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Precautions for the design of the bell-type annealing furnace

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  • Time of issue:2018-04-26 14:26
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(Summary description)First, the outer cover The outer cover is a welded structure of steel and steel plates. The following points should be noted when designing the outer cover structure:

Precautions for the design of the bell-type annealing furnace

(Summary description)First, the outer cover The outer cover is a welded structure of steel and steel plates. The following points should be noted when designing the outer cover structure:

  • Categories:Industry news
  • Author:
  • Origin:
  • Time of issue:2018-04-26 14:26
  • Views:378
Information
First, the outer cover
 
  The outer cover is a welded structure of steel and steel plates. The following points should be noted when designing the outer cover structure:  structure:
 
  (1) The steel structure should have sufficient rigidity and strength, and the weight should be minimized. The lifting part and its super convection spheroidizing annealing furnace must be determined by the strength of the trolley-type annealing furnace according to the strength calculation, and the lower furnace lining pallet structure should also consider the compensation of thermal expansion to prevent deformation.
 
  (2) The combustion device of the circular outer cover is preferably arranged in a tangential direction. Generally, two rows of burners are provided, and the rectangular outer cover can be used for a flat flame burner for a straight spheroidizing annealing furnace. This is advantageous for uniform furnace temperature and reduced burning of the inner cover. When the burner is installed radially, a fire wall must be provided.
 
  (3) In order to reduce the weight of the outer cover and improve the thermal efficiency of the furnace, it is necessary to use a light refractory material with good heat insulation performance, low heat storage capacity and good thermal stability as the inner cover of the outer cover. The burner area is made of light-weight clay brick or silicon-calcium-aluminum block with good thermal stability, and refractory ceramic fiber felt is used in other areas.
 
  (4) Auxiliary equipment such as fans and burners are installed on the outer cover, and some heat exchangers and control devices are also installed. Therefore, the geometric center of the outer cover is not the center of gravity of the outer cover. When designing the cover, calculate the center of gravity of the cover so that the position of the hook matches the center of gravity of the cover.of the cover.
 
Second, the inner cover  Second, the inner cover
 
  The inner cover is hermetically welded with a heat-resistant stainless steel plate. In order to improve the inner cover to reduce the deformation, the inner cover cylinder is no longer used with the light panel but is welded by the transverse tile ridge plate. In order to prolong the service life of the inner cover, the upper and lower parts of the inner cover are made of steel plates of different thicknesses. Generally, the thickness of the inner cover body and the burner area is 2 mm thicker than the upper half. The top of the inner cover is formed by a boiler heading machine, which not only improves the roundness of the inner cover, but also reduces the stress concentration of the top weld and prolongs the service life of the inner cover.
 
Third,the work base
 
  The furnace without the combustion device, the smoke exhaust device and the circulation fan has a simple structure, and the heat storage and heat dissipation of the furnace should be minimized during the design to improve the temperature under the furnace.
 
  The annealing furnace of the cold-rolled steel coil with the circulating fan is complicated, the furnace is subjected to the pressure of up to 150t steel coil, and it has to withstand the high temperature, and the heat of the furnace is small in order not to affect the cooling speed requirement. The furnace table is composed of a support portion composed of a heat-resistant steel casting and a casing sealed and welded by a steel plate. The gap between the structural parts of the supporting part was previously filled with dry diatomaceous earth powder. Since the diatomite powder has impurities such as iron oxide, the dew point of the protective gas is changed due to the reduction of iron in the initial stage of the furnace opening, and the filler has been changed to purer. The ceramic fiber also has a furnace that is made into a fully sealed structure. Two metal tubular guide columns of different heights are symmetrically mounted on the stove mounting platform (or the base of the table) for positioning when the outer cover, the inner cover, the cooling cover and the convection plate are placed.
 
