JP3893629B2 - Heating furnace operation method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for operating a continuous heating furnace.
[0002]
[Prior art]
When heating a material to be processed in a continuous heating furnace, the material to be processed is continuously passed through the heating furnace and heated by blowing a gas for heating while the material to be processed is transported in the heating furnace. ing. In this case, the temperature of the heating gas is set to a temperature suitable for the heat treatment applied to the material to be processed.
[0003]
According to the above method, the material to be treated can be continuously and efficiently heated. Moreover, since it heats with the heating gas of the temperature suitable according to the heat processing of a to-be-processed material, appropriate heating can be performed. For example, when the material to be treated is simply annealed, the temperature of the gas for heating is set high so that the difference between the temperature of the gas for heating and the predetermined heating temperature of the material to be treated (called a thermal head) is slightly larger. In this case, when the temperature of the material to be treated is raised quickly to improve productivity, or when the material to be treated is partially annealed, the temperature of the heating gas is set so that the thermal head becomes small. By setting, the material to be treated can be heated to a predetermined temperature with high accuracy to enable production of a good quality product free from hardness spots.
[0004]
By the way, when the heat treatment on the material to be treated is completed and another heat treatment is performed on another material to be treated next, the heating furnace is operated as follows. That is, after the previous material to be processed is finished, the temperature of the heating gas is changed to the temperature for heating the next material to be processed. While the change work is being performed, a dummy material is connected to the above-mentioned material to be processed and passed through a heating furnace. When the change of the temperature of the heating gas is completed, the other material to be treated is connected to the dummy material and passed through a heating furnace to heat it.
[0005]
[Problems to be solved by the invention]
However, it takes a long time to change the temperature of the heating gas. In the conventional method, since the operation as the heating furnace is substantially suspended for the long time, the productivity of the furnace is lowered. There was a problem.
[0006]
The furnace operating method of the present invention is provided in order to solve the above-mentioned problems (technical problems) of the prior art.
The first purpose is to heat the material to be treated efficiently by heating the material while passing it continuously through a heating furnace.
The second purpose is to change the temperature of the heating gas when heating another material to be treated for another heat treatment, thereby enabling heating at a temperature condition suitable for the heat treatment. is there.
The third purpose is to heat one material to be treated, and then to heat another material to be treated with a gas for heating at another temperature, passing the material to be treated through a heating furnace. By changing the temperature of the heating gas to the temperature for heating the next material to be processed while the process is being performed, when the heating of the previous material to be processed is completed, The material to be treated can be passed through a heating furnace to be heated, and the heating furnace can be operated without any downtime to improve its productivity.
The fourth object is to change the temperature of the heating gas to the temperature for heating the next material to be processed while heating the material to be processed as described above. Appropriate heating can be performed on the material to be processed, and the quality of the material to be processed can be maintained.
Another object of the present invention is to reduce the amount of blowing out the heating gas as the connecting portion between the preceding strip, which is the previous material to be processed, and the subsequent strip, which is the next material, passes through the heating furnace. In the case of control, the controllable width is wide so that the control can be easily performed.
Other objects and advantages will be readily apparent from the drawings and the following description associated therewith.
[0007]
[Means for Solving the Problems]
The operation method of the heating furnace in the present invention is as follows:
A plurality of strips with different heat treatment conditions are connected in cascade and passed sequentially through a heating furnace,
In the heating furnace, a furnace operation method in which each strip is heated while the respective strips are floated by making the furnace temperatures different from each other and blowing the gas of the different furnace temperatures as the heating gas. In
In the state where the furnace temperature is set to a temperature for heating the preceding strip, the preceding strip is passed at a conveying speed for applying predetermined heating thereto,
Next, if the preceding strip is near the end while the preceding strip is passing through the furnace,
The amount out blowing of heating gas in the heating furnace was changed to a maximum,
And to and change the speed for providing a predetermined heating preceding strip with the conveying speed at its maximum blown out of the heating gas,
Change the furnace temperature toward the furnace temperature for heating the subsequent strip,
Further, the transfer speed is changed to a speed for applying predetermined heating to the preceding strip with the heating gas at the furnace temperature being changed,
Further, when passing the connecting portion between the preceding strip and the succeeding strip into the heating furnace, the amount of blowing gas for heating in the heating furnace is changed from the above-mentioned maximum blowing amount to the minimum blowing amount necessary for levitation of the strip. Control between
Next, after the succeeding strip is put into the heating furnace, the transport speed is changed to a speed for applying the predetermined heating to the succeeding strip while the furnace temperature is set to a temperature for heating the succeeding strip. To do.
