JPS6345455B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a box-type heat treatment furnace, for example, a batch-type annealing furnace for annealing cold-rolled steel sheet coils (hereinafter referred to as cold-rolled coils) in a reducing atmosphere. In particular, the present invention relates to a heat treatment furnace that can improve the uniformity of the heating rate and cooling rate throughout the coil.

[Conventional technology]

Conventionally, in batch annealing of cold-rolled coils, a cooling coil is inserted into a box-shaped furnace body, heated to a predetermined temperature in a predetermined atmospheric gas state, and then cooled to a predetermined temperature. There is.

As such a box-type annealing furnace, there has conventionally been one shown in FIG. In the figure, 1 is a box-shaped furnace body, which forms a closed furnace shell with a steel plate reinforced on the outside with shaped steel, and a ceiling 2 of the furnace shell 2.
a, inner linings 3a, 3b, and 3c made of a fireproof heat insulating material such as ceramic fiber are attached to the inside of the side wall 2b and the rear hearth 2c, and the hearth 2
A hearth wall 3d made of fireproof and insulating bricks is formed on top of the wall 3d. In addition, the front part of this furnace shell 2,
That is, a charging port 2e is formed on the left side of FIG. 4, and an opening/closing door 4 is disposed outside the charging port 2e so as to be movable up and down. Note that 17 is an atmospheric gas supply device for supplying atmospheric gas into the furnace.

The hearth 2d has a cooling coil W which is a material to be heated.
A mounting table (not shown) is set upright, and a plenum chamber 5a of the suction duct 5 is disposed between the mounting tables, and the chamber 5a extends left and right in FIG.
A large number of suction ports are formed on the top surface, and a circulation duct 6 extending upward in the furnace is connected to a header 5b to which the base of the suction port is connected. An air outlet 6a is formed inside the furnace at the upper end of the circulation duct 6, and a guide vane 6b is attached to the air outlet 6a.

Further, an impeller 7a of a circulation fan 7 is inserted near the connection portion of the circulation duct 6 with the header 5b, and an impeller 7a of the circulation duct 6 is inserted.
An element 8a, which is a heat exchange part of the gas cooler 8, is arranged on the downstream side of a, and this element 8a is connected to the drive device 8.
b allows it to move freely in and out of the circulation duct 6.

Further, a large number of radiant tubes 9, which are radiant heat sources, are inserted into the upper part of the furnace shell 2. The radiant tube 9 is made of a heat-resistant cast steel pipe formed into a U-shape, and is arranged at an angle of 45 degrees when viewed from inside the furnace.A combustion burner is attached to one end of the radiant tube 9 that protrudes outside the furnace shell. The other end of the tube 9 is connected to an exhaust pipe, and the inner part of the tube 9 is suspended from the ceiling 2a by a hanging rod 10.

In the conventional cold-rolled coil annealing furnace described above, during heating, the element 8a of the gas cooler 8 is retracted to the outside of the circulation duct 6, and the radiant tube 9 is heated red-hot by the combustion burner, and the atmosphere inside the furnace is heated by the circulation fan 7. Gas suction duct 5
The air is sucked into the plenum chamber 5a and blown out from the upper air outlet 6a of the circulation duct 6. As a result, as shown by arrow A in FIG. The rolled coil W is heated.

In addition, during cooling, the element 8a of the gas cooler 8 enters the circulation duct 6 to cool the atmospheric gas, and the cooled atmospheric gas is circulated from above to below the cold-rolled coil W in the same manner as during heating. As a result, the cold rolled coil W is cooled.

[Problem that the invention seeks to solve]

In the above-mentioned conventional device, during heating, the atmospheric gas is circulated from above to below the cold-rolled coil W, so the temperature of this atmospheric gas decreases as it goes downward, and the cold-rolled coil W becomes less heated as it goes lower. Moreover, since the radiant heat from the radiant tube 9 also acts on the upper part of the cold-rolled coil W, the temperature increase rate is greatly different between the upper part and the lower part of the cold-rolled coil W.

In addition, during cooling, the cooled atmospheric gas is circulated from above to below the cold-rolled coil W in the same way as during heating, so the temperature of this atmospheric gas increases as it goes downward, and the cold-rolled coil W moves downward. Since the refractory bricks of the hearth wall 3d have a large amount of heat storage, the cooling rate is slower in the lower part, and the cooling rate also differs greatly between the upper part and the lower part. Therefore, in this conventional apparatus, there is a problem that there is a large difference in the temperature increase rate and temperature decrease rate between the upper and lower parts of the cold rolled coil W, which has a negative effect on the annealing quality, and it takes a long time before the entire temperature becomes uniform. There are problems in that it takes a long time and productivity is low.

The present invention was made to solve these conventional problems, and it is possible to equalize the heating rate and cooling rate at the upper and lower parts of the material to be treated, thereby improving the quality of heat treatment and improving productivity. The purpose is to provide a box-type heat treatment furnace.

