Industrial furnaces

Industrial furnace is in industrial production, the use of fuel combustion or thermal energy conversion, heating the material or workpiece thermal equipment. Broadly speaking, the boiler is also an industrial furnace, but it is not customary to include it within the scope of industrial furnaces.

The main components of industrial furnaces are: industrial furnace masonry, industrial furnace exhaust systems, industrial furnace preheater and industrial furnaces burning devices. Machinery and industrial applications There are many types of industrial furnaces in the foundry workshop, smelting metal cupola, induction furnace, resistance furnace, electric arc furnace, vacuum furnace, open hearth furnace, crucible furnace; has baked sand of sand drying oven, ferroalloy Ovens and castings annealing furnace; after forging workshop, ingot or billet to be heated before forging various furnace, and forging stress relieving heat treatment furnace; in metal heat treatment plant, to improve the mechanical properties of the workpiece various annealing , normalizing, quenching and tempering heat treatment furnace; in the welding workshop, weldments preheat furnace and post-weld furnace; workshop in sintered metal powder metallurgy furnace and so on.

Industrial furnaces are also widely applied in other industries, such as metal smelting furnace metallurgical industry, ore sintering furnace and coke oven; distillation furnace and cracking furnace oil industry; producer gas industry; Portland cement kilns and industrial glass melting, glass annealing furnace; oven and other food industries.

The creation and development of industrial furnaces for human progress plays a very important role. China appeared in the Shang Dynasty a more comprehensive copper furnace, furnace temperature reached 1200 ℃, stove inside diameter of 0.8 meters. In the Spring and Autumn Period, people on the basis of Copper Melting Furnace further improve temperature mastered the technology to produce cast iron.

In 1794, there have been melting iron straight world shaped cupola. After 1864, Frenchman Martin to use British Siemens regenerative furnace principle, the construction of a gas fuel heating of the first open-hearth steelmaking. He used the regenerator to the high-temperature preheated air and gas, steel required to ensure the temperature above 1600 ℃. 1900, power supply ample gradually began to use a variety of resistance furnace, electric arc furnaces and induction furnaces.

1950s, coreless induction furnaces have developed rapidly. Later appeared electron beam furnace, using an electron beam to impact solid fuel, can strengthen the surface heating and melting of high melting point materials.

First heating furnace for forging the hand forging furnace, its working space is a concave groove, the groove filled coal, the combustion air fed by the lower groove, buried in the coal in the heating of the workpiece. This low thermal efficiency of the furnace, heating the quality is not good, and only small parts of the heating, after the development of refractory bricks brick semi-closed or closed hearth furnace chamber can be coal, gas or oil as fuel can also be used as a heat source of electricity, heating the workpiece on the furnace.

To facilitate the heating of large workpieces, appeared suitable for heating large ingots and billets trolley furnace, in order to heat the elongated rod also appeared pit furnace. Then in the 1920s there has been able to increase productivity and improve working conditions stove variety of mechanization and automation furnace.

Industrial furnace fuel also with the progress of the development of the fuel and fuel conversion technology resources, and by the use of lump coal, coke, coal and other solid fuels gradually switch furnace gas, city gas, natural gas, diesel, fuel oil and other gases and liquid fuels, and developed various combustion means and adapted to the fuel used.

Structure, the heating process, temperature control and other industrial furnace atmosphere furnace, will directly affect the quality of products after processing. In forging furnace, improve the metal heating temperature deformation resistance can be reduced, but the temperature is too high will cause grain growth, oxidation or burnt, seriously affecting the quality of the workpiece. During the heat treatment, if the steel is heated to a point above the critical temperature, and then suddenly cooled, can improve the hardness and strength of steel; if heated to a point below the critical temperature after slow cooling, the hardness of the steel can also reduce leaving toughness increased.

In order to obtain accurate dimensions and surface finish of the workpiece, or to reduce the metal oxide in order to protect the mold, reducing the allowance purposes, you can use a variety of small non-oxidizing furnace. Open flame in a non-oxidizing furnace and less by the incomplete combustion of the fuel reducing gas, in which the heating of the workpiece can be reduced to 0.3%, the rate of oxidation loss.

