CN114761585B - Heat treatment device - Google Patents
Heat treatment device Download PDFInfo
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- CN114761585B CN114761585B CN202080083926.5A CN202080083926A CN114761585B CN 114761585 B CN114761585 B CN 114761585B CN 202080083926 A CN202080083926 A CN 202080083926A CN 114761585 B CN114761585 B CN 114761585B
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- dew point
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
- F27B9/04—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity adapted for treating the charge in vacuum or special atmosphere
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D7/00—Forming, maintaining or circulating atmospheres in heating chambers
- F27D7/06—Forming or maintaining special atmospheres or vacuum within heating chambers
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Engineering & Computer Science (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Furnace Details (AREA)
- Tunnel Furnaces (AREA)
Abstract
The present invention provides a heat treatment device for performing bright annealing treatment on a metal strip, which can inhibit the degradation of a heat insulating material made of ceramic fibers containing SiO 2 even in a reducing atmosphere. The heat treatment device (1) is provided with a heating belt (12) for heating a metal belt (3), a heat insulating material (17) which is used as the inner wall of the furnace of the heating belt (12) and is made of ceramic fibers containing SiO 2, and gas supply parts (9, 28 a) for supplying reducing gas to the heating belt (12) so as to maintain the dew point between an upper limit dew point capable of making the metal belt (3) bright and a lower limit dew point which does not reduce SiO 2 contained in the heat insulating material (17), and bright annealing the metal belt (3) in a reducing atmosphere.
Description
Technical Field
The invention relates to a heat treatment device for bright annealing of metal strips.
Background
In order to remove internal stress of a metal strip produced by cold rolling, a heat treatment apparatus for performing bright annealing of the metal strip in a reducing atmosphere is known.
Patent document 1 discloses a continuous annealing furnace for hot dip plating having a muffle structure in which a low-temperature holding belt is made of a steel plate, which is a so-called horizontal furnace for transporting a metal strip in a horizontal direction. Patent document 2 discloses a horizontal type bright continuous annealing furnace of a metal strip lined with refractory bricks. Patent document 3 discloses an apparatus for manufacturing a nickel plated steel sheet in which a heat insulating material in a furnace is made of ceramic fibers.
Prior art literature
Patent literature
Patent document 1: japanese patent application publication No. 03-1472
Patent document 2: japanese patent application laid-open No. 4268281
Patent document 3: japanese patent laid-open publication No. 2003-201595
Disclosure of Invention
Technical problem to be solved by the invention
In patent document 1, the muffle structure of the furnace body is formed of a steel plate, and therefore is deformed by heating at a high temperature. In particular, in the case of a horizontal furnace, since the roof is made of steel plates and has a long section, the roof sags due to its own weight, and the shape of the roof is greatly deformed, so that turbulence is generated in the air flow in the furnace, and the temperature distribution in the furnace is poor. In patent document 2, although the refractory bricks are not easily deformed, the weight of the refractory bricks is large, so that workability in assembly, maintenance and replacement is poor, and the weight of the annealing furnace is also heavy, so that it is necessary to install the annealing furnace in a place having a load resistance.
In patent document 3, since annealing of a steel sheet and diffusion treatment of nickel plating are performed at about 800 ℃ in a non-reducing atmosphere, ceramic fibers are used. The ceramic fiber is light in weight and excellent in workability, but contains SiO 2, so that reduction of SiO 2 occurs in a high-temperature reducing atmosphere, and SiO 2 is changed to Si. Therefore, the ceramic fiber is disintegrated, and maintenance and replacement of the ceramic fiber are required frequently. Dust is generated when the ceramic fiber disintegrates, and falls on the metal belt. In particular, in the case of a horizontal furnace, the area of the furnace roof is large, so that the amount of dust falling is large, and the quality of the metal strip is degraded.
Accordingly, an object of the present invention is to provide a heat treatment apparatus for bright annealing a metal strip, which can suppress deterioration of a heat insulating material made of ceramic fibers containing SiO 2 even in a reducing atmosphere.
Technical proposal adopted for solving the technical problems
In order to solve the above-described problems, a heat treatment apparatus according to an embodiment of the present invention is characterized in that: the method comprises a heating zone for heating a metal strip, a heat insulating material which is used as the inner wall of the heating zone and is made of ceramic fibers containing SiO 2, and a gas supply unit for supplying a reducing gas to the heating zone, wherein the metal strip is bright annealed in a reducing atmosphere under a condition that the dew point is maintained between an upper limit dew point capable of making the metal strip bright and a lower limit dew point which does not reduce SiO 2 contained in the heat insulating material.
In order to solve the above-described problems, a heat treatment apparatus according to an embodiment of the present invention is a heat treatment apparatus for bright annealing a metal strip in a reducing atmosphere, comprising: a furnace body having a heating belt for heating the metal strip and a cooling belt provided on a downstream side of the heating belt in a conveying direction of the metal strip; a heat insulating material which is used as an inner wall of the furnace of the heating belt and is made of ceramic fibers containing SiO 2; a gas supply unit configured to supply a reducing gas into the furnace body; a dew point measuring unit for measuring an atmosphere dew point in the heating zone; and a dew point adjusting unit that adjusts the dew point, wherein the dew point adjusting unit is controlled so that the dew point is maintained between an upper limit dew point at which the metal strip can have brightness and a lower limit dew point at which the SiO 2 contained in the heat insulating material is not reduced, based on the dew point measured by the dew point measuring unit.
