JP2000160258A - Continuous heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the passing speed of a strip without developing unevenness in the width direction of material and quality in the metallic strip to execute the heat treatment. SOLUTION: In a continuous annealing furnace 20 for continuously annealing a strip 21, electric heaters 23a, 23b and 23c arranged in a heating zone 22 are divided into three portions in the width direction and individually controlled with control devices 24a, 24b and 24c so that the center portion becomes higher setting temp. than these of both side portions. The temp. at both side portions of the strip 21 has a tendency to rise higher than the temp. at the center portion when the strip 21 is tried to be uniformely heated with the electric heaters 23a, 23b and 23c, also due to the heating with the radiation heat from the side surfaces in the furnace. This tendency is further remarkable in the case of improving the producing efficiency by quickening the passing speed of the strip. Since it is controlled that the temp. of the electric heater 23b at the center portion becomes higher than the temps. of the electric heaters 23a, 23c at both side portions, the temp. in the width direction of the strip 21 is uniformized and the material after annealing can be uniformized so as not to develop the unevenness in the width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous heating furnace for continuously heating a metal strip to perform heat treatment such as annealing.

[0002]

2. Description of the Related Art Conventionally, a continuous annealing furnace having a heating zone having a configuration as shown in FIG. 8 has been used as a continuous annealing furnace for a metal strip. FIG.
67 shows a configuration of a heating zone of the continuous annealing furnace disclosed in No. 67. The strip 1, which is a metal strip, is heated by an electric heater 3 provided in the heating zone 2, and reaches an annealing temperature. A heat radiation plate 4 is provided between the electric heater 3 and the strip 1 so that the entire surface of the strip 1 is uniformly heated without being locally heated.

FIG. 8B shows the configuration of a portion corresponding to the heating zone 2 of the prior art disclosed in Japanese Patent Application Laid-Open No. Hei 4-210431. In this prior art, the strip 1 is covered with a flat cylindrical muffle 5, and heated by an electric heater 6 divided into a plurality of sections in the running direction of the strip 1.

[0004] The electric heater 3 is controlled for the purpose of uniformly heating the surface of the strip 1. The production efficiency of the strip 1 to be passed through the continuous annealing furnace can be increased as the passing speed is increased. However, if the processing temperature of the metal strip fluctuates, it becomes impossible to obtain a metal strip of good quality. In the prior art shown in FIG. 8A or FIG. 8B, the heat radiating plate 4 or the muffle 5 attempts to uniformly transfer heat to the strip 1 on the inner peripheral side.

Japanese Unexamined Patent Publication (Kokai) No. 63-27713 discloses a method for producing a unidirectional silicon steel sheet having excellent magnetic properties by changing the annealing temperature continuously or stepwise in the longitudinal or width direction of the steel sheet. Is disclosed.
This concept requires not uniform heating but heating that changes the temperature. However, it is unknown how to change the annealing temperature.

FIG. 9 shows a schematic configuration of a terminal portion provided for supplying power to the electric heater 3 in a conventional continuous annealing furnace or the like. The conductive metal rod-shaped terminal rod 10 has a flange portion 11 and is inserted from outside the furnace wall 12 into a mounting seat 13 provided on a furnace wall 12 of a continuous annealing furnace. Furnace wall 12
Is formed of refractory bricks 14 except for the mounting seat 13. The mounting seat 13 is mounted when the refractory bricks 14 are bricked. An intermediate packing material 15 made of a heat-resistant ceramic fiber is pushed around the terminal rod 10 inserted into the mounting seat 13. Inside the furnace wall 12 is a sealing material 16 made of a heat-resistant material.
Sealed. The outer peripheral side of the intermediate packing material 15
It is pressed by the flange portion 11 via a plurality of gaskets 17. The flange portion 11 is fixed to a bolt 18 welded to the mounting seat 13 using a nut 19.

[0007]

In the prior art as shown in FIG. 8, the heat radiation plate 4 shown in FIG. 8A and the muffle 5 shown in FIG. Radiant heat transfer is performed uniformly without heating, and the strip 1
The material does not vary in the width direction. However, since the heat radiation plate 4 and the muffle 5 are formed of a heat-resistant metal material such as Inconel 600, for example, the heat-resistant temperature is 1%.
Since the temperature is about 150 ° C. and the difference between the target material temperature of the strip 1 and the furnace temperature is small, high-speed annealing for increasing the sheet passing speed cannot be performed.

