TWI836167B - Heat treatment device - Google Patents

Abstract

[Problem] To provide a heat treatment apparatus that can suppress the deterioration of a heat insulating material made of ceramic fibers containing SiO ₂ even in a reducing gas environment and perform glow annealing on a metal strip. [Solution] The heat treatment device is equipped with a heating belt for heating the metal belt, a heat insulating material made of ceramic fiber containing SiO ₂ used as the furnace inner wall of the heating belt, and a gas supply part for supplying reducing gas to the heating belt. , and perform glow annealing on the metal strip in a reducing gas environment so that the dew point is maintained between the upper limit dew point that allows the metal strip to have brightness and the lower limit dew point that does not reduce the SiO ₂ contained in the heat insulating material. .

Description

Heat treatment equipment

The present invention relates to a heat treatment device for bright annealing a metal strip.

There is known a heat treatment apparatus for performing bright annealing of a metal strip in a reducing gas atmosphere in order to remove the internal stress of the metal strip generated by cold rolling.

Patent document 1 discloses a continuous annealing furnace for molten metal coating, which has a low temperature holding belt and a muffle structure composed of steel plates, and is a so-called horizontal furnace in which the metal strip is transported in the horizontal direction. Patent document 2 discloses a horizontal bright surface annealing furnace for a metal strip lined with refractory bricks inside the furnace. Patent document 3 discloses a manufacturing device for a nickel-plated thin steel plate in which the heat insulation material inside the furnace is ceramic fiber. [Prior technical document] [Patent document]

[Patent document 1] Japanese Statute No. 03-1472 [Patent document 2] Japanese Patent No. 4268281 [Patent document 3] Japanese Patent Publication No. 2003-201595 [Summary of the invention] [Problem to be solved by the invention]

In Patent Document 1, since the muffle structure of the furnace body is made of steel plates, deformation occurs due to heating at high temperatures. Particularly in the case of horizontal furnaces, since the section where the roof is made of steel plates is long, the roof will hang down due to its own weight, causing greater shape deformation, causing turbulence in the air flow in the furnace, and worsening the temperature distribution in the furnace. In Patent Document 2, although the deformation of the refractory bricks is difficult to occur, the refractory bricks are heavy, so the workability during assembly, maintenance, or replacement is poor, and the weight of the annealing furnace is also increased, so it is necessary to install the annealing furnace somewhere. Load-resistant locations.

In Patent Document 3, ceramic fibers are used because the annealing of the steel plate and the diffusion treatment of nickel plating are performed at about 800° C. in a non-reducing gas environment. Ceramic fibers are lightweight and have excellent workability. However, since they contain SiO ₂ , in a high-temperature reducing gas environment, SiO ₂ is reduced and SiO ₂ is changed into Si. Therefore, the ceramic fibers break down, and the ceramic fibers need to be frequently repaired and replaced. When the ceramic fibers break down, dust is generated and the dust falls onto the metal strip. In particular, in the case of a horizontal furnace, since the area of the top plate becomes larger, the amount of falling dust increases, and the quality of the metal strip decreases.

Therefore, the subject of the present invention is to provide a heat treatment device for bright annealing a metal strip while suppressing the degradation of a heat insulating material made of ceramic fiber containing _SiO2 even in a reducing gas environment. [Means for Solving the Problem]

In order to solve the above-mentioned problem, a heat treatment device in one embodiment of the present invention is characterized in that it comprises: a heating belt for heating a metal belt; a heat insulating material, used as the inner wall of the furnace of the aforementioned heating belt and made of ceramic fiber containing _SiO2 ; and a gas supply part, which supplies a reducing gas to the aforementioned heating belt so that the dew point is maintained between an upper limit dew point that can make the aforementioned metal belt have brightness and a lower limit dew point that cannot reduce the aforementioned _SiO2 contained in the aforementioned heat insulating material, and the aforementioned metal belt is brightly annealed in a reducing gas environment.

In order to solve the above-mentioned problem, a heat treatment device in one embodiment of the present invention is a heat treatment device for performing bright annealing on a metal strip in a reducing gas environment, wherein the heat treatment device comprises: a furnace body having a heating belt for heating the metal strip, and a cooling belt disposed on the downstream side of the heating belt in the conveying direction of the metal strip; a heat insulating material used as the furnace inner wall of the heating belt and comprising SiO ₂ ceramic fiber; a gas supply unit for supplying reducing gas into the furnace; a dew point measuring unit for measuring the dew point of the gas environment in the heating belt; and a dew point adjusting unit for adjusting the dew point, and controlling the dew point adjusting unit based on the dew point measured by the dew point measuring unit so that the dew point is maintained between an upper limit dew point that allows the metal belt to have brightness and a lower limit dew point that cannot be included in the aforementioned heat insulating material to reduce the aforementioned _SiO2 . [Effect of the Invention]

The less moisture in the gas environment in the furnace, the more oxidation of the surface of the metal strip can be suppressed, so it is beneficial to the brightness of the metal strip. However, when using lightweight ceramic fibers as insulation materials for the inner wall of the furnace, due to It acts in the direction of reducing SiO ₂ contained in the heat insulating material, so it is detrimental to the heat insulating material. Therefore, the inventor of this case focused on the existence of an appropriate range of dew point (that is, moisture content) that can maintain brightness and prevent the reduction of SiO ₂ to coexist, and arrived at the present invention.