[0008]
[Action]
When processing materials connected in cascade are sequentially passed through a heating furnace to heat them, in a state where the temperature of the heating gas is set to the temperature for heating the previous processing material, the previous processing material is set to the predetermined temperature. It passes at the conveyance speed to give the heating. Accordingly, it is possible to appropriately heat the preceding material to be processed. If the preceding material to be processed is near the end, the temperature of the heating gas is changed to the temperature for heating the subsequent material to be processed while the preceding material to be processed passes. In this case, the conveying speed of the material to be processed is changed to a speed for applying predetermined heating to the preceding material to be processed with the heating gas at the temperature being changed. Accordingly, the preceding material to be processed can be appropriately heated regardless of the temperature change of the heating gas. After the succeeding material to be passed through the heating furnace, the transport speed is changed to a speed for applying predetermined heating to the succeeding material, so that the subsequent material is also heated appropriately. it can.
[0009]
【Example】
Hereinafter, drawings showing examples of the present application will be described. In FIG. 1, A indicates a continuous heat treatment furnace for continuously heat-treating a material to be treated, for example, a heating furnace 1 for continuously heating a material to be treated and a heated material to be treated as is well known. And a cooling chamber 2 for continuously cooling. The heating furnace 1 is composed of elements indicated by reference numerals 3 to 9. That is, 3 is a furnace body, 4 is an inlet of a material to be processed, 5 is an outlet, 6 is a spraying means for spraying a heating gas to heat and float the material to be processed. The upper and lower plenum chambers 7 for blowing out the heating gas and holding it in the heated and floating state, and the fans for feeding the heating gas in the furnace body 3 into the upper and lower plenum chambers 7 for blowing out 8 is an example. Numerous heating gas outlets are provided on the lower surface of the upper plenum chamber and the upper surface of the lower plenum chamber, respectively. The spraying means 6 is configured to vary the amount of heating gas sprayed onto the material to be treated. For example, the spraying amount can be varied by varying the blowing speed of the heating gas from the plenum chamber 7. However, the blowing amount of the heating gas from the plenum chamber 7 toward the material to be processed may be varied with the blowing speed kept constant. As a specific means of the former, for example, the rotation speed of the fan 8 is configured to be variable, and this is increased or decreased to increase or decrease the blowing speed of the heating gas from the plenum chamber 7. Alternatively, the amount of heated gas from the fan 8 to the plenum chamber 7 is changed by a damper provided in the middle thereof. As the specific means of the latter, the heating gas is blown out of a large number of blowing ports provided for blowing the heating gas toward the material to be treated on the surface facing the material to be treated in the plenum chamber 7. Change the number of things to do. Note that the former means and the latter means may be performed by arbitrarily combining them. The heating furnace 1 is divided into a plurality of zones in the passing direction of the material to be treated (left and right direction in the figure) (the figure shows an example divided into two zones Z1 and Z2 for simplicity), and the spraying means 6 is provided for each zone, and the spraying amount can be individually changed for each zone. Next, 9 is a heating means for heating the heating gas in the furnace body 3, and the calorific value is variable. For example, a burner is shown, but a radiant tube, a heating wire or the like may be used.
[0010]
Similarly, the cooling chamber 2 has a well-known configuration, 11 is a casing, 12 is the presence of a cooling gas spraying means, and 13 is a cooling gas sprayed on the material to be treated and kept in its cooled and floating state. The upper and lower plenum chambers for performing are shown. The outlet 5 serves as an inlet for the cooling chamber 2. Although not shown, the heat treatment furnace A includes a driving means for driving the material to be processed, which is inserted through the heating furnace 1 and the cooling chamber 2 in order, and the driving means is a conveying speed of the material to be processed. Is configured to be variable. M1 and M2 are strips shown as materials to be treated, which are connected in cascade to pass through the heat treatment furnace A in order, and M1 passed through the furnace A first passes through the preceding strip, and then passes through the furnace A. M2 is called the subsequent strip. J indicates a connection portion (called a plate joint) between the former end and the latter start. These strips are, for example, metal strips such as aluminum, copper, and stainless steel, and have various thicknesses of 0.3 mm to 4 mm and widths of several hundred mm to 2,000 mm.