If the heat radiation plate 4 shown in FIG. 8A and the muffle 5 shown in FIG. 8B are not used and the temperature of the heating zone is increased and the radiation heat is directly transferred from the electric heater to the strip 1, high-speed annealing is performed. However, since radiation from the side is also applied, the outer edges in the width direction receive more radiation heat than the central portion in the width direction of the strip 1, the temperature is easily increased, and the variation in the material is reduced. It gets bigger. For example, in a continuous annealing furnace in which stainless steel is to be annealed, in the case of SUS304, as shown in the following Table 1, the hardness indicating the effect of annealing varies between the central portion and the left and right edge portions, and varies between the left and right edge portions. This shows that the edge portion has a lower hardness and a higher annealing temperature than the central portion.

[0009]

[Table 1]

Further, in the structure of the terminal portion as shown in FIG. 9, for example, the periphery of the sealing material 16 and the intermediate packing material 15 cannot be completely airtightly sealed, and the atmosphere inside the heating zone is disturbed. Therefore, even when the heat treatment is to be performed in a reducing atmosphere in the heating zone, oxygen or the like invades easily and a colored region is easily formed on the surface of the metal band.

An object of the present invention is to provide a continuous heating furnace capable of preventing variations in the material and quality of a metal strip to be heat-treated and increasing the sheet passing speed.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a continuous heating furnace having a heating zone for heating a continuously passed metal strip to a target material temperature, wherein the heating zone faces a surface of the metal strip with the heating zone. The heating zone heater includes a heating zone heater that is divided into three or more in the width direction perpendicular to the direction in which the metal strip passes, and a control device that individually controls the heating output of the divided portions of the heating zone heater. It is a continuous heating furnace.

According to the present invention, the heating zone heater is divided into three or more in the width direction perpendicular to the metal plate passing direction, and the control device individually controls the heating output of each divided portion. In addition, the material temperature in the width direction of the metal strip is adjusted to be uniform, the variation in the material is prevented, the sheet passing speed is increased, and the productivity can be improved.

Further, in the present invention, the control device may be configured such that the heating zone heater is configured such that a divided portion corresponding to a central portion in the width direction of the metal band is separated from divided portions opposed to both side edges in the width direction of the metal band. A high temperature control system is provided.

According to the present invention, the divided portion of the heating zone heater divided into three or more in the width direction of the metal band is divided into a portion facing the central portion of the metal band and a portion facing both side edges in the width direction. Since the temperature is controlled to be high, the central portion, which is lower in temperature than the side edge portion when heating uniformly, can be heated equally to the side edge portion to perform uniform heat treatment.

Further, in the present invention, the heating zone has a furnace wall formed of refractory bricks, and a portion for supplying power to the heating zone heater from outside is inserted into a through hole formed in the furnace wall, and the heating zone heater is provided with an inner wall. A terminal rod having a flange portion having a diameter larger than the inner diameter of the through-hole near the outer end, and a flange protruding from the inside of the flange portion of the terminal rod and the surface of the furnace wall. Terminal rod so as to cover between the inner gasket made of a heat-resistant material, the outer diameter of which is larger than the outer diameter of the flange portion, and the surface of the inner gasket from outside the flange portion of the terminal rod. An outer gasket inserted into the outer end of the outer gasket, a pressing plate for fixing the outer peripheral portion of the outer gasket to the furnace wall, and an inner peripheral portion of the outer gasket and a terminal rod. A sealing member covering the gap between the outer circumference of the terminal rod and the outer end side of the terminal rod, and made of a heat-resistant material; and a pressing member for pressing the packing against the outer gasket surface at the outer end side of the terminal rod. Features.

