WO2021117516A1

WO2021117516A1 - Heat treatment apparatus

Info

Publication number: WO2021117516A1
Application number: PCT/JP2020/044346
Authority: WO
Inventors: 真人永田; 素史赤阪
Original assignee: 中外炉工業株式会社
Priority date: 2019-12-09
Filing date: 2020-11-27
Publication date: 2021-06-17
Also published as: TW202130823A; JP2021091960A; CN114761585A

Abstract

Provided is a heat treatment apparatus which makes it possible to prevent the deterioration of a heat insulation material made from a ceramic fiber containing SiO₂ even in a reductive atmosphere and can be used for the bright annealing of a metal strip. The heat treatment apparatus 1 is provided with a heating zone 12 in which a metal strip 3 is heated, a heat insulation material 17 which is used as an in-furnace wall of the heating zone 12 and is made from a ceramic fiber containing SiO₂, and gas supply units 9, 28, 28a which supply a reducing gas to the heating zone 12, wherein the metal strip 3 is bright-annealed in a reductive atmosphere in such a manner that a dew point can be kept between an upper limit dew point at which the metal strip 3 can have photoluminescence and a lower limit dew point at which SiO₂ contained in the heat insulation material 17 cannot be reduced.

Description

Heat treatment equipment

The present invention relates to a heat treatment apparatus for brightly annealing a metal strip.

A heat treatment apparatus is known in which bright annealing of a metal strip is performed in a reducing atmosphere in order to remove the internal stress of the metal strip generated by cold rolling.

Patent Document 1 discloses a so-called horizontal furnace in which a hot-dip galvanizing continuous annealing furnace having a muffle structure in which a low-temperature holding zone is made of a steel plate and a metal strip is conveyed in the horizontal direction. Patent Document 2 discloses a horizontal bright continuous annealing furnace of a metal strip whose inside is lined with refractory bricks. Patent Document 3 discloses a manufacturing facility for a nickel-plated thin steel sheet in which the heat insulating material in the furnace is made of ceramic fiber.

Jitsufuku No. 03-1472 Gazette Japanese Patent No. 4268281 Japanese Unexamined Patent Publication No. 2003-201595

In Patent Document 1, since the muffle structure of the furnace body is made of steel plate, it is deformed by heating at a high temperature. Especially in the case of a horizontal furnace, since the section where the ceiling is made of steel plate is long, the ceiling hangs down due to its own weight, the shape distortion becomes large, the air flow in the furnace is turbulent, and the temperature distribution in the furnace deteriorates. .. In Patent Document 2, deformation of the refractory brick is unlikely to occur, but since the weight of the refractory brick is large, workability during assembly, maintenance and replacement is inferior, and the weight of the annealing furnace is also heavy. It is necessary to install it in the place where there is.

In Patent Document 3, ceramic fibers are used because the annealing of the steel sheet and the diffusion treatment of nickel plating are performed at about 800 ° C. in a non-reducing atmosphere. Ceramic fibers is excellent in light weight and workability, because they contain SiO _2, in a high temperature reducing atmosphere, occurs the reduction of SiO _2, SiO ₂ is changed to Si. Therefore, the ceramic fiber collapses, and it is necessary to frequently maintain and replace the ceramic fiber. When the ceramic fiber collapses, dust is generated and the dust falls onto the metal strip. In particular, in the case of a horizontal furnace, the area of the ceiling becomes large, so that the amount of dust falling increases and the quality of the metal strip deteriorates.

Therefore, an object of the present invention is to provide a heat treatment apparatus for brightly anhydrating a metal strip, which can suppress deterioration of a heat insulating material made of a ceramic fiber containing _{SiO 2 even in a reducing atmosphere.}

In order to solve the above problems, the heat treatment apparatus according to one aspect of the present invention is provided.
A heating band that heats the metal strip,
A heat insulating material made of ceramic fiber containing _{SiO 2} and used as an inner wall of the heating zone.
A gas supply unit for supplying a reducing gas to the heating zone is provided.
The metal strip is maintained so that a dew point is maintained between an upper dew point that allows the metal strip to have brilliance and a lower dew point that prevents reduction of the _{SiO 2 contained in the insulating material.} It is characterized by brightly bleaching in a reducing atmosphere.

In order to solve the above problems, the heat treatment apparatus according to one aspect of the present invention is provided.
A heat treatment apparatus for brightly annealing a metal strip in a reducing atmosphere.
A furnace body having a heating zone for heating the metal strip and a cooling zone provided on the downstream side of the metal strip in the transport direction with respect to the heating zone.
A heat insulating material made of ceramic fiber containing _{SiO 2} and used as an inner wall of the heating zone.
A gas supply unit that supplies reducing gas into the furnace body and
A dew point measuring unit that measures the dew point of the atmosphere in the heating zone,
A dew point adjusting unit for adjusting the dew point is provided.
Based on the dew point measured by the dew point measuring unit, the upper limit dew point that enables the metal strip to have brilliance and the lower limit dew point that disables the reduction of the _{SiO 2 contained in the heat insulating material.} The dew point adjusting unit is controlled so that the dew point is maintained between them.