[0011]
The heat treatment (for example, partial annealing) of the strip M1 in the heat treatment furnace A configured as described above is as follows. The heating gas in the furnace body 3 is set to a temperature for heating the strip M1 (for example, 500 ° C.). In that state, the strip M1 is passed through the furnace A. That is, the heating furnace 1 is introduced into the furnace body 3 through the inlet 4, transported through the furnace body 3, reaches the cooling chamber 2 through the outlet 5, and is transported through the cooling chamber 2. The transport speed of the strip M1 at this time is a transport speed for applying a predetermined heating to the strip M1 at the heating temperature. In the state where the strip M1 is conveyed as described above, the heating gas blown from the plenum chamber 7 is blown to the strip M1 in the heating furnace 1, and the strip M1 is heated while being floated. When the strip M1 moves in the heating furnace 1 in the above state, the temperature of the strip M1 is raised to a predetermined temperature (for example, 400 ° C.). Next, in the cooling chamber 2, the strip M1 is cooled by the cooling gas blown out from the plenum chamber 13, and the cooling is performed. In this way, the partial annealing of the strip M1 is continuously performed.
[0012]
Next, another strip M2 is connected to the strip M1 in cascade, and the strips M1 and M2 are subjected to different heat treatments (for example, the partial annealing for the strip M1 and the complete annealing for the strip M2). An operation in the case where the strips M1 and M2 are heated with heating gases having different temperatures in the heating furnace 1 will be described. First, FIG. 2 shows a case where the furnace temperature for heating the strip M2 (for example, 650 ° C.) is higher than the furnace temperature for heating the strip M1 (temperature of the heating gas in the heating furnace 1; for example, 500 ° C.). Based on
[0013]
In period 21, the preceding strip M1 is heated under normal conditions. That is, the preceding strip M1 is passed through the heating furnace 1 and heated in a state where the conveying speed 22, the furnace temperature 23, and the heating gas blow-out speed 24 from the plenum chamber satisfy the conditions suitable for heating the preceding strip M1 as usual. . Next, when the preceding strip M1 is near the end, preparation control 25 for dummyless control is performed. That is, the blowing amount of the heating gas is maximized. For example, in this example, the heating gas blowing speed is increased to the maximum speed (100% blowing speed) 27 as indicated by reference numeral 26. Along with this, the transport speed of the strip is changed to a speed for applying a predetermined heating to the preceding strip M1 with the heating gas of the maximum spray amount. That is, even if the blowing speed is increased, the conveying speed corresponds to the maximum blowing speed 27 as indicated by reference numeral 28 so that the strip M1 passing through the heating furnace 1 is heated with a predetermined amount of heat. Increase to speed 29.
[0014]
Next, after the preparation control is completed, dummyless control, that is, control 31 for continuously performing the heat treatment operation of the strip even when the furnace temperature is changed is performed. The control first increases the furnace temperature to a temperature 33 (for example, 650 ° C.) for heating the subsequent strip M2, as indicated by reference numeral 32. Along with the change, the conveyance speed is changed to a speed for applying predetermined heating to the preceding strip M1 with the heating gas at the temperature being changed. That is, in the process of raising and after raising the furnace temperature, the conveying speed is set to each furnace temperature so that heating of a predetermined amount of heat is performed while the strip M1 passes through the heating furnace 1 even if the furnace temperature is raised. The speed is set and increased according to the control 34, and the speed is increased to the speed 35 corresponding to the temperature 33. Note that the conveying speed is such that the amount of heat by which the strip is heated to the set temperature is given from the material conditions such as the thickness and width of the strip and the heat transfer conditions such as convection by radiation and jet flow in the heating furnace 1. For example, by calculation.
[0015]
Next, after the operation as described above, the plate joint portion J reaches the inlet 4 of the heating furnace 1, passes through the heating furnace 1, and exits from the outlet 5. The change of the blowing speed 38 and the accompanying change of the conveying speed 39).
