Keywords: Electric Furnace, Electric Furnace Network, Industrial Electric Furnace, Electric Furnace Wire, Laboratory Electric Furnace, Resistance Furnace, Muffle Furnace, Chamber Resistance Furnace, Pit Resistance Furnace, Bogie Resistance Furnace, Electric Furnace for Steel Making, Electric Furnace Transformer, Experimental Electric Furnace, Price of Electric Furnace, Electric Furnace Factory, Electric Furnace Dedusting, Vacuum Furnace, Furnace Fittings, Furnace Equipment, Energy Saving Electric Furnace,

Electric furnace

　　Electric furnace: electric heating to achieve the desired process purpose (such as material smelting, melting, heating, heat treatment, sintering, drying, etc.) of the electric heating equipment called electric furnace. Cited the use of electric heating effect of heating industrial furnace electric furnace is divided into industrial electric furnace and household electric furnace two kinds, industrial electric furnace is divided into resistance furnace, induction furnace two kinds, with the development of modern industrial technology induction furnace becomes the most energy-saving electric furnace in the electric conversion heating method, widely used in the family, medicine, chemical industry, metallurgy, and other fields.

Advantages of Electric Furnace

　　Compared with the fuel furnace, the advantages of electric furnace include: the atmosphere in the furnace is easy to control, and even can be pumped into vacuum; the material is heated quickly, the heating temperature is high, and the temperature is easy to control; it is easier to realize the mechanization and automation of the production process; the labor hygiene conditions are good; the thermal efficiency is high; the quality of the products is good and so on. Metallurgical industry electric furnace is mainly used for iron and steel, ferroalloys, non-ferrous metals, such as melting, heating and heat treatment. 19th century the end of the emergence of industrial-scale electric furnaces, the 20th century since the 1950s, due to the growth of the demand for high-level metallurgical products and the cost of electricity with the development of the power industry and the decline in the ratio of electric furnaces in the metallurgical furnace equipment is rising year by year. Electric furnace can be divided into resistance furnace, induction furnace (Shenguang electric furnace), electric arc furnace, plasma furnace, electron beam furnace. 

Resistance Furnace

　　Resistance Furnace is a furnace that uses the Joule heat generated by the electric current passing through the conductor as the heat source. According to the way of generating electric heat, resistance furnace is divided into direct heating and indirect heating two kinds. In the direct heating resistance furnace, the current passes through the material directly, because the electric power is concentrated in the material itself, so the material is heated very quickly, applicable to the requirements of rapid heating process, such as forging billet heating. This kind of resistance furnace can heat the material to a very high temperature, such as graphitization of carbon materials electric furnace, can heat the material to more than 2500□. Direct heating resistance furnace can be made into a vacuum resistance heating furnace or through the protective gas resistance heating furnace, in powder metallurgy, commonly used in sintering tungsten, tantalum, niobium and other products. The use of this furnace heating should be noted: ① in order to make the material heated uniformly, the requirements of the material parts of the conductive cross-section and conductivity of the same; ② due to the material's own resistance is quite small, in order to achieve the required electric power, the working current is quite large, so the power supply electrodes and the material contact to be good so as not to start the arc burns the material, and the power supply busbar resistance should be small in order to reduce the loss of the circuit; ③ in the supply of alternating current, it is necessary to Reasonable configuration of the short network, so as to avoid excessive inductive resistance and make the power factor too low. Resistance furnace thermal efficiency is not high when one of his shortcomings. 

　　Most of the resistance furnace is indirectly heated resistance furnace, which is equipped with a special used to realize the electrical - thermal transition of the resistance body, called the electric body, by which the heat energy to the furnace materials (Figure 1 indirectly heated resistance furnace). 