According to the present invention, by keeping the dew point (i.e., the moisture content) of the gas environment in the heating belt between the upper dew point and the lower dew point, the moisture content in the gas environment becomes appropriate for maintaining the brightness of the metal belt and preventing the reduction of _SiO2 contained in the thermal insulation material. As a result, the metal belt has brightness and the deterioration of the thermal insulation material caused by the reduction of _SiO2 contained in the thermal insulation material can be prevented.

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

[First embodiment] The heat treatment device 1 of the first embodiment will be described with reference to FIG1. FIG1 is a schematic cross-sectional view of the heat treatment device 1 of the first embodiment.

As shown in FIG. 1 , a gloss annealing furnace (heat treatment device 1 ) for continuously performing gloss annealing on a metal strip 3 includes a furnace body 10 , gas supply parts 9 and 28 , a dew point measurement part 22 , and dew point adjustment parts 24 and 27 , and the control unit 20. The glow surface annealing furnace (heat treatment device) 1 shown in Figure 1 is a horizontal furnace in which the furnace body extends in the transverse direction (horizontal direction). The horizontal furnace can simplify the conveying mechanism for conveying the metal strip 3 and can suppress the height of the heat treatment device 1 from increasing.

The metal strip 3 is conveyed horizontally from left to right in FIG. 1 . The metal band 3 is made of a stainless steel material containing Cr, for example. Stainless steel materials containing Cr are, for example, SUS304, a Worthfield iron-based stainless steel, or SUS430, a fat-grained iron-based stainless steel.

The furnace body 10 is composed of a steel box and has a heating zone 12 and a cooling zone 14 . The heating belt 12 extends in the transverse direction (horizontal direction) and is provided on the upstream side in the conveyance direction of the metal belt 3 (the entry side of the metal belt 3). The heating belt 12 is heated by the heating unit 16 . The heating unit 16 is, for example, an electric heater. The control unit 20 controls the heating belt 12 to a predetermined annealing temperature based on the temperature measured by a temperature measuring unit (not shown) (the temperature here refers to the heating step in the heating step and the cooling step of the annealing). temperature.). The annealing temperature in this case refers to the ambient temperature of the furnace gas in the heating zone 12 . For example, in general stainless steel materials, the annealing temperature suitable for glow annealing is in the range of 800°C to 1250°C. The control unit 20 controls the heating unit 16 so that the annealing temperature falls within the aforementioned temperature range.

The cooling belt 14 is provided on the downstream side in the conveyance direction of the metal belt 3 (the outlet side of the metal belt 3). In the cooling zone 14, although the annealing is performed, the heating mechanism and the heat insulating material 17 are not provided because cooling is mainly performed by standing cooling. However, the cooling belt 14 may be provided with any cooling mechanism depending on the situation.

The heat insulating material 17 is installed on the inner surface of the furnace wall (furnace inner wall) called the side wall, ceiling plate and floor of the furnace body 10 . The heat insulating material 17 is made of ceramic fiber containing _SiO2 . The heat insulating material 17 can be configured to be held by inserting a ceramic fiber plate or felt into a plurality of rod-shaped bolts installed on the furnace wall and pressing it with a washer-shaped metal member. The heat insulating material 17 is a fiber whose main components are Al ₂ O ₃ (aluminum oxide) and SiO ₂ (silicon dioxide). For example, the Al ₂ O ₃ content is 30 to 60 mass% and the SiO ₂ content is 30 to 60% by mass. 40~70% by mass alumina-silica ceramic fiber.

The interior of the furnace body 10 of the glow surface annealing furnace 1 is filled with reducing ambient gas. The inlet sealing roller 13 and the outlet sealing roller 15 are respectively arranged at the inlet opening and the outlet opening of the furnace body 10 . The inside of the furnace body 10 is maintained at a high pressure slightly higher than the atmospheric pressure by the inlet sealing roller 13 and the outlet sealing roller 15, thereby preventing outside air from intruding into the furnace body 10. However, even if the metal belt 3 is sandwiched between the entrance sealing roller 13 and the exit sealing roller 15, a trace amount of moisture will be brought into the furnace body from the outside air while adhering to the surface of the metal belt 3 at the entrance sealing roller 13. 10 interior. In addition, at the exit sealing roller 15, a trace amount of ambient gas will flow out of the furnace in the same pattern. Therefore, it is necessary to frequently measure and adjust the dew point (moisture content) of the gas environment in the heating zone 12 .

