electric arc furnace, that is, each smelting furnace is regarded as a cycle; Continuous operation electric arc furnace, which has two forms. One is rotary furnace, the other is that two furnaces share a DC power supply, that is, when one furnace is finished smelting, switch the power supply to the other furnace to start the smelting of the next furnace immediately.

4. According to the furnace structure, it can be divided into fixed electric arc furnace and rotary electric arc furnace.

Common electric arc furnace

1. Three phase electric arc furnace

This kind of electric arc furnace uses three-phase alternating current as power supply, and generally uses carbon electrode or graphite electrode. The arc occurs between the electrode and the melted charge, which is directly heated by the arc. The arc length is adjusted by electrode lifting. In order to improve the smelting quality, the large electric arc furnace is equipped with an electromagnetic stirrer at the bottom of the furnace to drive the molten metal in the furnace to circulate in a certain direction. Electric arc furnaces of more than 50 tons are often equipped with furnace body rotary mechanism, which can rotate left and right at a certain angle, so that the furnace materials can be heated evenly, and the furnace body can be tilted when the metal liquid comes out of the furnace. Three phase electric arc furnace is widely used for steelmaking.

2. Consumable arc furnace

The electrode of this electric arc furnace is the raw material of the steel to be melted. During smelting, with the continuous melting of steel raw materials, the electrode is continuously lowered. The molten steel drops into a red copper cylindrical crucible cooled with water and condenses into steel ingots. This kind of furnace is mainly used for smelting alloy steel. Consumable arc furnaces for smelting active metals such as titanium, zirconium, tungsten, molybdenum, tantalum, niobium and refractory metals are generally operated under vacuum, so they are called vacuum consumable arc furnaces.

3. Single phase electric arc furnace

This type of electric arc furnace is powered by single-phase alternating current. The charge is heated indirectly by electric arc. Single phase electric arc furnace is mainly used for smelting copper and copper alloy.

4. Resistance arc furnace

The furnace structure is similar to that of steel making electric arc furnace. During operation, the lower end of the electrode is buried in the furnace charge to start the arc. In addition to the heat generated by the arc between the electrode and the furnace charge, the resistance of the furnace charge also generates considerable heat when the current passes through the furnace charge. This type of electric arc furnace is mainly used for smelting ores, so it is also called submerged arc furnace.

Steel grades can be produced

The raw materials of electric arc steelmaking furnace are mainly solid scrap with alloy and pig iron for adjusting carbon content. Direct reduced iron or hot metal can also be used. The range of raw materials is wide; Therefore, most of the steel grades can be smelted except for some ultra-low carbon steels, or varieties and special alloy materials that must be used by special means such as vacuum treatment.