Effects of the invention
The less the moisture in the atmosphere in the furnace, the more advantageous the oxidation of the metal belt surface can be suppressed and the brightness of the metal belt is achieved, but when a lightweight ceramic fiber is intended to be used as a heat insulating material for the inner wall of the furnace, it acts in the direction of reducing SiO 2 contained in the heat insulating material, and is therefore disadvantageous for the heat insulating material. Accordingly, the present inventors have focused on the existence of a dew point (i.e., a moisture amount) in an appropriate range capable of simultaneously achieving both maintaining brightness and preventing reduction of SiO 2, and have achieved the present application.
According to the present invention, by maintaining the dew point (i.e., the moisture amount) of the atmosphere in the heating belt between the upper limit dew point and the lower limit dew point, the moisture amount in the reducing atmosphere is suitable for maintaining the brightness of the metal belt and preventing the reduction of SiO 2 contained in the heat insulating material. As a result, the metal strip can be made bright, and deterioration of the heat insulating material due to reduction of SiO 2 contained in the heat insulating material can be prevented.
Drawings
Fig. 1 is a schematic cross-sectional view of a heat treatment apparatus of a first embodiment.
Fig. 2 is a diagram schematically illustrating a relationship between temperature and dew point of an atmosphere.
Fig. 3 is a diagram schematically illustrating a relationship between temperature and dew point of an atmosphere.
Fig. 4 is a schematic cross-sectional view of a heat treatment apparatus according to another embodiment of the first embodiment.
Fig. 5 is a schematic cross-sectional view of a heat treatment apparatus of a second embodiment.
Fig. 6 is a schematic cross-sectional view of a heat treatment apparatus according to another embodiment of the second embodiment.
Detailed Description
Hereinafter, an embodiment of the heat treatment apparatus 1 according to the present invention will be described with reference to the drawings.
First embodiment
Referring to fig. 1, a heat treatment apparatus 1 according to a first embodiment will be described. Fig. 1 is a schematic cross-sectional view of a heat treatment apparatus 1 of a first embodiment.
As shown in fig. 1, a bright annealing furnace (heat treatment apparatus) 1 for continuously bright annealing a metal strip 3 includes a furnace body 10, a gas supply unit 9,28, a dew point measuring unit 22, dew point adjusting units 24,27, and a control unit 20. The bright annealing furnace (heat treatment apparatus) 1 shown in fig. 1 is a horizontal furnace in which a furnace body extends in a lateral direction (horizontal direction). In the horizontal furnace, a conveying mechanism for conveying the metal strip 3 can be simplified, and the height of the heat treatment apparatus 1 can be suppressed from increasing.
In fig. 1, the metal strip 3 is horizontally conveyed from left to right. The metal strip 3 is formed of, for example, a stainless steel material containing Cr. The stainless steel material containing Cr is, for example, austenitic stainless steel SUS304 or ferritic stainless steel SUS430.
The furnace body 10 is formed of a steel box body, and includes a heating belt 12 and a cooling belt 14. The heating belt 12 extends in the lateral direction (horizontal direction) and is disposed on the upstream side of the metal belt 3 in the conveying direction (the inlet side of the metal belt 3). The heating belt 12 is heated by the heating section 16. The heating portion 16 is, for example, an electrothermal heater. The control unit 20 controls the heating belt 12 to reach a predetermined annealing temperature (here, the temperature in the heating step during annealing and the temperature in the heating step during cooling step) based on the temperature measured by a temperature measuring unit (not shown). The annealing temperature in the present application means the temperature of the furnace atmosphere in the heating zone 12. For example, in the case of a general stainless steel material, the annealing temperature suitable for bright annealing is in the temperature range of 800 ℃ to 1250 ℃, and the control unit 20 controls the heating unit 16 so that the annealing temperature falls within the above temperature range.
The cooling belt 14 is provided on the downstream side in the conveying direction of the metal belt 3 (the outlet side of the metal belt 3). The cooling belt 14 is mainly cooled by cooling down due to annealing, and therefore, a heating device or a heat insulating material 17 is not provided. The cooling belt 14 may be provided with some cooling means as the case may be.
A heat insulating material 17 is attached to the inner surfaces (inner walls of the furnace) of the furnace walls such as the side walls, the top and bottom of the furnace body 10. The insulating material 17 is made of ceramic fibers containing SiO 2. The heat insulating material 17 may be configured to be held by, for example, piercing a plate or felt made of ceramic fibers into a large number of rod-like studs attached to the furnace wall and pressing the same with a washer-like metal fitting. The heat insulating material 17 is a fiber containing Al 2O3 (alumina) and SiO 2 (silica) as main components, and is, for example, an alumina-silica ceramic fiber having a content of Al 2O3 of 30 to 60 mass% and a content of SiO 2 of 40 to 70 mass%.
