JPS62116725A - Annealing furnace - Google Patents

Abstract

PURPOSE:To uniformize heating, soaking and cooling of material to be treated and to improve quality, by providing plural injecting nozzles to a plenum chamber and housing plural auxiliary heating devices at a bottom part of a wind box. CONSTITUTION:A cooler 33 is drawn out and housed in a housing 34 by a driving gear 35, and atmospheric gas in annealing furnace is circulated in an arrow direction by a circulation fan 31. Atmospheric gas in furnace is heated by a radiation tube 25, drawn into an intake box 26 and lowered in the wind box 24, further heated by the auxiliary heating device 36 provided at bottom part of the box 24. The atmospheric gas is allowed to flow into a lower part header 23 in the plenum chamber 21 and upwardly injected from the injecting nozzles 22. In this way, heating - soaking of a coil W on the chamber 21 can uniformly be carried out in a short time. Cooling of the coil W is carried out by stopping the heating, then inserting the cooler 33 into the box 24 by the gear 35 to circulate atmospheric gas in an arrow direction by the fan 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a box-shaped tight annealing furnace used in a thin plate heat treatment process in a cold rolling mill of a steel mill.

[Prior Art] FIG. 8 shows a schematic cross section of a conventional box-shaped coil annealing furnace. The object to be processed in this example is a tightly wound thin plate with a thickness of about 0.2 to 3.2 mm, and is called a tight coil. The plenum chamber 1 that supports such a coil W is made of metal plates arranged in a lattice shape to allow air to flow freely. A fan 3 connected to a motor 2 is provided at one end of the plenum chamber l, and a wind box 4 is provided on the discharge side of the fan 3. This wind box 4, together with the plenum chamber 1, forms a series of gas flow paths for circulating atmospheric gas. A plurality of radiation tubes 5 are supported above the coil W. A burner (
(not shown), and an exhaust duct (not shown) is installed at the other end.

A cooler 8 is provided in the middle of the wind box 4, penetrating the furnace shell 6 and the heat insulating material 7, and this cooler 8 includes a tarla drive device 9 that moves the cooler 8 itself into and out of the wind box 4, and a roller drive device 9 that moves the cooler 8 itself into and out of the wind box 4. A bellows 10 is provided for the purpose of sealing. On the other hand, in front of the furnace, there is provided a door 11 that opens and closes when loading and unloading the coil W, and a door sealing device 12 that completely seals the inside and outside of the furnace at the contact area between the door 11 and the furnace shell 6. There is.

The coil W is heated to about 750° C. due to its metallurgical requirements, and after being sufficiently soaked, it is cooled. A mixed gas of nitrogen and hydrogen is sealed inside the furnace. During the heating and soaking period, the cooler 8 is sufficiently pulled out of the furnace by the cooler drive device 9 as shown by the solid line in the figure. Radiant heat is emitted from the outer surface of a radiation tube 5 that contains high-temperature combustion gas generated by the burner, and a fan 3 circulates the furnace atmosphere gas in the direction of the arrow in the figure as the motor 2 operates.

The heating mechanism of the coil W will be explained with reference to FIG. Thermal radiation emitted outward from the outer surface of the radiation tube 5 generally consists of a portion directed toward the coil W, a portion directed toward the upper (ceiling) heat insulating material 7, and a portion absorbed by the furnace atmosphere gas. Radiation is emitted from the surface of the upper (ceiling) heat insulating material 7 to the coil W.

For this reason, the upper surface of the coil W is generally heated actively by the thermal radiation of the radiation tube 5 and the upper (ceiling) insulation material 7 and the convection caused by the atmospheric gas flow. The side surface of the coil W is mainly heated by convection heating due to the atmospheric gas flow from that angle, and the amount of radiation from the radiation tube 5 is reduced. Also, coil W
The lower surface is heated only by convection due to the atmospheric gas flow.