The gas supply part is equipped with a gas supply device 9 and a second regulating valve 28 , and supplies the reducing gas into the furnace body 10 through the gas supply pipe 5 , in other words, supplies the reducing gas to the heating belt 12 . The gas supply device 9 is a gas bottle, for example. The reducing gas is a gas containing hydrogen, for example, a mixture of hydrogen and nitrogen at a ratio of 3:1. By adjusting the opening of the second regulating valve 28 provided in the gas supply pipe 5, the supply amount of the reducing gas is controlled. The opening of the second regulating valve 28 is controlled by the control unit 20 . By supplying the reducing gas, the leakage portion from the inlet sealing roller 13 and the outlet sealing roller 15 is replenished. Furthermore, in the glow surface annealing furnace 1 shown in FIG. 1 , the gas supply pipe 5 is arranged on the upstream side of the cooling zone 14 . However, the supply position of the reducing gas is not particularly limited. The reducing gas supplied from the gas supply pipe 5 diffuses as ambient gas throughout the entire furnace body 10 including the heating zone 12 and then goes out to the outside of the furnace body 10 .

Conventionally, the reducing gas supplied from the gas supply device 9 is a gas with a low dew point (i.e., a low water content), for example, a gas with a dew point of -70°C in JIS hydrogen grade 1. However, in the present case, the dew point of the gas environment in the furnace can be adjusted by the dew point adjustment device 24 having the dehumidification device 25 and the humidification device 26, so the reducing gas supplied from the gas supply device 9 does not necessarily have to have a low dew point (i.e., 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 conventional JIS hydrogen grade 1, for example, a gas with a dew point of -60°C in JIS hydrogen grade 2 can be used.

The dew point measuring unit 22 measures the dew point of the gas environment (hereinafter, sometimes referred to as "ambient 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, an electrostatic capacitance type dew point meter or a mirror cooling type dew point meter. The measurement data of the dew point is sent to the control unit 20 and stored in the memory unit of the control unit 20 . Furthermore, in the glow surface annealing furnace 1 shown in FIG. 1 , the dew point measurement pipe 6 is arranged on the downstream side of the heating belt 12 . However, the dew point measurement position is not particularly limited.

The dew point adjustment section includes a dew point adjustment device 24 and a first regulating valve 27 for adjusting the dew point of the gas environment in the heating belt 12. The dew point adjustment device 24 includes at least one of a dehumidification device 25 and a humidification device 26. Thus, the dew point of the gas environment in the heating belt 12 can be appropriately adjusted in accordance with the dew point of the reducing gas supplied by the gas supply parts 9 and 28 and the dew point of the target gas environment.

The dew point adjustment device 24 discharges a part of the gas environment through the inlet pipe 7 provided on the upstream side of the conveyance direction of the heating belt 12, and adjusts the dew point, that is, the moisture content of the discharged gas environment, through the inlet pipe 7 provided on the upstream side of the conveyance direction of the heating belt 12. The outlet pipe 8 on the downstream side in the conveyance direction of the heating belt 12 returns to the furnace body 10 . By the ambient gas circulating between the dew point adjusting device 24 and the furnace body 10, the dew point of the gas environment in the heating zone 12 is maintained at a predetermined dew point.

The dew point adjustment device 24 (that is, the dehumidification device 25 and the humidification device 26) is controlled by the control unit 20. By adjusting the opening of the first regulating valve 27 provided in the inlet pipe 7, the circulation amount of the ambient gas is controlled. The opening of the first regulating valve 27 is controlled by the control unit 20 .

The dehumidifier 25 removes moisture contained in the gas environment (dehumidification of the gas environment) and has the function of lowering the dew point of the gas environment. The dehumidifier 25 has, for example, an adsorption tower and a desorption tower filled with an adsorbent. The adsorbent is a synthetic zeolite such as a molecular filter (molecular sieve), a natural zeolite, activated carbon, silica gel, alumina, activated alumina, etc. Dehumidification using an adsorbent can easily control the dew point of the gas environment after dehumidification to a predetermined dew point, and the resulting gas environment is extremely clean.

The humidification device 26 has the following function: generates water-containing gas that is a mixture of water vapor or liquid phase and a gas environment, and sends the water-containing gas into the furnace body 10, thereby adding moisture to the gas environment (gas environment). (humidification), causing the dew point of the gas environment to rise. The humidification device 26 is, for example, a bubbling type that causes the gas environment to pass through water stored in a container, a nozzle type that sprays water vapor into a mist form into the gas environment, or a type that uses a hollow fiber membrane with high water vapor permeability. Membrane exchange type, etc. The control unit 20 is electrically connected to the dew point measuring unit 22 , the dew point adjusting device 24 , the first regulating valve 27 , the second regulating valve 28 , and the heating unit 16 . The control unit 20 can be configured using a computer or the like including a computing 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 and 28 and the dew point adjustment units 24 and 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 of the second regulating valve 28 . Furthermore, the control unit 20 controls the circulation amount of the ambient gas of the dew point adjustment device 24 by controlling the opening of the first regulating valve 27 . This makes it possible to automate glow annealing (heat treatment).