The furnace body 10 of the bright annealing furnace 1 is filled with a reducing atmosphere. The inlet seal roll 13 and the outlet seal roll 15 are provided at the inlet opening and the outlet opening of the furnace body 10, respectively. The inlet seal roller 13 and the outlet seal roller 15 prevent the invasion 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, a small amount of moisture is carried from the outside air into the furnace body 10 while adhering to the surface of the metal strip 3 at the inlet seal roll 13. In addition, at the outlet seal roller 15, a minute amount of the atmosphere 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 regulating valve 28, and supplies the reducing gas into the furnace body 10, in other words, the heating belt 12, through the gas supply pipe 5. The gas supply device 9 is, for example, a gas cylinder. The reducing gas is a gas containing hydrogen, for example, a gas in which hydrogen and nitrogen are mixed at a ratio of 3:1. The amount of the reducing gas supplied can be controlled by adjusting the opening of the second regulator valve 28 provided in the gas supply pipe 5. The opening degree of the second regulator valve 28 is controlled by the control unit 20. By supplying the reducing gas, the amount of leakage from the inlet seal roller 13 and the outlet seal roller 15 can be replenished. In the bright annealing furnace 1 shown in fig. 1, the gas supply pipe 5 is disposed upstream of the cooling belt 14, but the position of supply of the reducing gas is not particularly limited. The reducing gas supplied from the gas supply pipe 5 is diffused as an atmosphere gas in the entire inside of the furnace body 10 including the heating belt 12, and then discharged to the outside of the furnace body 10.
The reducing gas supplied from the gas supply device 9 is a low dew point (i.e., low moisture content) gas, for example, a JIS hydrogen grade 1 gas having a dew point of-70 ℃. Therefore, in the present application, the dew point adjusting unit 24 including the dehumidifying device 25 or the humidifying device 26 can adjust the dew point of the furnace atmosphere, and therefore, the reducing gas supplied from the gas supply device 9 does not need to have a low dew point (i.e., a low moisture content). That is, as the reducing gas supplied from the gas supply device 9, a gas containing a larger amount of moisture than the conventional JIS hydrogen grade 1 may be used, and for example, a gas corresponding to the JIS hydrogen grade 2 and having a dew point of-60℃may be used.
The dew point measuring unit 22 measures the dew point of the atmosphere (hereinafter, sometimes referred to as "atmosphere gas") in the heating zone 12 of the furnace body 10 through the dew point measuring pipe 6. The dew point measuring unit 22 is, for example, a capacitance dew point meter or a mirror-cooled dew point meter. The dew point measurement data is sent to the control unit 20 and stored in the storage unit of the control unit 20. In the bright annealing furnace 1 shown in fig. 1, the dew point measuring tube 6 is disposed downstream of the heating belt 12, but the position of measuring the dew point 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 a dehumidifying device 25 and a humidifying device 26. Thereby, the dew point of the atmosphere in the heating belt 12 can be appropriately adjusted according to the dew point of the reducing gas supplied from the gas supply unit 9,28 and the dew point of the target atmosphere.
The dew point adjusting device 24 extracts a part of the atmosphere through the inlet side duct 7 provided on the upstream side in the conveying direction of the heating belt 12, adjusts the dew point of the extracted atmosphere, that is, the moisture amount, and returns the atmosphere to the furnace body 10 through the outlet side duct 8 provided on the downstream side in the conveying direction of the heating belt 12. The atmosphere gas circulates between the dew point adjusting means 24 and the furnace body 10, and thereby the dew point of the atmosphere in the heating zone 12 is maintained at a predetermined dew point.
The dew point adjusting means 24 (i.e., the dehumidifying means 25 and the humidifying means 26) is controlled by the control portion 20. The circulation amount of the atmosphere gas can be controlled by adjusting the opening degree of the first adjusting valve 27 provided in the inlet side duct 7. The opening degree of the first regulator valve 27 is controlled by the control unit 20.
The dehumidifying device 25 has the 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 separation tower filled with an adsorbent. The adsorbent is synthetic zeolite such as molecular sieve (molecular sieve), natural zeolite, active carbon, silica gel, alumina, active alumina, etc. The dehumidification using the adsorbent can easily control the dew point of the dehumidified atmosphere to a predetermined dew point, and the obtained atmosphere is very clean.
The humidifying device 26 has an effect of adding moisture to the atmosphere (humidifying the atmosphere) and raising the dew point of the atmosphere by generating a moisture-containing gas obtained by mixing water vapor or liquid-phase water with the atmosphere and sending the moisture-containing gas into the furnace body 10. The humidifying device 26 is, for example, a bubbling type in which the atmosphere is passed through water stored in a container, a spray nozzle type in which water vapor is sprayed in a mist form to the atmosphere, a membrane exchange type in which a hollow fiber membrane having high water vapor permeability is used, or the like.
The control section 20 is electrically connected to the dew point measuring section 22, the dew point adjusting means 24, the first adjusting valve 27, the second adjusting valve 28, and the heating section 16. The control unit 20 may be configured using a computer or the like including a computing unit such as a CPU (central processing unit), a storage unit such as a RAM (random access memory) and a ROM (read only memory).
