Heating method of metal material, heating facility, and operation method of heating furnace

Abstract

To provide a heating method of a metal material, a heating facility, and an operation method of a heating furnace for controlling a scale generation amount in an appropriate range when reducing an emission amount of carbon dioxide by using hydrogen or ammonia as a fuel gas of the heating furnace for heating the metal material.SOLUTION: A heating method of a metallic material includes: a first heating process for heating the metal material by burner heating using a hydrogen-based gas containing either or both of hydrogen and ammonia as a total amount as a fuel gas; and a second heating process for heating the metal material heated in the first heating process by electric heating in an inert gas atmosphere in a furnace. It is preferable that the first heating process is performed by burner heating using a fuel gas that is a mixed gas obtained by mixing a hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas. In the first heating process, the amount of water vapor in the furnace is preferably controlled within a predetermined range on the basis of the flow rate of the fuel gas used for burner heating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for heating a metallic material, a heating facility, and a method for operating a heating furnace using the heating method. [Background technology]

[0002] In integrated steelworks, blast furnace gas discharged from the top of a blast furnace that reduces iron ore to produce molten iron, as well as by-product gases generated in converters and coke ovens, have been effectively used as fuel gases. However, in recent years, with the demand for reducing carbon dioxide emissions, combustion technologies have been required to reduce the amount of by-product gas used. For example, in heating furnaces that heat steel materials in hot rolling lines in integrated steelworks, it has been required to reduce the amount of by-product gas used and the amount of carbon dioxide emissions. In this case, technologies that use hydrogen or ammonia as fuel gas for heating furnaces have attracted attention. That is, hydrogen and ammonia, which do not contain carbon elements, mainly generate water and nitrogen when burned, so they are highly effective in reducing carbon dioxide emissions, and their application to heating furnaces is desirable.

[0003] In the heating furnace, scale (also called oxide scale) is formed on the surface of the steel material during the process of heating the steel material. The scale formed in the heating furnace is also called primary scale, and is removed by a descaling device installed in a hot rolling line or the like. Therefore, if the thickness of the scale formed in the heating furnace becomes too thick, the weight of the steel material to be made into a steel plate product decreases, which is a problem in that the product yield decreases.

[0004] On the other hand, impurities generated during casting and foreign matter resulting from mold powder mixed in during casting may be present near the surface of the steel material charged into the heating furnace. If hot rolling is performed with impurities or foreign matter still present on the surface of the steel material extracted from the heating furnace, these will become caught between the steel material and the rolling rolls, causing defects on the surface of the steel plate. For this reason, the scale of the steel material generated in the heating furnace is grown to a certain thickness, and the impurities and foreign matter on the surface are removed together with the scale by a descaling device before hot rolling.

[0005] In other words, in steel heating furnaces, it is necessary to control scale generation to an appropriate amount in order to prevent a decrease in product yield by suppressing excessive scale generation, and to actively generate a specified amount of scale to suppress the occurrence of surface defects.

[0006] In order to solve these problems, techniques for controlling the formation of scale on the steel surface have been proposed. Patent Document 1 discloses a non-oxidizing heating method for steel as a technology for suppressing excessive scale formation, in which high-temperature non-oxidizing gas that has been preheated to a temperature equal to or higher than the temperature of the steel being heated or approximately equal to the furnace temperature is supplied around the steel in a heating furnace.

[0007] Patent Document 2 discloses a steel heating furnace that is equipped with a plurality of regenerative heating devices that supply high-temperature inert gas into the interior of the heating furnace and a plurality of gas burners that supply combustion gas into the furnace, and that is controlled so that the supply of high-temperature inert gas and the supply of combustion gas are carried out independently. It is said that this makes it possible to heat steel without oxidizing it by alternately supplying high-temperature inert gas from multiple regenerative heating devices.

[0008] Meanwhile, as a technique for generating a predetermined amount of scale, Patent Document 3 discloses a method for heating steel material, in which moisture is supplied into a heating furnace to adjust the dew point inside the heating furnace when the steel material to be subjected to hot rolling is heated in the heating furnace. This promotes oxidation of the steel material surface, and casting defects concentrated within a position of about 0.5 mm from the surface layer of the steel material can be removed together with the scale, which is said to improve the surface quality of steel plate products. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 9-20919 [Patent Document 2] JP 2000-248314 A [Patent Document 3] Japanese Patent Application Publication No. 5-331532 Summary of the Invention [Problem to be solved by the invention]

[0010] However, when applying conventional techniques to control the amount of scale generation on steel materials within an appropriate range in a heating furnace that uses hydrogen or ammonia as a fuel gas, the following problems arise.

[0011] The technology described in Patent Document 1 supplies a high-temperature non-oxidizing gas into a heating furnace in order to create a localized non-oxidizing atmosphere around steel material charged into the heating furnace. However, when hydrogen or ammonia is burned as fuel gas in a heating furnace, the hydrogen in the fuel gas combines with the oxygen in the combustion air to generate water vapor, which poses a problem that the generated water vapor promotes the growth of scale on the steel surface even if a non-oxidizing atmosphere is formed in the heating furnace.

[0012] The technology described in Patent Document 2 uses a regenerative heating device to recover the sensible heat contained in the exhaust gas produced by burning fuel gas using a heat storage body, and then passes an inert gas through the heat storage body to supply high-temperature inert gas into the heating furnace, thereby attempting to suppress the growth of scale on steel in the heating furnace. However, when hydrogen or ammonia is used as the fuel gas, the heat storage body also recovers water vapor in the exhaust gas, so that the inert gas passing through the heat storage body is humidified before being supplied to the heating furnace. Therefore, as in the above, even if high-temperature inert gas is supplied to the heating furnace, the water vapor promotes the formation of scale on the steel surface, so there is a problem that the amount of scale formation cannot be controlled within an appropriate range.

[0013] In Patent Document 3, the effect of promoting the oxidation of the steel surface by supplying moisture into the heating furnace and improving the surface quality of steel plate products can be expected. However, when hydrogen or ammonia is used as the fuel gas, the oxidation of the steel is further promoted, causing excessive scale growth, resulting in a problem that the amount of scale generation cannot be controlled within an appropriate range.

[0014] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for heating a metallic material, heating equipment, and a method for operating a heating furnace, which are capable of controlling the amount of scale formation within an appropriate range when attempting to reduce carbon dioxide emissions by using hydrogen or ammonia as a fuel gas in a heating furnace that heats a metallic material. [Means for solving the problem]

[0015] The method for heating a metal material according to the present invention, which advantageously solves the above problems, is configured as follows.

[0016] [1] A method for heating a metallic material, comprising: a first heating step in which a metallic material is heated by burner heating using a hydrogen-based gas containing either hydrogen or ammonia or both as a fuel gas; and a second heating step in which the metallic material heated in the first heating step is heated by electrical heating in an inert gas atmosphere inside a furnace. [2] In the above [1], the method for heating a metallic material includes a first heating step of heating the metallic material by burner heating using a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas as a fuel gas. [3] In the above [1] or [2], the first heating step is a method for heating a metal material, in which the amount of water vapor in the furnace is controlled within a preset range based on the flow rate of the fuel gas used for the burner heating. [4] In the above [1] or [2], the first heating step is a method for heating a metallic material, in which the amount of water vapor in the furnace is controlled based on at least one operational parameter selected from the heating time, heating temperature, and flow rate of fuel gas used for the burner heating in the first heating step, so that the thickness of an oxide layer formed on the surface of the metallic material is within a preset range. [5] In the above [1] or [2], the metal material is a steel material, and the first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050°C, and the second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250°C. A method for heating metal materials. [6] In the above [3], the metal material is a steel material, and the first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050°C, and the second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250°C. A method for heating metal materials. [7] In the above [4], the metal material is a steel material, and the first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050°C, and the second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250°C. A method for heating metal materials. [8] The method for heating a metallic material according to [5] above, wherein in the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %. [9] The method for heating a metallic material according to [6] above, wherein in the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %.

[10] The method for heating a metallic material in the above [7], wherein in the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %.

[0017] The metallic material heating equipment and the method for operating a heating furnace according to the present invention, which advantageously solve the above problems, are configured as follows.

[11] A heating facility for metal materials comprising: a first heating furnace which heats metal materials by burner heating using a hydrogen-based gas whose fuel gas is either hydrogen or ammonia or both; and a second heating furnace into which metal materials discharged from the first heating furnace are loaded, and which heats the metal materials by electrical heating while maintaining an inert gas atmosphere inside the furnace.

[12] In the above

[11] , the heating equipment for metal materials has a first heating furnace which heats metal materials by burner heating using a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon-based gas as a fuel gas.

[13] In the above

[11] or

[12] , the first heating furnace is a heating equipment for metal materials having a flow rate setting unit that sets the flow rate of fuel gas used for the burner heating, and a water vapor amount control unit that controls the amount of water vapor in the first heating furnace within a preset range.

[14] A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material described in [5] above.

[15] A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material described in [6] above.