According to the present invention, the portion of the heating zone to which power is supplied to the heating zone heater from the outside is formed by sandwiching the flange portion of the terminal rod between the inner gasket and the outer gasket and forming a through hole in the furnace wall through which the terminal rod is inserted. The space between the terminal rod and the terminal rod can be reliably sealed. Since the gap between the outer periphery of the terminal rod and the inner periphery of the outer gasket is sealed by pressing the packing from the outer end of the terminal rod with a pressing member, the gap is 3 mm in the width direction perpendicular to the direction in which the metal strip passes. Even if the through-hole through which the terminal rod of the power supply part to the heating zone heater that is arranged and divided is inserted is increased, the airtightness is increased, without impairing the atmosphere in the heating zone,
Heating of the metal strip can be performed.

[0018]

FIG. 1 shows a schematic configuration of a main part of a continuous annealing furnace 20 according to an embodiment of the present invention. The continuous annealing furnace 20 has a heating zone 22 for heating to a temperature required for heat treatment such as annealing while continuously passing a strip 21 which is a metal zone such as a stainless steel strip. Electric heaters 23 a and 23 divided into three in the width direction perpendicular to the direction in which the strip 21 passes are provided in the heating zone 22.
b, 23c. Each electric heater 23a, 23b, 2
3c are individually controlled by the control devices 24a, 24b and 24c, respectively, so that the set temperature of the electric heater 23b in the central portion is higher than the set temperature of the electric heaters 23a and 23c in the edge portions on both side edges. You. Strip 2
1, a central portion in the width direction is heated by radiation from the electric heater 23b, and both edge portions in the width direction are
a, and is heated by radiant heat from 23c. The set temperature of the electric heater 23b in the central portion is the electric heater 2 in both edge portions.
Since the temperatures of the strips 21 are set to be higher than the temperatures of the strips 3a and 23c, the heating in the width direction of the strip 21 can be performed uniformly with the central portion and both side portions being substantially the same.

FIG. 2 shows the electric heaters 23a and 23 shown in FIG.
The configuration of the parts b and 23c is shown. The furnace wall of the continuous annealing furnace 20 includes a refractory brick lining 25, a refractory brick outer layer 26, and an outer wall flange 27 made of a steel material. As shown in FIG. 3, the electric heaters 23a, 23b,
23c is connected so that each part of the strip 21 divided into three in the width direction is electrically continuous. As shown in FIG. 4, each heater wire 28 is suspended by a support 29. The heater wire 28 is formed of a heat-resistant metal such as molybdenum (Mo).

FIG. 5 shows a schematic configuration of a continuous bright annealing facility 30 including the continuous annealing furnace 20 shown in FIG. In the continuous bright annealing equipment 30, the strip 21 is supplied from the pay-off reels 31, 32, and is annealed in a reducing atmosphere containing hydrogen or the like while being wound up by the tension reel 33. The plurality of payoff reels 31 and 32 are used alternately in order to continuously and rapidly pass the strip 21. For example, when the strip 21 supplied from one payoff reel 31 is about to end, The strip 21 supplied from the other payoff reel 32 is connected by welding with a welding machine 34. Strip 21 continuously from a plurality of payoff reels 31 and 32
Is supplied to the continuous annealing furnace 20 via the entrance looper 36 after the deformed state is corrected by the shaping machine 35. The continuous annealing furnace 20 is of a vertical type, and performs a bright annealing process of annealing the inside of the strip 21 while keeping the inside thereof in a reducing atmosphere so as not to oxidize the surface of the strip 21.

The strip 21 taken into the continuous annealing furnace 20 rises from the lower inlet to the top and further descends from the top to the lower outlet while heating zone 2
2 and air cooling after the heating. The strip 21 coming out of the outlet of the continuous annealing furnace 20 is connected to the outlet looper 3.
7, reaches the shearing machine 38, is cut for each original coil, and is wound around the tension reel 33. Strip 2
Reference numeral 1 designates an entrance looper 36 and an exit looper 37 for exchanging the pay-off reels 31 and 32 and for changing each coil on the tension reel 33 so that the threading speed can be maintained as constant as possible in the continuous annealing furnace 20. For the time required for the winding process, the sheet passing speed upstream of the entrance looper 36 or downstream of the exit looper 37 can be reduced or stopped.