The control unit 20 controls the gas supply unit 9,28 and the dew point adjusting units 24 and 27 based on the dew point measured by the dew point measuring unit 22. That is, the control unit 20 controls the opening degree of the second regulator valve 28, thereby controlling the supply amount of the reducing gas supplied from the gas supply device 9. The control unit 20 controls the opening degree of the first regulator valve 27 to control the circulation amount of the atmosphere gas by the dew point adjusting means 24. Thereby, automation of bright annealing (heat treatment) can be realized.
The control unit 20 controls the dehumidification device 25 or the humidification device 26 in the dew point adjusting device 24 to operate. When the control unit 20 controls the dehumidifier 25 to operate, the moisture contained in the atmosphere is removed, and the dew point of the atmosphere, that is, the moisture content is reduced. The control unit 20 controls the humidifying device 26 so that the dew point of the atmosphere, that is, the amount of moisture increases by increasing the amount of moisture contained in the atmosphere. Thereby, automation of bright annealing (heat treatment) can be realized.
[ Other aspects of the first embodiment ]
As described above, even if the sealing structure in which the metal strip 3 is sandwiched by the inlet sealing rollers 13 is adopted, a small amount of moisture is carried from the outside air into the furnace body 10 in a state of adhering to the surface of the metal strip 3, and thus the dew point (moisture amount) of the atmosphere rises. Therefore, by using hydrogen gas having an extremely low dew point as the reducing gas, the moisture contained in the atmosphere can be diluted, and the dew point of the atmosphere can be reduced. In addition, 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 regulating valve 28. In addition, when a small amount of moisture is prevented from being introduced into the furnace body 10 from the outside air by some means, the use of hydrogen gas having a slightly higher dew point as the reducing gas can increase the moisture contained in the atmosphere and raise the dew point of the atmosphere.
Therefore, the dew point of the atmosphere in the heating belt 12 can be adjusted without using the dehumidifying device 25 or the humidifying device 26 shown in fig. 1. 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, thereby adjusting the flow rate of the reducing gas supplied from the gas supply device 9, and thereby adjusting the dew point of the atmosphere in the furnace body 10 including the heating zone 12. Thereby, automation of bright annealing (heat treatment) can be realized. Here, depending on the amount of moisture carried into the furnace body 10 from the outside air, hydrogen gas having an extremely low dew point or hydrogen gas having a slightly high dew point may be used as the reducing gas supplied from the gas supply device 9. Thereby, the gas supply device 9 and the second regulator valve 28 function as the dew point adjusting means 24a. With this, the dew point adjusting means 24a can be constituted by a simple configuration.
[ Control of dew Point of atmosphere ]
As described above, the less the moisture in the atmosphere in the heating belt 12 of the furnace body 10, the more advantageous the surface oxidation of the metal belt 3 is, and therefore the brightness of the metal belt 3 is, but the less advantageous the heat insulating material 17 is because it acts in the direction of reducing the SiO 2 contained in the heat insulating material 17. Accordingly, the present inventors have focused on the existence of a dew point (i.e., a moisture amount) in an appropriate range capable of simultaneously achieving both maintaining brightness and preventing reduction of SiO 2, and have achieved the present application.
Control of the dew point of the atmosphere in the heating belt 12 will be described with reference to fig. 2. Fig. 2 is a diagram schematically illustrating a relationship between temperature and dew point of an 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 the dew point of-30℃and S is an oxidation-reduction equilibrium curve of SiO 2. Above the equilibrium curve S, siO 2 is oxidized and below the equilibrium curve S, siO 2 is reduced. Further, the intersections of the straight line a with the annealing temperatures 800 ℃ and 1250 ℃ are a and b, respectively, and the intersections of the equilibrium curve S with the equilibrium temperatures 800 ℃ and 1250 ℃ are c and d, respectively. These temperatures and intersections correspond, for example, to the annealing of stainless steel materials.
The dew point of the atmosphere corresponds to the amount of moisture contained in the atmosphere. For example, the water content is about 338 (g/m 3) at-30 ℃, about 203 (g/m 3) at-35 ℃, about 119 (g/m 3) at-40 ℃, about 68 (g/m 3) at-45 ℃, about 38 (g/m 3) at-50 ℃, about 21 (g/m 3) at-55 ℃, about 11 (g/m 3) at-60 ℃, about 5.6 (g/m 3) at-65 ℃, and about 2.7 (g/m 3) at-70 ℃. Therefore, as the dew point of the atmosphere decreases, the amount of moisture 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. In the case where the metal strip 3 is a stainless steel material containing Cr, an oxide film formed by combining Cr and Fe with oxygen is formed. It is said that in order to suppress surface oxidation of the metal strip 3, it is desirable that the dew point of the atmosphere is as low as possible, that is, the amount of moisture contained in the atmosphere is as small as possible.