[16] A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material described in [7] above. Effect of the Invention

[0018] According to the present invention, by using hydrogen or ammonia as the fuel gas for the heating furnace, it is possible to reduce carbon dioxide emissions, and by controlling the amount of scale generation within an appropriate range, it is possible to reduce the occurrence of surface defects in metal materials while suppressing deterioration of product yields. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram illustrating a heating furnace according to one embodiment. [Diagram 2] FIG. 2 is a configuration diagram showing the arrangement of burner equipment in a heating furnace. [Diagram 3] FIG. 1 is a configuration diagram of an example of a burner facility. [Figure 4] FIG. 2 is a configuration diagram showing the arrangement inside the first heating furnace of burners, including burner equipment using coal gas and hydrogen-based burner equipment using hydrogen-based gas. [Diagram 5] FIG. 1 is a configuration diagram of an example of a hydrogen-based burner facility. [Figure 6] FIG. 2(a) is a front view of a second heating furnace using electric heating, and FIG. 2(b) is a side view of the second heating furnace. [Figure 7] 4 is a graph showing the temperature history of a steel material heated by the method for heating a metallic material of the present embodiment. [Figure 8] 4 is a graph showing the effect of the surface temperature of a steel material on the thickness of scale formed on the surface of the steel material. [Figure 9] 1 is a graph showing the relationship between the thickness of scale on the surface of a steel material and heating time when the water vapor concentration in a furnace is changed. [Figure 10] 1 is a graph showing the relationship between the surface temperature and scale thickness of a material heated in a combustion gas heating furnace in a preliminary experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The metallic material heating equipment according to this embodiment will be described below.

[0021] The heating equipment for metal materials in this embodiment is equipped with a first heating furnace that heats metal materials by burner heating using a hydrogen-based gas containing either hydrogen or ammonia or both as a fuel gas, and a second heating furnace into which the metal material removed from the first heating furnace is loaded, an inert gas atmosphere is created inside the furnace, and the metal material is heated by electrical heating.

[0022] First, a heating furnace equipped with a burner system will be described. <Heating equipment> FIG. 1 is a schematic cross-sectional view of a heating facility for metal materials according to an embodiment of the present invention. The heating facility is a facility in which a material to be heated is placed inside and heated to a predetermined temperature. The material to be heated is a metal material, but may be either an iron-based metal or a non-ferrous metal as long as it is a metal material that generates an oxide (hereinafter referred to as scale) on its surface by oxidation. The heating temperature of the material to be heated is 500 to 1400° C. In the following, a heating facility for heating steel material will be described, taking steel material as the metal material.

[0023] 1 is installed in a hot rolling line for producing steel plates or steel strips, for example, and heats cast steel material to a predetermined heating temperature (approximately 1100 to 1300°C). However, the steel material to be heated is not limited to slabs that are used as steel plate materials, but includes billets, blooms, and other steel materials that are used as materials for shaped steel, wire rods, steel pipes, and the like. The heating equipment 100 includes a first heating furnace 1 which heats steel material by burner heating using a hydrogen-based gas whose total amount is either hydrogen or ammonia or both as a fuel gas, and a second heating furnace 2 into which the steel material unloaded from the first heating furnace 1 is loaded, an inert gas atmosphere is created inside the furnace, and the steel material is further heated by electrical heating. Here, the process of heating the metal material to be heated in the first heating furnace is called the first heating process. The process of further heating the metal material to be heated in the second heating furnace is called the second heating process. In addition, in the heating equipment 100, it is preferable to install a control computer 101 that performs data analysis of various operational parameters in order to control the operation of the heating process.

[0024] <1st heating furnace> The first heating furnace 1 includes a first charging section 8 for charging (hereinafter also referred to as "carrying in") the steel material S, and a first unloading section 9 for unloading (hereinafter also referred to as "extracting") the steel material S. For example, steel material (slabs) produced in a continuous casting line is transported to a yard on the charging side of the first heating furnace 1, and is charged from the first charging section 8 into the first heating furnace 1 according to a production schedule of a hot rolling line or the like.

[0025] The inside of the first heating furnace 1 is divided into a plurality of zones, and from the upstream side in the steel material transport direction, it is composed of a preheating zone 3 divided into 1 to 3 zones, a heating zone 4 divided into 2 to 8 zones, and a soaking zone 5 divided into 1 to 3 zones. A conveying device 10 is disposed in the first heating furnace 1 to sequentially convey the steel material S from the first charging section 8 to the first unloading section 9. Each zone of the first heating furnace 1 is controlled to a different atmospheric temperature, and as the first conveying device 10 conveys the steel material S through the pre-heating zone 3, the heating zone 4, and the soaking zone 5 in that order, the average temperature of the steel material S charged into the first heating furnace 1 gradually increases and the steel material S is heated to a predetermined target heating temperature (first heating temperature) in the first heating furnace 1.

[0026] The first conveying device 10 is equipped with a support mechanism for the steel material S called a skid, and includes a fixed skid 10a that supports the steel material S and a movable skid 10b that lifts and moves the steel material S. The movable skid 10b conveys the steel material S toward the first discharge section 9 by repeatedly ascending and descending, moving forward, descending, and retreating within the first heating furnace 1.

[0027] A plurality of burners 6 are provided inside the first heating furnace 1 along the transport direction of the steel material S. The burners 6 are arranged to heat the inside of the first heating furnace 1 by combustion. When the inside of the first heating furnace 1 is heated by the burners 6, the temperature of the steel material S increases due to radiation from the furnace wall of the first heating furnace 1. Also, a flow of atmospheric gas may occur inside the first heating furnace 1, and the temperature of the steel material S may be increased by convection. Furthermore, the temperature of the steel material S may be increased by directly contacting the flame of the burner 6 with the steel material S. In any case, the burner 6 heats the steel material S inside the first heating furnace 1 by increasing the temperature inside the first heating furnace 1.

[0028] The burners 6 are arranged in each of a plurality of zones inside the first heating furnace 1. However, the number of zones does not necessarily have to match the number of burners. In the first heating furnace 1 shown in FIG. 1, an upper burner 6a is arranged on the upper surface side of the steel material S from the first charging section 8 toward the first discharge section 9, and a lower burner 6b is arranged on the lower surface side of the steel material S. In addition, in the first heating furnace 1 shown in FIG. 1, a side burner that injects a flame from one side wall surface in the conveying direction of the steel material S toward the opposite side wall surface is illustrated as a schematic, but an axial burner that injects a flame in the same direction as the conveying direction of the steel material S or a roof burner that injects a flame from the ceiling of the heating furnace into the inside may be used.

[0029] 2 shows the piping system of the burners 6 arranged in the first heating furnace 1, taking as an example some of the zones constituting the first heating furnace 6. The burners 6 (upper burner 6a, lower burner 6b) arranged in the first heating furnace 1 are connected to a fuel gas supply system 31 that supplies fuel gas G and a combustion air supply system 32 that supplies combustion air A. The fuel gas supply system 31 and the combustion air supply system 32 are connected to a blower (not shown) and the like, and supply the fuel gas G and the combustion air A to the burners 6. As a result, fuel gas G and combustion air A are injected from the burner 6, and the fuel gas G is burned by diffusion, and a flame is blown into the inside of the heating furnace. The combustion air A may be air collected from the atmosphere. However, air that has been reformed by removing nitrogen from the air or adding pure oxygen may be used as the combustion air. Increasing the oxygen content of the combustion air promotes the oxidation reaction of the fuel gas G and reduces the flow rate of the combustion air supplied from the combustion air supply system 32, thereby reducing the power consumption of pumps, etc. In addition, a mixed gas in which oxygen is mixed with combustion exhaust gas may be used as the combustion air A. Reducing the oxygen content of the combustion air makes it possible to make the atmosphere inside the first heating furnace a reducing atmosphere, and promotes the reduction of nitrogen oxides generated by the combustion of ammonia, etc.

[0030] Fig. 3 shows a schematic diagram of a burner equipment 60 that performs burner heating. Note that a burner means a device that injects a flame into a furnace, and particularly refers to a part that injects a flame into a furnace. Also, the burner equipment refers to the entire device including ancillary devices for injecting a flame.

[0031] The burner equipment 60 includes a burner nozzle 7 that forms a flow path for fuel gas G and combustion air A for spraying a flame by the burner 6, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. The burner nozzle 7 is, for example, a double-pipe nozzle, and fuel gas G is injected from the inside toward the furnace interior 38, and combustion air A is supplied to the outside. As a result, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is injected from the burner 6 toward the inside of the first heating furnace 1.

[0032] The burner equipment 60 may include a fuel gas flow rate control valve 33 for adjusting the flow rate of the fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of the fuel gas G. This makes it possible to adjust the combustion energy supplied into the first heating furnace 1. The burner equipment 60 may also be provided with a combustion air flow rate regulating valve 35 for regulating the flow rate of the combustion air A supplied from the combustion air supply system 32 to the burner nozzle 7, and a combustion air flow meter 36 for measuring the flow rate of the combustion air A. This makes it possible to adjust the air ratio of the fuel gas to the theoretical air amount in the burner 6.