FIG. 7 shows a temperature rise and temperature drop curve A at point A on the upper surface of the coil W and a temperature rise and temperature drop curve B at point B on the lower surface. The temperature rise at the points on the top surface is delayed compared to the points on the bottom surface. This depends on the presence or absence of the above-mentioned radiation, the heating of point B on the bottom surface with the remaining hot gas absorbed near point A on the top surface, and the fact that point B on the bottom surface is in contact with the metal plenum chamber 1, which has a large heat capacity. This is because a relatively large time delay T occurs as shown in FIG.

In Figure 7, the time periods are divided into three, with ■ being a heating period, ■ being a soaking period, and ■ being a cooling period.

After point B on the lower surface reaches the target temperature, soaking is performed, and then cooling is performed. At that time, the burner at the end of the radiation tube 5 is extinguished, and the cooler 8 is inserted into the wind box 4 by the cooler drive device 9. The cooler 8 has a group of cooling water pipes therein, and cools the atmospheric gas passing therethrough. The atmospheric gas is cooled, and the temperature of the heat insulating material 7, the coil plenum chamber, the fan 3, the radiant pipe 5, and the wind box 4 gradually decreases due to the cooled circulating gas.

Viewed from the coil W, the coldest atmospheric gas hits the top surface of the coil W, then along the sides and finally through the plenum chamber 1 to be cooled. Therefore, when comparing point A on the upper surface and point B on the lower surface, the temperature drop at the point on the lower surface is significantly delayed, resulting in a relatively large time delay T as shown in FIG.

[Problems to be Solved by the Invention] As described above, in the conventional annealing furnace, there is a large time delay in heating and cooling the point B on the lower surface of the coil W.
Point B on the bottom surface of the coil W is the worst condition point during both the heating and cooling periods. As a result, the following problems occurred.

■Since the operating time is determined by the temperature at the bottom of the coil,
The operation time for heating, soaking, and cooling cannot be shortened and takes a long time.

■ Production volume is limited.

■It consumes a lot of fuel and is uneconomical.

(2) The temperature difference between the top and bottom surfaces of the coil is large, which is disadvantageous in terms of quality.

This invention solves these conventional problems, improves production capacity by shortening heating, soaking, and cooling times, saves energy, and improves the temperature distribution of the coil to be processed, thereby improving quality. The purpose is to provide an annealing furnace that can.

[Means for Solving the Problems] In order to achieve the object, the present invention circulates high-temperature atmospheric gas in a furnace containing the workpiece to heat and soak the workpiece. After that, in an annealing furnace that cools the workpiece by circulating low-temperature atmospheric gas, a radiant tube that heats the workpiece, an atmospheric gas jet nozzle, a gas flow path formed in the furnace, and this gas A circulation fan provided in the flow path to eject atmospheric gas from the ejection nozzle and circulate it into the furnace; and a circulation fan provided in the gas flow path between the circulation fan and the ejection nozzle to heat the object to be processed. The apparatus is characterized in that it includes an auxiliary heating device that heats the atmospheric gas during soaking, and a cooler that is provided in the gas flow path and cools the atmospheric gas during cooling of the object to be processed.

[Function] The annealing furnace of the present invention heats the workpiece by the heating action of the radiation tube and by ejecting heated atmospheric gas into the furnace from a predetermined position, and also by ejecting the cooled atmospheric gas from a predetermined position. The object to be treated is cooled by blowing it out into the furnace.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

FIG. 1 is a block diagram of an annealing furnace, and 21 in the figure is a plenum chamber that supports a coil W to be annealed. This plenum chamber 21 is made up of metal plates arranged in a lattice shape, and inside the groove of this plenum chamber 21 is a duct-shaped lower header 23 in which a plurality of top-blowing jet nozzles 22 are attached.
are arranged in multiple rows. A lower header 23 to which this jet nozzle 22 is attached is connected to a wind box 24. A plurality of radiation tubes 25 are arranged above the coil W.

Coil W1 radiant tube 25, plenum chamber 21 wind box 24
, and the suction box 26 on the upper part of this wind box 24, etc., include a heat insulating material 27, a furnace shell 28, a door 29 that opens and closes when charging and extracting the coil W, and a contact area between this door 29 and the furnace shell 28. Door seal device 30 that completely seals the inside and outside of the furnace
It is stored by etc. The furnace shell 28 has a box shape, and the wind box 2 is installed along the side wall (the rear wall in this embodiment) of the furnace shell 28.
4 is placed.