The less water in the atmosphere inside the furnace, the more the oxidation of the surface of the metal strip is suppressed, which is advantageous for the brilliance of the metal strip. It is disadvantageous for a heat insulating material because it works in the direction of reducing _{SiO 2} contained in. Therefore, the inventors of the present application have arrived at the present invention by paying attention to the existence of a dew point (that is, a water content) in an appropriate range capable of achieving both _{maintenance of brilliance and prevention of reduction of SiO 2.}

According to the present invention, the dew point (that is, the water content) of the atmosphere in the heating zone is maintained between the upper limit dew point and the lower limit dew point, so that the water content in the reducing atmosphere maintains the brilliance of the metal strip. It is suitable for preventing the reduction of _{SiO 2} contained in the heat insulating material. As a result, the metal strip can have a brilliant property, and deterioration of the heat insulating material due to reduction of _{SiO 2 contained in the heat insulating material can be prevented.}

It is a schematic cross-sectional view of the heat treatment apparatus which concerns on 1st Embodiment. It is a figure which schematically explains the relationship between the temperature and the dew point of an atmosphere. It is a figure which schematically explains the relationship between the temperature and the dew point of an atmosphere. It is a schematic cross-sectional view of the heat treatment apparatus which concerns on another aspect of 1st Embodiment. It is a schematic cross-sectional view of the heat treatment apparatus which concerns on 2nd Embodiment. It is a schematic cross-sectional view of the heat treatment apparatus which concerns on another aspect of 2nd Embodiment.

Hereinafter, embodiments of the heat treatment apparatus 1 according to the present invention will be described with reference to the drawings.

[First Embodiment]
The heat treatment apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the heat treatment apparatus 1 according to the first embodiment.

As shown in FIG. 1, the bright tanning furnace (heat treatment device) 1 that continuously brightly blisters the metal strip 3 includes a furnace body 10,

gas supply units

9 and 28, a dew point measurement unit 22, and a dew point adjustment unit 24. , 27 and a control unit 20. The bright quenching furnace (heat treatment apparatus) 1 shown in FIG. 1 is a horizontal furnace in which the furnace body extends in the horizontal direction (horizontal direction). In the horizontal furnace, the transport mechanism for transporting the metal strip 3 can be simplified, and the height of the heat treatment apparatus 1 can be suppressed from increasing.

The metal strip 3 is horizontally conveyed from left to right in FIG. The metal strip 3 is made of, for example, a stainless steel material containing Cr. The stainless steel material containing Cr is, for example, SUS304 of austenitic stainless steel or SUS430 of ferritic stainless steel.

The furnace body 10 is made of a steel box and has a heating zone 12 and a cooling zone 14. The heating zone 12 extends in the lateral direction (horizontal direction) and is provided on the upstream side (inside side of the metal strip 3) in the transport direction of the metal strip 3. The heating zone 12 is heated by the heating unit 16. The heating unit 16 is, for example, an electric heater. In the control unit 20, the heating zone 12 has a predetermined annealing temperature based on the temperature measured by a temperature measuring unit (not shown) (here, the temperature in the heating step of the heating step and the cooling step in annealing). Control to be. The annealing temperature in the present application refers to the temperature of the atmosphere in the furnace in the heating zone 12. For example, in a general stainless steel material, the annealing temperature suitable for bright annealing is in the temperature range of 800 ° C. to 1250 ° C., and the control unit 20 controls the heating unit 16 so that the annealing temperature falls within the temperature range. ..

The cooling zone 14 is provided on the downstream side of the metal strip 3 in the transport direction (outside of the metal strip 3). In the cooling zone 14, since it is annealed, it is mainly cooled by allowing it to cool, so that no heating means or heat insulating material 17 is arranged. However, the cooling zone 14 may be provided with some cooling means in some cases.

A heat insulating material 17 is attached to the inner surface (inner wall of the furnace) of the furnace wall such as the side wall, the ceiling, and the floor of the furnace body 10. The heat insulating material 17 is made of a ceramic fiber containing _{SiO 2.} The heat insulating material 17 can be configured to hold, for example, a ceramic fiber board or blanket by piercing a large number of rod-shaped studs attached to the furnace wall and pressing them with washer-shaped metal fittings. The heat insulating material 17 is _{a fiber containing Al 2} O ₃ (alumina) and SiO ₂ (silica) as main components. For example, _{the content of Al 2} O ₃ is 30 to 60% by mass and the content of _{SiO 2 is 40.} ~ 70% by mass of alumina-silica ceramic fiber.