[0033] In addition to the nozzle using the double-tube nozzle described above, a nozzle mix type burner that mixes the fuel gas and the combustion air in the middle of the burner nozzle may be used for the burner equipment 60. In this case, the combustion air may be preheated using exhaust gas or the like before it is mixed with the fuel gas.

[0034] 2, a combustion air flow control valve 35 that adjusts the flow rate of the combustion air supplied to each burner 6 and a combustion air flow meter 36 that measures the flow rate of the combustion air are disposed in a combustion air supply system 32 that supplies combustion air to the burners 6. However, the combustion air flow control valve 35 and the combustion air flow meter 36 do not need to be provided for each burner 6, and a plurality of burners may be treated as one group, and the flow rate of the combustion air may be adjusted for each group.

[0035] [Burner heating using coal gas] Conventional steel heating furnaces have used by-product gases generated in steelworks and other facilities as fuel gases to be supplied to the burner equipment. By-product gases are mainly gases obtained from coal, and the It is also called coal gas because it is produced due to incomplete combustion. Coal gas includes coke oven gas, blast furnace gas, converter gas, electric furnace gas, etc. Blast furnace gas is a by-product gas produced when iron ore is reduced in a blast furnace to produce pig iron. Coke oven gas is a by-product gas produced by high-temperature carbonization of coal to produce coke. Converter gas is a by-product gas produced in the steelmaking process in a converter. Electric furnace gas is a by-product gas produced by incomplete combustion of the auxiliary fuel (recarburizer) used in electric furnaces. By-product gas has various component compositions depending on the process in which it is produced.

[0036] For example, the typical composition of blast furnace gas is 21-30% by volume of combustible carbon monoxide, 50-60% by volume of incombustible nitrogen, and 10-22% by volume of carbon dioxide. The lower heating value of blast furnace gas is 3.45 MJ / Nm 3 The typical composition of coke oven gas is 46-60% by volume of hydrogen, 20-35% by volume of methane, 5-10% by volume of carbon monoxide, and 2-4% by volume of hydrocarbons such as ethylene. The lower heating value of coke oven gas is 18.0MJ / Nm 3 Converter furnace gas contains approximately 75% by volume of carbon monoxide, approximately 13% by volume of carbon dioxide, and trace amounts of oxygen, nitrogen, and hydrogen. The lower heating value of converter furnace gas is 8.2 MJ / Nm 3The typical composition of electric furnace gas is about 10% by volume of carbon monoxide, about 22% by volume of carbon dioxide, about 5% by volume of oxygen, and about 56% by volume of nitrogen. The lower heating value of electric furnace gas is 2.8 MJ / Nm 3 That's about it. Coal gas also includes a suitable mixture of blast furnace gas, coke oven gas, and converter gas (sometimes called M gas). By mixing coal gases with different heating values, the amount of heat required to heat the material to be heated can be supplied, ensuring stable operation of the heating furnace.

[0037] <Hydrogen burner equipment> In the heating equipment 100 of this embodiment, at least one of the burner equipments arranged in the first heating furnace uses a fuel gas of hydrogen and ammonia as a fuel gas. Hereinafter, among the burner equipments arranged in the heating furnace, the burner equipment that uses a fuel gas containing a hydrogen-based gas whose total amount is either hydrogen or ammonia or both is called a hydrogen-based burner equipment. Also, hydrogen and ammonia used as the fuel gas are called a hydrogen-based gas.

[0038] First, an embodiment will be described in which a hydrogen-based gas containing either or both of hydrogen and ammonia in its entirety is used as fuel.

[0039] Hydrogen is a colorless gas at room temperature, with an autoignition point of 560°C and a low heating value of 10.5MJ / Nm 3 When hydrogen is burned, the flame temperature is high and the combustion speed is fast, so the tip of the burner nozzle is likely to become very hot. For this reason, it is advisable to use a burner nozzle that mixes the hydrogen with the combustion air after it is ejected. This allows for slow combustion and reduces the thermal load on the burner nozzle. In a hydrogen burner facility that uses hydrogen as fuel gas G, for example, the flow rate of hydrogen ejected from the burner is 185 Nm 3 / hr, combustion air flow rate 370~601Nm 3 Combustion is carried out under operating conditions of 10000 / hr.

[0040] Ammonia is a colorless gas at room temperature, with an autoignition point of 651°C and a low heating value of 14.1MJ / Nm3 When ammonia is burned, the flame temperature is relatively low and the combustion speed is slow, so the ammonia combustion reaction can be stabilized by using a burner nozzle that actively mixes the ammonia with the combustion air. In a hydrogen burner facility that uses ammonia as fuel gas G, for example, the flow rate of ammonia injected from the burner is 185 Nm 3 / hr, combustion air flow rate 370~601Nm 3 Combustion is carried out under operating conditions of 10000 / hr.

[0041] The hydrogen-based burner equipment 70 applied to this embodiment may be the same as the burner equipment 60 shown in Fig. 3. That is, the hydrogen-based burner equipment 70 is the same burner equipment as the burner equipment that uses coal gas as the fuel gas, and is a burner equipment that uses hydrogen-based gas HG as the fuel gas G. By using hydrogen-based gas as the fuel gas, the hydrogen-based burner equipment suppresses the generation of carbon dioxide, and therefore the amount of carbon dioxide discharged from the heating furnace can be reduced.

[0042] The configuration of the hydrogen-based burner equipment 70 applied to this embodiment will be described with reference to FIG. 3. The hydrogen-based burner equipment 70 performs burner heating by injecting a flame into the furnace using hydrogen-based gas HG as fuel gas G and combustion air A. The hydrogen-based burner equipment 70 includes a burner nozzle 7 for injecting a flame into the furnace, a fuel gas supply system 31 for supplying fuel gas G to the burner nozzle 7, and a combustion air supply system 32 for supplying combustion air A to the burner nozzle 7. The burner nozzle 7 is, for example, a double-tube nozzle, in which the fuel gas G is injected toward the furnace interior 38 from the inside, and the combustion air A is supplied to the outside. As a result, a combustible mixture is formed in which the hydrogen-based gas HG is used as the fuel gas G and the combustion air A is mixed, and a flame is injected from the burner 6 toward the inside of the first heating furnace 1.

[0043] The hydrogen-based burner equipment 70 preferably includes a fuel gas flow rate control valve 33 for adjusting the flow rate of the fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of the fuel gas G. The hydrogen-based burner equipment 70 also preferably includes a flow rate setting unit 47 for setting the flow rate of the hydrogen-based gas. The flow rate setting unit 47 is, for example, a control controller, and issues a control command to adjust the valve opening of the fuel gas flow rate control valve 33 so that the actual value of the flow rate measured by the fuel gas flow meter 34 matches the flow rate set value of the hydrogen-based gas HG that is set in advance. This makes it possible to control the combustion energy of the flame injected from the hydrogen-based burner equipment 70 into the first heating furnace 1 and the amount of carbon dioxide exhausted from the first heating furnace 1.

[0044] The hydrogen-based burner equipment 70 is preferably provided with a steam amount control unit 48 that controls the amount of steam in the first heating furnace 1 within a preset range, in addition to the flow rate setting unit 47. The steam amount control unit 48 is configured by, for example, a computer. The water vapor amount control unit 48 calculates the amount of water vapor in the first heating furnace 1, and sends a command to the flow rate setting unit 47 for the flow rate setting value of the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70 so that the calculated amount of water vapor in the furnace falls within a preset target range for the water vapor amount (target water vapor range). Since the amount of water vapor in the first heating furnace 1 affects the scale formation behavior on the surface of the steel material S, the water vapor amount control unit 48 can control the scale formation behavior on the surface of the steel material S by sending a command for the flow rate setting value of the hydrogen-based gas HG to the flow rate setting unit 47. In this case, it is preferable to install a dew point meter 49 in the first heating furnace 1 and estimate the amount of water vapor in the first heating furnace 1 based on dew point information acquired by the dew point meter 49. The method of estimating the amount of water vapor in the first heating furnace 1 will be described later.

[0045] 4 shows an example in which a burner equipment 60 using coal gas CG as fuel gas G and a hydrogen-based burner equipment 70 using hydrogen-based gas HG as fuel gas G are arranged in the first heating furnace 1 as the burners 6. In this case, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the burner equipment 60 is connected to a supply source of coal gas CG, and the burner equipment 60 injects a flame generated by combustion of coal gas into the inside of the first heating furnace 1. On the other hand, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the hydrogen-based burner equipment 70 is connected to a supply source of hydrogen-based gas HG, and the hydrogen-based burner equipment 70 injects a flame produced by combustion of the hydrogen-based gas into the inside of the first heating furnace 1. In this case, the combustion air supply system that supplies combustion air A to the burner equipment 60 and the hydrogen-based burner equipment 70 may be shared by the burner equipment 60 and the hydrogen-based burner equipment 70.