The control unit 20 controls the dehumidification device 25 or the humidification device 26 in the dew point adjustment device 24 to operate. The control unit 20 controls the dehumidifier 25 to reduce the dew point of the gas environment, that is, the moisture content by removing moisture contained in the gas environment when the dehumidification device 25 is activated. The control unit 20 controls the moisture contained in the gas environment to increase when the humidification device 26 is activated, thereby increasing the dew point of the gas environment, that is, the moisture content. This makes it possible to automate glow annealing (heat treatment).

[Other aspects of the first embodiment] As mentioned above, even if the metal strip 3 is sandwiched by the inlet seal rollers 13, a trace amount of moisture will be brought into the furnace body 10 from the outside air in a state of adhering to the surface of the metal strip 3, so the gas environment The dew point (moisture content) will rise. Therefore, by using hydrogen gas with an extremely low dew point as a reducing gas, the moisture contained in the gas environment can be diluted and the dew point of the gas environment can be lowered. In addition, even if hydrogen gas with an extremely low dew point is used as the reducing gas, the flow rate of the reducing gas can be reduced by the second regulating valve 28, thereby increasing the dew point of the gas environment. Furthermore, any means can be used to prevent trace amounts of moisture from being brought into the interior of the furnace body 10 from the outside air. By using hydrogen with a high dew point as the reducing gas, the moisture contained in the gas environment can be increased, thereby improving the efficiency of the furnace. The dew point of the gas environment.

Therefore, the dehumidification device 25 and the humidification device 26 shown in FIG. 1 can be used to adjust the dew point of the gas environment in the heating belt 12 . That is, as shown in FIG. 4 , the control unit 20 controls the second regulating valve 28 based on the dew point of the gas environment measured by the dew point measuring unit 22 to adjust the reducing gas supplied by the gas supply device 9 . flow, whereby the dew point of the gas environment in the furnace body 10 containing the heating belt 12 can be adjusted. This makes it possible to automate glow annealing (heat treatment). Here, depending on the amount of moisture brought into the furnace body 10 from outside air, hydrogen gas with an extremely low dew point or hydrogen gas with a high dew point is used as the reducing gas supplied from the gas supply device 9 . In this way, the gas supply device 9 and the second regulating valve 28 operate as the dew point adjusting device 24a. Thereby, the dew point adjustment device 24a can be constructed with a simple structure.

[Control of dew point of gas environment] As mentioned above, the less moisture in the gas environment in the heating zone 12 of the furnace body 10, the more beneficial it is to the brightness of the metal strip 3 because it will inhibit the oxidation of the surface of the metal strip 3. However, Since it acts in the direction of reducing _SiO2 contained in the heat insulating material 17, it is disadvantageous to the heat insulating material 17. Therefore, the inventor of this case focused on the existence of an appropriate range of dew point (that is, moisture content) that can maintain brightness and prevent SiO ₂ reduction, and arrived at this invention.

The control of the dew point of the gas environment of the heating zone 12 will be described with reference to FIG. 2 . FIG. 2 is a diagram schematically illustrating the relationship between temperature and dew point of a gas environment. In FIG. 2 , the horizontal axis shows the annealing temperature in the heating zone 12 and the oxidation-reduction equilibrium temperature of SiO ₂ , and the vertical axis shows the dew point of the gas environment in the heating zone 12 . In Fig. 2, A is a straight line showing the dew point of -30°C, and S is an equilibrium curve showing the oxidation-reduction of _SiO2 . When the dew point is higher than the equilibrium curve S, SiO ₂ is oxidized, and when the dew point is lower than the equilibrium curve S, SiO ₂ is reduced. Furthermore, the intersection points of the straight line A and the annealing temperatures of 800°C and 1250°C are a and b respectively, and the intersection points of the equilibrium curve S and the equilibrium temperatures of 800°C and 1250°C are c and d respectively. These temperatures and intersection points correspond to, for example, annealing of stainless steel materials.

The dew point of a gas environment is the amount of moisture corresponding to the moisture contained in the gas environment. For example, when the dew point is -30°C, the moisture content is about 338 (g/m ³ ), when the dew point is -35°C, the moisture content is about 203 (g/m ³ ), and when the dew point is -40°C, the moisture content is about 119 (g/m 3 ). ³ ), the moisture content is about 68 (g/m ³ ) when the dew point is -45℃, the moisture content is about 38 (g/m ³ ) when the dew point is -50℃, and the moisture content is about 21 (g/m 3 ) when the dew point is -55℃. m ³ ), the moisture content is about 11 (g/m ³ ) when the dew point is -60℃, the moisture content is about 5.6 (g/m ³ ) when the dew point is -65℃, and the moisture content is about 2.7 (g/m 3 ) when the dew point is -70℃ /m ³ ). Therefore, as the dew point of the gas environment becomes lower, the amount of moisture contained in the gas environment becomes smaller.