The inside of the furnace body 10 of the bright burning blunt furnace 1 is filled with a reducing atmospheric gas. The inlet seal roll 13 and the outlet seal roll 15 are arranged at the inlet opening and the outlet opening of the furnace body 10, respectively. The inlet seal roll 13 and the outlet seal roll 15 prevent the intrusion of outside air into the furnace body 10 by keeping the inside of the furnace body 10 at a pressure slightly higher than the atmospheric pressure. However, even if the metal strip 3 is sandwiched between the inlet seal roll 13 and the outlet seal roll 15, the inlet seal roll 13 has a small amount of water adhering to the surface of the metal strip 3 from the outside air to the inside of the furnace body 10. Brought to. Further, in the outlet seal roll 15, a small amount of atmospheric gas flows out from the furnace in the same manner. Therefore, it is necessary to constantly measure and adjust the dew point (moisture content) of the atmosphere in the heating zone 12.

The gas supply unit includes a gas supply device 9 and a second control valve 28, and supplies reducing gas into the furnace body 10 or, in other words, reducing gas to the heating zone 12 via the gas supply pipe 5. The gas supply device 9 is, for example, a gas cylinder. The reducing gas is a gas containing hydrogen gas, for example, a gas in which hydrogen gas and nitrogen gas are mixed at a ratio of 3: 1. The amount of reducing gas supplied is controlled by adjusting the opening degree of the second control valve 28 provided in the gas supply pipe 5. The opening degree of the second control valve 28 is controlled by the control unit 20. By supplying the reducing gas, the amount leaked from the inlet seal roll 13 and the outlet seal roll 15 is replenished. In the bright quenching furnace 1 shown in FIG. 1, the gas supply pipe 5 is arranged on the upstream side of the cooling zone 14, but the supply position of the reducing gas is not particularly limited. The reducing gas supplied from the gas supply pipe 5 diffuses the entire inside of the furnace body 10 including the heating zone 12 as an atmospheric gas, and then goes out of the furnace body 10.

Conventionally, the reducing gas supplied from the gas supply device 9 has a low dew point (that is, a low water content), for example, a JIS hydrogen first grade gas having a dew point of −70 ° C. However, in the present application, since the dew point of the atmosphere in the furnace can be adjusted by the dew point adjusting unit 24 including the dehumidifying device 25 and the humidifying device 26, the reducing gas supplied from the gas supply device 9 does not necessarily have a low dew point ( That is, it does not have to have a low water content). That is, as the reducing gas supplied from the gas supply device 9, a gas containing a larger amount of water than the conventional JIS hydrogen 1st grade, for example, a JIS hydrogen 2nd grade having a dew point equivalent to -60 ° C can be used. is there.

The dew point measuring unit 22 measures the dew point of the atmosphere (hereinafter, may be referred to as “atmospheric gas”) in the heating zone 12 of the furnace body 10 via the dew point measuring pipe 6. The dew point measuring unit 22 is, for example, a capacitance type dew point meter or a mirror cooling type dew point meter. The dew point measurement data is sent to the control unit 20 and stored in the memory unit of the control unit 20. In the bright quenching furnace 1 shown in FIG. 1, the dew point measurement pipe 6 is arranged on the downstream side of the heating zone 12, but the dew point measurement position is not particularly limited.

The dew point adjusting unit includes a dew point adjusting device 24 and a first adjusting valve 27, and adjusts the dew point of the atmosphere in the heating zone 12. The dew point adjusting device 24 includes at least one of the dehumidifying device 25 and the humidifying device 26. As a result, the dew point of the atmosphere in the heating zone 12 can be appropriately adjusted according to the dew point of the reducing gas supplied by the

gas supply units

9 and 28 and the dew point of the target atmosphere.

The dew point adjusting device 24 extracts a part of the atmosphere through the inlet pipe 7 arranged on the upstream side in the transport direction of the heating zone 12, adjusts the dew point, that is, the amount of water in the extracted atmosphere, and then transports the heating zone 12. It is returned to the inside of the furnace body 10 through the outlet pipe 8 arranged on the downstream side. By circulating the atmospheric gas between the dew point adjusting device 24 and the furnace body 10, the dew point of the atmosphere in the heating zone 12 is maintained at a predetermined dew point.

The dew point adjusting device 24 (that is, the dehumidifying device 25 and the humidifying device 26) is controlled by the control unit 20. The circulation amount of the atmospheric gas is controlled by adjusting the opening degree of the first control valve 27 provided in the inlet pipe 7. The opening degree of the first control valve 27 is controlled by the control unit 20.

The dehumidifying device 25 has a function of removing moisture contained in the atmosphere (dehumidifying the atmosphere) and lowering the dew point of the atmosphere. The dehumidifying device 25 has, for example, an adsorption tower and a desorption tower filled with an adsorbent. The adsorbent is synthetic zeolite such as molecular sieve (molecular sieve), natural zeolite, activated carbon, silica gel, alumina, activated alumina and the like. In dehumidification using an adsorbent, the dew point of the atmosphere after dehumidification can be easily controlled to a predetermined dew point, and the obtained atmosphere is extremely clean.