[0046] The first heating furnace shown in FIG. 4 includes hydrogen-based burner equipment that uses hydrogen-based gas HG as fuel gas G, compared to conventional heating furnaces in which all burner equipment uses coal gas CG as fuel gas G, and therefore reduces the amount of carbon dioxide emissions discharged from the heating furnace.

[0047] <Another embodiment of the hydrogen burner equipment> Another embodiment of the hydrogen-based burner equipment will be described, in which a mixed gas obtained by mixing hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon-based gas is used as the fuel gas. Here, the mixed gas refers to a case where a hydrogen-based gas containing either or both of hydrogen and ammonia is mixed with coal gas (containing hydrogen) or a hydrocarbon-based gas (methane, ethane, propane, etc.).

[0048] The hydrogen-based burner equipment may use a mixed gas containing the hydrogen-based gas HG and other fuels as the fuel gas G. For example, a mixed gas of the hydrogen-based gas and coal gas can be used as the fuel gas G.

[0049] 5 shows a hydrogen-based burner equipment 71, as another example of the hydrogen-based burner equipment, which uses a mixed gas of hydrogen-based gas HG and coal gas CG as fuel gas G. The hydrogen-based burner equipment 71 shown in FIG. 5 is similar to the hydrogen-based burner equipment 70 shown in FIG. 3 in that it includes a burner nozzle 7 that emits a flame into the heating furnace, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. It is also similar in that the combustion air A is supplied from the combustion air supply system 32 to the burner nozzle 7, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is emitted from the burner 6 toward the inside of the first heating furnace.

[0050] On the other hand, the fuel gas supply system 31 of the hydrogen-based burner equipment 71 shown in Fig. 5 includes a mixing section 40 that mixes the hydrogen-based gas HG supplied through the hydrogen-based gas supply system 45 and the coal gas CG supplied through the coal gas supply system 46. The mixing section 40 generates the fuel gas G by mixing the hydrogen-based gas HG and the coal gas CG. The fuel gas G generated in the mixing section 40 is further mixed with the combustion air A to form a combustible mixture, which is sprayed as a flame from the burner 6 toward the inside of the heating furnace 1.

[0051] The mixing section 40 refers to a portion where a hydrogen-based gas supply system 45 that supplies a hydrogen-based gas HG and a coal gas supply system 46 that supplies a coal gas CG join together. The hydrogen-based gas HG and the coal gas CG are supplied from respective supply pipes, and by joining together, mixing is performed without providing a special stirring mechanism. Therefore, the mixing section 40 may be configured as a certain space in the portion where these supply pipes intersect.

[0052] However, the mixer 40 may be equipped with a static mixer or other static mixer, or a dynamic mixer equipped with a stirring function. This is preferable in that the hydrogen-based gas HG and the coal gas CG are mixed more uniformly into a mixed gas.

[0053] The hydrogen-based burner equipment 71 may include a hydrogen-based gas flow rate control valve 41 for adjusting the flow rate of the hydrogen-based gas HG supplied to the mixing section 40 through a hydrogen-based gas supply system 45, and a hydrogen-based gas flow meter 42 for measuring the flow rate of the hydrogen-based gas HG. The hydrogen-based burner equipment 71 may also include a coal gas flow rate control valve 43 for adjusting the flow rate of the coal gas CG supplied from the coal gas supply system 46 to the mixing section 40, and a coal gas flow meter 44 for measuring the flow rate of the coal gas CG.

[0054] These make it possible to adjust the mixture ratio of the hydrogen-based gas HG and the coal gas CG contained in the fuel gas G. When the mixture ratio of the hydrogen-based gas HG contained in the fuel gas G is increased, the effect of reducing the emission of carbon dioxide discharged from the first heating furnace 1 becomes greater compared to conventional burner heating that uses only the coal gas CG as fuel gas.

[0055] On the other hand, when ammonia is used as the hydrogen-based gas, ammonia is a flame-retardant fuel that is more difficult to ignite and burns slower than general fuel gases, so if the mixture ratio of ammonia contained in the fuel gas G becomes large, combustion in the burner 6 may become unstable. By adjusting the mixture ratio of ammonia and coal gas contained in the fuel gas G, it is possible to ensure the stability of burner heating while reducing carbon dioxide emissions.

[0056] The hydrogen-based burner equipment 71 preferably further includes a flow rate setting unit 47 that sets the flow rate of the hydrogen-based gas HG to be supplied to the mixing unit 40. The flow rate setting unit 47 is, for example, a control controller, and issues a control command to adjust the valve opening of the hydrogen-based gas flow rate adjustment valve 41 so that the actual value of the flow rate measured by the hydrogen-based gas flowmeter 42 matches the flow rate set value of the hydrogen-based gas HG that is set in advance. This makes it possible to control the combustion energy of the flame injected from the hydrogen-based burner equipment 71 into the first heating furnace 1 and the amount of carbon dioxide exhausted from the first heating furnace 1.

[0057] Furthermore, the flow rate setting unit 47 may be configured to provide a control command to adjust the valve opening of the coal gas flow rate control valve 43 so that the actual value of the flow rate measured by the coal gas flowmeter 44 matches the flow rate set value of the coal gas CG, relative to a preset flow rate set value of the coal gas CG, in addition to the function of setting the flow rate of the hydrogen-based gas HG to the mixing unit 40. This makes it possible to individually set the flow rates of the hydrogen-based gas HG and the coal gas CG to be supplied to the mixing unit 40, and to adjust the combustion energy supplied into the first heating furnace 1 and the amount of carbon dioxide discharged from the first heating furnace 1.

[0058] The hydrogen-based burner equipment 71 may be provided with a steam amount control unit 48 that controls the amount of steam in the first heating furnace 1 within a preset range, in addition to the flow rate setting unit 47. The function of the steam amount control unit 48 is similar to that of the steam amount control unit 48 described above with reference to FIG.

[0059] When M gas, which is coal gas, and hydrogen, which is a hydrogen-based gas, are mixed and burned, the hydrogen mixing ratio (the ratio of the flow rate of hydrogen supplied through the hydrogen-based gas supply system 45 to the flow rate of hydrogen supplied through the M gas and hydrogen-based gas supply system 45) can be selected arbitrarily. For example, when the hydrogen mixing ratio is 60%, the hydrogen flow rate injected from the burner is 111 Nm 3 / hr, M gas flow rate 74Nm 3 / hr, combustion air flow rate 370~601Nm 3 Combustion is carried out under the operating conditions of 1000 sq. m. / hr. The composition of the M gas is 20 vol.% carbon monoxide, 13 vol.% carbon dioxide, 24 vol.% hydrogen, 13 vol.% methane, 1.2 vol.% hydrocarbons such as ethylene, and 28.8 vol.% nitrogen. When M gas and ammonia are mixed and burned, the ammonia mixing ratio (the ratio of the ammonia flow rate supplied through the hydrogen-based gas supply system 45 to the flow rate of ammonia supplied through the M gas and hydrogen-based gas supply system 45) becomes unstable when the ammonia mixing ratio is high, so the ammonia mixing ratio is about 50%. As an example, if the ammonia mixture ratio is 30%, the ammonia flow rate injected from the burner is 50 Nm 3 / hr, M gas flow rate 117Nm 3 / hr, combustion air flow rate is 480~624Nm 3 Combustion is carried out under the operating conditions of 100000000 / hr.

[0060] <Second heating furnace> The second heating furnace 2 carries out a second heating step in which the metal material heated in the first heating furnace 1 is further heated by electrical heating while controlling the interior of the furnace to an inert gas atmosphere.

[0061] The second heating furnace 2 shown in Fig. 1 includes a second charging section 26 into which the steel material S heated in the first heating furnace 1 is charged, and a second discharge section 27 from which the steel material S is discharged (extracted). When the steel material S heated in the first heating furnace 1 is discharged from the first discharge section 9 of the first heating furnace, it is transferred to the second charging section 26 of the second heating furnace 2 by a transfer device 14 arranged between the first heating furnace 1 and the second heating furnace 2. Next, the steel material S is charged into the second heating furnace 2 from the second charging section 26, and the second heating step is performed. The steel material S that has been subjected to the second heating step is discharged from the second discharge section 27. For example, when the heating equipment 100 is disposed in a hot rolling line that performs hot rolling of steel material, the steel material S discharged from the second heating furnace 2 has primary scale removed by a descaling device in the hot rolling line, and then hot rolling is performed.

[0062] The inside of the second heating furnace 2 is divided into one or more zones, and the average temperature of the steel material S charged into the second heating furnace 2 is controlled to be a predetermined target heating temperature (second heating temperature). The second heating furnace 2 shown in Fig. 1 is provided with a non-oxidation heating zone 21 as one zone.