In this example, a circulation fan 31 is installed in the middle of the wind box 24.
is provided. This fan 31 is attached with a motor 32 that drives it. A cooler 33 and a cooler housing 34 are installed below the wind box 24. The cooler housing 34 includes a bellows or bellows (not shown) that completely seals the inside and outside of the furnace at the opening;
A cooler drive device 35 for inserting and pulling out the cooler 33 is provided. Furthermore, a plurality of auxiliary heating devices 36 are stored in a room at the bottom of the wind box 24.

A mixed gas of nitrogen (Nt) and hydrogen (Hl) is sealed in the furnace, and is circulated within the furnace as an internal furnace atmosphere gas by operation of the circulation fan 31. A burner (not shown) is provided at one end of each of the radiation tube 25 and the auxiliary heating device 36.
, the other end is provided with an exhaust duct (not shown).

In addition to burner combustion, the auxiliary heating device 36 includes:
There are also heating methods using electric heaters. Also, 3 in the diagram
7 is a partition wall.

Next, the effect will be explained.

The annealing operation consists of three steps: heating, soaking, and cooling, as in the conventional case described above.

First, the mode of heating and soaking will be explained with reference to FIGS. 2 and 3.

The cooler 33 is pulled out and stored in the cooler housing 34 by a cooler drive device 35.

Atmospheric gas is circulated in the direction of the arrow in FIG. 2 by the circulation fan 3I. That is, the atmospheric gas in the furnace is heated by the radiant tube 25 and then drawn into the suction box 26 from left to right in FIG. It is further heated by an auxiliary heating device 36 provided in a chamber at the bottom of the tank, flows into the plural rows of lower headers 23, and is ejected upward from the ejection nozzles 22 at high speed. This lower header 23 has a sufficient capacity (volume) and equalizes the internal pressure to eject circulating gas from each ejection nozzle 22 at high speed and in a well-balanced manner. On the other hand, thermal radiation is emitted from the outer periphery of the radiation tube 25.

The heating mechanism at this time will be explained in detail with reference to FIG.

Thermal radiation from the radiation tube 25 is divided into a portion directed toward the coil W, a portion directed toward the heat insulating material 27 on the ceiling, and a portion heated the atmospheric gas in the furnace. The heat absorbed by the ceiling insulation material 27 is reradiated to the coil W. On the other hand, the high-temperature atmospheric gas pressurized by the circulation fan 31 passes around the auxiliary heating device 36 and is blown toward the lower surface of the coil W at high speed through the jet nozzle 22, thereby heating the lower surface of the coil W.

As a result, the upper surface of the coil W is heated mainly by radiation heating, and the lower surface is heated by convection heating due to the jet flow. The balance of heating between the upper and lower surfaces of the coil W can be easily controlled by adjusting the rotation speed of the circulation fan 31 and adjusting the auxiliary heating device 36.

Note that the atmospheric gas blown onto the lower surface of the coil W is
After passing around the coil W, it passes around the radiation pipe 25 and is sucked into the suction pipe 26 again, where it is repeatedly circulated by the circulation fan 31. Also,
In this example, the partition wall 37 and the entrance of the suction box 26 are designed so that the atmospheric gas blown into the furnace can effectively pass around the coil W and the radiation tube 25. The position of the suction box 26 in the vertical direction is also an important factor, and this example has a configuration that fully takes these into consideration.

Next, the mode of cooling will be explained with reference to FIGS. 4 and 5.

The cooler 33 is inserted into the wind box 24 from inside the cooler housing 34 by a cooler drive device 35.

The radiant pipe 25 and the burner of the auxiliary heating device 36 are extinguished. Then, the atmospheric gas is circulated in the direction of the arrow in FIG. 4 by the circulation fan 31, and the atmospheric gas pressurized by the circulation fan 31 is cooled by the cooler 33 in the wind box 24. This cooled atmospheric gas is sent below the wind box 24, flows into the lower header 23, and is ejected upward from the ejection nozzle 22 at high speed.