　　This kind of electric furnace shell made of steel plate, the hearth lined with refractory material, inside the material. The most commonly used heaters are ferrochromium-aluminum heaters, nickel-chromium heaters, silicon carbide rods and molybdenum disilicide rods. According to the need, the furnace atmosphere can be ordinary atmosphere, protective atmosphere or vacuum. General power supply voltage 220 V or 380 V, if necessary, equipped with an intermediate transformer can be adjusted voltage. Small furnace (<10 kW) single-phase power supply, large furnace three-phase power supply. For a single species, batch size of materials, it is appropriate to use continuous furnace heating. Furnace temperature below 700□ resistance furnace, most of the device blower to strengthen the furnace heat transfer to ensure uniform heating. Used for melting fusible metals (lead, lead-bismuth alloy, aluminum and magnesium and its alloys, etc.) of the resistance furnace, can be made into a crucible furnace; or made into a reflecting furnace with a melting pool, in the top of the furnace is equipped with an electric heater. Electroslag furnaces are resistance furnaces in which the electrothermal transformation is realized by a dissolved slag (see Electroslag Remelting). 

Induction furnace

　　An electric furnace that heats or melts materials by utilizing the induced electrothermal effect of the materials. The basic part of the induction furnace is the induction loop wound with copper tubing. Induction loop on both sides of the AC voltage, producing alternating electromagnetic field, conductive materials placed in the induction loop, due to electromagnetic induction in the material to produce eddy currents, by the role of resistance and make the electrical energy into heat to heat the material; therefore, can also be considered as induction heating is a direct heating type of resistance heating. Famous domestic manufacturers Hangzhou Electric Furnace Manufacturing Co. 

　　Induction heating is characterized by the transformation of the heated material in the electric power (current distribution) is very uneven, the surface of the largest, the center of the smallest, known as the skin effect. In order to improve the thermal efficiency of induction heating, the power supply frequency should be appropriate, small melting furnace or surface heating of materials using high-frequency electricity, large-scale melting furnace or deep penetration of the material heating using intermediate frequency or industrial frequency electricity. Induction loop is a fairly large inductance load, its power factor is generally very low. In order to improve the power factor, the induction loop is generally connected in parallel with a capacitor, known as the compensation capacitor. The gap between the induction loop and the material should be small, the induction loop should be made of square copper tube, the tube is cooled by water, the turn-to-turn gap of the induction loop should be as small as possible, and the insulation should be good. Induction heating device, mainly used for heating and melting casting of steel, copper, aluminum and zinc, etc., fast heating, less burnout, high degree of mechanization and automation, suitable for configuration in the automatic operating line. 

　　Induction furnace series heating furnace features

　　Fast heating speed, high production efficiency, less oxidization and decarburization, saving material and mold cost. 

　　As the principle of medium frequency induction heating for electromagnetic induction, the heat generated in the workpiece itself, ordinary workers with medium frequency electric furnace can be forged after ten minutes of continuous work tasks, do not need to burn the furnace to focus on the workers in advance to burn the furnace and seal the furnace work. Do not have to worry about due to power outages or equipment failure caused by the coal furnace has been heated billet waste phenomenon. Because of the heating method of heating speed, so the oxidation is very little, each ton of forgings and burning coal furnace compared to save at least 20-50 kg of steel raw materials, the material utilization rate of up to 95%. Because of the heating mode heating uniformity, core surface temperature difference is very small, so in the forging also greatly increase the life of the forging die, the roughness of the surface of the forgings is less than 50um. 

　　Superior working environment, improve the labor environment of workers and the company's image, no pollution, low energy consumption 

　　Induction heating furnace and coal furnace, compared with the workers will not be subjected to the hot sun under the coal furnace baking and smoke, but also to meet the requirements of the environmental protection department of the indicators, and at the same time to establish the company's external image and the future development trend of the forging industry. Induction heating is the most energy-saving heating in the electric heating furnace from room temperature to 1100 ℃ tons of forgings consume less than 360 degrees. 

　　Uniform heating, very small temperature difference between core and surface, high precision temperature control 

　　Induction heating heat generated in the workpiece itself, so the heating is uniform, the core table temperature difference is very small. The application of temperature control system can realize the precise control of temperature to improve product quality and qualification rate. 

　　Induction heating furnace has a small size, light weight, high efficiency, thermal processing quality and favorable environment and other advantages are rapidly eliminated coal-fired furnaces, gas furnaces, oil furnaces and ordinary resistance furnace, is a new generation of metal heating equipment. 

