annealing furnace structural components

In recent years, with the rapid development of economy, annealing furnace is mainly used for returning materials and cooling, which brings too much convenience to operators. Then, do you know the structure composition of annealing furnace? What are the performance advantages? I hope I can give you some useful help. The following is an introduction to "Structural components and performance characteristics of annealing furnaces".

What are the three parts of the cowl annealing furnace?

The bright annealing furnace consists of three parts: fixed base, movable inner cover and outer cover. Furnace covers are either round or rectangular. Generally, the rolled sheet is annealed in a rectangular furnace, while the rolled sheet is annealed in a circular furnace. A cowl furnace can also be considered as a continuous operation in which the cowl is moved from one base to another.

The tightly rolled strips are stacked vertically along the axis on the base, each with three or four layers. After stacking, the inner cover (muff cover) is fastened, and the outer layer is called the outer cover (heating cover), on which heaters are installed. There are three heating methods: open flame direct heating, radiation tube indirect heating, resistance heating. Annealing temperature is 600-700℃.

The inside of the shield is filled with protective gas, mainly N2, COZ suitably matched with HZ, CO, COZ (also with full hydrogen atmosphere), with strong fan to make the protective gas intense convection circulation. The coil is heated, homogenized, and cooled within the housing, which takes longer than the heating furnace heating time. Longer annealing time, more uniform temperature, better product quality, but affect the productivity improvement.

Therefore, efforts are always made to shorten the cooling time, such as the use of cooling enclosures with circulating fans, the use of protective gas for circulating cooling, and the use of heat-resistant steel pipe for water cooling and water-cooled inner enclosures.

There are many types of hood furnace. Hood furnace can be used for annealing strip coil and sheet sheet stack. It can be divided into single stack multi-coil annealing furnace and multi-stack annealing furnace. The former is a steel coil stack, stacked several layers of steel coil, this form is widely used; The latter is a common hearth with several charging stations, each stacked with 2-4 steel coils, each with a muff cover and a common heating cover.

With the increase of roll weight and loading quantity, the furnace has developed into a larger type. Now the loading quantity has been expanded to 120-150t, and the unit heat consumption is smaller than that of single-stack furnace, but it is not as flexible as single-stack furnace.

Cover type furnace is open - fire heating mode at the beginning, burner radial layout. In this way, the flame rushes directly to the inner cover, making the inner cover easily damaged. Later, they tried to add a fire damper between the burner and the inner cover, but the damper soon burned out or was knocked off when the cover was removed. Then the burner was changed to tangential arrangement, and the situation was improved, but not fundamentally solved.

Therefore, the use of radiation tube heating, flame does not directly spray to the cover, to avoid the above defects. But the radiant tube furnace has low thermal efficiency and high exhaust temperature. It is necessary to recover the waste heat. Meanwhile, the equipment cost of radiation tube is high, and the shield and radiation tube are likely to collide and be damaged during the buckle. Moreover, the heating time of radiation tube furnace is longer than that of direct heating mode.

Since the appearance of the flat flame burner, the cover type furnace has been directly heated by the flat flame burner. The flame of this burner diffuses to all sides and is parallel to the inner wall of the heating cover rather than directly to the inner wall, which has a large radiation area and avoids the disadvantages of the first two methods. A hood furnace may also be used as a resistance hood furnace with an electric heater as a heating element.

Another important improvement on the hood furnace is the use of refractory fibers. In the past, the weight of a furnace cover is very large, the weight of a furnace cover can be up to ten tons, the structure of the plant must be very strong. The light enclosure made of refractory fiber makes the furnace lighter and compact, which reduces the load of crane and reduces the cost of workshop construction.

When the refractory fiber is used as the lining of the outer cover, the insulation performance is good, it can save fuel more than 20%, and also shorten the heating time of the empty furnace. Refractory fiber can be used not only as the lining material of furnace cover, but also as the sealing material. In the past, the inner and outer cover of the annealing furnace with steel cover is generally sand seal, poor sealing, the workshop environment is easy to be polluted, if oil seal is used, oil is also polluted by heat evaporation.

Refractory fiber seal is reliable, which improves the annealing quality of steel plate and does not pollute the environment.

The recrystallization annealing of strip steel has been used in the early stage. However, the heat of tight coil is slower, completely depends on steel conduction and the temperature is not uniform. In order to overcome this shortcoming, the 1960s introduced the unrolled strip annealed furnace, which is characterized by the unwinding of the strip coils (in effect, the loosening of the coiled coils) so that the layers remain 0. 52.

With a clearance of 5mm, the high-temperature protective gas can contact more steel surfaces, and the heating time can be shortened, which is less than half of the annealing time of tight coil. Fuel consumption is reduced, and the cooling time is correspondingly shortened. The performance of the strip is uniform, and the surface quality is also improved. But because the loose coil cover type annealing furnace of the hearth is larger, the exhaust gas temperature is higher. So it affects the thermal efficiency of the furnace.

At present, the recrystallization annealing of strip steel is still using the compact coiling type annealing furnace. There are two kinds of gas heating and electric heating in the cover type annealing furnace of sheet stack.