When the surface of the metal belt 3 is oxidized, an oxide film is formed on the surface of the metal belt 3. When the metal belt 3 is a stainless steel material containing Cr, an oxide film is formed in which Cr and Fe are combined with oxygen. To suppress the surface oxidation of the metal belt 3, it is said that it is desirable to make the dew point of the gas environment as low as possible, that is, the amount of water contained in the gas environment 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 becomes smaller. Therefore, by setting the upper limit dew point of the gas atmosphere to -30° C. or less, the formation of an oxide film on the metal belt 3 is suppressed, and the metal belt 3 has brightness above a certain level and has few product problems. The straight line A in FIG. 2 is the dew point showing the upper limit of suppressing the formation of an oxide film on the metal strip 3 . Moreover, the intersection point a is the upper limit dew point at 800°C, and the intersection point b is the upper limit dew point at 1250°C.

When the metal strip 3 made of stainless steel with brightness is commercialized, it is suitable to adjust the upper limit dew point of the gas environment to -30°C or less. In order to obtain the metal strip 3 with a high degree of brightness among stainless steel materials, the upper limit dew point of the gas environment can be adjusted to -45°C or less. In order to obtain the metal strip 3 with a higher degree of brightness, the upper limit dew point of the gas environment can be adjusted to -65°C (straight line X in the figure) or less. Therefore, in stainless steel materials, depending on the brightness level of the metal strip 3 to be glow annealed, the upper limit dew point that allows the metal strip 3 to have brightness is set in the range of -30°C to -65°C. According to this configuration, the metal strip 3 having desired brightness can be obtained.

A heat insulating material 17 made of ceramic fiber is arranged on the inner surface of the furnace wall (furnace inner wall). Conventionally, when high-purity alumina bricks containing high-purity Al ₂ O ₃ (alumina) were used in a horizontal glow-surface annealing furnace 1 in an arch-shaped stacked structure, there was a so-called rise and fall of the furnace temperature. The expansion and contraction of the bricks generate dust, which degrades the quality of the metal strip 3.

In the horizontal glow annealing furnace 1 of this application, by using ceramic fibers containing SiO ₂ as the heat insulating material 17 , the generation of dust can be suppressed and a high-quality metal strip 3 can be obtained. However, it is considered that the reduction resistance of SiO ₂ contained in ceramic fibers is lower than that of Al ₂ O ₃ (aluminum oxide). When ceramic fibers are used in a highly reducing gas environment, the ceramic fibers will deteriorate due to the reduction of SiO ₂ And become brittle and produce dust.

In the present invention, the inventor of the present case focused on the oxidation-reduction characteristics (thermodynamic characteristics) of SiO ₂ , so that the thermal insulation material 17 made of ceramic fiber containing SiO ₂ can be used even in a highly reducing gas environment. As shown in FIG2 , with the oxidation-reduction equilibrium curve S of SiO ₂ as the boundary, the upper side of the equilibrium curve S is the region where SiO ₂ remains in an oxidized state, and the lower side of the equilibrium curve S is the region where SiO ₂ is reduced.

The dew point at the intersection c where the equilibrium curve S of oxidation-reduction of _SiO2 intersects the equilibrium temperature of 800°C is about -95°C, and the dew point at the intersection d where the equilibrium temperature of 1250°C is about -60°C. This dew point is the lower limit dew point at which _SiO2 contained in the heat insulating material 17 cannot be reduced in the equilibrium temperature of 800°C to 1250°C suitable for the bright annealing of stainless steel, for example. Therefore, when the annealing temperature of the heating belt 12 is in the range of 800°C to 1250°C, the control unit 20 controls the dew point of the gas environment to not be lower than the equilibrium curve S, so that _SiO2 cannot be reduced. In this way, dust can be prevented from being generated due to the deterioration of the heat insulating material 17 made of ceramic fiber, and a high-quality metal belt 3 can be obtained.

When the annealing temperature of the heating belt 12 is from 800°C to 1250°C (for example, when the metal strip 3 is made of stainless steel), the control unit 20 controls the dew point adjustment units 24 and 27 so that the dew point of the gas environment is maintained at the level shown in FIG. 2 Within the area surrounded by the middle intersection points a, b, d and c. Thereby, the metal strip 3 can have brightness, and the deterioration of the heat insulating material 17 caused by the reduction of SiO ₂ contained in the heat insulating material 17 can be prevented.