　　Industrial applications of induction melting furnace crucible furnace (coreless induction furnace) and melting ditch furnace (core induction furnace), see Figure 2 induction furnace furnace structure schematic. The crucible is made of refractory material or steel, with a capacity from several kilograms to tens of tons. The melting is characterized by the crucible melt by the electric force, forcing the molten pool surface raised, the melt from the center of the liquid surface flow to the surrounding area and cause the circulation flow. This phenomenon is called electric effect, can make the melt composition uniform, the disadvantage is that the slag is biased toward the periphery, poor coverage. Compared with the melting ditch furnace, crucible furnace operation flexibility, high melting temperature, but the power factor is low, high power consumption. Melting groove furnace inductor by the iron core, induction ring and melting groove furnace lining composition, the melting groove for one or two band ring ditch, which is full of melts and melting pool connected to the melt. In principle, the groove furnace can be regarded as the secondary only one turn coil and short-circuit core transformer. The induced current flows in the melt in the trench, which realizes the electro-thermal transformation. 

　　In production, after each furnace metal melting, can not empty the melt pool, otherwise it is easy to dry out, must retain a part of the melt as the next furnace of the starting melt. Melting ditch temperature is higher than the melt pool, and bear the melt flow scouring, so the melting ditch furnace lining is easy to damage, in order to facilitate maintenance, the modern furnace inductor made of easy to replace the fittings. Melting ditch furnace capacity from a few hundred kilograms to more than a hundred tons. Melting ditch furnace for industrial frequency electricity, due to the iron core made of silicon steel sheet for the magnetic flux path, electrical efficiency and power factor are very high. Melting ditch furnace is mainly used for cast iron, copper, zinc, brass and other melting, but also as a mixing Shanghai, used to store and heat the melt. 

Electric Arc Furnaces

　　Utilizing the thermal effect of electric arc melting metal and other materials of the electric furnace (Figure 3 electric arc furnace type). According to the heating method is divided into three types: ① indirect heating arc furnace. Arc generated between the two electrodes, without contact with the material, relying on thermal radiation to heat the material. This furnace noise, low efficiency, gradually eliminated. ② direct heating arc furnace. Arc generated between the electrode and the material, direct heating of the material; steelmaking three-phase arc furnace is the most commonly used direct heating arc furnace (see arc furnace steelmaking). ③ submerged arc furnace, also known as reduction furnace or mineral heat furnace. One end of the electrode is buried in the material layer, the formation of an electric arc in the material layer and the use of the material layer of its own resistance to heat heating materials; commonly used in smelting ferroalloys (see ferroalloys furnace), smelting ice nickel, ice copper (see nickel, copper), as well as the production of calcium carbide calcium carbide (calcium carbide) and so on. 

Vacuum electric arc furnace

　　An electric furnace for melting metals by direct heating with an electric arc in an evacuated furnace body. Furnace gas thin, mainly by the molten metal vapor arc, in order to make the arc stable, generally for direct current. According to the melting characteristics, divided into metal remelting furnace and casting furnace. According to the melting process whether the electrode consumption (melting), divided into self-consumption furnace and non-self-consumption furnace, most of the industrial applications are self-consumption furnace. Vacuum arc furnaces are used for melting special steels, active and refractory metals such as titanium, molybdenum and niobium (see vacuum metallurgy). 

　　Electric arc heating can be thought of as arc resistance heating. Stabilization of the electric arc (arc resistance) is necessary for normal furnace production. AC arc furnaces usually use industrial frequency electricity, in order to stabilize the arc, the furnace power supply circuit to have the appropriate inductive resistance, but the presence of inductive resistance will reduce the power factor and electrical efficiency. Reduce the current frequency is the development of AC arc furnace way. Arc resistance resistance value is quite small, in order to obtain the necessary heat, the furnace needs quite a large working current, so the furnace short network resistance should be as small as possible, so as to avoid excessive circuit losses. For three-phase arc furnace, to make the three-phase impedance close to the same, so as to avoid three-phase load imbalance. 