However, in the actual heat treatment step, it was found that when the thickness of the oxide film formed on the surface of the metal strip 3 becomes thinner than a certain thickness, the influence on the brightness of the metal strip 3 is reduced. Therefore, by setting the upper limit dew point of the atmosphere to-30 ℃ or lower, the formation of oxide film in the metal strip 3 can be suppressed, and the metal strip 3 has a certain degree or higher of brightness, and there is little problem in the product. The line a in fig. 2 shows the maximum upper limit dew point at which oxide film formation in the metal strip 3 is suppressed. The intersection a is the maximum upper dew point at 800 ℃, and the intersection b is the maximum upper dew point at 1250 ℃.
In the case of commercializing the metallic strip 3 of a bright stainless steel material, it is preferable to adjust the upper dew point of the atmosphere to-30 ℃. In order to obtain a metal strip 3 having a higher brightness in the stainless steel material, the upper dew point of the atmosphere may be adjusted to-45 ℃. In order to obtain the metal strip 3 having a higher brightness, the upper dew point of the atmosphere may be adjusted to-65 ℃ (line X in the figure) or less. Therefore, in the stainless steel material, the upper limit dew point at which the metallic strip 3 can have the brightness is set to be in the range of-30 ℃ to-65 ℃ depending on the degree of brightness of the metallic strip 3 to be bright annealed. According to this constitution, the metal strip 3 having a desired brightness can be obtained.
A heat insulating material 17 made of ceramic fiber is provided on the inner surface of the furnace wall (inner wall of the furnace). Conventionally, when a refractory brick made of high-purity alumina containing high-purity Al 2O3 (alumina) is used in an arch-shaped laminated structure in a horizontal bright annealing furnace 1, there is a problem in that dust is generated and the quality of a metal strip 3 is lowered due to expansion and contraction of the refractory brick when the temperature in the furnace is raised and lowered.
In the horizontal bright annealing furnace 1 of the present application, the use of ceramic fibers containing SiO 2 as the heat insulating material 17 can suppress the generation of dust and can obtain the high-quality metal strip 3. However, siO 2 contained in the ceramic fiber has a lower reduction resistance than Al 2O3 (alumina), and when the ceramic fiber is used in an atmosphere having a high reduction property, it is considered that the ceramic fiber is deteriorated and embrittled by the reduction of SiO 2, and dust is generated.
In the present application, the inventors focused on the oxidation-reduction characteristics (thermodynamic characteristics) of SiO 2, so that the heat insulating material 17 made of ceramic fiber containing SiO 2 can be used also in an atmosphere with high reducibility. As shown in fig. 2, the upper side of the equilibrium curve S is a region where SiO 2 is kept in an oxidized state, and the lower side of the equilibrium curve S is a region where SiO 2 is reduced, bounded by the oxidation-reduction equilibrium curve S of SiO 2.
The dew point at the intersection point c of the oxidation-reduction equilibrium curve S of SiO 2, which intersects the equilibrium temperature 800 c, is about-95 c and the dew point at the intersection point d, which intersects the equilibrium temperature 1250 c, is about-60 c. The dew point is a lower limit dew point at which SiO 2 contained in the heat insulating material 17 is not reduced at an equilibrium temperature of 800 to 1250 ℃ suitable for bright annealing of a stainless steel material, for example. Therefore, when the annealing temperature of the heating belt 12 is in the range of 800 to 1250 ℃, the control unit 20 can control the dew point of the atmosphere so as not to fall below the equilibrium curve S, thereby not reducing SiO 2. Thereby, dust generation due to deterioration of the heat insulating material 17 made of ceramic fiber is prevented, and the high-quality metal strip 3 can be obtained.
When the annealing temperature of the heating belt 12 is 800 to 1250 ℃ (for example, when the metal belt 3 is made of stainless steel), the control unit 20 controls the dew point adjusting units 24 and 27 so that the dew point of the atmosphere is maintained in the region surrounded by the intersections a, b, d, and c in fig. 2. Thereby, the metal strip 3 can be made bright, 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
Referring to fig. 5, a heat treatment apparatus 1 according to a second embodiment will be described. Fig. 5 is a schematic cross-sectional view of the heat treatment apparatus 1 of the second embodiment.
As shown in fig. 5, the bright annealing 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. In comparison with the bright annealing furnace (heat treatment apparatus) 1 of the first embodiment shown in fig. 1, the bright annealing furnace (heat treatment apparatus) 1 of the second embodiment omits the control section 20 such as a computer. Therefore, an operator who operates the bright annealing furnace (heat treatment apparatus) 1 becomes a substitute for the control section 20.
The operator can manually control at least one of the second regulating valve (dew point adjusting part) 28a and the first regulating valve (dew point adjusting part) 27a based on the dew point measured by the dew point measuring part 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 adjusting valve (dew point adjusting unit) 28a based on the measured dew point. The operator can control the circulation amount of the atmosphere gas by the dew point adjusting means 24 by controlling the first adjusting valve (dew point adjusting portion) 27a based on the measured dew point.
The operator controls the dehumidification device 25 of the dew point adjustment device 24 to operate, thereby removing moisture contained in the atmosphere, and the dew point of the atmosphere, that is, the moisture amount is reduced. The operator controls the humidifying device 26 of the dew point adjusting device 24 to operate, so that the moisture contained in the atmosphere increases, and the dew point of the atmosphere, that is, the moisture amount increases.