[0063] The target heating temperature (second heating temperature) in the second heating furnace 2 is set to a temperature higher than the target heating temperature (first heating temperature) in the first heating furnace 1, thereby further heating the steel material S. A second conveying device 28 is disposed in the second heating furnace 2, which conveys the steel material S successively from the second charging section 26 toward the second discharge section 27. The second conveying device 28 is equipped with a support mechanism for the steel material S called a skid, and is composed of a fixed skid 28a that supports the steel material S, and a movable skid 28b that lifts and moves the steel material S. The movable skid 28b moves the steel material S toward the second discharge section 27 by repeatedly ascending and descending, moving forward, descending, and retreating within the second heating furnace 2.

[0064] An inert gas supply unit 23 for controlling the inside of the furnace to an inert gas atmosphere is disposed in the second heating furnace 2. The inert gas supply unit 23 is, for example, a gas injection nozzle that injects gas into the second heating furnace 2. The inert gas supply unit 23 is connected to an inert gas supply source, and the inert gas NAG is supplied into the second heating furnace 2 through an inert gas supply system 30. The inert gas NAG can be nitrogen gas, argon, helium, or the like, which inhibits the progression of oxidation of the steel material S. The inert gas supply system 30 may include an inert gas flow rate control valve 25 for adjusting the flow rate of the inert gas NAG supplied into the second heating furnace 2, and an inert gas flow meter 24 for measuring the flow rate of the inert gas NAG. This allows the atmosphere in the second heating furnace 2 to be adjusted to be non-oxidizing.

[0065] Methods for supplying the inert gas into the second heating furnace 2 include an inner furnace pressure control method and a flow rate control method. The furnace pressure control method is a method of supplying an inert gas from the inert gas supply unit 23 so that the atmospheric pressure inside the second heating furnace 2 is within a predetermined range. In the case of the furnace pressure control method, the supply flow rate of the inert gas NAG is controlled so that the pressure inside the second heating furnace 2 is, for example, 3 to 7 kPa. The flow rate control method is a method of supplying inert gas from the inert gas supply unit 23 so that the flow rate of the inert gas supplied into the second heating furnace 2 is within a predetermined range. In the flow rate control method, the supply amount of inert gas varies depending on the internal volume of the second heating furnace 2, but the flow rate is controlled within a predetermined range for a furnace capacity of 1 m 3 2~4m per 3 / hr. Note that if the temperature of the inert gas NAG supplied from the inert gas supply unit 23 to the second heating furnace 2 is low, the atmospheric temperature in the second heating furnace 2 may drop, so it is preferable to preheat the inert gas NAG to a temperature of 200° C. or higher before supplying it.

[0066] The inert gas atmosphere in the second heating furnace 2 may be determined by sampling the atmospheric gas in the furnace and using an oxygen concentration meter. Alternatively, the probe of the oxygen concentration meter may be inserted into the second heating furnace 2 to measure the oxygen concentration of the inert gas atmosphere in the second heating furnace 2. As the inert gas atmosphere in the second heating furnace 2, it is preferable to control the oxygen concentration in the furnace to be low, and it is preferable to set the oxygen concentration in the second heating furnace 2 to 10 ppm or less. Therefore, it is preferable to maintain the pressure in the second heating furnace 2 higher than atmospheric pressure so that outside air is less likely to enter the second heating furnace 2. Also, when the oxygen concentration in the second heating furnace 2 exceeds a preset value, the flow rate of the inert gas NAG supplied from the inert gas supply unit 23 into the second heating furnace 2 may be increased.

[0067] In the second heating furnace 2, electric heating is applied as a heating means for carrying out the second heating step. Electric heating is a heating method for heating a metal material using electricity.

[0068] The electric heating for carrying out the second heating step can be resistance heating or induction heating. Resistance heating is a method of heating metal materials by passing an electric current through a resistance heating element and using the resulting Joule heat. There are two methods of resistance heating: indirect resistance heating and direct resistance heating. Indirect resistance heating is a method of transferring heat generated by a resistance heating element to a metal material through radiation, convection, and conduction. Direct resistance heating is a method of directly heating a metal material by generating Joule heat in the metal material. Induction heating is a non-contact heating method that uses electromagnetic induction to pass an electric current through a metal material to generate heat. Electric heating can heat metal materials without using oxygen, making it easier to maintain an inert gas atmosphere in the second heating furnace 2. In addition, by using electricity generated using renewable energy sources such as solar power and wind power as the power source for electric heating, carbon dioxide emissions can be reduced compared to gas heating using conventional hydrocarbon fuel gas.

[0069] It is preferable to apply indirect resistance heating to the electric heating for carrying out the second heating step. This is because indirect resistance heating is less affected by the shape of the metal material and the atmospheric gas and temperature in the furnace when carrying out the second heating step, and the heating temperature of the metal material is easy to control. When indirect resistance heating is applied to the second heating furnace 2, it is preferable to use a Kanthal wire or Pyromax wire of an Fe-Cr-Al alloy as the resistance heating element. In addition, platinum wire, molybdenum, tungsten, etc. may be used as the resistance heating element.

[0070] FIG. 6 shows an example of a second heating furnace 2 that performs electric heating by indirect resistance heating. The electric heating section 22 that performs indirect resistance heating is composed of a resistance heating element 51 and a heat-resistant tube 52. Electric power is supplied to the resistance heating element 51 from a power source (not shown) installed outside the furnace wall 54 of the second heating furnace 2 via a power supply cable 53. This causes the resistance heating element 51 to generate heat by Joule heat. The heat-resistant tube 52 is a tubular member into which the resistance heating element 51 is inserted. The heat-resistant tube 52 radiates the heat generated by the resistance heating element 51 into the second heating furnace 2. This causes the steel material S in the second heating furnace 2 to be heated. The heat-resistant tube 52 is made of Fe-Cr-Al alloy, ceramics, NiCr alloy, etc. The heat-resistant tube 52 is not limited to a straight tube shape as long as it is cylindrical, and may be bent to increase the radiation area. The heat-resistant tube 52 is preferably installed along the furnace wall 54 inside the second heating furnace 2. The heat-resistant tube 52 and the steel material S are preferably spaced apart from each other by a distance of 0.5 to 2.0 m. The resistance heating element inserted inside one heat-resistant tube is preferably provided with a heating capacity of about 20 to 100 kW. A plurality of resistance heating elements are preferably arranged inside the second heating furnace 2, and the total heating capacity of the resistance heating elements is preferably set to about 10 to 15 MW.

[0071] [Transfer device] The first heating furnace 1 and the second heating furnace 2 are separated from each other so that the atmospheric gases inside them do not flow between each other. In the heating equipment 100 of Fig. 1, the atmospheric gases inside the first heating furnace 1 and the second heating furnace 2 are blocked from flowing between each other by a first discharge section 9 which is an outlet for discharging the steel material S from the first heating furnace 1 and a second charging section 26 which is an inlet for charging the steel material S into the second heating furnace 2. Then, in response to the opening and closing operation of the first discharge section 9, the transfer device 14 transfers the steel material S to the second heating furnace 2 and charges it from the second charging section 26 into the second heating furnace 2. As a result, the steel material S heated in the first heating furnace 1 is further heated in the second heating furnace 2.

[0072] The transfer device 14 is a device having a function of transferring the steel material S from the first discharge section 9 to the second charging section 26. For example, a conveying machine for transferring the steel material S in a high temperature state, such as a table roll, a dolly, a crane, a forklift, or a chain, may be used. The transfer device 14 preferably has a capacity to transfer the steel material S discharged from the first discharge section 9 to the second charging section 26 in about 10 to 60 minutes. If the waiting time between the first heating furnace 1 and the second heating furnace 2 is long after the first heating step, the temperature of the steel material S will drop and scale will easily grow on the surface of the steel material S due to oxygen in the outside air, and this is to prevent this.

[0073] In the heating equipment shown in Fig. 1, the first discharge section 9 of the first heating furnace 1 and the second charging section 26 of the second heating furnace 2 are separated from each other. This is to make the steel material S discharged from the first discharge section 9 wait temporarily before being charged into the second charging section 26.

[0074] In terms of the specific transfer method, first, when the steel material S is transported from the first heating furnace 1, the door of the first discharge section 9 is temporarily opened and the steel material S is made to wait at a standby position. Next, the door of the first discharge section 9 is closed to prevent the gas inside the first heating furnace 1 from flowing out to the outside from the first discharge section 9. Thereafter, the door of the second charging section 26 is temporarily opened, the steel material S is charged into the second heating furnace 2, and then the door of the second charging section 26 is closed. This makes it possible to prevent the combustion gas in the first heating furnace 1 from flowing into the inside of the second heating furnace 2, and to reliably maintain an inert atmosphere inside the second heating furnace 2. It is preferable that the first discharge section 9 of the first heating furnace 1 and the second charging section 26 of the second heating furnace 2 are separated by a distance sufficient to allow the steel material S to be temporarily placed on standby.

[0075] <Metal material heating method> Next, a method for heating a metal material will be described. The method for heating a metal material according to this embodiment includes a first heating step in which the metal material is heated by burner heating using a fuel gas containing a hydrogen-based gas whose total amount is either hydrogen or ammonia or both, and a second heating step in which the metal material heated in the first heating step is heated by electric heating in an inert gas atmosphere in a furnace.