The humidifying device 26 generates a water-containing gas that is a mixture of water vapor or liquid phase water and an atmosphere, and sends the water-containing gas into the furnace body 10 to add water to the atmosphere (humidification of the atmosphere). It has the function of raising the dew point of the atmosphere. The humidifying device 26 uses, for example, a bubbling type that allows the atmosphere to pass through the water stored in the container, a spray nozzle type that injects water vapor into a mist with respect to the atmosphere, and a hollow fiber membrane having high water vapor permeability. It is a membrane exchange type.
The control unit 20 is electrically connected to the dew point measurement unit 22, the dew point adjustment device 24, the first control valve 27, the second control valve 28, and the heating unit 16. The control unit 20 can be configured by using a computer including a calculation unit such as a CPU (Central Processing Unit) and a memory unit such as a RAM (Random Access Memory) and a ROM (Read Only Memory).

The control unit 20 controls the

gas supply units

9, 28 and the dew

point adjustment units

24, 27 based on the dew point measured by the dew point measurement unit 22. That is, the control unit 20 controls the supply amount of the reducing gas supplied from the gas supply device 9 by controlling the opening degree of the second control valve 28. Further, the control unit 20 controls the circulation amount of the atmospheric gas by the dew point adjusting device 24 by controlling the opening degree of the first control valve 27. This makes it possible to automate bright annealing (heat treatment).

The control unit 20 controls the dehumidifying device 25 or the humidifying device 26 in the dew point adjusting device 24 to operate. When the control unit 20 controls the dehumidifying device 25 to operate, the moisture contained in the atmosphere is removed, so that the dew point of the atmosphere, that is, the amount of moisture is reduced. When the control unit 20 controls the humidifying device 26 to operate, the dew point of the atmosphere, that is, the amount of water increases, due to the increase in the amount of water contained in the atmosphere. This makes it possible to automate bright annealing (heat treatment).

[Other Aspects of First Embodiment]
As described above, even if the metal strip 3 is sandwiched by the inlet seal roll 13, a small amount of water is brought into the furnace body 10 from the outside air in a state of being attached to the surface of the metal strip 3. The dew point (moisture content) of the atmosphere rises. Therefore, by using hydrogen gas having an extremely low dew point as the reducing gas, the water content in the atmosphere can be diluted to lower the dew point in the atmosphere. Further, even if hydrogen gas having an extremely low dew point is used as the reducing gas, the dew point of the atmosphere can be raised by reducing the flow rate of the reducing gas by the second control valve 28. Further, when a small amount of water can be prevented from being brought into the furnace body 10 from the outside air by some means, the water content in the atmosphere is increased by using hydrogen gas having a high dew point as a reducing gas. It is possible to raise the dew point of the atmosphere.

Therefore, it is possible to adjust the dew point of the atmosphere in the heating zone 12 without using the dehumidifying device 25 and the humidifying device 26 shown in FIG. That is, as shown in FIG. 4, the control unit 20 controls the second control valve 28 based on the dew point of the atmosphere measured by the dew point measuring unit 22 to control the reducing gas supplied by the gas supply device 9. By adjusting the flow rate, the dew point of the atmosphere in the furnace body 10 including the heating zone 12 can be adjusted. This makes it possible to automate bright annealing (heat treatment). Here, hydrogen gas having an extremely low dew point or hydrogen gas having a high dew point is used as the reducing gas supplied from the gas supply device 9 according to the amount of water brought into the furnace body 10 from the outside air. In this way, the gas supply device 9 and the second control valve 28 act as the dew point adjustment device 24a. Thereby, the dew point adjusting device 24a can be configured by a simple configuration.

[Control of dew point of atmosphere]
As described above, the smaller the amount of water in the atmosphere in the heating zone 12 of the furnace body 10, the more the oxidation of the surface of the metal strip 3 is suppressed, which is advantageous for the brilliance of the metal strip 3, but the heat insulating material 17 It is disadvantageous to the heat insulating material 17 because it works in the direction of reducing the contained SiO _2. Therefore, the inventors of the present application have arrived at the present invention by paying attention to the existence of a dew point (that is, a water content) in an appropriate range capable of achieving both _{maintenance of brilliance and prevention of reduction of SiO 2.}

Controlling the dew point of the atmosphere in the heating zone 12 will be described with reference to FIG. FIG. 2 is a diagram schematically explaining the relationship between the temperature and the dew point of the atmosphere. In FIG. 2, the horizontal axis represents the annealing temperature in the heating zone 12 and _{the equilibrium temperature of oxidation-reduction of SiO 2} , and the vertical axis represents the dew point of the atmosphere in the heating zone 12. In FIG. 2, A is a straight line indicating a dew point at −30 ° C., and S is an equilibrium curve of oxidation-reduction of _{SiO 2.} If the dew point is higher than the equilibrium curve S, SiO ₂ is oxidized, and if the dew point is lower than the equilibrium curve S, SiO ₂ is reduced. The intersections of the straight line A with the annealing temperatures of 800 ° C. and 1250 ° C. are a and b, respectively, and the intersections of the equilibrium curve S with the equilibrium temperatures of 800 ° C. and 1250 ° C. are c and d, respectively. These temperatures and intersections correspond to, for example, annealing of stainless steel.

The dew point of the atmosphere corresponds to the amount of water contained in the atmosphere. For example, if the dew point is -30 ° C, the water content is about 338 (g / m ³ ), if the dew point is -35 ° C, the water content is about 203 (g / m ³ ), and if the dew point is -40 ° C, the water content is about 119 (g / m 3). g ^{/ m} 3), moisture content of about 68 if a dew point of ^{-45 ℃ (g / m 3)} , moisture content of about 38 if a dew point of ^{-50 ℃ (g / m 3)} , the water content if a dew point of -55 ° C. Is about 21 (g / m ³ ), if the dew point is -60 ° C, the water content is about 11 (g / m ³ ), if the dew point is -65 ° C, the water content is about 5.6 (g / m ³ ), and the dew point is about 5.6 (g / m 3). At −70 ° C., the water content is about 2.7 (g / m ³ ). Therefore, as the dew point of the atmosphere becomes lower, the amount of water contained in the atmosphere decreases.

When the surface of the metal strip 3 is oxidized, an oxide film is formed on the surface of the metal strip 3. When the metal strip 3 is a stainless steel material containing Cr, an oxide film in which Cr and Fe are combined with oxygen is formed. In order to suppress surface oxidation of the metal strip 3, it has been said that it is desirable that the dew point of the atmosphere is as low as possible, that is, the amount of water contained in the atmosphere is as small as possible.

However, in the actual heat treatment step, it is known that when the thickness of the oxide film formed on the surface of the metal strip 3 is thinner than a certain thickness, the influence on the brilliance of the metal strip 3 is reduced. Therefore, by setting the upper dew point of the atmosphere to −30 ° C. or lower, the formation of an oxide film on the metal strip 3 is suppressed, the metal strip 3 has a certain degree of brilliance or more, and there are almost no problems in the product. There is no. The straight line A in FIG. 2 indicates the maximum dew point that suppresses the formation of the oxide film on the metal strip 3. The intersection point a is the maximum dew point at 800 ° C., and the intersection b is the maximum dew point at 1250 ° C.

When commercializing a brilliant stainless steel metal strip 3, it is suitable to adjust the upper limit dew point of the atmosphere to -30 ° C or less. In order to obtain the metal strip 3 having a higher degree of brilliance in the stainless steel material, the upper limit dew point of the atmosphere may be adjusted to −45 ° C. or lower. In order to obtain the metal strip 3 having a higher degree of brilliance, the upper limit dew point of the atmosphere may be adjusted to −65 ° C. (straight line X in the figure) or less. Therefore, in the stainless steel material, the upper limit dew point that enables the metal strip 3 to have brilliance is set in the range of −30 ° C. to −65 ° C., depending on the degree of brilliance of the metal strip 3 to be brilliantly annealed. Will be done. According to this configuration, a metal strip 3 having a desired brilliance can be obtained.

A heat insulating material 17 made of ceramic fiber is arranged on the inner surface of the furnace wall (inner wall of the furnace). _{Conventionally, when high-purity alumina-based bricks containing Al 2} O ₃ (alumina) with high purity are used in an arch-stacked structure in a horizontal bright annealing furnace 1, the bricks expand and contract when the temperature inside the furnace is raised or lowered. Therefore, there is a problem that dust is generated and the quality of the metal strip 3 is deteriorated.

In the horizontal bright quenching furnace 1 of the present application, _{by using a ceramic fiber containing SiO 2} as the heat insulating material 17, it is possible to suppress the generation of dust and obtain a high quality metal strip 3. _{However, the reduction resistance of SiO 2} contained in the ceramic fiber is lower than that of Al ₂ O ₃ (alumina), and when the ceramic fiber is used in a highly reducing atmosphere, _{the reduction of SiO 2} causes the ceramic fiber to deteriorate. It is thought that it becomes brittle and dust is generated.

In the present invention, the inventors of the present application have made the oxidation-reduction property (thermodynamic property) of _{SiO 2} so that the heat insulating material 17 made of ceramic fiber containing _{SiO 2 can be used even in a highly reducing atmosphere.} I paid attention to. As shown in FIG. 2, with the equilibrium curve S of oxidation-reduction of _{SiO 2} _{as a boundary, the region above the equilibrium curve S is the region where SiO 2} maintains an oxidized state, and the region below the equilibrium curve S is SiO. _This is the region where 2 is reduced.

The dew point at the intersection c where the oxidation-reduction equilibrium curve S of SiO ₂ intersects the equilibrium temperature 800 ° C. is about −95 ° C., and the dew point at the intersection d where the equilibrium temperature 1250 ° C. intersects is about −60 ° C. .. The dew point is a lower limit dew point that disables reduction of _{SiO 2} contained in the heat insulating material 17 at an equilibrium temperature of 800 ° C. to 1250 ° C. suitable for bright annealing of a stainless steel material, for example. Therefore, when the annealing temperature of the heating zone 12 is in the range of 800 ° C. to 1250 ° C., the control unit 20 can prevent the SiO ₂ from being reduced by controlling the dew point of the atmosphere so as not to fall below the equilibrium curve S. .. As a result, it is possible to prevent dust from being generated due to deterioration of the heat insulating material 17 made of ceramic fiber, and to obtain a high-quality metal strip 3.

When the annealing temperature of the heating zone 12 is 800 ° C. to 1250 ° C. (for example, when the metal strip 3 is made of stainless steel), the dew point of the atmosphere is within the region surrounded by the intersections a, b, d and c in FIG. The control unit 20 controls the dew

point adjusting units

24 and 27 so as to be maintained. As a result, the metal strip 3 can have a brilliant property, and deterioration of the heat insulating material 17 due to reduction of _{SiO 2 contained in the heat insulating material 17 can be prevented.}

[Second Embodiment]
The heat treatment apparatus 1 according to the second embodiment will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view of the heat treatment apparatus 1 according to the second embodiment.

As shown in FIG. 5, the bright bleaching furnace (heat treatment apparatus) 1 according to the second embodiment includes a furnace body 10, a gas supply unit 9, a dew point measuring unit 22, and dew

point adjusting units

24, 27a, 28a. Be prepared. In comparison with the bright annealing furnace (heat treatment apparatus) 1 according to the first embodiment shown in FIG. 1, the bright annealing furnace (heat treatment apparatus) 1 according to the second embodiment omits a control unit 20 such as a computer. There is. Therefore, the operator who operates the brilliant quenching furnace (heat treatment apparatus) 1 substitutes for the control unit 20.

The operator can manually control at least one of the second control valve (dew point adjustment unit) 28a and the first control valve (dew point adjustment unit) 27a based on the dew point measured by the dew point measurement unit 22. That is, the operator can visually acquire the dew point measured by the dew point measuring unit 22 through a monitor or the like. Further, the operator can control the supply amount of the reducing gas supplied from the gas supply device 9 by manually controlling the second control valve (dew point adjusting unit) 28a based on the measured dew point. Further, the operator can control the circulation amount of the atmospheric gas by the dew point adjusting device 24 by controlling the first adjusting valve (dew point adjusting unit) 27a based on the measured dew point.

Further, by controlling the dehumidifying device 25 in the dew point adjusting device 24 to operate, the moisture contained in the atmosphere is removed, and the dew point of the atmosphere, that is, the amount of moisture is reduced. Further, when the operator controls the humidifying device 26 in the dew point adjusting device 24 to operate, the moisture contained in the atmosphere increases, so that the dew point of the atmosphere, that is, the amount of moisture increases.

As a result, the dew point (that is, the amount of water) of the atmosphere in the heating zone 12 is maintained between the upper limit dew point and the lower limit dew point, so that the amount of water in the reducing atmosphere maintains the brilliance of the metal strip 3 and insulates it. It becomes appropriate for preventing reduction of _{SiO 2} contained in the material 17. As a result, the metal strip 3 can have a brilliant property, and deterioration of the heat insulating material 17 due to reduction of _{SiO 2 contained in the heat insulating material 17 can be prevented.}

[Other aspects of the second embodiment]
As shown in FIG. 6, the dew point adjusting device 24 (dehumidifying device 25 and humidifying device 26) is further omitted in addition to the control unit 20, and the gas supply device 9 and the second adjusting valve (dew point adjusting unit) 28a are dew point. It can also be an adjusting device 24a. As a result, the dew point adjusting device 24a can be easily configured. The operator can control the dew point adjusting device 24a based on the dew point of the atmosphere measured by the dew point measuring unit 22. That is, the operator can visually acquire the dew point measured by the dew point measuring unit 22 through a monitor or the like. Further, the operator can control the flow rate of the reducing gas supplied by the gas supply device 9 by manually controlling the second control valve (dew point adjusting unit) 28a based on the measured dew point.

The manual control in the second embodiment does not need to be continuously performed by the operator, and the operator monitors the dew point occasionally or periodically, and if there is no abnormality, the operator particularly controls the dew point. Including the case where is not performed.

Although specific embodiments and numerical values of the present invention have been described, the present invention is not limited to the above embodiments and numerical values, and can be variously modified and implemented within the scope of the present invention.

Instead of the control unit 20, the operator acquires the dew point measured by the dew point measuring unit 22, and maintains the dew point between the upper limit dew point and the lower limit dew point based on the dew point measured by the dew point measuring unit 22. At least one of the dew

point adjusting units

27a and 28a can be controlled so as to drip.

The bright burning blunting furnace (heat treatment device) 1 can also be a vertical furnace in which the furnace body 10 extends in the vertical direction (vertical direction).

In the bright bleaching furnace (heat treatment apparatus) 1, an inlet seal band may be provided on the upstream side of the heating zone 12 in the transport direction, and the inlet seal roll 13 may be arranged on the inlet seal band. An outlet seal band may be provided on the downstream side of the cooling band 14 in the transport direction, and the outlet seal roll 15 may be arranged on the outlet seal band. The heating zone 12 may be composed of an entrance seal zone, pre-tropical and even-tropical (neither shown) or the like. The cooling zone 14 may be composed of an outlet seal zone, a quenching zone, a slow cooling zone (none of which are shown), or the like.

The bright bleaching furnace 1 shown in FIG. 1 is provided with both the dehumidifying device 25 and the humidifying device 26, but it is also possible to have a configuration in which either the dehumidifying device 25 or the humidifying device 26 is provided.

FIG. 3 shows an equilibrium curve C of oxidation-reduction of _{Cr 2} O ₃ (chromium oxide) in which the Cr component in the stainless steel material is oxidized. In the above embodiment, the upper limit dew point is set to −30 ° C., but it is also possible to prevent the oxidation of the stainless steel material by controlling _{the dew point of the atmosphere so as not to exceed the oxidation-reduction equilibrium curve C of Cr 2} O _3. Conceivable. Therefore, in the case of the stainless steel material, the control unit 20 controls the dew

point adjusting units

24 and 24a so that the dew point of the atmosphere is maintained in the region surrounded by the intersections e, f, d and c in FIG. May be good.

The metal strip 3 that is brightly annealed in a reducing atmosphere can be used for various metal materials such as pure metals such as nickel, titanium and copper, low expansion alloys, magnetic alloys, heat-resistant alloys and corrosion-resistant alloys, in addition to the above-mentioned stainless steel materials. Is also applicable.

The present invention and embodiments can be summarized as follows.

The heat treatment apparatus 1 according to one aspect of the present invention is
A heating zone 12 for heating the metal strip 3 and
A heat insulating material 17 made of ceramic fiber containing _{SiO 2} and used as an inner wall of the heating zone 12 and
The heating zone 12 is provided with

gas supply units

9, 28, 28a for supplying reducing gas.
The dew point is maintained between the upper limit dew point that allows the metal strip 3 to have brilliance and the lower limit dew point that disables the reduction of the _{SiO 2 contained in the heat insulating material 17.} The metal strip 3 is brightly annealed in a reducing atmosphere.

According to the above configuration, the dew point (that is, the water content) of the atmosphere in the heating zone 12 is maintained between the upper limit dew point and the lower limit dew point, so that the water content in the reducing atmosphere is the brilliance of the metal strip 3. It becomes suitable for _{maintenance and prevention of reduction of SiO 2} contained in the heat insulating material 17. As a result, the metal strip 3 can have a brilliant property, and deterioration of the heat insulating material 17 due to reduction of _{SiO 2 contained in the heat insulating material 17 can be prevented.}

The heat treatment apparatus 1 according to one aspect of the present invention is
A heat treatment apparatus 1 for brightly annealing a metal strip 3 in a reducing atmosphere.
A furnace body 10 having a heating zone 12 for heating the metal strip 3 and a cooling zone 14 provided on the downstream side of the metal strip 3 in the transport direction with respect to the heating zone 12.
A heat insulating material 17 made of ceramic fiber containing _{SiO 2} and used as an inner wall of the heating zone 12 and

Gas supply units

9, 28, 28a for supplying reducing gas into the furnace body 10 and
A dew point measuring unit 22 for measuring the dew point of the atmosphere in the heating zone 12 and
A dew

point adjusting unit

24, 24a, 27, 27a, 28, 28a for adjusting the dew point is provided.
Based on the dew point measured by the dew point measuring unit 22, the upper limit dew point that enables the metal strip 3 to have brilliance and the lower limit that disables the reduction of the _{SiO 2 contained in the heat insulating material 17} The dew

point adjusting units

24, 24a, 27, 27a, 28, 28a are controlled so that the dew point is maintained between the dew point and the dew point.

Further, in the heat treatment apparatus 1 of the embodiment,
The control of the dew

point adjusting units

24, 27, 28 is performed by the control unit 20.

According to the above embodiment, it is possible to automate the bright annealing (heat treatment).

Further, in the heat treatment apparatus 1 of the embodiment,
The upper limit dew point is −30 ° C.

According to the above embodiment, a metal strip 3 having a brilliant property can be obtained.

Further, in the heat treatment apparatus 1 of the embodiment,
The upper limit dew point is set in the range of −30 ° C. to −65 ° C., depending on the degree of brightness of the metal strip 3 to be brightly annealed.

According to the above embodiment, the metal strip 3 having the desired brilliance can be obtained.

Further, in the heat treatment apparatus 1 of the embodiment,
The dew point adjusting unit 24 includes at least one of a dehumidifying device 25 and a humidifying device 26.

According to the above embodiment, the dew point of the atmosphere in the heating zone 12 can be appropriately adjusted according to the dew point of the reducing gas supplied by the

gas supply units

9, 28, 28a and the dew point of the target atmosphere.

Further, in the heat treatment apparatus 1 of the embodiment,
The

gas supply units

9, 28, 28a include a gas supply device 9 and a

control valve

28, 28a for adjusting the flow rate of the reducing gas supplied by the gas supply device 9, and the gas supply device 9 and the

gas supply unit

9, 28, 28a are provided. The

control valves

28, 28a act as the dew

point adjustment portions

24, 24a.

According to the above embodiment, the dew

point adjusting devices

24 and 24a can be configured by a simple configuration.

Further, in the heat treatment apparatus 1 of the embodiment,
The heat treatment apparatus 1 is a horizontal furnace in which the furnace body 10 extends in the lateral direction.

According to the above embodiment, the transport mechanism for transporting the metal strip 3 can be simplified, and the height of the heat treatment apparatus 1 can be suppressed from increasing. Further, since the collapse of the ceramic fiber and the generation of dust can be prevented, the lightweight ceramic fiber heat insulating material 17 can be used even in a horizontal furnace having a large ceiling area.

Further, in the heat treatment apparatus 1 of the embodiment,
The metal strip 3 is made of a stainless steel material containing Cr.

According to the above embodiment, the formation of the oxide film on the metal strip 3 is suppressed, and the metal strip 3 can have a brilliant property.

Further, in the heat treatment apparatus 1 of the embodiment,
The temperature range of the heating zone 12 is 800 ° C. to 1250 ° C.

According to the above embodiment, the metal strip 3 can be heated at a temperature suitable for bright annealing.

Further, in the heat treatment apparatus 1 of the embodiment,
The reducing gas includes hydrogen gas.

According to the above embodiment, the metal strip 3 can be reduced and brilliantly annealed.

1 ... Bright baking furnace (heat treatment equipment)
3 ... Metal strip 5 ... Gas supply pipe 6 ... Dew point measurement pipe 7 ... Enter side pipe 8 ... Outer side pipe 9 ... Gas supply device (gas supply part, dew point adjustment part)
10 ... Furnace 12 ... Heating zone 13 ... Inlet seal roll 14 ... Cooling zone 15 ... Outlet seal roll 16 ... Heating unit 17 ... Insulation material 20 ... Control unit 22 ... Dew point measurement unit 24 ... Dew point adjustment device (Dew point adjustment unit)
24a ... Dew point adjusting device (dew point adjusting unit)
25 ... Dehumidifier 26 ... Humidifier 27 ... First control valve (dew point adjustment unit)
27a ... 1st control valve (dew point adjustment part)
28 ... Second control valve (gas supply unit, dew point adjustment unit)
28a ... Second control valve (gas supply unit, dew point adjustment unit)
A ... Straight line showing the dew point at -30 ° C C ... _{Oxidation-reduction equilibrium curve of Cr 2} O ₃ S ... Oxidation-reduction equilibrium curve of SiO ₂

Claims

A heating band that heats the metal strip,
A heat insulating material made of ceramic fiber containing SiO 2 and used as an inner wall of the heating zone.
A gas supply unit for supplying a reducing gas to the heating zone is provided.
The metal strip is maintained so that a dew point is maintained between an upper dew point that allows the metal strip to have brilliance and a lower dew point that prevents reduction of the SiO 2 contained in the heat insulating material. A heat treatment apparatus characterized by brightly bleaching in a reducing atmosphere.
A heat treatment apparatus for brightly annealing a metal strip in a reducing atmosphere.
A furnace body having a heating zone for heating the metal strip and a cooling zone provided on the downstream side of the metal strip in the transport direction with respect to the heating zone.
A heat insulating material made of ceramic fiber containing SiO 2 and used as an inner wall of the heating zone.
A gas supply unit that supplies reducing gas into the furnace body and
A dew point measuring unit that measures the dew point of the atmosphere in the heating zone,
A dew point adjusting unit for adjusting the dew point is provided.
Based on the dew point measured by the dew point measuring unit, the upper limit dew point that enables the metal strip to have brilliance and the lower limit dew point that disables the reduction of the SiO 2 contained in the heat insulating material. A heat treatment apparatus, characterized in that the dew point adjusting unit is controlled so that the dew point is maintained between them.
The heat treatment apparatus according to claim 2, wherein the control of the dew point adjusting unit is performed by the control unit.
The heat treatment apparatus according to any one of claims 1 to 3, wherein the upper limit dew point is −30 ° C.
Any of claims 1 to 3, wherein the upper limit dew point is set in the range of −30 ° C. to −65 ° C. depending on the degree of brightness of the metal strip to be brightly annealed. The heat treatment apparatus according to item 1.
The heat treatment apparatus according to any one of claims 2 to 5, wherein the dew point adjusting unit includes at least one of a dehumidifying device and a humidifying device.
The gas supply unit includes a gas supply device and a control valve for adjusting the flow rate of the reducing gas supplied by the gas supply device, and the gas supply device and the control valve act as the dew point adjustment unit. The heat treatment apparatus according to any one of claims 2 to 5, wherein the heat treatment apparatus is characterized.
The heat treatment apparatus according to any one of claims 2 to 7, wherein the heat treatment apparatus is a horizontal type furnace in which the furnace body extends in the lateral direction.
The heat treatment apparatus according to any one of claims 1 to 8, wherein the metal strip is made of a stainless steel material containing Cr.
The heat treatment apparatus according to any one of claims 1 to 9, wherein the temperature range of the heating zone is 800 ° C. to 1250 ° C.
The heat treatment apparatus according to any one of claims 1 to 10, wherein the reducing gas contains hydrogen gas.