Fourth, the circulating fan and guide
 
  The circulating fan and the guide cooperate to form a protective gas forced circulation device. The shape and distribution of the inner guide plates of the guide have a great influence on the efficiency of the circulating fan. Generally, it is determined by aerodynamic test. In addition, the guide is also subjected to the weight of the steel coil. During the heat treatment, the guide is repeatedly Heating and cooling. Therefore, the guide is required to have high strength, small thermal deformation, long life, and low flow resistance to the circulating gas.
 
  The circulating fan provides the flow and pressure required for the shielding gas, is highly efficient and can be used for a long time at high temperatures; it is structurally sealed from the furnace table to prevent air intrusion. The fan motor can be directly connected to the transmission or the belt drive. The motor is an AC motor. Generally, the constant speed motor also has a two-speed motor. In recent years, the AC variable frequency speed control device has been adopted. The seal between the circulating fan and the furnace is double sealed, that is, the mechanical seal and the protective gas seal are used, and the water jacket indirect cooling device is provided.
 
V. Convection plate
 
  The convection plate, also called the septum or pad, has the middle convection plate and the top convection plate. The middle convection plate is ribbed on both sides, and the gas can pass from the upper and lower sides of the convection plate, while the top convection plate is only ribbed in the downward direction. The gap between the convection plate ribs should pass the shielding gas flow at a certain speed, increase the convective heat transfer coefficient, and effectively transfer the heat to the steel coil. The ribs of the convection plate are subjected to the pressure of the upper steel coil, and the pressure excessively damages the end of the steel coil and causes the end of the steel coil to be bonded. Therefore, the contact area between the rib and the steel coil should be increased as much as possible to reduce the pressure. The convection plate is generally welded, and the total thickness is about 70-80 mm. The contact surface between the rib and the steel coil should be machined to maintain the straightness of the convection plate.
 
Sixth, the sealing structure
 
  A seal is required between the outer cover and the inner cover and the table. The seal between the outer cover and the furnace is to prevent the furnace gas from overflowing during heating and to deteriorate the working environment. The outer cover seal adopts a sand seal with simple structure, low cost and easy maintenance, and the sealing knife on the outer cover is inserted into the sand sealing groove of the quartz sand with the quartz sand. A disadvantage of this type of construction is that the sand sticking to the sealing knife can scatter and contaminate the equipment when the outer cover is lifted. Now the seal between the outer cover and the table is to place a ceramic fiber felt or asbestos braid in the sealing groove of the table, and seal the gap between the cover and the table by its compressibility.
 
  The seal between the inner cover and the furnace is to ensure that the shielding gas in the inner cover does not leak and the negative pressure is generated at the bottom of the inner cover without inhaling air. For the bell-type furnace with protective gas and forced circulation, the sealing between the inner cover and the furnace table is particularly important, especially the all-hydrogen convection bell-type type furnace, which has higher requirements for sealing between the inner cover and the furnace table. The seal between the inner cover and the table is to insert a high temperature resistant silicone rubber ring into the water jacketed cooling flange on the table, and the flange at the bottom of the inner cover is pressed thereon, and is clamped by a pneumatic or hydraulic mechanism. seal.
 
The seal between the inner cover and the table is to insert a high temperature resistant silicone rubber ring into the water jacketed cooling flange on the table, and the flange at the bottom of the inner cover is pressed thereon, and is clamped by a pneumatic or hydraulic mechanism. seal.
 
The seal between the inner cover and the furnace is to ensure that the shielding gas in the inner cover does not leak and the negative pressure is generated at the bottom of the inner cover without inhaling air. For the bell-type furnace with protective gas and forced circulation, the sealing between the inner cover and the furnace table is particularly important, especially the all-hydrogen convection bell-type type furnace, which has higher requirements for sealing between the inner cover and the furnace table. The seal between the inner cover and the table is to insert a high temperature resistant silicone rubber ring into the water jacketed cooling flange on the table, and the flange at the bottom of the inner cover is pressed thereon, and is clamped by a pneumatic or hydraulic mechanism. seal.

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