[Second implementation type] The heat treatment apparatus 1 of the second embodiment will be described with reference to FIG. 5 . 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 glow surface annealing furnace (heat treatment apparatus) 1 in the second embodiment includes a furnace body 10 , a gas supply part 9 , a dew point measurement part 22 , and dew point adjustment parts 24 , 27 a , and 28 a . Compared with the glow surface annealing furnace (heat treatment device) 1 in the first embodiment shown in FIG. 1 , the glow surface annealing furnace (heat treatment device) 1 in the second embodiment omits the control unit 20 such as a computer, for example. . Therefore, the operator who operates the glow surface annealing furnace (heat treatment apparatus) 1 replaces the control unit 20 .

The operator can manually control at least one of the second regulating valve (dew point adjusting unit) 28a and the first regulating valve (dew point adjusting unit) 27a based on the dew point measured by the dew point measuring unit 22. That is, the operator can visually obtain the dew point measured by the dew point measuring unit 22 through a display or the like. Furthermore, the operator can manually control the second regulating valve (dew point adjusting unit) 28a based on the measured dew point, thereby controlling the supply amount of the reducing gas supplied from the gas supply device 9. Furthermore, the operator can control the first regulating valve (dew point adjusting unit) 27a based on the measured dew point, thereby controlling the circulation amount of the ambient gas using the dew point adjusting device 24.

Furthermore, the operator controls the dehumidifier 25 in the dew point adjusting device 24 to operate, thereby removing the moisture contained in the gas environment, and the dew point of the gas environment, that is, the moisture content, is lowered. Furthermore, the operator controls the humidifier 26 in the dew point adjusting device 24 to operate, thereby increasing the moisture contained in the gas environment, and the dew point of the gas environment, that is, the moisture content, is raised.

Thereby, by maintaining the dew point (that is, the moisture content) in the gas environment of the heating belt 12 between the upper limit dew point and the lower limit dew point, the moisture content in the reducing gas environment is important for maintaining the brightness of the metal belt 3 and preventing inclusion in the metal belt 3 . The SiO ₂ reduction of the heat insulating material 17 becomes appropriate. As a result, the metal strip 3 can have brightness, 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 implementation type) As shown in FIG. 6 , in addition to the control unit 20 , the dew point adjustment device 24 (dehumidification device 25 and humidification device 26 ) is omitted, and the gas supply device 9 and the second regulating valve (dew point adjustment unit) 28 a may be used as the dew point Adjustment device 24a. Thereby, the dew point adjustment device 24a can be easily constructed. The operator can control the dew point adjusting device 24a based on the dew point of the gas environment measured by the dew point measuring unit 22. That is, the operator can visually obtain the dew point measured by the dew point measuring unit 22 through a monitor or the like. Furthermore, the operator can control the flow rate of the reducing gas supplied through the gas supply device 9 by manually controlling the second regulating valve (dew point adjusting section) 28a based on the measured dew point.

Thus, by maintaining the dew point (i.e., the moisture content) of the gas environment of the heating belt 12 between the upper dew point and the lower dew point, the moisture content in the reducing gas environment becomes appropriate for maintaining the brightness of the metal belt 3 and preventing the reduction of _SiO2 contained in the heat insulating material 17. As a result, the metal belt 3 can have brightness and the deterioration of the heat insulating material 17 caused by the reduction of _SiO2 contained in the heat insulating material 17 can be prevented.

Furthermore, the manual control in the second embodiment does not require the operator to perform it continuously all the time. The operator monitors the dew point occasionally or regularly, and also includes the case where the operator does not perform special control if there is no abnormality.

Although specific embodiments and numerical values of the present invention are described, the present invention is not limited to the above-mentioned embodiments and numerical values, and various modifications and implementations can be made within the scope of the present invention.

The operator, instead of the control unit 20 , can perform at least one control of the dew point adjustment units 27 a and 28 a based on the acquisition of the dew point measured by the dew point measurement unit 22 and the dew point measured by the dew point measurement unit 22 so that the dew point is maintained. Between the upper dew point and the lower dew point.

The glow surface annealing furnace (heat treatment device) 1 may also be a vertical furnace in which the furnace body 10 extends in the longitudinal direction (vertical direction).

In the bright surface annealing furnace (heat treatment device) 1, an inlet sealing belt may be provided on the upstream side of the conveying direction of the heating belt 12, and an inlet sealing roller 13 may be provided on the inlet sealing belt. An outlet sealing belt may be provided on the downstream side of the conveying direction of the cooling belt 14, and an outlet sealing roller 15 may be provided on the outlet sealing belt. The heating belt 12 may also be composed of an inlet sealing belt, a preheating belt, and a uniform heating belt (all not shown). The cooling belt 14 may also be composed of an outlet sealing belt, a rapid cooling belt, and a slow cooling belt (all not shown).

The glow surface annealing furnace 1 shown in FIG. 1 is provided with both the dehumidifier 25 and the humidifier 26. However, it may be configured to include either the dehumidifier 25 or the humidifier 26.

FIG3 shows the oxidation-reduction equilibrium curve C of Cr ₂ O ₃ (chromium trioxide) after the Cr component in the stainless steel is oxidized. In the above embodiment, although the upper limit dew point is described as -30°C, it is also considered that the oxidation of the stainless steel can be prevented by controlling the dew point of the gas environment so that it does not exceed the oxidation-reduction equilibrium curve C of Cr ₂ O _3. Therefore, in the case of stainless steel, the control unit 20 can also control the dew point adjustment unit 24, 24a to keep the dew point of the gas environment within the area surrounded by the intersections e, f, d and c in FIG3.

The metal strip 3 to be surface annealed in the reducing gas environment may be made of various metal materials, in addition to the above-mentioned stainless steel materials, such as pure metals such as nickel, titanium or copper, low expansion alloys, magnetic alloys, heat-resistant alloys or corrosion-resistant alloys.

The present invention and its embodiments are summarized as follows.

A heat treatment device 1 according to one embodiment of the present invention is characterized in that it comprises: a heating belt 12 for heating a metal belt 3; a heat insulating material 17, which is used as the inner wall of a furnace of the heating belt 12 and is made of ceramic fiber containing _SiO2 ; and a gas supply unit 9, 28, 28a, which supplies a reducing gas to the heating belt 12, so that the dew point is maintained between an upper limit dew point that allows the metal belt 3 to have brightness and a lower limit dew point that cannot reduce the _SiO2 contained in the heat insulating material 17, thereby performing bright annealing on the metal belt 3 in a reducing gas environment.

According to the above configuration, the dew point (i.e., the moisture content) of the gas environment of the heating belt 12 is maintained between the upper dew point and the lower dew point, so that the moisture content in the reducing gas environment becomes appropriate for maintaining the brightness of the metal belt 3 and preventing the reduction of _SiO2 contained in the heat insulating material 17. As a result, the metal belt 3 can have brightness, and the deterioration of the heat insulating material 17 caused by the reduction of _SiO2 contained in the heat insulating material 17 can be prevented.

The heat treatment device 1 according to one aspect of the present invention is a heat treatment device 1 for performing glow annealing on a metal strip 3 in a reducing gas environment. It is characterized in that the heat treatment device 1 is provided with: a furnace body 10 having a heating element. The heating zone 12 of the metal strip 3 and the cooling zone 14 provided on the downstream side in the conveyance direction of the metal strip 3 with respect to the heating zone 12; the heat insulating material 17 is used as the furnace inner wall of the heating zone 12 and is included. Made of SiO ₂ ceramic fiber; gas supply parts 9, 28, 28a supply reducing gas into the furnace body 10; dew point measurement part 22 measures the dew point of the gas environment in the heating zone 12; dew point adjustment parts 24, 24a , 27, 27a, 28, 28a, the dew point is adjusted, based on the dew point measured by the dew point measuring unit 22, so that the dew point is maintained at the upper limit dew point that allows the metal strip 3 to have brightness, and is not included in the dew point. The heat insulating material 17 controls the dew point adjusting portions 24, 24a, 27, 27a, 28, and 28a so as to be between the lower limit dew points of _SiO2 reduction.

According to the above structure, by maintaining the dew point (that is, the moisture content) of the gas environment in the heating zone 12 between the upper limit dew point and the lower limit dew point, the moisture content in the reducing gas environment plays an important role in maintaining the brightness of the metal belt 3 and preventing The reduction of SiO ₂ contained in the heat insulating material 17 becomes appropriate. As a result, the metal strip 3 can have brightness, and deterioration of the heat insulating material 17 caused by reduction of SiO ₂ contained in the heat insulating material 17 can be prevented.

In addition, in the heat treatment apparatus 1 of one embodiment, the control of the dew point adjustment units 24, 27, and 28 can be performed by the control unit 20.

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

Furthermore, in one embodiment of the heat treatment apparatus 1, the upper limit of the dew point is -30°C.

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

Furthermore, in the heat treatment apparatus 1 of one embodiment, the upper limit of the dew point is set within the range of -30°C to -65°C according to the brightness of the metal strip 3 to be surface annealed.

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

Moreover, in the heat treatment apparatus 1 of one embodiment, the dew point adjustment part 24 is equipped with at least one of a dehumidification device 25 and a humidification device 26.

According to the above embodiment, the dew point of the gas environment in the heating zone 12 can be appropriately adjusted in accordance with the dew point of the reducing gas supplied through the gas supply parts 9, 28, 28a and the dew point of the target gas environment.

Furthermore, in one embodiment of the heat treatment device 1, the aforementioned gas supply part 9, 28, 28a has a gas supply part 9 and a regulating valve 28, 28a for adjusting the flow rate of the aforementioned reducing gas supplied by the aforementioned gas supply part 9, and the aforementioned gas supply device 9 and the aforementioned regulating valve 28, 28a function as the aforementioned dew point adjusting part 24, 24a.