[0016]
Thereafter, in a period 40 in which the subsequent strip M2 is passed through the entire length of the furnace body 3, the conveying speed is changed to a speed 41 for applying predetermined heating to the subsequent strip M2, and the heating gas is blown out. The speed is changed to the same speed 43, and the subsequent strip M2 is heated under the transport speed 41, the blow-out speed 43, and the new furnace temperature 42 (equal to the changed furnace temperature 33).
[0017]
By the above operation, the preceding strip M1 can be heated to an appropriate temperature (for example, 400 ° C.) with a furnace temperature (for example, 500 ° C.) suitable for its heat treatment (for example, partial annealing). In addition, the subsequent strip M2 can be heated to an appropriate temperature (for example, 530 ° C.) with a furnace temperature (for example, 650 ° C.) suitable for the heat treatment (for example, complete annealing).
[0018]
It should be noted that the operations indicated by reference numerals 26 and 28 and the operations indicated by reference numerals 32 and 34 may be performed with the operations of reference numerals 32 and 34 first and the operations of reference numerals 26 and 28 later.
[0019]
Next, a case where the furnace temperature at the time of heating the strip M2 is lower than the furnace temperature at the time of heating the strip M1 will be described with reference to FIG. The operation in this case is the same as the operation in the case of FIG. 2 except for a part thereof, and the description is duplicated. Therefore, the same part is denoted by the same reference numeral as in FIG. Only the differences will be described. That is, in the period of the dummyless control 31, the furnace temperature is lowered to a temperature 33 suitable for heating the subsequent strip M2, as indicated by reference numeral 45. In the descending process, the transport speed is set to a transport speed corresponding to each furnace temperature so that the amount of heat given while the strip M1 passes through the heating furnace 1 does not change even if the furnace temperature is lowered. Then, the lowering control 46 is performed to lower the speed 35 corresponding to the temperature 33.
[0020]
Next, the plate joint control will be described. First, the case where the plate thickness of the preceding strip M1 is thin and the plate thickness of the subsequent strip M2 is thick will be described with reference to FIG. When the plate joint J approaches the inlet 4 of the heating furnace 1, the conveying speed is lowered from the speed 35 to the speed 41 as indicated by reference numeral 51. Along with the lowering, the blowing speed is lowered from the maximum speed 27 to the speed 53 at which the predetermined amount of heat can be given to the preceding strip M1 at the speed 41 as indicated by reference numeral 52. In this case, the controllable range of the blowing speed 53 is the entire range from the maximum speed 27 to the lower limit speed at which the stable floating of the strip M2 can be performed, so that the setting of the speed 53 is easy. Next, in the above state, if the plate joint J passes the boundary 54 between the zone Z1 and the zone Z2, the blowing speed in the zone Z1 is increased to the blowing speed 43 as indicated by reference numeral 55. If the plate joint J passes the outlet 5, the blowing speed in the zone Z2 is also increased to the blowing speed 43 as indicated by reference numeral 56.
[0021]
Next, a case where the plate thickness of the preceding strip M1 is thick and the plate thickness of the subsequent strip M2 is thin will be described with reference to FIG. If the plate joint J approaches the inlet 4 of the heating furnace 1, the blowing speed in the zone Z1 is given a predetermined amount of heat to the subsequent strip M2 at the speed 35 as shown by the reference numeral 52 from the maximum speed 27. Decrease to speed 53. Next, if the plate joint J approaches the boundary 54 between the zone Z1 and the zone Z2 in the above state, the blowing speed in the zone Z2 is lowered to the speed 53 as in the zone Z1, as indicated by reference numeral 52 '. On the other hand, as for the conveyance speed, as long as the plate joint portion J passes through the heating furnace 1, the conveyance is performed at the speed 35 described above. The speed is increased to 41. The blowing speed is also increased to the blowing speed 43 as indicated by reference numeral 56.
[0022]
Next, three or more strips may be connected in cascade to perform heat treatment in order. In this case, in the present specification, when the leading strip is passed through the heating furnace 1, the strip is referred to as the preceding strip, and the second strip subsequent thereto is referred to as the succeeding strip. When the second strip is passed through the heating furnace 1, the strip is referred to as the preceding strip, and the third strip subsequent thereto is referred to as the subsequent strip. In the same way, the strip inserted into the heating furnace 1 is referred to as the preceding strip, and the subsequent strips subsequently passed through the heating furnace 1 are referred to as the subsequent strip.