[0076] The first heating step and the second heating step can be carried out by the heating equipment 100 described above. 7 shows an example of the temperature history of a steel material heated by the metal material heating method of this embodiment. The steel material S is heated to a target heating temperature (first heating temperature) of the first heating step by a first heating step. Next, after a transfer time for transferring the steel material from the first heating furnace 1 to the second heating furnace 2, the second heating step is performed in the second heating furnace 2, and the steel material S is heated to the target heating temperature (second heating temperature) of the second heating step, and then extracted from the heating equipment 100.

[0077] In the first heating step, the metal material is heated to a first heating temperature by heating means including burner heating using a hydrogen-based gas HG as a fuel gas G in a first heating furnace 1 . In the first heating step, burner heating is performed using hydrogen-based gas HG, and water vapor is generated by the combustion of hydrogen and ammonia contained in fuel gas G. In this situation, water penetrates through the surface of the metal material in the first heating furnace 1, and the oxygen constituting the water molecules oxidizes the metal material in the first heating furnace 1 while releasing hydrogen. The hydrogen diffuses inside the oxide layer formed on the surface of the metal material, and combines with the oxygen in the oxide layer at the interface between the oxide layer and the base material to generate water vapor. The generated water vapor then further oxidizes the metal material, promoting the generation of the oxide layer.

[0078] Therefore, in a heating furnace using hydrogen or ammonia as fuel gas, water vapor contained in the combustion gas penetrates the interface with the oxide layer of the metal material and promotes the oxidation of the metal material, so it is difficult to suppress the formation of scale on the metal material even when the inside of the heating furnace is controlled to be a non-oxidizing atmosphere. On the other hand, if there are foreign matters caused by impurities generated during casting or mold powder mixed in during casting on the surface of the metal material before it is charged into the heating equipment 100, the combustion of hydrogen-based gas can promote the formation of scale on the metal material. Therefore, the occurrence of surface defects on the metal material can be suppressed by removing the oxide layer using a descaling device or the like after the metal material is discharged from the heating equipment 100.

[0079] In this embodiment, it is preferable to provide a flow rate setting unit 47 in the hydrogen-based burner equipment of the first heating furnace to control the flow rate of the hydrogen-based gas HG supplied to the burner nozzle 7. By changing the flow rate of the hydrogen-based gas HG, the amount of water vapor generated in the first heating furnace 1 changes, and this makes it possible to control the thickness of the oxide layer formed on the surface of the metal material. In other words, as an operational parameter of the first heating step, the amount of water vapor in the furnace can be controlled based on the flow rate of the fuel gas so that the thickness of the oxide layer formed on the surface of the metal material falls within a preset range. Furthermore, the operation parameters for controlling the amount of water vapor in the furnace can be set based on the heating time or heating temperature of the first heating step, in addition to the flow rate of the fuel gas.

[0080] Furthermore, a steam amount control unit 48 may be provided to control the amount of steam in the first heating furnace 1 within a preset range, and a flow rate setting value of the hydrogen-based gas HG to be supplied to the burner nozzle 7 may be set in the flow rate setting unit 47 based on the amount of steam in the first heating furnace 1 calculated by the steam amount control unit 48.

[0081] In this case, the water vapor amount control unit 48 estimates the amount of water vapor in the first heating furnace 1 based on dew point information acquired by a dew point meter 49 installed in the first heating furnace 1, and sends a command to the flow rate setting unit 47 for the flow rate setting value of the hydrogen-based gas HG to be supplied to the burner nozzle 7 so that the estimated water vapor amount falls within a predetermined target range for the water vapor amount (target water vapor range). This makes it possible to control the amount of scale formed on the surface of the metal material in the first heating step.

[0082] A method for estimating the amount of water vapor in the first heating furnace 1 performed by the water vapor amount control unit 48 will be described. First, the water vapor amount control unit 48 acquires the measured dew point value of the atmospheric gas acquired by the dew point meter 49. From the acquired measured dew point value, the water vapor pressure of the atmospheric gas is calculated using the known relationship between the amount of saturated water vapor and temperature. Then, from the calculated water vapor pressure and the pressure (total pressure) of the atmospheric gas, the volume fraction of water vapor contained in the atmospheric gas is calculated, and the amount of water vapor in the first heating furnace 1 can be calculated from the furnace inner volume of the first heating furnace 1. As a known relationship between the amount of saturated steam and the temperature, for example, the Tenens equation or the Murray equation may be applied. In this manner, the steam amount control unit 48 can estimate the amount of steam in the first heating furnace 1.

[0083] As an example of a method for heating a metal material, an example of heating a steel material will be described. In the method for heating a steel material of this embodiment, it is preferable to heat the steel material S so that the surface temperature of the steel material S becomes 850 to 1050°C in the first heating step. In the first heating step, burner heating using a hydrogen-based gas HG is performed in a furnace, so that oxidation of the steel material S is promoted by water vapor contained in the combustion gas of the hydrogen-based gas HG, and a predetermined scale thickness can be generated by the time the first heating step is completed.

[0084] As a result, even if the steel material before being subjected to the first heating process contains foreign matter such as impurities generated during casting or mold powder mixed in during casting, the occurrence of surface defects can be suppressed by removing the scale using a descaling device or the like after the first heating process and the second heating process are completed.

[0085] However, if the first heating temperature is less than 850°C, scale of an appropriate thickness may not be generated, so the first heating temperature is set to 850°C or higher. The first heating temperature is more preferably 900°C or higher, and further preferably 950°C or higher. On the other hand, if the first heating temperature exceeds 1050°C, the thickness of the scale generated in the first heating step becomes too thick, resulting in a decrease in product yield, so the first heating temperature is set to 1050°C or lower.

[0086] Here, it is known that the growth of scale on the steel material in the first heating furnace 1 is diffusion-limited, and increases exponentially with respect to the surface temperature, as shown in formula (1).

number

[0087] Figure 8 shows an example of measuring the thickness of the scale formed on the surface of a steel material when the steel material was heated for 30 minutes while being maintained at a prescribed temperature in a water vapor atmosphere. It can be seen from Figure 8 that the higher the surface temperature of the steel material, the thicker the scale becomes, and that the growth of the scale rapidly accelerates when the surface temperature exceeds 1050°C. Furthermore, in steel materials containing alloy elements such as Cu and Si, a complex oxide in which Cu and Si are concentrated is formed at the interface between the base material and the scale. This is because when the surface temperature of the steel exceeds 1050°C, the composite oxides of Cu and Si may melt, which may further accelerate the oxidation of the base material near the interface between the base material and the scale. For these reasons, the first heating temperature in the first heating step is preferably 1050°C or lower.

[0088] It may be difficult to directly measure the temperature of the steel material S being transported inside the first heating furnace 1, so it is advisable to use a temperature model that calculates the temperature of the steel material S to estimate the surface temperature of the steel material S inside the first heating furnace 1, and control the operating conditions of the first heating process so that the estimated temperature becomes the first heating temperature.

[0089] In this case, a temperature model of the steel material in the heating furnace takes into consideration the effect of radiant heat from the furnace wall to the steel material, and the surface temperature of the steel material is calculated based on the actual measured atmospheric temperature in the heating furnace, positional information (tracking information) of the steel material in the heating furnace, etc. The temperature model of the steel material may be loaded into a control computer (process computer) 101 and configured to execute temperature calculations. The temperature calculation method is to replace the steel material with a mesh divided into finite parts in the thickness and width directions, and solve the heat conduction equation using the finite difference method or finite element method to calculate the temperatures in the thickness and width directions. In this case, the surface temperature of the steel material is the temperature calculated for the mesh located at the outermost layer in the thickness direction.

[0090] In the first heating step, it is preferable to control the amount of steam in the first heating furnace 1 to 20 to 35 volume % by further setting the flow rate of the hydrogen-based gas HG used for burner heating. If the amount of steam in the first heating furnace 1 in which the first heating step is performed is less than 20 volume %, the thickness of the scale formed on the surface of the steel material may be insufficient. On the other hand, if the amount of steam in the first heating furnace 1 exceeds 35 volume %, scale is likely to grow on the surface of the steel material, and excessive scale may be generated. From this viewpoint, the amount of steam in the first heating furnace 1 is more preferably 24 volume % or more and 30 volume % or less.

[0091] Fig. 9 shows an example in which the first heating temperature of the steel material S heated in the first heating step was set to 1000°C, and the amount of steam in the furnace was controlled to 10 volume % and 25 volume %, and the thickness of scale formed on the surface of the steel material S was investigated. In this case, it is known in advance that a scale formation amount of 500 μm is required to remove casting defects present on the surface of the steel material before the first heating step is performed.

[0092] 9, when the amount of water vapor in the furnace is as low as 10 volume %, the thickness of the scale formed on the surface of the steel material S is less than 500 μm. Therefore, in order to form a scale of sufficient thickness on the surface of the steel material S in the first heating step, the heating time of the first heating step needs to be extended, which causes a problem of a decrease in the production efficiency of the heating equipment 100. On the other hand, when the amount of water vapor in the furnace is 25 volume %, the thickness of the scale formed on the surface of the steel material is 500 μm or more, and it is confirmed that sufficient scale is formed to remove casting defects present on the surface of the steel material.