Plasma furnace

　　The use of the working gas is ionized when the plasma generated by the heating or melting of the furnace. The device that generates plasma is usually called a plasma gun, and there are two types of plasma guns: arc plasma guns and high-frequency induction plasma guns. The working gas into the plasma gun, the gun has an electric arc or high-frequency (5 ~ 20 MHz) electric field device, the working gas is ionized by the action, generated by the electrons, positive ions, and gas atoms and molecules mixed with the plasma. Plasma from the plasma gun nozzle, the formation of high-speed high-temperature plasma arc flame, the temperature is much higher than the general arc. The most commonly used working gas is argon, which is a monoatomic gas that is easily ionized and is an inert gas that protects materials. The working temperature can be as high as 20000□; used for melting special steel, titanium and titanium alloy, superconducting materials and so on. Furnace types include water-cooled copper crystallizer furnaces, hollow cathode furnaces, plasma furnaces with induction heating, and plasma furnaces with refractory linings (see Plasma Metallurgy). 

Electron beam furnace

　　With high-speed electron bombardment of the material to heat the melting of the furnace (Figure 4 electron beam furnace schematic). In the vacuum furnace shell, with a low-voltage electric filament heating cathode, so that the emission of electrons, electron beams accelerated by the role of high-voltage electric field accelerated anode and accelerated movement, bombardment of metal materials located in the anode, so that the electrical energy into thermal energy. Because the electron beam can be highly concentrated by electromagnetic focusing device, so the material can be bombarded in the part of the high temperature. Electron beam furnaces are used for melting special steel, refractory and active metals. 

　　Electric furnaces for industrial use are categorized into two types: cyclic operation furnaces and continuous operation furnaces. 

　　Periodic operation furnace is divided into: box furnace, sealed box furnace, pit-type furnace, bell-type furnace, cart furnace, dumping drum furnace. 

　　Continuous operation of the furnace is divided into: kiln car furnace, pusher furnace, roller furnace, vibration bottom furnace, rotary furnace, step furnace, traction furnace, continuous roller furnace, conveyor belt furnace and so on. Among them, the conveyor belt furnace can be divided into: there are mesh belt furnace, stamping chain plate furnace, casting chain plate furnace, etc.... 

Electric Furnace

Electric Furnace

　　Electric furnace can use metal heaters or non-metallic heaters to generate heat source, its simple structure, very wide range of uses is its main feature, can be widely used in annealing, normalizing, quenching, tempering, carburizing and carburizing nitriding. The main metal heaters include Ni-Cr electric hot wire (the most common, up to 1200 ℃), Mo-Si alloys and W, Mo and other pure metals; non-metallic heaters including SiC (the most common, the highest can be heated to 1600 ℃), LaCrO3 and graphite rods (vacuum or protective atmosphere can be heated to 2000 ℃). 

1, the electric furnace has the advantages

(1) Compared with the fuel furnace is easy to get high temperature. 

(2) can be heated from within the material to warm up. 

(3) easy to use in the controlled atmosphere furnace and vacuum furnace. 

(4) The electric furnace does not have the exhaust heat loss of the fuel furnace, so the thermal efficiency is high. 

5） It is easy to control the temperature, remote control and fine adjustment. 

6） It can be heated quickly. 

(7) good operating performance, not polluting the environment. 

2, the shortcomings of the electric furnace

1) Need to increase the cost of power distribution equipment. 

(2) high cost of electricity. 

(3) resistance heating temperature of more than 1000 ℃, the refractory material may be conductive, need to pay attention to the insulation problem. 

The main types of electric furnace

I. Industrial furnace

　　Industrial furnace: divided into electric furnaces and combustion furnaces (the narrow sense of the industrial furnace refers to combustion furnaces) 

II. Main products

　　Seven categories: resistance furnace, induction furnace, vacuum furnace, electron beam furnace, heat treatment (or melting) unit, heat treatment equipment, combustion furnace. 