[Means for solving problems]

In a box-type heat treatment furnace, the present invention provides a suction duct having a large number of suction ports above a radiant heat source such as a radiant tube disposed above the material to be processed, and a large number of blow-off ducts below the material to be processed. It is characterized in that a blow-off duct having a mouth is provided, the two ducts are communicated with each other by a circulation duct, and a circulation fan is provided on the upstream side of the circulation duct, and a gas cooler is provided on the downstream side.

[Effect]

In the box-type heat treatment furnace according to the present invention, during heating, high-temperature atmospheric gas near the radiant tube is sucked into the suction duct in the upper part, passes through the circulation duct, and is ejected upward from the blow-off duct in the lower part. is heated by the radiant heat of the radiant tube, and the lower surface is heated by the high-temperature jet, so that the temperature rise rate of the upper and lower parts of the material to be treated is equalized. Further, during cooling, since the cooled atmospheric gas is ejected from the lower side where the amount of heat storage is large, the cooling time is shortened, and productivity is improved accordingly.

〔Example〕

Below, embodiments of the invention will be described with reference to the figures.

FIG. 1 shows a cold rolled coil annealing furnace according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 4 indicate the same or corresponding parts, and above the radiant tube 9, a large number of blowing ducts 11 are arranged so as to cross the radiant tube 9, and each of the suction ducts 11 has a large number of suction nozzles 11
a is attached at an angle of 45 degrees, and the tip of each suction nozzle 11a is located between adjacent radiant tubes 9. Each of the suction ducts 11 is connected to an upper header 12.

Further, a large number of blow-off ducts 13 are arranged between workpiece mounting tables (not shown) arranged on the hearth wall 3d. Each of the blow-off ducts 13 extends parallel to the suction duct 11, that is, in the front-rear direction of the furnace, has a blow-off port 13a formed on its upper surface, and is connected to the lower header 14 at its base.

The lower header 14 and the upper header 12 are connected by a circulation duct 15. An impeller 7a of the circulation fan 7 is inserted into the upper part of the circulation duct 15, and an element 8a of the gas cooler 8 is installed downstream of the impeller 7a.
It is arranged so that it can move forward and backward.

Further, a radiant tube 16 as an auxiliary heating device is inserted into the circulation duct 15 on the downstream side of the cooler, and a combustion burner is attached to the outside portion of the radiant tube 16. This auxiliary heat device compensates for the amount of heat released from the circulated atmospheric gas to each duct and the hearth wall 3d.
This is to equalize the temperature at the top and bottom of the cold-rolled coil.

Next, the effects of this embodiment will be explained.

In the annealing treatment of the cold-rolled coil in the apparatus of this embodiment, the entire coil is uniformly heated to a predetermined temperature, for example, 600°C.
The entire coil is then uniformly cooled to a predetermined temperature, for example 80°C. In this case, first open the charging door 4 and place the cold-rolled coil W on the workpiece mounting table using the cart, then close the charging door 4 and replace the inside of the furnace with atmospheric gas, thereby preparing for annealing. finish.

To heat the cold-rolled coil W, the combustion burner is ignited while the element 8a of the gas cooler 8 is retracted outside the circulation duct 15. Then,
The radiant tube 9 is heated to red heat, and the radiant heat from the tube 9 is input from the upper surface of the cold-rolled coil W, and the atmospheric gas heated by the radiant heat is sucked into the suction duct 11 by the circulation fan 7, and then 15, is heated by the radiant tube 16 of the auxiliary heating device at the lower part of the duct 15, and then is injected upward from the blow-off duct 13. As a result, the cold rolled coil W
The upper surface of the tube is heated by the radiant heat from the radiant tube 9, and the lower surface of the tube is heated by the high-temperature jet gas, so that the heating rate at the upper and lower portions is made uniform and the heating quality is improved. Further, the time required for the entire cold-rolled coil W to reach the same temperature, that is, the necessary heating time, is shortened by the equalization of the heating rate, and as a result, productivity is improved.

Next, when cooling the cold-rolled coil W, the combustion burner and the auxiliary burner are extinguished, the element 8a of the gas cooler 8 is inserted into the circulation duct 15, and in this state, the circulation fan 7 sucks atmospheric gas into the duct 11, circulation duct 15, blowout duct 13,
Circulate in the furnace inside the furnace. As a result, the atmospheric gas cooled by the gas cooler 8 is blown out from the lower surface of the cold-rolled coil W, and the coil W is cooled from the lower surface.

Here, there is a hearth wall 3d made of refractory insulating bricks and having a large amount of heat storage below the cold-rolled coil W. Therefore, when cooling by circulating atmospheric gas from above to below, the cooling rate of the lower part is was slow, and it took a long time to cool the entire coil to a predetermined temperature. On the other hand, in this embodiment, as mentioned above,
Since the atmospheric gas is ejected from below the cold-rolled coil W, the cooling rate can be improved and the cooling time can be shortened.
Productivity can be improved from this point as well.