Controlled atmosphere furnace is prepared using artificial atmosphere, the gas can be introduced into the furnace carburizing, carbonitriding, bright quenching, normalizing, annealing heat treatment: in order to change the microstructure, the purpose of improving the mechanical properties of the workpiece. In the flow of particles in the furnace, the combustion of the gaseous fuel, fluidizing agents, or other externally applied, forced to flow through the furnace bed of graphite particles or other inert particle layer, the particle layer is embedded in the workpiece to achieve enhanced heat infiltration can also be carbon, nitrogen, and other non-oxidizing heating. In a salt bath furnace, a molten salt solution as a heating medium to prevent oxidation of the workpiece and decarburization.

In cupola furnace smelting iron, often influenced by the quality of coke, air supply, charge air temperature conditions and other conditions, so that the melting process is difficult to stabilize, easy access to high-quality iron. Hot air cupola can effectively improve the hot metal temperature, reducing the alloy burning, reduce the rate of iron oxide, which can produce a high iron.

With the emergence of coreless induction furnaces, cupola has gradually been replaced by the trend. This induction furnace melting iron grade work without any restrictions, it is possible from a grade of iron smelting, quickly switch to another level of iron smelting, will help improve the quality of molten iron. Some special alloy steel, such as ultra-low carbon stainless steel and rolls and turbine rotors and other steel used need to be open-hearth or general arc melting out of the molten steel in the furnace by vacuum degassing refining and argon stirring to the complex, and further refine the high purity, high quality steel capacity.

Industrial furnace by heating divided into two categories: one is the flame furnace (or fuel stove), with a solid, liquid or gaseous fuel in the combustion heat of the furnace for heating the workpiece; second category is electric, furnace The electrical energy is converted into heat for heating.

Wide flame furnace fuel source, low price, easy to take a different structure of local conditions, help to reduce production costs, but the flame furnace difficult to achieve precise control of environmental pollution, low thermal efficiency. EAF is characterized by temperature uniformity and facilitate the realization of automatic control, good heating quality. By energy conversion method can be divided into electric resistance furnace, induction furnace and electric arc furnace.

Industrial furnaces by thermal system can be divided into two categories: one is known as intermittent furnace furnace cycle, which is characterized by intermittent production furnace, the furnace temperature in each heating cycle is changing, such as the chamber furnace, car-type furnace, pit furnace; second category is a continuous furnace, which is characterized by continuous production stove, the furnace temperature zone division. During the heating process the temperature of each segment is constant, a preheating zone of the workpiece from the cryogenic temperature to gradually enter the heating zone as the continuous heating furnace and the heat treatment furnace, annular furnace, furnace step, vibration Hearth Furnace and so on.

The heating power of the furnace in the hearth unit time per unit area of ​​the furnace known as the calculated productivity. Faster heating stove, oven loading capacity is larger, the higher the furnace productivity. In general, the higher the productivity of the furnace, the heating units per kilogram of the material the lower the calories consumed. Therefore, in order to reduce energy consumption, should be at full capacity to maximize the productivity of the furnace, while the implementation of fuel and combustion air to the combustion device to automatically adjust the ratio, the amount of air in order to prevent excessive or inadequate. Also, reducing the furnace wall heat storage and heat loss, water-cooled heat loss components, various openings of radiant heat loss, away from the furnace flue gas heat losses.

Heating a metal or a heat absorbing material fed into the furnace and the ratio of the amount of heat, the thermal efficiency of the furnace is called. Continuous furnace thermal efficiency than high intermittent furnaces, continuous furnaces since the production rate, and the continuous work of the furnace heat the system is stable, there is no loss of regenerative furnace wall periodically, but also because the chamber has an internal pre- Heat the charge zone, flue gas heat as part of a warm-up due to the charge inside the furnace section, part of the flue gas into the furnace heat is absorbed by the cooling of the workpiece, reducing the temperature of the flue gas from the furnace.

In order to achieve the prescribed furnace temperature constant heating rate and, in addition must be based on process requirements, preheater and furnace mechanical type, fuel and combustion device categories, such as industrial furnace exhaust from the furnace to determine the fine structure, but also the need for fuel and combustion air flow and pressure, or electric power and other control variables mutually adjusted by various control units, in order to achieve the furnace temperature, furnace atmosphere or the furnace pressure control.