Three. Resistance furnace: three major components: heater, lining, heat-resistant components 

1. Divided into two categories of cyclic and continuous 

2. The characteristics of the periodic furnace: 

A. Charge at the same time to join the same time to take out 

B. Heating the charge is basically immobile (except for special circumstances: such as drum furnace, roller-hearth furnace) 

C. Strive for uniform temperature in the working area 

3. Classification of Periodic Resistance Furnace

A. Box-type furnace 

B. Bogie hearth furnace (divided into self-propelled and traction type), used for annealing, after heating the workpiece with the furnace cooling 

C. pit-type furnace 

D. Hood furnace (mainly for annealing, heating hood can be lifted) 

E. Bottom-lifting hooded furnace (hood fixed, lifting base, suitable for large furnaces) 

F. Rotary Furnace 

G． Sealed box-type furnace (also known as multi-purpose furnace, can be carburizing, bright quenching, carbon and nitrogen co-infiltration and other heat treatment process. Adopting radiation tube heating, radiation tube is a refractory ceramic disk fixed resistance wire in a sealed heat-resistant steel tube, so that the structure of the furnace atmosphere will not have an impact on the heating element) 

4. Continuous Resistance Furnaces

A. Pusher-type furnace 

B．Conveyor belt furnace 

C. Mesh Belt Furnace (for thin small parts of the annealing, sintering, brazing and solution treatment. Structure similar to the conveyor belt furnace) 

D. Continuous rotary furnace (drum furnace)

E. Roller-hearth furnace (material disk moving on rollers) 

F．Turnbottom furnace 

Electric Furnace Transformer

　　Furnace transformer is a transformer specially designed to provide power for various electric furnaces. Industrial furnace transformers can be roughly divided into three categories: resistance furnace transformer, arc furnace transformer and induction furnace transformer. 

　　Resistance furnace transformer for mechanical parts heating, heat treatment, powder metallurgy sintering, non-ferrous metal melting resistance furnace and salt bath furnace. Because the resistance of its heating body is too small, or the resistance of the heating body changes too much during the warming process, it is necessary to equip a resistance furnace transformer between the furnace and the power grid to reduce and regulate the input voltage of the furnace. 

　　Electric Arc Furnace Transformer Specialized transformer to supply power to electric arc furnace used for steel smelting. Large capacity, complex structure, high technical requirements. Its side voltage is low, generally from tens of volts to hundreds of volts, and requires a larger range of regulation; side current often reaches thousands to tens of thousands of amps. In addition in the steel smelting, melting period requires power, requiring transformers to be able to have 20% overload capacity within 2 hours. In the steelmaking process, due to the collapse of the charge is easy to cause the electrode short circuit, so the primary side of the arc furnace transformer should be strung into the current-limiting reactor, or so that it has a large impedance, in order to limit the short-circuit current. 

　　Induction furnace transformer Induction furnace for melting ferrous and non-ferrous metals is essentially a special furnace transformer. Transformer original winding connected to the power supply, the secondary winding is actually only a turn, it is installed in the melting tank of molten metal. When the original winding is energized with current, the secondary winding produces an induced current, which circulates in the slot, thus emitting heat and melting the metal. 

Structure of electric furnace:

　　The whole set of electric furnace equipment contains medium frequency power cabinet, compensation capacitor, furnace body (two) and water-cooled cable, reducer. Furnace body consists of four parts: furnace shell, induction coil, furnace lining, tilting furnace gearbox, etc. Furnace shell is made of non-magnetic material, induction coil is a spiral cylinder made of rectangular hollow tube, and cooling water is passed inside the tube during melting. The coil leads to the copper row and water-cooled cable connection, the furnace lining is close to the induction coil, made of quartz sand compacted and sintered, the tilting of the furnace body by the tilting furnace gearbox direct rotation. Tilting furnace gearbox is a two-stage turbine speed, self-locking performance, smooth and reliable rotation, emergency power failure to see the collector tilting furnace, to avoid danger. The control of the motor of the tilting gearbox of the two furnaces can be selected through the furnace selector switch, and the switch box with four-core rubber wires enables the operator to stand in the right position to control the tilting and resetting of the furnace at the point of action.

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