[0093] The method for heating a metallic material according to the present embodiment further includes a second heating step in which the metallic material heated in the first heating step is further heated by electrical heating in a furnace controlled to an inert gas atmosphere. In this case, the target heating temperature (second heating temperature) in the second heating step is set to a temperature higher than the target heating temperature (first heating temperature) in the first heating step, thereby further heating the steel material S.

[0094] In the second heating step, the inside of the furnace is controlled to an inert gas atmosphere, and electric heating without oxygen is performed, so the growth of the oxide layer formed on the surface of the metal material in the first heating step is suppressed. As a result, the oxide layer formed on the surface of the metal material after the first and second heating steps is removed by a descaling device or the like, so the occurrence of surface defects in the subsequent manufacturing steps can be suppressed. In addition, because an excessive oxide layer is not formed on the surface of the metal material, a decrease in product yield is also suppressed.

[0095] The second heating step will be described using a method for heating a steel material as an example. In the method for heating a steel material, it is preferable to heat the steel material so that the surface temperature of the steel material in the second heating step is 1050 to 1250°C. In the second heating step, the inside of the second heating furnace 2 is controlled to an inert gas atmosphere, so that oxidation of the steel material S is suppressed. Furthermore, in the second heating furnace 2, the steel material S is heated by electrical heating, so there is no need to inject oxygen for combustion into the furnace, and it is possible to prevent the surface of the steel material S from being oxidized by excess oxygen. That is, as shown in Fig. 8, the thickness of the scale formed on the surface of the steel material increases rapidly when the surface temperature exceeds 1050°C in an atmosphere containing water vapor, whereas the growth of the scale is suppressed by the second heating step in which electrical heating is performed in an inert gas atmosphere.

[0096] However, when the second heating temperature is less than 1050°C, the second heating temperature may be lower than the first heating temperature, and the energy required to heat the steel material is wasted. Therefore, it is preferable that the second heating temperature is higher than the first heating temperature and is 1050°C or higher. On the other hand, although the upper limit of the second heating temperature is not particularly determined, the practical upper limit of the heating temperature of steel material to be supplied to a hot rolling line, etc. may be 1250°C. If the second heating temperature exceeds 1250°C, the energy required to heat the steel material becomes excessive.

[0097] As for the temperature of the steel material S in the second heating process, as in the case of the first heating process, it is advisable to estimate the surface temperature of the steel material using a temperature model that calculates the temperature of the steel material S in the heating furnace, and to control the operating conditions of the second heating process so that the estimated temperature becomes the second heating temperature.

[0098] As described above, the method for heating a metallic material according to this embodiment promotes the growth of an oxide layer that is generated on the surface of the metallic material in the first heating step. Then, in the second heating step in which the metallic material is heated to a higher temperature, the growth of the oxide layer is suppressed, thereby making it possible to suppress the occurrence of surface defects in the metallic material and to suppress a decrease in product yield. In the first heating step, the metal material is heated by burner heating of fuel gas using a hydrogen-based gas whose total amount is either hydrogen or ammonia or both, so that the amount of carbon dioxide emitted from the heating equipment 100 can be reduced compared to conventional burner heating that uses only a carbon-based gas.

[0099] <Another embodiment of the method for heating a metal material> Another embodiment of the method for heating a metallic material according to the present embodiment is a method for heating a metallic material, in which the amount of steam in the furnace is controlled in the first heating step based on at least one operation parameter selected from the heating time, heating temperature, and flow rate of fuel gas used for burner heating, so that the thickness of the oxide layer formed on the surface of the metallic material falls within a preset range. This makes it possible to further suppress the decrease in product yield while suppressing the occurrence of surface defects on the metallic material.

[0100] In this embodiment, a target range (target scale range) of the thickness of the oxide layer generated on the surface of the metal material in the first heating step is set in advance. The target scale range is set to a range equivalent to the thickness from the surface where impurities generated during casting and foreign matter caused by mold powder mixed in during casting, which are distributed near the surface of the metal material before the first heating step, are distributed, and the target scale range is set to a range equivalent to such a thickness. For example, the target scale range of the metal material to be heated is set to about 50 to 1000 μm. When the metal material is a steel material, it is set to 300 to 600 μm. This is because impurities generated during casting and foreign matter caused by mold powder mixed in during casting are often present in large amounts in a range of about 300 to 600 μm from the surface of the steel material.

[0101] On the other hand, the thickness of the scale formed on the surface of the metal material in the first heating step is determined by the growth of the oxide. It is advisable to estimate the scale thickness using a mathematical model (scale thickness prediction model) that models the behavior. For example, the scale growth of steel can be estimated using the following equation (2).

number

[0102] The scale thickness prediction model determined in advance as described above may be loaded into a control computer 101 that sets the operating conditions of the heating equipment 100, and a predicted value of the thickness of scale formed on the surface of the metal material may be calculated based on information acquired by the control computer 101 from the first heating furnace 1.

[0103] Specifically, the operation parameters of the first heating furnace 1 are acquired from the control computer 101 (acquisition step). Next, based on the acquired operation parameters of the first heating furnace 1, the scale thickness at the stage of completing the first heating process is predicted (prediction step). Then, it is determined whether the predicted scale thickness (predicted scale thickness) is within a preset target scale range (determination step). In the determination step, if the predicted scale thickness is within the target scale range, a command is issued to the control computer 101 to maintain the current operating conditions of the first heating furnace 1. On the other hand, in the determination step, if the predicted scale thickness is not within the target scale range, a setting command is issued to the control computer 101 to change the operation parameters of the first heating furnace 1 (setting step).

[0104] The operation parameter of the first heating furnace 1, which is set by the setting step and commanded to the control computer 101, is at least one operation parameter selected from the heating time of the first heating step, the heating temperature, and the flow rate of the fuel gas used for burner heating using the fuel gas containing a hydrogen-based gas whose total amount is either hydrogen or ammonia or both. Since the ratio of the hydrogen-based gas contained in the fuel gas is specified in advance, the flow rate of the hydrogen-based gas HG may be used as the flow rate of the fuel gas.

[0105] By changing the heating time of the first heating step, the thickness of the scale of the metal material generated in the first heating step changes. Also, by changing the heating temperature of the first heating step (ambient temperature in each zone inside the first heating furnace), the thickness of the scale of the metal material generated in the first heating step changes. In this case, the heating temperature of the first heating step is preferably changed by changing the ambient temperature of the soaking zone. On the other hand, when the flow rate of the hydrogen-based gas HG used in the first heating step is changed, the amount of water vapor generated by the burner heating changes, which in turn changes the thickness of the scale on the metallic material. Among these, the parameter to be changed as the operation parameter for the first heating step is the flow rate of the hydrogen-based gas HG used for burner heating. If the heating time for the first heating step is changed, the efficiency of the heating equipment 100 may decrease. Also, if the heating temperature for the first heating step is changed, it may take time for the atmospheric temperature in the furnace to change because the internal volume of the first heating furnace is large. EXAMPLES

[0106] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples.

[0107] <Example 1> As an embodiment of the present invention, an example in which a steel material was heated using a test device simulating the above-mentioned first and second heating steps will be described. The test device used in this embodiment is a combustion gas heating furnace that performs burner heating, and an electric heating furnace that can control the inside of the furnace to an inert gas atmosphere.

[0108] The combustion gas heating furnace in which the first heating step was carried out had internal dimensions of 800mm high x 500mm wide x 1000mm long. The combustion gas heating furnace had burners placed on the top and bottom of the test pieces to be placed in the furnace, and was configured to supply a mixed gas of hydrogen-based gas and coal gas from a fuel gas supply system. The hydrogen-based gas used in the mixed gas was ammonia, and the coal gas used was M gas, a mixture of by-product gases generated in steelworks.

[0109] The combustion conditions used in the examples were ammonia flow rate of 67 Nm 3 / hr, M gas flow rate 100Nm 3 / hr, the ammonia volume ratio in the mixed gas was 40%, and the M gas volume ratio was 60%. The M gas used had a composition that would cause 13% by volume of carbon dioxide to be discharged into the exhaust gas under complete combustion conditions. Meanwhile, in the embodiment, the burner heating conditions were set so that the carbon dioxide concentration in the exhaust gas in the first heating step would be 8% by volume by adjusting the mixing ratio of ammonia.

[0110] The electric heating furnace used in the second heating step also had an internal size of 800 mm high x 500 mm wide x 1000 mm long. Argon was supplied as an inert gas into the electric heating furnace, and the pressure inside the furnace was controlled to 5 kPa by adjusting the opening of the inert gas flow control valve. A resistance heating element made of Kanthal wire was placed inside the electric heating furnace to indirectly heat the material to be heated.