The cooling mechanism at this time will be explained in detail with reference to FIG.

The atmospheric gas cooled by the cooler 33 is ejected upward at high speed from the ejection nozzle 22 attached to the lower header 23, collides with the lower surface of the coil W, and removes heat from the coil W. Thereafter, the atmospheric gas blown into the furnace passes around the coil W, further absorbing heat from the coil W, and is again sucked into the suction box 26 by the circulation fan 3I, cooled by the cooler 33, and ejected. Nozzle 2
2 toward the lower surface of the coil W. The atmospheric gas circulates in this way.

The balance of cooling between the upper and lower surfaces of the coil W can be easily controlled by adjusting the rotation speed of the circulation fan 31 and the amount of cooling water supplied to the cooler 33.

Further, in this example, the configuration is such that the atmospheric gas flowing in the furnace effectively passes around the coil W, as in the heating period.

FIG. 6 shows temperature curves at the 0 point, D point, and E point of the coil W in FIG. 5. - In the figure, curve C is the temperature curve at point 0 and curve 1 is the temperature curve at point D, and they are almost the same curve. On the other hand, the temperature curve E at point E in the center of the coil W is slightly delayed. However, this delay T3. T 4 is less than half of the delay T , , T , in the conventional case. Therefore, the soaking time can also be shortened, and the time can be shortened in all of the heating, soaking, and cooling periods.

[Effects of the Invention] As explained above, the annealing furnace of the present invention heats the workpiece by the heating action of the radiation tube and the jetting of the heated atmospheric gas, and also heats the workpiece by the jetting of the cooled atmospheric gas. Since it is configured to cool the air, it has the following excellent effects.

(2) By using the ejection position of the atmospheric gas as one variable, the heating and cooling forms for the object to be processed can be diversified, and the temperature distribution of the object to be processed can be made uniform. For example, by heating the coil as the object to be processed from both the top and bottom surfaces, and cooling it mainly from the bottom surface, which is difficult to cool, during the cooling period, the layer temperature point and the coldest point within the coil will be at the center of the coil, and the temperature distribution within the coil will be improved. The temperature has become uniform and there are no temperature differences.

Based on the results of ■ and ■, the quality improved.

■The operating time has been significantly shortened and the production volume has increased.

■Reduced fuel consumption and improved fuel consumption.

[Brief explanation of drawings]

Figures 1 to 6 are diagrams for explaining one embodiment of the present invention, in which Figure 1 is a sectional view, Figure 2 is a sectional view in a heating-soaking state, and Figure 3 is a heating mechanism. FIG. 4 is a cross-sectional view in a cooling state, FIG. 5 is a diagram for explaining the cooling mechanism, and FIG. 6 is a diagram showing temperature curves at each point of the object to be processed. 7 to 9 are diagrams for explaining the conventional example, and FIG. 7 is a diagram showing the temperature curve at each point of the object to be treated;
FIG. 8 is a sectional view in a heating-soaking state, and FIG. 9 is a diagram for explaining the heating mechanism. 2! ... Plenum chamber, 22 ... Ejection nozzle, 23 ... Lower header, 24 ... Wind box, 25 ... Radiation pipe, 27 ...Insulation material, 31...Circulation fan, 33...Cooler, 36...Auxiliary heating device, W...Coil (to be treated) thing). α t5 &'t:'t 25 y Fig. 6 Time □ Fig. 7v4 Pair interval □

Claims (1)

[Claims] In an annealing furnace, the workpiece is heated and soaked by circulating high-temperature atmospheric gas in the furnace containing the workpiece, and then cooled down by circulating low-temperature atmospheric gas. A radiation tube that heats things, a nozzle that blows out atmospheric gas,
a gas flow path formed in the furnace; a circulation fan provided in the gas flow path to eject atmospheric gas from the jet nozzle and circulate it in the furnace; and a circulation fan and the jet nozzle in the gas flow path. an auxiliary heating device that is provided between the object to be processed and heats the atmospheric gas during heating and soaking of the object to be processed, and a cooler that is provided in the gas flow path and that cools the atmospheric gas during the cooling of the object to be processed; An annealing furnace characterized by comprising: