Heat treatment equipment

Abstract

Heat treatment equipment for heat treating a metal strip comprises: a first heating part and a second heating part each configured to heat the metal strip by a heating means that does not include an induction heating device; a first furnace body part that houses the first heating part; a second furnace body part that houses the second heating part; and an induction heating part that includes an induction heating device for heating the metal strip. The first heating part, the induction heating part, and the second heating part are arranged in this order in the transport direction of the metal strip, and a bypass passage for guiding gas inside the second furnace body part to the inside of the first furnace body part by bypassing the induction heating part is provided.

Description

Heat Treatment Equipment

[0001] The present disclosure relates to heat treatment equipment.

[0002] An induction heater is sometimes used as a heating means in heat treatment equipment.

[0003] Patent Document 1 describes a method in which a steel strip is uniformly heated in the longitudinal direction to an annealing temperature exceeding the Curie point by using a gas burner or an electric heater in combination with an induction heating device in a continuous annealing facility.

[0004] Patent No. 5135534

[0005] For example, when using an induction heating device to enhance the heating capacity of a continuous annealing furnace (heat treatment equipment) including a preheating zone and a heating zone, it is easy to install the induction heating device on the inlet side of the preheating zone (i.e., upstream of the continuous annealing furnace). However, by installing the induction heating device between the preheating zone and the heating zone, the temperature of the metal strip in the preheating zone is lower than when the induction heating device is installed upstream of the preheating zone, and the temperature difference between the metal strip and the furnace gas temperature is larger. This increases the amount of heat exchange between the two, which is thought to improve the heating efficiency of the continuous annealing furnace. However, in this case, high-temperature gas from the heating zone may flow into the preheating zone through the installation location of the induction heating device, exposing the induction heating device to high-temperature gas and increasing the risk of damage to the induction heating device due to high temperatures.

[0006] In view of the above circumstances, at least one embodiment of the present invention aims to provide heat treatment equipment that can efficiently heat a metal strip while reducing the risk of damage to an induction heating device.

[0007] At least one embodiment of the present invention provides heat treatment equipment for heat treating a metal strip, comprising: a first heating section and a second heating section, each configured to heat the metal strip with a heating means not including an induction heating device; a first furnace body section accommodating the first heating section; a second furnace body section accommodating the second heating section; and an induction heating section including an induction heating device for heating the metal strip, wherein the first heating section, the induction heating section, and the second heating section are arranged in this order in the transport direction of the metal strip, and a bypass passage is provided for guiding gas inside the second furnace body section to the inside of the first furnace body section, bypassing the induction heating section.

[0008] According to at least one embodiment of the present invention, a heat treatment facility is provided that can efficiently heat a metal strip while reducing the risk of damage to an induction heating device.

[0009] 1 is a schematic diagram of a heat treatment facility according to an embodiment; FIG. 2 is a schematic diagram of a heat treatment facility according to an embodiment; FIG. 3 is a schematic diagram of an induction heating unit according to an embodiment;

[0010] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0011] 1 and 2 are schematic diagrams of heat treatment equipment according to one embodiment. As shown in FIGS. 1 and 2, the heat treatment equipment 1 is equipment for heat treating a metal strip S and includes a first heating section 6 and a second heating section 8 for heating the metal strip S. The second heating section 8 is provided downstream of the first heating section 6 in the transport direction of the metal strip S. As shown in FIG. 2, the heat treatment equipment 1 may also include a cooling section 30 located downstream of the second heating section 8 in the transport direction of the metal strip S. The cooling section 30 may include, for example, a cooling nozzle 32 configured to spray a cooling fluid onto the metal strip S.

[0012] In some embodiments, the heat treatment equipment 1 may be a continuous annealing equipment that includes a first heating section 6 constituting a preheating zone, a second heating section 8 constituting a heating zone, and a cooling section 30 constituting a cooling zone, and that continuously anneals the metal strip S. The heat treatment equipment 1 as a continuous annealing equipment may further include a soaking zone 28 (see FIG. 2 ) that is provided between the heating zone (second heating section 8) and the cooling zone (cooling section 30) in the transport direction of the metal strip S, an overaging zone (not shown) that is provided downstream of the cooling zone, and the like.

[0013] Note that the heat treatment facility according to some embodiments is not limited to an annealing facility. For example, in some embodiments, the heat treatment facility may include a heat treatment furnace for performing heat treatments other than annealing, such as quenching, tempering, and normalizing.

[0014] The heat treatment equipment 1 includes a furnace body 2 that houses a first heating section 6, a second heating section 8, and / or a cooling section 30. The furnace body 2 shown in Figures 1 and 2 includes a first furnace body section 2a that houses the first heating section 6, and a second furnace body section 2b that houses the second heating section 8.

[0015] A plurality of transport rolls 4 for transporting the metal strip S may be provided inside the furnace body 2 .

[0016] The heat treatment equipment 1 may include, for example, a horizontal furnace in which the metal strip S is transported horizontally in the first heating section 6 and the second heating section 8 as shown in FIG. 1, or may include, for example, a vertical furnace in which the metal strip S is transported vertically in the first heating section 6 and the second heating section 8 as shown in FIG. 2.

[0017] In some embodiments, the first heating section 6 and the second heating section 8 are each configured to heat the metal strip S with a heating means that does not include an induction heating device.

[0018] The first heating section 6 may be configured to heat the metal strip S by utilizing the heat of the atmospheric gas inside the first furnace body section 2a. For example, the first heating section 6 may be configured to heat the metal strip S by convection heating using the atmospheric gas inside the first furnace body section 2a. Alternatively, the first heating section 6 may be configured to heat the metal strip S by spraying a fluid (gas, etc.) heated outside the furnace body 2 onto the metal strip S using a nozzle or the like provided inside the first furnace body section 2a.

[0019] The second heating section 8 may be configured to heat the metal strip S heated in the first heating section 6 to a temperature higher than the sheet temperature at the outlet of the first heating section 6. In some embodiments, the second heating section 8 may include a heating device 16 (see FIGS. 1 and 2 ) for heating the metal strip S.

[0020] In one embodiment, the second heating section 8 may be configured to burn fuel and heat the metal strip using heat generated by the combustion of the fuel.

[0021] For example, the second heating section 8 may include, as the heating device 16, a burner configured to combust fuel and emit a flame generated by the combustion of the fuel toward the metal strip S. That is, the second heating section 8 may be a direct-fire furnace configured to directly heat the metal strip S with the flame of the burner. In this case, the combustion gas generated in the second heating section 8 may be introduced into the first furnace body section 2a and used as atmospheric gas in the first heating section 6 to heat the metal strip S.

[0022] Alternatively, the second heating section 8 may include a radiant tube configured to be supplied with combustion gas generated by combustion of fuel as the heating device 16. In this case, gas heated by heat exchange with the combustion exhaust gas discharged to the outside from the radiant tube may be supplied to the first heating section 6 as a heating fluid.

[0023] As shown in FIG. 1, the first furnace body 2 a may be provided with an exhaust duct 20 for discharging the atmospheric gas from the first heating section 6 .

[0024] In some embodiments, as shown in Figures 1 and 2, the heat treatment equipment 1 includes an induction heating section 10 including an induction heating device 12 for heating the metal strip S. The induction heating section 10 is provided between the first heating section 6 and the second heating section 8 in the transport direction of the metal strip S (i.e., downstream of the first heating section 6 and upstream of the second heating section 8). The induction heating section 10 may be housed in a third furnace body section 2c constituting the furnace body 2. Here, the first heating section 6 and the second heating section 8 may be able to communicate with each other via the induction heating section 10.

[0025] The heat treatment equipment 1 also includes a bypass passage 14 for guiding the gas inside the second furnace body 2b into the inside of the first furnace body 2a, bypassing the induction heating section 10. In the exemplary embodiment shown in Figures 1 and 2, the bypass passage 14 includes a duct provided outside the first furnace body 2a and the second furnace body 2b. The duct may have both ends connected to the first furnace body 2a and the second furnace body 2b, respectively.

[0026] 3 is a schematic diagram of the induction heating unit 10 according to one embodiment. As shown in FIG. 3, the induction heating device 12 includes a coil 36 for generating a magnetic flux. The coil 36 of the induction heating device 12 may be configured to generate a magnetic flux along an in-plane direction of the metal strip S (e.g., the longitudinal direction of the metal strip S), or may be configured to generate a magnetic flux along an out-of-plane direction of the metal strip S (e.g., a direction perpendicular to the surface of the metal strip S).

[0027] In the heat treatment equipment 1 according to the above embodiment, the induction heating device 12 is provided between the first heating section 6 and the second heating section 8. This reduces the sheet temperature in the first heating section 6 compared to when the induction heating device 12 is provided upstream of the first heating section 6 in the transport direction of the metal strip S. This increases the temperature difference between the atmospheric gas in the first heating section 6 and the metal strip S, thereby increasing the amount of heat exchange between them, thereby enabling efficient heating of the metal strip S. Furthermore, in the heat treatment equipment 1 described above, high-temperature gas (combustion gas or atmospheric gas) from the second heating section 8 can be introduced into the first heating section 6 via a bypass passage 14 that bypasses the induction heating section 10. This allows the metal strip S to be heated in the first heating section 6 using the high-temperature gas from the second heating section 8 while reducing the amount of high-temperature gas flowing into the induction heating section 10 from the second heating section 8. Therefore, the heat treatment equipment 1 described above allows efficient heating of the metal strip S while protecting the induction heating device 12 from high temperatures and reducing the risk of damage.

[0028] When the metal strip S is heated in the second heating section 8 using a burner that emits a flame toward the metal strip S, the combustion gas generated by the combustion of fuel in the second heating section 8 (inside the second furnace body 2b) is led to the first heating section 6 (inside the first furnace body 2a) via the bypass passage 14. When the metal strip S is heated in the second heating section 8 using a radiant tube, the atmospheric gas in the second furnace body 2b is led to the first heating section 6 (inside the first furnace body 2a) via the bypass passage 14.

[0029] When the second heating section 8 is a direct-fire furnace that heats the metal strip S using a burner that emits a flame toward the metal strip S, the first heating section 6 may include an afterburner 18 (see FIG. 1) for burning fuel contained in the gas inside the first furnace body section 2a. Also, the first heating section 6 may be configured to heat the metal strip S by utilizing the heat generated by the combustion of fuel in the afterburner 18.

[0030] Generally, when heating the metal strip S using a burner, an excess amount of fuel relative to the air (or oxygen) may be supplied to the burner in order to suppress oxidation of the metal strip S. Even when an excess amount of fuel is supplied to the burner in this manner in the second heating section 8, the temperature of the metal strip S in the first heating section 6 is kept relatively low as described above by providing the induction heating section 10 between the first heating section 6 and the second heating section 8. Therefore, even if the excess fuel contained in the combustion gas from the second heating section 8 is burned in the afterburner 18 or the like in the first heating section 6 and used as a heat source, oxidation of the metal strip S in the first heating section 6 can be suppressed.

[0031] In some embodiments, the heat treatment equipment 1 includes a sealing device 22 provided at least one between the first heating section 6 and the induction heating section 10 or between the induction heating section 10 and the second heating section 8 in the transport direction of the metal strip S, and configured to prevent gas from flowing inside the first furnace body 2a or the second furnace body 2b into the induction heating section 10. In the exemplary embodiment shown in Figures 1 and 2, a sealing device 22 is provided between the first heating section 6 and the induction heating section 10 and between the induction heating section 10 and the second heating section 8, respectively.

[0032] In this way, by providing the sealing device 22 at least either between the first heating section 6 and the induction heating section 10 or between the induction heating section 10 and the second heating section 8, it is possible to more effectively prevent high-temperature gas from the second heating section 8 (gas flowing directly from the second heating section 8 into the induction heating section 10, or gas led from the second heating section 8 into the first furnace body section 2a via the bypass passage 14) from flowing into the induction heating section 10. This further reduces the risk of damage to the induction heating device 12 by high-temperature gas.

[0033] 3, the sealing device 22 may include a sealing member 23 provided facing the surface of the metal strip S. In one embodiment, the sealing member 23 may include a sealing roll provided so as to be in contact with the surface of the metal strip S and capable of rotating as the metal strip S is conveyed. In one embodiment, the sealing member 23 may include a plate-like or box-like gate member having a flat opposing surface facing the surface of the metal strip S. In the exemplary embodiment shown in FIG. 3, the sealing device 22 includes a pair of sealing rolls (seal members 23) provided so as to face both sides of the metal strip S, respectively.

[0034] The sealing member 23 may be configured to be driven in a direction perpendicular to the surface of the metal strip S. For example, the sealing member 23 (see FIG. 1 or FIG. 3) installed in a portion where the metal strip S is transported horizontally may be configured to be driven in an up-down direction (or a vertical direction). Furthermore, the sealing member 23 (see FIG. 2) installed in a portion where the metal strip S is transported vertically (or a vertical direction) may be configured to be driven in a horizontal direction.

[0035] Furthermore, the sealing device 22 may include a drive unit (for example, a motor or a fluid pressure cylinder) for driving the sealing member 23 as described above.

[0036] In the above-described embodiment, the seal member 23 provided facing the surface of the metal strip S can move in a direction perpendicular to the surface. Therefore, for example, by moving the seal member 23 to increase the distance between the surface of the metal strip S and the seal member 23, the metal strip S can be smoothly threaded at the location where the seal member 23 is installed, or by adjusting the position of the seal member 23 according to the thickness of the metal strip S, the size of the gap between the metal strip S and the seal member 23 can be maintained appropriately.

[0037] 1 to 3, the heat treatment equipment 1 includes a low-temperature gas supply unit 24 for supplying gas that is at a lower temperature than the gas (combustion gas or atmospheric gas) inside the second furnace body 2b to the induction heating unit 10. As shown in Fig. 3, the low-temperature gas supply unit 24 may include a supply pipe 24a provided between a low-temperature gas storage unit (such as a gas tank) (not shown) and the induction heating unit 10, and a supply valve 24b provided on the supply pipe 24a.

[0038] The low-temperature gas may contain a reducing gas such as hydrogen or an inert gas such as nitrogen. In addition, if the influence of oxidation of the metal strip S is small or there is no concern about oxidation (for example, when the metal strip S is stainless steel), the low-temperature gas may be a gas other than the reducing gas or inert gas (for example, air).

[0039] In the above-described embodiment, the low-temperature gas supply unit 24 can supply gas that is lower in temperature than the gas inside the second furnace body 2b to the induction heating unit 10, thereby more effectively protecting the induction heating unit 10 from high temperatures and further reducing the risk of damage to the induction heating unit 10.

[0040] 1 to 3, the heat treatment equipment 1 may include a low-temperature gas discharge unit 26 for discharging gas (including low-temperature gas) in the induction heating unit 10 to the furnace body 2. As shown in Fig. 3, the low-temperature gas discharge unit 26 may include an exhaust pipe 26a for discharging the gas in the induction heating unit 10 to the outside, and an exhaust valve 26b provided on the exhaust pipe 26a.

[0041] In this way, by providing the low-temperature gas discharge section 26, the low-temperature gas supplied to the induction heating section 10 can be discharged to the outside of the furnace body 2, and the low-temperature gas in the induction heating section 10 can be prevented from flowing into the first heating section 6 or the second heating section 8 via the sealing device 22. Therefore, a decrease in the heating efficiency of the metal strip S in the heat treatment equipment 1 can be prevented.

[0042] In some embodiments, the induction heating device 12 may include insulation 38 disposed between the coil 36 and the metal strip S, as shown, for example, in FIG.

[0043] In this way, by providing the heat insulating material 38 between the coil 36 of the induction heating device 12 and the metal strip S, the heat of the high-temperature gas that may flow into the induction heating unit 10 is less likely to be transmitted to the coil 36. Therefore, the induction heating unit 10 can be more effectively protected from high temperatures, and the risk of damage to the induction heating device 12 can be further reduced.

[0044] In some embodiments, as shown in Fig. 3, the induction heating device 12 may include an airtight material 40 inside the furnace body 2, which separates the space through which the metal strip S passes from the space in which the coil 36 is provided, to prevent in-furnace gas from entering the space in which the coil 36 is provided. The airtight material 40 may include a sheet made of a resin such as silicone or Teflon (registered trademark). The airtight material 40 may be provided so as to surround the coil 36. The airtight material 40 may be fixed to the furnace body 2 with bolts.

[0045] By providing the airtight material 40 described above, the possibility that the coil 36 will be exposed to high-temperature gas can be reduced, and thus the induction heating unit 10 can be more effectively protected from high temperatures.

[0046] In an annealing furnace including a preheating zone and a heating zone, an induction heating device may be installed upstream of the preheating zone (i.e., on the inlet side of the annealing furnace) to enhance the heating capacity. In this case, the preheating zone may be reduced due to restrictions on the overall equipment length of the annealing furnace. In such a case, a self-heat recovery burner may be employed in the heating zone (direct fire zone) as a heat recovery means instead of the preheating zone. The self-heat recovery burner is a burner equipped with a heat exchanger for exchanging heat between the combustion gas generated in the burner and the fuel or air to be combusted in the burner, and is designed to preheat the fuel or air using the heat of the combustion gas.

[0047] The contents described in each of the above embodiments can be understood, for example, as follows.

[0048] [1] A heat treatment equipment (1) according to at least one embodiment of the present invention is a heat treatment equipment for heat treating a metal strip (S), comprising: a first heating section (6) and a second heating section (8), each configured to heat the metal strip by a heating means not including an induction heating device; a first furnace body section (2a) accommodating the first heating section; a second furnace body section (2b) accommodating the second heating section; and an induction heating section (10) including an induction heating device (12) for heating the metal strip, wherein the first heating section, the induction heating section, and the second heating section are arranged in this order in the transport direction of the metal strip; and a bypass passage (14) for guiding gas inside the second furnace body section to the inside of the first furnace body section, bypassing the induction heating section.

[0049] In the configuration [1] above, since the induction heating device is provided between the first heating section and the second heating section, the strip temperature in the first heating section is lower than when the induction heating device is provided upstream of the first heating section in the metal strip transport direction. This results in a larger temperature difference between the atmospheric gas in the first heating section and the metal strip, increasing the amount of heat exchange between them, thereby enabling efficient heating of the metal strip. Furthermore, in the configuration [1] above, high-temperature gas (combustion gas or atmospheric gas) from the second heating section can be guided to the first heating section via a bypass passage that bypasses the induction heating section. This allows the metal strip to be heated in the first heating section using the high-temperature gas from the second heating section while reducing the amount of high-temperature gas flowing from the second heating section to the induction heating section. Therefore, the configuration [1] above allows efficient heating of the metal strip while protecting the induction heating device from high temperatures and reducing the risk of damage.

[0050] [2] In some embodiments, in the configuration of [1] above, the second heating section is configured to burn fuel and heat the metal strip using the heat generated by the combustion of the fuel, and the first heating section is configured to heat the metal strip by convection heating using atmospheric gas inside the first furnace body section.

[0051] According to the configuration [2] above, in a heat treatment equipment including a first heating unit for heating the metal strip by convection heating using atmospheric gas and a second heating unit for heating the metal strip using heat generated by fuel combustion, as described in [1] above, the metal strip can be efficiently heated, and the metal strip can be heated in the first heating unit using high-temperature gas from the second heating unit while reducing the amount of high-temperature gas passing through the induction heating device. Therefore, according to the configuration [2] above, the metal strip can be efficiently heated while protecting the induction heating device from high temperatures and reducing the risk of damage.

[0052] [3] In some embodiments, in the configuration of [2] above, the second heating section includes a burner configured to combust the fuel and emit a flame generated by the combustion of the fuel toward the metal strip, and the combustion gas generated by the combustion of the fuel in the second heating section is configured to be guided into the interior of the first furnace body section through the bypass passage.

[0053] According to the configuration [3] above, since the second heating unit includes a burner that emits a flame toward the metal strip, high-temperature combustion gas generated by the combustion of fuel in the burner is guided to the first heating unit via the bypass passage, so that the metal strip can be effectively heated by convection heating using atmospheric gas containing the combustion gas in the first heating unit, and the amount of high-temperature combustion gas passing through the induction heating device can be reduced. Therefore, according to the configuration [3] above, the metal strip can be efficiently heated while protecting the induction heating device from high temperatures and reducing the risk of damage.

[0054] In addition, when a metal strip is heated using a burner, an excess amount of fuel relative to the air (or oxygen) is generally supplied to the burner to suppress oxidation of the metal strip. Even in such a case, in the configuration [3] above, by providing an induction heating unit between the first heating unit and the second heating unit, the temperature of the metal strip in the first heating unit is kept relatively low as described above. Therefore, even if the excess fuel contained in the combustion gas from the second heating unit is burned in the first heating unit and used as a heat source, oxidation of the metal strip in the first heating unit can be suppressed.

[0055] [4] In some embodiments, in the configuration of [1] above, the second heating section includes a radiant tube configured to heat the metal band, the first heating section is configured to heat the metal band by convection heating using atmospheric gas inside the first furnace body section, and the atmospheric gas inside the second furnace body section is configured to be guided into the inside of the first furnace body section through the bypass passage.

[0056] According to the configuration [4] above, in a heat treatment equipment including a first heating section for heating the metal strip by convection heating using atmospheric gas and a second heating section for heating the metal strip using a radiant tube, as described in [1] above, the metal strip can be efficiently heated, and the metal strip can be heated in the first heating section using high-temperature gas from the second heating section while reducing the amount of high-temperature gas passing through the induction heating device. Therefore, according to the configuration [4] above, the metal strip can be efficiently heated while protecting the induction heating device from high temperatures and reducing the risk of damage.

[0057] [5] In some embodiments, in the configuration of any one of the above [1] to [4], the bypass passage includes a duct provided outside the first furnace body section and the second furnace body section.

[0058] According to the configuration [5] above, a bypass passage that bypasses the induction heating unit can be formed with a simple configuration including ducts provided outside the first furnace body and the second furnace body, thereby protecting the induction heating device from high temperatures and reducing the risk of damage, while efficiently heating the metal strip.

[0059] [6] In some embodiments, in any of the configurations [1] to [5] above, the heat treatment equipment includes a sealing device (22) provided at least between the first heating section and the induction heating section or between the induction heating section and the second heating section in the transport direction of the metal strip, and configured to suppress the inflow of gas inside the first furnace body section or the second furnace body section into the induction heating section.

[0060] According to the configuration [6] above, since a sealing device is provided between the first heating unit and the induction heating unit or between the induction heating unit and the second heating unit, it is possible to more effectively prevent high-temperature gas from the second heating unit from flowing into the induction heating unit, thereby further reducing the risk of damage to the induction heating unit by high-temperature gas.

[0061] [7] In some embodiments, in the configuration of [6] above, the sealing device includes a sealing member (23) that is provided facing the surface of the metal strip and is configured to be driven along a direction perpendicular to the surface of the metal strip.

[0062] According to the configuration [7] above, the seal member provided facing the surface of the metal strip can move in a direction perpendicular to the surface. Therefore, for example, by moving the seal member to increase the distance between the surface of the metal strip and the seal member, the metal strip can be smoothly threaded through the location where the seal member is installed, or by adjusting the position of the seal member depending on the thickness of the metal strip, the size of the gap between the metal strip and the seal member can be maintained appropriately.

[0063] [8] In some embodiments, in the configuration of [6] or [7] above, the heat treatment equipment includes a low-temperature gas supply unit (24) for supplying gas at a lower temperature than the gas inside the second furnace body unit to the induction heating unit.

[0064] According to the configuration [8], the low-temperature gas supply unit can supply gas that is lower in temperature than the gas inside the second furnace body unit to the induction heating unit, so that the induction heating unit can be more effectively protected from high temperatures, thereby further reducing the risk of damage to the induction heating unit.

[0065] [9] In some embodiments, in any of the configurations [1] to [8] above, the induction heating device includes a coil (36) for generating a magnetic flux, and a heat insulating material (38) provided between the coil and the metal strip.

[0066] According to the configuration [9] above, since a heat insulating material is provided between the coil of the induction heating device and the metal strip, the heat of the high-temperature gas that may flow into the induction heating part is less likely to be transmitted to the coil. Therefore, the induction heating device can be more effectively protected from high temperatures, and the risk of damage to the induction heating part can be further reduced.

[0067]

[10] In some embodiments, in any of the configurations [1] to [9] above, the heat treatment equipment includes a cooling section (30) that is provided downstream of the second heating section in the transport direction of the metal strip and that cools the metal strip.

[0068] According to the configuration of

[10] above, in a heat treatment facility (e.g., a continuous annealing facility) in which a cooling unit (e.g., a cooling zone) is provided downstream of a first heating unit (e.g., a preheating zone) and a second heating unit (e.g., a heating zone), as described in [1] above, the metal strip can be efficiently heated and the amount of high-temperature gas flowing from the second heating unit into the induction heating unit can be reduced. Thus, according to the configuration of

[10] above, the metal strip can be efficiently heated while protecting the induction heating device from high temperatures and reducing the risk of damage.

[0069] The above describes an embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and also includes forms in which the above-described embodiment is modified, or forms in which these forms are appropriately combined.

[0070] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0071] REFERENCE SIGNS LIST 1 Heat treatment equipment 2 Furnace body 2a First furnace body section 2b Second furnace body section 2c Third furnace body section 4 Conveyor roll 6 First heating section 8 Second heating section 10 Induction heating section 12 Induction heating device 14 Bypass passage 16 Heating device 18 Afterburner 20 Exhaust duct 22 Sealing device 23 Sealing member 24 Low-temperature gas supply section 24a Supply pipe 24b Supply valve 26 Low-temperature gas discharge section 26a Discharge pipe 26b Discharge valve 28 Soaking zone 30 Cooling section 32 Cooling nozzle 36 Coil 38 Heat insulating material 40 Airtight material S Metal strip

Claims

1. A heat treatment facility for heat treating a metal strip, comprising: a first heating section and a second heating section, each configured to heat the metal strip with a heating means not including an induction heating device; a first furnace body section accommodating the first heating section; a second furnace body section accommodating the second heating section; and an induction heating section including an induction heating device for heating the metal strip, wherein the first heating section, the induction heating section, and the second heating section are arranged in this order in the transport direction of the metal strip; and the heat treatment facility comprises a bypass passage for guiding gas inside the second furnace body section to the inside of the first furnace body section, bypassing the induction heating section.

2. The heat treatment equipment according to claim 1, wherein the second heating section is configured to burn fuel and heat the metal strip using the heat generated by the combustion of the fuel, and the first heating section is configured to heat the metal strip by convection heating using atmospheric gas inside the first furnace body section.

3. The heat treatment equipment according to claim 2, wherein the second heating section includes a burner configured to combust the fuel and emit a flame generated by the combustion of the fuel toward the metal strip, and wherein the combustion gas generated by the combustion of the fuel in the second heating section is guided into the interior of the first furnace body section via the bypass passage.

4. The heat treatment equipment according to claim 1, wherein the second heating section includes a radiant tube configured to heat the metal band, the first heating section is configured to heat the metal band by convection heating using atmospheric gas inside the first furnace body section, and the atmospheric gas inside the second furnace body section is configured to be led into the inside of the first furnace body section via the bypass passage.

5. The heat treatment facility according to any one of claims 1 to 4, wherein the bypass passage includes a duct provided outside the first furnace body section and the second furnace body section.

6. Heat treatment equipment according to any one of claims 1 to 4, comprising a sealing device provided at least between the first heating section and the induction heating section or between the induction heating section and the second heating section in the transport direction of the metal strip, and configured to prevent gas inside the first furnace body section or the second furnace body section from flowing into the induction heating section.

7. The heat treatment equipment according to claim 6, wherein the sealing device includes a sealing member that is provided facing the surface of the metal strip and configured to be driven along a direction perpendicular to the surface of the metal strip.

8. The heat treatment equipment according to claim 6, further comprising a low-temperature gas supply section for supplying gas at a temperature lower than that of the gas inside the second furnace body section to the induction heating section.

9. The heat treatment equipment according to any one of claims 1 to 4, wherein the induction heating device includes: a coil for generating a magnetic flux; and a heat insulating material provided between the coil and the metal strip.

10. The heat treatment equipment according to any one of claims 1 to 4, further comprising a cooling section provided downstream of the second heating section in the transport direction of the metal strip for cooling the metal strip.

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