Further, since the gas cooler 8 is provided downstream of the circulation fan 7, the temperature increase in the atmospheric gas caused by the rotation of the circulation fan 7 can be absorbed and then blown out to the cold rolled coil W.

FIG. 2 shows the heating and cooling characteristics for explaining the effects of this example. In the figure, curves T, M, and B represent the heating and cooling characteristics of the upper, middle, and lower parts of the cold-rolled coil, respectively, in a conventional furnace. The curves t, m,
b shows the heating and cooling characteristics of the upper, middle, and lower parts of the cold-rolled coil in the furnace of this example, respectively. Also
TR and TC are radiant tube temperatures, respectively.
It is the atmospheric gas temperature.

During heating, as is clear from Figure 2a, in the conventional furnace, the rising speed of the center (curve M) and lower part (curve B) is very slow compared to the rising speed of the upper part (curve T). The speed is uneven. In comparison, in the furnace of this example, the rising speed of the upper part (curve t) and the lower part (curve b) is almost the same, and the rising speed of the central part (curve m) is also greatly increased. The heating speed is uniform, and as a result, the required heating time required for the entire coil to rise to a predetermined temperature is 5 hours shorter in the furnace of this embodiment than in the conventional furnace.

Furthermore, during cooling, as is clear from Fig. 2b, the cooling rate in the upper, middle, and lower parts of the furnace of this embodiment is faster than that of the conventional furnace, and as a result, the entire coil is cooled to a predetermined temperature. The required cooling time for this example furnace is 8 times longer than that of the conventional furnace.
Time has been shortened.

FIG. 3 shows a modification of the above embodiment. 1st in the diagram
The same reference numerals as those in the drawings indicate the same or corresponding parts. In this embodiment, the upper header 12 is disposed above the blowing duct 11 so as to cross it, and the circulation fan 7 and the gas cooler 8 are arranged in the furnace shell 2. It is placed on the ceiling 2a.

In this modification, the same effects as in the above embodiment can be obtained, and there is also an effect that the space for placing the furnace can be narrowed.

In each of the above embodiments, a centrifugal fan was used as the circulation fan, but an axial flow fan may be used instead. Further, in each of the above embodiments, an annealing furnace for cold-rolled coils has been described, but the present invention is not limited to annealing furnaces, and can be applied to any batch type heat treatment furnace that performs heating and cooling. can also be applied.

〔Effect of the invention〕

As described above, according to the box-type heat treatment furnace according to the present invention, the suction duct is arranged above the radiant heat source such as a radiant tube arranged above the material to be treated, and the blow-off duct is arranged below the material to be treated. The material to be treated is heated by radiant heat from the top surface and a jet of high-temperature gas from the bottom surface, and cooled by a jet of low-temperature gas from the bottom surface, so the heating and cooling rates of the material to be treated are uniform. This has the effect of improving heat treatment quality, as well as increasing productivity by increasing heating and cooling rates.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional side view of a cold rolled coil annealing furnace according to an embodiment of the present invention, Fig. 2 is for explaining the effect thereof, Fig. 2a is a heating characteristic diagram, and Fig. 2b is
is a cooling characteristic diagram, FIG. 3 is a sectional side view showing a modification of the above embodiment, and FIG. 4 is a sectional side view showing a conventional cold rolled coil annealing furnace. In the figure, 1 is the furnace body, 7 is a circulation fan, and 8
is a gas cooler, 9 is a radiant tube (radiant heat source), 11 is a suction duct, 11a is a suction nozzle (suction port), 13 is a blowout duct, 13a
15 is an air outlet, 15 is a circulation duct, and W is a cold-rolled coil (material to be treated).

Claims (1)

[Scope of Claims] 1. A box-shaped heat treatment furnace in which a material to be treated is heated to a predetermined temperature in a box-shaped furnace main body and then cooled to a predetermined temperature. A large number of radiant heat sources for heating the material to be treated with radiant heat are arranged above the material, a suction duct having a number of suction ports on the lower surface is arranged above the radiant heat source, and a large number of air outlets are arranged on the upper surface. A blow-off duct having a mouth is disposed below the material to be treated, the blow-off duct and the suction duct are connected through a circulation duct, a circulation fan is disposed in the circulation duct, and a circulation fan of the circulation duct is connected to the suction duct. A box-shaped heat treatment furnace characterized by a gas cooler installed on the downstream side. 2. The heat treatment furnace is a batch annealing furnace for cold-rolled steel sheet coils, and the radiant heat source is a U-shaped radiant tube disposed within the furnace body.
2. The box-type heat treatment furnace according to claim 1, wherein the suction port is a tubular suction nozzle extending from a suction duct between adjacent radiant tubes.