By this, by keeping the dew point (i.e., the moisture amount) of the atmosphere in the heating belt 12 between the upper limit dew point and the lower limit dew point, the moisture amount in the reducing atmosphere is suitable for maintaining the brightness of the metal belt 3 and preventing the reduction of SiO 2 contained in the heat insulating material 17. As a result, the metal strip 3 can be made bright, 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 means 24 (the dehumidifying means 25 and the humidifying means 26) is omitted in addition to the control unit 20, and the gas supply means 9 and the second regulating valve (dew point adjusting means) 28a may be used as the dew point adjusting means 24a. Thereby, the dew point adjusting means 24a can be simply constituted. The operator can control the dew point adjusting means 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. The operator can control the flow rate of the reducing gas supplied from the gas supply device 9 by manually controlling the second regulator valve (dew point adjusting unit) 28a based on the measured dew point.
By this, by keeping the dew point (i.e., the moisture amount) of the atmosphere in the heating belt 12 between the upper limit dew point and the lower limit dew point, the moisture amount in the reducing atmosphere is suitable for maintaining the brightness of the metal belt 3 and preventing the reduction of SiO 2 contained in the heat insulating material 17. As a result, the metal strip 3 can be made bright, 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 manual control in the second embodiment does not require the operator to constantly and continuously monitor the dew point, and includes a case where the operator does not perform special control if there is no abnormality.
The present invention has been described with reference to specific embodiments and numerical values, but the present invention is not limited to the above-described embodiments and numerical values, and various modifications and implementations are possible within the scope of the present invention.
The operator may perform at least one of the following operations as an alternative to the control section 20: the dew point measured by the dew point measuring unit 22 is acquired, and the dew point adjusting units 27a and 28a are controlled so that the dew point is maintained 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.
The bright annealing furnace (heat treatment apparatus) 1 may be a vertical furnace in which the furnace body 10 extends in the longitudinal direction (vertical direction).
In the bright annealing furnace (heat treatment apparatus) 1, an inlet sealing belt may be provided upstream of the heating belt 12 in the conveying direction, and the inlet sealing roller 13 may be disposed in the inlet sealing belt. An outlet seal belt may be provided downstream of the cooling belt 14 in the conveying direction, and the outlet seal roller 15 may be disposed in the outlet seal belt. The heating belt 12 may be composed of an inlet sealing belt, a preheating belt, a soaking belt (all not shown), and the like. The cooling zone 14 may be composed of an outlet seal zone, a quench zone (neither shown), or the like.
The bright annealing furnace 1 shown in fig. 1 includes both the dehumidifier 25 and the humidifier 26, but may be configured to include either the dehumidifier 25 or the humidifier 26.
Fig. 3 shows an oxidation-reduction equilibrium curve C of Cr 2O3 (chromium oxide) obtained by oxidizing a Cr component in a stainless steel material. In the above embodiment, the explanation was made with the upper limit dew point of-30 ℃, but it is considered that oxidation of the stainless steel material can be prevented by controlling the dew point of the atmosphere so as not to exceed the oxidation-reduction equilibrium curve C of Cr 2O3. Therefore, in the case of stainless steel materials, the control section 20 may also control the dew point adjusting sections 24,24a so that the dew point of the atmosphere is maintained within the region surrounded by the intersections e, f, d, and c in fig. 3.
The metal strip 3 subjected to bright annealing in a reducing atmosphere can be applied to various metal materials such as pure metals including nickel, titanium, and copper, low expansion alloys, magnetic alloys, heat resistant alloys, and corrosion resistant alloys, in addition to the above-described stainless steel materials.
The invention and embodiments may be summarized as follows.
The heat treatment apparatus 1 according to an embodiment of the present invention is characterized in that: the method comprises heating a metal strip (3), heating a metal strip (12), a heat insulating material (17) made of ceramic fibers containing SiO 2) used as an inner wall of the furnace of the heating strip (12), and gas supply parts (9, 28 a) for supplying a reducing gas to the heating strip (12) so as to maintain the dew point between an upper limit dew point capable of making the metal strip (3) bright and a lower limit dew point not reducing the SiO 2 contained in the heat insulating material (17), and bright annealing the metal strip (3) in a reducing atmosphere.
According to the above configuration, by keeping the dew point (i.e., the moisture amount) of the atmosphere in the heating belt 12 between the upper limit dew point and the lower limit dew point, the moisture amount in the reducing atmosphere is suitable for maintaining the brightness of the metal belt 3 and preventing the reduction of SiO 2 contained in the heat insulating material 17. As a result, the metal strip 3 can be made bright, 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 an embodiment of the present invention is a heat treatment apparatus 1 for bright annealing a metal strip 3 in a reducing atmosphere, wherein the heat treatment apparatus 1 includes: a furnace body 10, the furnace body 10 having a heating belt 12 for heating the metal strip 3 and a cooling belt 14 provided on a downstream side of the heating belt 12 in a conveying direction of the metal strip 3; a heat insulating material 17, the heat insulating material 17 being used as an inner wall of the furnace of the heating belt 12 and made of ceramic fibers containing SiO 2; gas supply units 9,28 a for supplying a reducing gas into the furnace body 10; a dew point measuring unit 22 for measuring an atmosphere dew point in the heating belt 12; and dew point adjusting parts 24,24a,27 a,28 a for adjusting the dew point, wherein the dew point adjusting parts 24,24a,27 a,28 a are controlled so that the dew point is maintained between an upper limit dew point at which the metal strip 3 can have brightness and a lower limit dew point at which the SiO 2 contained in the heat insulating material 17 is not reduced, based on the dew point measured by the dew point measuring part 22.
According to the above configuration, by keeping the dew point (i.e., the moisture amount) of the atmosphere in the heating belt 12 between the upper limit dew point and the lower limit dew point, the moisture amount in the reducing atmosphere is suitable for maintaining the brightness of the metal belt 3 and preventing the reduction of SiO 2 contained in the heat insulating material 17. As a result, the metal strip 3 can be made bright, and deterioration of the heat insulating material 17 due to reduction of SiO 2 contained in the heat insulating material 17 can be prevented.
In the heat treatment apparatus 1 according to one embodiment, the control unit 20 controls the dew point adjusting units 24,27, and 28.
According to the above embodiment, automation of bright annealing (heat treatment) can be realized.
In the heat treatment apparatus 1 according to one embodiment, the upper limit dew point is-30 ℃.
According to the above embodiment, the metal strip 3 having brightness can be obtained.
In the heat treatment apparatus 1 according to one embodiment, the upper limit dew point is set to be within a range of-30 ℃ to-65 ℃ according to the degree of brightness of the metal strip 3 to be bright annealed.
According to the above embodiment, the metal strip 3 having a desired brightness can be obtained.
In the heat treatment apparatus 1 according to one 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 belt 12 can be appropriately adjusted according to the dew point of the reducing gas supplied from the gas supply portion 9,28 a and the dew point of the target atmosphere.
In the heat treatment apparatus 1 according to one embodiment, the gas supply unit 9,28 a includes a gas supply device 9 and a regulating valve 28,28a for regulating the flow rate of the reducing gas supplied from the gas supply device 9, and the gas supply device 9 and the regulating valve 28,28a function as the dew point adjusting unit 24,24 a.
According to the above embodiment, the dew point adjusting means 24,24a can be constituted by a simple constitution.
In addition, in the heat treatment apparatus 1 of an 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 conveying mechanism for conveying the metal strip 3 can be simplified, and the height of the heat treatment apparatus 1 can be suppressed from increasing. Further, since the disintegration of ceramic fibers and the generation of dust can be prevented, even in a horizontal furnace having a large furnace roof area, the heat insulating material 17 made of lightweight ceramic fibers can be used.
In addition, in the heat treatment apparatus 1 of an embodiment, the metal strip 3 is formed of a stainless material containing Cr.
According to the above embodiment, the formation of the oxide film in the metal strip 3 can be suppressed, and the metal strip 3 can be made bright.
In the heat treatment apparatus 1 according to one embodiment, the temperature of the heating belt 12 is in the range of 800 to 1250 ℃.
According to the above embodiment, the metal strip 3 can be heated at a temperature suitable for bright annealing.
In addition, in the heat treatment apparatus 1 of an embodiment, the reducing gas contains hydrogen.
According to the above embodiment, the metal strip 3 can be reduced and bright annealed.
Symbol description
1 … … Bright annealing furnace (Heat treatment equipment)
3 … … Metal strap
5 … … Gas supply pipeline
6 … … Dew point measuring pipeline
7 … … Inlet side pipeline
8 … … Outlet side pipeline
9 … … Gas supply device (gas supply unit, dew point adjusting unit)
10 … … Furnace body
12 … … Heating belt
13 … … Inlet seal roller
14 … … Cooling belt
15 … … Outlet seal roller
16 … … Heating part
17 … … Heat insulating material
20 … … Control part
22 … … Dew point measuring unit
24 … … Dew point adjusting device (dew point adjusting part)
24A … … dew point adjusting device (dew point adjusting part)
25 … … Dehumidifier
26 … … Humidifier
27 … … First regulating valve (dew point adjusting part)
27A … … first regulating valve (dew point adjusting part)
28 … … Second control valve (gas supply unit, dew point adjusting unit)
28A … … second regulating valve (gas supply unit, dew point adjusting unit)
A … … represents a straight line of dew point of-30 DEG C
Oxidation-reduction equilibrium curve of C … … Cr 2O3
Oxidation-reduction equilibrium curve of S … … SiO 2.