FIG. 6 shows a continuous annealing furnace 20 according to the embodiment of FIG.
1 shows a configuration of a power supply unit for the electric heaters 23a, 23b, and 23c provided in the first embodiment. The distal ends of the electric heaters 23a, 23b, and 23c are welded to the distal ends of the metal terminal rods 40, and are electrically joined. Terminal rod 40
Has a rod flange portion 41 at a portion closer to the outside. A portion closer to the inner side than the rod flange portion 41 is inserted into a through hole 42 formed in the refractory brick lining 25 and the refractory brick outer layer 26 of the furnace wall of the continuous annealing furnace 20. An inner gasket 43 is interposed between the outer wall flange 27 and the rod flange 41 from around the opening of the through hole 42 to hermetically seal.
Outside the rod flange 41, an outer gasket 44 is provided.
Is inserted into the outer end of the terminal rod 40. The outer diameter of the inner gasket 43 and the outer gasket 44 is
It is larger than the outer diameter of the rod flange 41. Portions of the inner gasket 43 and the outer gasket larger than the rod flange 41 are pressed from the outside by a pressing plate 45, and are fixed to the outer wall flange 27 of the furnace wall by bolts.

The pressing plate 45 has an annular shape such that the inner peripheral side slightly covers the inner side in the radial direction from the outer periphery of the rod flange portion 41. The inner peripheral sides of the inner gasket 43 and the outer gasket 44 are provided to extend radially inward from the inner periphery of the holding plate 45. Inner peripheral sides of inner gasket 43 and outer gasket 44 and terminal rod 4
The gap between the outer periphery of the terminal rod 40 and the outer periphery of the terminal rod 40 is sealed by a packing 47 inserted from the outer end side of the terminal rod 40. The packing 47 is pressed against an end face of a terminal 48 attached to an outer end of the terminal rod 40. The terminal 48, which is a pressing member, is screwed into a screw 49 formed at the outer end of the terminal rod 40, and presses the packing 47 at the end face.

The inner gasket 43 is composed of a core material 50 and surface materials 51 and 52 on both surfaces thereof, and is divided into semicircular portions.
3 can be combined. Outer gasket 44
Is composed of a core material 53 and a surface material 54, and is inserted from the outer end of the terminal rod 40, so that it is integrally formed. The gap between the inner peripheral side of the outer gasket 44 and the inner gasket 43 and the outer peripheral side of the terminal rod 40 is sealed by a packing 47.

The packing 47 is made of a heat-resistant material that does not contain asbestos, such as "T / # 6840 Hemisal 20" manufactured by Nichias Corporation. The core members 50 and 53 are also formed of a similar heat-resistant material or silicon rubber. As the surface materials 51, 52, and 54, for example, a heat-resistant material such as “T / # 1995 Hemisal 10” (trade name) manufactured by Nichias Corporation is used.

With the configuration of the power supply part as shown in FIG. 6, the airtightness of the continuous annealing furnace 20 can be improved, and a good bright material without discoloration can be produced by the continuous bright annealing equipment 30 as shown in FIG. Obtainable.

FIG. 7 shows a schematic configuration of a continuous annealing furnace 60 according to another embodiment of the present invention. In the present embodiment, of the electric heaters 23a, 23b, and 23c provided in the heating zone 22, the central heater 23b is controlled by the controller 64a, and the electric heaters 23a and 23c on both sides are controlled by the controller 64.
Control with b. Also in the present embodiment, the electric heater 23b in the central portion and the electric heaters 23a and 23c in both side portions are separately controlled, and in particular, control can be performed so that the temperature of the electric heater 23b in the central portion becomes high.

In each of the above embodiments, continuous annealing is performed on the stainless steel strip 21.
It can be similarly used for heating for heat treatment. In addition, the present invention can be applied not only to stainless steel but also to other materials.
Further, although the electric heaters 23a, 23b, and 23c are divided into three in the width direction of the strip 21, if the division is three or more, the central portion and the both side portions can be divided and the temperature can be similarly controlled.

[0029]

As described above, according to the present invention, the heating zone heaters divided into three or more in the width direction of the metal strip can be individually controlled, so that the material temperature in the width direction of the metal strip can be reduced. By making adjustments to be uniform, variations in the material and quality are reduced, and the sheet passing speed is increased to improve productivity.