[0023]
Next, in the above embodiment, the plenum chamber type is exemplified as the means for blowing the gas to the material to be processed. However, the means may be constituted by a static pressure pad and a dynamic pressure nozzle. Moreover, although the floating furnace is exemplified as the continuous heat treatment furnace, a catenary furnace or other continuous furnace may be used. Furthermore, the material to be treated is not limited to the strip material, but may be a wire material.
[0024]
【The invention's effect】
As described above, the present invention achieves the first to fourth objects with the configuration of claim 1 and has the following effects. That is,
When the material to be processed M1 is heated, the material to be processed M1 is heated while being continuously passed through the heating furnace 1, so that the material to be processed M1 can be efficiently heated.
Further, when heating for another heat treatment is performed on another material to be treated M2, there is an effect that the heating gas can be heated at a temperature condition suitable for the heat treatment by changing the temperature of the heating gas.
Further, when heating is performed on one material to be processed M1, and then another material to be processed M2 is heated with a heating gas at another temperature, in the present invention, the material to be processed M1 is placed in the heating furnace 1 in the present invention. Since the temperature of the heating gas is changed to the temperature for heating the next material to be processed M2 when the heating is performed through the material, when the heating of the previous material to be processed M1 is finished, the material to be processed The next material M2 can be passed through the heating furnace 1 in succession to M1 and heated, and the heating furnace can be operated without any pauses and the productivity can be improved. There is.
Moreover, even if the temperature of the heating gas is changed to the temperature for heating the next processed material M2 while the previous processed material M1 is heated as described above, At the time of change, since the conveying speed of the material to be processed M1 is changed to a speed for applying predetermined heating thereto, the previous material to be processed M1 can be appropriately heated, and the material to be processed The effect that can maintain the quality of.
Further, according to the second aspect of the present invention, in addition to the first to fourth objects, the other objects are achieved and the following effects are obtained. That is,
During the passage of the preceding strip M1, the amount of heating gas blown to the strip is maximized in advance, so that the connecting portion J between the preceding strip M1 and the succeeding strip M2 passes through the heating furnace 1 for heating. In the case of controlling the amount of gas blown out, the entire range from the minimum necessary for the levitation of the strip to the maximum is the controllable width, and therefore, there is an effect that appropriate control can be easily performed.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a part of a continuous heat treatment furnace.
FIG. 2 is a diagram for explaining an operation for raising the temperature of a heating gas.
FIG. 3 is a diagram for explaining an operation when lowering the temperature of a heating gas.
FIG. 4 is a diagram for explaining plate joint control when the succeeding strip is thicker than the preceding strip.
FIG. 5 is a diagram for explaining plate joint control when the succeeding strip is thinner than the preceding strip.
[Explanation of symbols]
1 Heating furnace 6 Spraying means
M1 leading strip
M2 trailing strip

Claims (1)

A plurality of strips with different heat treatment conditions are connected in cascade and passed sequentially through a heating furnace,
In the heating furnace, a furnace operation method in which each strip is heated while the respective strips are floated by making the furnace temperatures different from each other and blowing the gas of the different furnace temperatures as the heating gas. In
In the state where the furnace temperature is set to a temperature for heating the preceding strip, the preceding strip is passed at a conveying speed for applying predetermined heating thereto,
Next, if the preceding strip is near the end while the preceding strip is passing through the furnace,
The amount out blowing of heating gas in the heating furnace was changed to a maximum,
And to and change the speed for providing a predetermined heating preceding strip with the conveying speed at its maximum blown out of the heating gas,
Change the furnace temperature toward the furnace temperature for heating the subsequent strip,
Further, the transfer speed is changed to a speed for applying predetermined heating to the preceding strip with the heating gas at the furnace temperature being changed,
Further, when passing the connecting portion between the preceding strip and the succeeding strip into the heating furnace, the amount of blowing gas for heating in the heating furnace is changed from the above-mentioned maximum blowing amount to the minimum blowing amount necessary for levitation of the strip. Control between
Next, after the succeeding strip is put into the heating furnace, the transport speed is changed to a speed for applying the predetermined heating to the succeeding strip while the furnace temperature is set to a temperature for heating the succeeding strip. A method for operating a heating furnace, characterized in that:

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