AC electric arc furnace steelmaking equipment includes three parts: furnace body, mechanical equipment and electrical equipment. The layout of the electric furnace equipment is shown in the figure.
The equipment structure of the electric arc furnace is mainly determined by the steelmaking process, and it is also related to the capacity of the electric furnace, the charging method, the transmission method, etc. The basic structure of the electric arc furnace is shown in the figure.
The furnace body of the electric arc furnace is composed of two parts: metal components and furnace lining. Metal components include parts made of metal materials such as furnace shell, furnace door, tapping mechanism, furnace cover ring and electrode sealing ring. The electric arc furnace lining refers to the inner lining of the electric arc furnace melting chamber, which is made of refractory materials to withstand high temperature molten steel and slag.
The main mechanical equipment of electric arc furnace includes furnace body tilting device, electrode lifting device, charging system, etc. In order to tap steel and slag in the electric arc furnace, the furnace body should be able to tilt, and the tilting mechanism is the device used to complete the tilting of the furnace. During the smelting process of the electric arc furnace, the lifting and lowering of the electrode is completed by the electrode lifting device, and the electrode lifting mechanism is composed of an electrode holder, a column, a cross arm and a transmission mechanism;
The structure of the electrode lifting device has two types: movable column type and fixed column type. Larger electric furnaces generally use movable column structure. There are three transmission modes: wire rope transmission, gear and rack transmission, and hydraulic transmission. Large-scale electric furnaces mostly use hydraulic transmission.
There are two charging methods for electric arc furnaces: door charging and furnace top charging. Manual charging of furnace door is only suitable for small electric furnaces, and most electric furnaces use furnace top charging. According to the position change of furnace body and furnace cover during charging, it can be divided into three types: furnace body open type, furnace cover rotary type and furnace cover open type.
The electrical equipment of the electric arc furnace includes the main circuit electrical equipment and the auxiliary circuit electrical equipment.
The main circuit is directly supplied by the high-voltage cable to the furnace transformer, and then sent to the electrode. The main circuit electrical equipment is mainly composed of isolating switch, high-voltage circuit breaker, reactor, electric furnace transformer, low-voltage short-circuit network and electrodes.
The auxiliary circuit is supplied by the high-voltage cable to the factory substation, and then sent to the low-voltage equipment of the electric arc furnace. Auxiliary circuit electrical includes high and low voltage control system and its corresponding cabinet, electrode automatic regulator, etc. Auxiliary circuit electrical is also called electric arc furnace electric control equipment. Schematic diagram of the basic structure of the electric arc furnace body.
1 . furnace shell
The furnace shell is the outer shell of the furnace body, which is composed of three parts: the cylindrical furnace body, the bottom of the furnace shell and the upper reinforcement ring. The furnace shell is required to have sufficient strength and rigidity to withstand the weight and dead weight of the lining, steel, slag, as well as high temperature and lining expansion. Usually the thickness of the shell is about 1/200 of the outer diameter of the furnace shell, which is generally welded with a steel plate with a thickness of 12 to 30 mm. The inner lining is refractory: the furnace shell is easily deformed by high temperature, especially in the later stage of the furnace service. There is a reinforcement ring or reinforcement on the furnace shell: the reinforcement ring on the upper edge of the furnace shell is welded with steel plate or section steel and cooled by water. There is a sand seal right in the upper sealing groove of the reinforcement ring, which is convenient for the furnace cover ring to be inserted into the sand groove for sealing.
The shape of the bottom of the furnace shell is flat bottom, truncated cone and spherical, as shown in the figure(图4). The flat hearth furnace shell is simple to manufacture, but has the worst medical properties and the largest furnace lining volume, so it is mostly used in large electric furnaces. The frustoconical bottom shell is easier to manufacture than the spherical bottom shell, but the spherical bottom is inferior to the performance, and requires a little more lining material, so it is often used. The spherical bottom has the highest firmness, small dead angle and small furnace lining, but it is difficult to form a spherical bottom with a large diameter, so the spherical bottom is mostly used in medium and small furnaces.
2 . furnace doors
It consists of three parts: metal door frame, furnace door and furnace door lifting mechanism. The furnace door frame plays the role of protecting the furnace lining and elements near the furnace door. The door and casting parts are cooled by water inside. In order to make the furnace door and the door frame close, the wall of the door frame water tank is made into a slope of 5° to 10°. Hollow water-cooled furnace doors are usually used. The lifting mechanism of the furnace door can be realized by means of electric, pneumatic or hydraulic transmission.
Small and medium-sized furnaces have only one furnace door, which is located opposite the tapping hole. In order to facilitate the operation of large electric arc furnaces, a side door is often added, and the positions of the two furnace doors are 90°. The size of the furnace door should be easy to observe and repair the furnace bottom and furnace slope.
3 . tapping grooves
Electric furnace tapping methods are divided into groove tapping, center bottom tapping (CBT), eccentric bottom tapping (EBT), etc. At present, the electric furnace is mainly based on the eccentric bottom tapping method.
Click here: Introduction to Tapping grooves