According to the above embodiment, the dew point adjustment devices 24 and 24a can be configured with a simple structure.

Furthermore, in one embodiment of the heat treatment apparatus 1, the heat treatment apparatus 1 is a horizontal furnace in which the furnace body 10 extends in a horizontal 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 device 1 can be suppressed from increasing. Furthermore, since the collapse of the ceramic fibers and the generation of dust can be prevented, the lightweight ceramic fiber heat insulating material 17 can be used even in a horizontal furnace with a large ceiling area.

Furthermore, in the heat treatment apparatus 1 of one embodiment, the metal belt 3 is made of a stainless steel material containing Cr.

According to the above embodiment, the formation of an oxide film in the metal belt 3 can be suppressed, and the metal belt 3 has brightness.

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

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

Furthermore, in one embodiment of the heat treatment apparatus 1, the reducing gas includes hydrogen gas.

According to the above embodiment, the metal strip 3 can be reduced and its glow surface can be annealed.

1: Surface annealing furnace (heat treatment device) 3: Metal belt 5: Gas supply pipe 6: Dew point measurement pipe 7: Inlet pipe 8: Outlet pipe 9: Gas supply device (gas supply unit, dew point adjustment unit) 10: Furnace body 12: Heating belt 13: Inlet sealing roller 14: Cooling belt 15: Outlet sealing roller 16: Heating unit 17: Heat insulation material 20: Control unit 22: Dew point measurement unit 24: Dew point adjustment unit (dew point adjustment unit) 24a: Dew point adjustment unit (dew point adjustment unit) 25: Dehumidification device 26: Humidification device 27: First regulating valve (dew point adjustment unit) 27a: First regulating valve (dew point adjustment unit) 28: Second regulating valve (gas supply unit, dew point adjustment unit) 28a: Second regulating valve (gas supply unit, dew point adjustment unit) A: Line showing the dew point of -30°C C: Balance curve showing the oxidation-reduction of Cr ₂ O ₃ S: Balance curve showing the oxidation-reduction of SiO ₂

Fig. 1 is a schematic cross-sectional view of the heat treatment apparatus according to the first embodiment. FIG. 2 is a diagram schematically illustrating the relationship between temperature and dew point of a gas environment. FIG. 3 is a diagram schematically illustrating the relationship between temperature and dew point of a gas environment. 4 is a schematic cross-sectional view of another heat treatment device according to the first embodiment. Fig. 5 is a schematic cross-sectional view of the heat treatment device according to the second embodiment. 6 is a schematic cross-sectional view of another heat treatment device according to the second embodiment.

1: Surface annealing furnace (heat treatment device)

3:Metal belt

5: Gas supply piping

6: Dew point measurement piping

9: Gas supply device (gas supply part, dew point adjustment part)

10: Furnace body

12: Heating belt

13:Inlet sealing roller

14: Cooling zone

15: Export sealing roller

16:Heating part

17:Insulation material

22: Dew point measurement department

24a: Dew point adjustment device (dew point adjustment unit)

28a: Second regulating valve (gas supply part, dew point adjustment part)

Claims (3)

A heat treatment device is characterized by comprising: a heating belt for performing bright annealing of a metal belt made of a stainless steel material containing Cr in a reducing gas environment; a heat insulating material used as the inner wall of the furnace of the heating belt and made of ceramic fiber containing _SiO2 ; a temperature control unit for controlling the heating temperature in the heating belt; and a dew point adjustment unit for controlling the dew point of the gas environment in the heating belt by dehumidification and humidification. In a graph illustrating the relationship between the heating temperature and the dew point of the gas environment, a range suitable for the bright annealing is defined, and the range is surrounded by the following lines: an upper limit temperature line indicating an upper limit annealing temperature, a lower limit temperature line indicating a lower limit annealing temperature, and a temperature line corresponding to _Cr2O2 . ₃ 's oxidation-reduction equilibrium curve can provide an upper limit dew point line of brightness, and corresponding to the oxidation-reduction equilibrium curve of the aforementioned SiO ₂ , a lower limit dew point line that makes the aforementioned SiO ₂ irreducible, the aforementioned temperature control unit and the aforementioned dew point adjustment unit are respectively controlled so that the aforementioned heating temperature and the aforementioned gas environment dew point are within the aforementioned range. The heat treatment device of claim 1, wherein the dew point adjustment part has: a dew point measurement part to measure the dew point of the gas environment; and both a dehumidification device and a humidification device. The heat treatment device of claim 1 or 2, wherein the dew point adjustment part has: a dew point measurement part to measure the dew point of the gas environment; a gas supply device to supply reducing gas to the heating zone; and A regulating valve is provided between the heating zone and the gas supply device to regulate the flow rate of the reducing gas.

Images