According to the present invention, when heating uniformly, the heating zone heater facing the central portion having a lower temperature than the peripheral portion is controlled to have a higher temperature than the heating zone heater facing the peripheral portion. Therefore, it is possible to control the ultimate temperature of the metal strip to be uniform in the width direction, to increase the sheet passing speed of the metal strip, and to improve the productivity.

According to the present invention, the number of through-holes through which the terminal rods of the portions for supplying power to the heating zone heaters, which are divided into three or more divided in the width direction perpendicular to the metal plate passing direction, are increased. Even if the holes are formed, the airtightness is improved, the atmosphere for heat treatment of the metal strip is stabilized, and heating with less variation in the material and appearance can be performed.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a heating zone 22 in the embodiment of FIG.

FIG. 3 is a diagram showing a connection state of heater wires of electric heaters 23a, 23b, and 23c in FIG. 2;

FIG. 4 is a cross-sectional view showing a state in which the heater wire 28 of FIG.

FIG. 5 is a simplified sectional view showing a schematic configuration of a continuous bright annealing facility 30 using the continuous annealing furnace 20 of FIG.

FIG. 6 shows an electric heater 23a, 2 in the continuous annealing furnace 20 of FIG.
It is sectional drawing which shows the structure of the part which feeds to 3b and 23c.

FIG. 7 is a simplified perspective view showing a schematic configuration of a continuous annealing furnace 60 according to another embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a schematic configuration of a conventional continuous annealing furnace.

FIG. 9 is a cross-sectional view showing a configuration of a portion for supplying power to an electric heater in a conventional continuous annealing furnace.

[Explanation of symbols]

 20, 60 Continuous annealing furnace 21 Strip 22 Heating zone 23a, 23b, 23c Electric heater 24a, 24b, 24c, 64a, 64b Control device 25 Refractory brick lining 26 Refractory brick outer layer 27 Outer wall flange portion 28 Heater wire 29 Supporting tool Reference Signs List 30 continuous bright annealing equipment 40 terminal rod 41 rod flange part 42 through hole 43 inner gasket 44 outer gasket 45 holding plate 47 packing 48 terminal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoto Takeuchi 3-6-1, Kitahama, Chuo-ku, Osaka-shi, Osaka Nisshin Steel Co., Ltd. Osaka branch office F-term (reference) 4K038 AA01 BA01 CA01 DA01 EA02 FA01 4K043 BB04 CA03 DA05 EA04 FA07 FA12 GA01 GA10

Claims (3)

[Claims] 1. A continuous heating furnace provided with a heating zone for heating a metal strip continuously passed to a target material temperature, wherein the heating zone faces the surface of the metal strip, A continuous heating furnace, comprising: a heating zone heater arranged in three or more divisions in a width direction perpendicular to the heating zone; and a control device for individually controlling a heating output of a divided portion of the heating zone heater. 2. The control device, wherein the heating zone heater comprises:
2. The continuous system according to claim 1, further comprising a control system for setting a temperature of a divided portion corresponding to a central portion of the metal band in the width direction to be higher than a temperature of the divided portions facing both side edges of the metal band in the width direction. heating furnace. 3. The heating zone has a furnace wall formed of refractory bricks, and a portion for supplying power to the heating zone heater from the outside is inserted into a through hole formed in the furnace wall, and has an inner tip. A terminal rod connected to the heating zone heater and having a flange having a diameter larger than the inner diameter of the through-hole near the outer end; and a flange protruding from the inside of the terminal rod flange and the surface of the furnace wall. The outer end of the terminal rod is provided so as to cover between the inner gasket made of heat-resistant material and having an outer diameter larger than the outer diameter of the flange portion and the outer surface of the inner gasket from outside the flange portion of the terminal rod. An outer gasket inserted into the outer wall, a presser plate for fixing the outer peripheral portion of the outer gasket to the furnace wall, and a space between the inner periphery of the outer gasket and the outer periphery of the terminal rod. The gasket, which covers the gap from the outer end of the terminal rod and is made of a heat-resistant material, and a pressing member that presses the packing against the outer gasket surface at the outer end of the terminal rod. 3. The continuous heating furnace according to 1 or 2.