Claims (6)
1. A heat treatment apparatus comprising a heating zone for bright annealing a metal strip made of a stainless steel material containing Cr in a reducing atmosphere, a heat insulating material made of ceramic fibers containing SiO 2 and used as an inner wall of a furnace of the heating zone, a temperature control unit for controlling a heating temperature in the heating zone, a dew point measuring unit for measuring an atmosphere dew point in the heating zone, and a dew point adjusting unit for controlling the atmosphere dew point in the heating zone by dehumidification and humidification,
In a graph illustrating the relationship between the heating temperature and the atmosphere dew point, a range suitable for the bright annealing is defined,
The range is surrounded by an upper limit temperature line indicating an upper limit bright annealing temperature, a lower limit temperature line indicating a lower limit bright annealing temperature, an upper limit dew point line corresponding to an oxidation-reduction equilibrium curve of Cr 2O3 and capable of providing brightness, and a lower limit dew point line corresponding to an oxidation-reduction equilibrium curve of SiO 2 and not causing reduction of SiO 2,
The temperature control section and the dew point adjustment section are controlled so that the heating temperature and the atmosphere dew point are within the ranges, respectively.
2. The heat treatment apparatus according to claim 1, wherein the dew point adjusting unit includes both a dehumidifying device and a humidifying device.
3. The heat treatment apparatus according to claim 1 or 2, wherein the dew point adjusting portion has a gas supply device that supplies a reducing gas to the heating belt, and an adjusting valve that is provided between the heating belt and the gas supply device and adjusts a flow rate of the reducing gas.
4. The heat treatment apparatus according to claim 1, wherein the upper limit dew point is set in a range of-30 ℃ to-65 ℃ according to the degree of brightness of the metal strip to be bright annealed.
5. The heat treatment apparatus according to claim 1, wherein the temperature of the heating belt ranges from 800 ℃ to 1250 ℃.
6. The heat treatment apparatus according to claim 1, wherein the ceramic fiber contains 40 to 70 mass% of the SiO 2.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019-222033 | 2019-12-09 | ||
| JP2019222033 | 2019-12-09 | ||
| JP2020-193632 | 2020-11-20 | ||
| JP2020193632A JP2021091960A (en) | 2019-12-09 | 2020-11-20 | Heat treatment device |
| PCT/JP2020/044346 WO2021117516A1 (en) | 2019-12-09 | 2020-11-27 | Heat treatment apparatus |
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| Publication Number | Publication Date |
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| CN114761585A CN114761585A (en) | 2022-07-15 |
| CN114761585B true CN114761585B (en) | 2024-10-01 |
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| JP (1) | JP2021091960A (en) |
| CN (1) | CN114761585B (en) |
| TW (1) | TWI836167B (en) |
| WO (1) | WO2021117516A1 (en) |
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| JP7318086B1 (en) | 2022-09-22 | 2023-07-31 | 株式会社ノリタケカンパニーリミテド | Continuous heating furnace |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51136514A (en) * | 1975-05-22 | 1976-11-26 | Shiraishi Denki Kogyo Kk | Process and apparatus for heat treatment of metals |
| JPS62156254A (en) * | 1985-12-27 | 1987-07-11 | Nippon Kinzoku Kogyo Kk | Ferritic stainless steel hardly undergoing coloring in temper color and having superior rust resistance |
| JPH055124A (en) * | 1991-06-26 | 1993-01-14 | Nippon Steel Corp | Low dew point heat treatment furnace |
| JPH09256074A (en) * | 1996-03-25 | 1997-09-30 | Kawasaki Steel Corp | Bright anneling method of stainless steel |
| JP3664340B2 (en) * | 1996-09-10 | 2005-06-22 | 新日本製鐵株式会社 | Continuous bright annealing furnace for strip metal materials |
| SE515593C2 (en) * | 1999-03-01 | 2001-09-03 | Avesta Sheffield Ab | Apparatus for heating a metal band |
| JP4963043B2 (en) * | 2006-06-22 | 2012-06-27 | 新日鐵住金ステンレス株式会社 | Bright annealed ferritic stainless steel sheet with excellent rust resistance and workability and method for producing the same |
| JP4833922B2 (en) * | 2007-06-14 | 2011-12-07 | 新日本製鐵株式会社 | Continuous induction heating furnace for steel strip and method for continuous heat treatment of steel strip using the same |
| CN100567521C (en) * | 2007-12-01 | 2009-12-09 | 徐建永 | Horizontal continuous unmuffled light annealing equipment of stainless steel band |
| DE102011088633A1 (en) * | 2011-12-14 | 2013-06-20 | Ebner Industrieofenbau Gmbh | Hood furnace with positioned within a protective hood heat dissipation device, in particular fed by an oven-external energy source, for discharging heat to annealing gas |
| JP5505430B2 (en) * | 2012-01-17 | 2014-05-28 | Ｊｆｅスチール株式会社 | Continuous annealing furnace and continuous annealing method for steel strip |
| JP5863499B2 (en) * | 2012-02-17 | 2016-02-16 | 三菱重工業株式会社 | Heat treatment method |
-
2020
- 2020-11-20 JP JP2020193632A patent/JP2021091960A/en active Pending
- 2020-11-27 WO PCT/JP2020/044346 patent/WO2021117516A1/en active Application Filing
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| CN114761585A (en) | 2022-07-15 |
| WO2021117516A1 (en) | 2021-06-17 |
| JP2021091960A (en) | 2021-06-17 |
| TW202130823A (en) | 2021-08-16 |
| TWI836167B (en) | 2024-03-21 |
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