[0111] In the embodiment, carbon steel with plate thickness of 220 mm × plate width of 300 mm × plate length of 500 mm was used as the metal material to be heated. The heated material was taken by machining from the slab after casting, and a K-sheathed thermocouple with a diameter of 0.5 mm was attached at a position 2 mm deep from the surface at the center of the plate width and plate length. This allowed the temperature rise behavior of the heated material in the first heating process and the second heating process to be measured, and the surface temperature of the heated material was estimated based on the measurement results.

[0112] Here, the heating conditions in the combustion gas heating furnace were changed in advance to investigate the relationship between the first heating temperature and the thickness of scale formed on the surface of the heated material. Figure 10 shows the relationship between the surface temperature of the material heated in a combustion gas heating furnace and the thickness of the scale. The thickness of the scale was measured by removing the material from the combustion gas heating furnace when the surface temperature set in the furnace was reached and immediately cooling it with water. This prevented further growth of scale. An evaluation sample was then machined from the material to be heated, and the cross section of the material was observed under an optical microscope to determine the thickness of the scale.

[0113] From FIG. 10, it can be seen that in a combustion gas heating furnace, the higher the surface temperature of the heated material, the thicker the scale becomes, and when the surface temperature exceeds 1050°C, the scale thickness increases rapidly.

[0114] In contrast, in the invention example, the first heating temperature was set to 1050°C, and the second heating temperatures were set to 1100, 1150, and 1200°C, and the first heating step was performed using a combustion gas heating furnace and the second heating step was performed using an electric heating furnace. First, the material to be heated was charged into the combustion gas heating furnace, and the first heating step was performed so that the first heating temperature became 1050°C. Thereafter, while maintaining the heated state, the material to be heated was charged into the electric heating furnace and heated to the second heating temperature. Note that the material to be heated was briefly exposed to the atmosphere between when it was extracted from the combustion gas heating furnace and when it was charged into the electric heating furnace, but the time between this was 20 seconds, and it was considered that the growth of scale on the material to be heated between the completion of the first heating step and the start of the second heating step could essentially be ignored. When the surface temperature of the material to be heated reached the second heating temperature by the second heating step, the material to be heated was removed from the electric heating furnace and immediately cooled with water to prevent further growth of scale, and the thickness of the scale formed on the surface of the material to be heated was measured using the same method as above.

[0115] FIG. 10 shows the thickness of scale formed on the heated material in the embodiment. As can be seen from the figure, when the heated material is heated to 1100-1200°C in the embodiment, the scale thickness formed on the heated material is approximately 400-410 μm, which is only a slight increase from the temperature of 1050°C at the end of the first heating process. In other words, compared to the results of a preliminary experiment using only the first heating process, it was confirmed that the thickness of scale formed on the heated material was suppressed for the same second heating temperature. That is, according to this embodiment, it was confirmed that by using ammonia, which is a hydrogen-based gas, in the first heating step, the carbon dioxide concentration in the exhaust gas can be reduced more than in the case of using coal gas as fuel, and that excessive increase in the oxide layer on the heated material due to water vapor generated by the combustion of ammonia can be suppressed.

[0116] <Example 2> As a second embodiment of the present invention, another example in which steel material was heated using the test apparatus used in the above embodiment will be described. However, in this embodiment, by changing the connection of the supply piping as the fuel gas supply system of the combustion gas heating furnace that executes the first heating step, it is possible to set a condition in which hydrogen, ammonia, and coal gas are used alone as the fuel gas G, and a condition in which a mixed gas of two or more fuel gases selected from hydrogen, ammonia, and coal gas is used.

[0117] In this embodiment, a fuel gas flow meter and a combustion air flow meter for measuring the flow rates of the fuel gas G and the combustion air A are arranged in the fuel gas supply system and the combustion air supply system of the combustion gas heating furnace, so that the flow rates of the fuel gas G and the combustion air A supplied to the burner equipment can be measured. Also, a fuel gas flow control valve and a combustion air flow control valve for adjusting the flow rates of the fuel gas G and the combustion air A are installed in the fuel gas supply system and the combustion air supply system, so that the amounts of the fuel gas G and the combustion air A supplied to the burner nozzle can be adjusted.

[0118] In addition, the atmospheric gas in the combustion gas heating furnace was sampled for each test condition, and the atmosphere in the combustion gas heating furnace was measured using a dew point meter and a gas analyzer. The coal gas used was M gas, as in the above-mentioned embodiment. In the first heating step using the above-mentioned test apparatus, the flow rate of the hydrogen-based gas HG was adjusted so that the carbon dioxide concentration in the exhaust gas discharged from the combustion gas heating furnace was 9% by volume or less under all conditions. The electric heating furnace for carrying out the second heating step was the same as that in the above-mentioned embodiment, and argon was supplied as the inert gas, and the pressure inside the furnace was controlled to 5 kPa by adjusting the aperture of the inert gas flow rate control valve.

[0119] In this example, carbon steel with plate thickness of 220 mm, plate width of 300 mm, and plate length of 500 mm was used as the metal material to be heated. The heated material was machined from the cast slab, and a K-sheathed thermocouple with a diameter of 0.5 mm was attached at a position 2 mm deep from the surface at the center of the plate width and length. This allowed the temperature rise behavior of the heated material in the first and second heating steps to be measured, and the surface temperature of the heated material was estimated based on the measurement results.

[0120] In this embodiment, the material to be heated was charged into a combustion gas heating furnace, and a first heating step was performed so that the first heating temperature was 900 to 1200° C. Thereafter, while maintaining the heated state of the material to be heated, the material was charged into an electric heating furnace, and a second heating step was performed so that the second heating temperature was 1200° C.

[0121] The material was briefly exposed to the atmosphere between the time it was extracted from the combustion gas heating furnace and the time it was charged into the electric heating furnace. However, this time period was only 20 seconds, and it was considered that the growth of scale on the material between the completion of the first heating step and the start of the second heating step could essentially be ignored. When the surface temperature of the material reached the second heating temperature in the second heating step, the material was removed from the electric heating furnace and immediately cooled with water to prevent further growth of scale. Then, an evaluation sample was taken from the heated material by machining, and the cross section of the heated material was observed under an optical microscope to determine the scale thickness.

[0122] Here, the thickness at which impurities generated during casting and foreign matter caused by mold powder mixed in during casting are distributed is specified based on the chemical composition of the carbon steel used for the heated material, and the target scale range was set to 350 to 550 μm. In other words, if the scale thickness formed on the evaluation sample taken from the heated material is less than 350 μm, the scale thickness will be insufficient and there is a risk of surface defects occurring when the material is subjected to hot rolling or the like. On the other hand, if the thickness of the scale from the heated material exceeds 550 μm, excessive scale generation may result in a decrease in product yield. From the above, the case where the scale thickness of the heated material is within the target scale range of 350 to 550 μm was judged as pass (◯). On the other hand, the case where the scale thickness of the heated material is outside the target scale range of 350 to 550 μm was judged as fail (×).

[0123] The heating conditions and test results are shown in Table 1. Conditions 1 to 9 are examples in which a first heating step is carried out in which the material to be heated is heated by burner heating using a fuel gas containing either hydrogen or ammonia as a hydrogen-based gas, and a second heating step is carried out in which the material to be heated in the first heating step is further heated by electrical heating while controlling the inside of the furnace to an inert gas atmosphere. In conditions 1 to 9, the first heating temperature in the first heating step was 900 to 1060° C., and the second heating temperature in the second heating step was 1200° C. In conditions 3, 4, and 9, a hydrogen-based gas was used alone as the fuel gas, and in other invention examples, a mixed gas of a hydrogen-based gas and M gas was used as the fuel gas. Table 1 shows the mixture ratio (volume ratio of hydrogen-based gas HG) of the hydrogen-based gas HG supplied from the hydrogen-based gas supply system 45 contained in the fuel gas G. In this case, when a fuel gas containing only hydrogen and / or ammonia is used, the mixture ratio of the hydrogen-based gas HG is 100%. Also, the "water vapor amount" in Table 1 shows the result of calculating the amount of water vapor in the combustion gas heating furnace using the known relationship between the amount of saturated water vapor and temperature from the measurement results of the dew point, pressure, and temperature of the atmospheric gas in the combustion gas heating furnace.

[0124] As can be seen from Table 1, in conditions 1 to 9, which are examples of the invention, the scale thickness generated on the evaluation sample taken from the heated material was within the target scale range of 350 to 550 μm, and therefore was judged to be pass (◯). In particular, under conditions 1 to 7, since the first heating temperature in the first heating step was in the range of 900 to 1050° C., excessive scale generation was suppressed. In addition, because the amount of steam in the furnace was in the range of 20 to 32 volume percent, an appropriate scale thickness was formed. As a result, under conditions 1 to 7, the scale thickness formed on the evaluation sample was 40 A scale thickness of 0 to 500 μm with little variation was obtained. In contrast, in the comparative examples under conditions 10 and 11, the second heating step was not applied, and heating was performed in a combustion gas heating furnace with the first heating temperature in the first heating step set to 1200° C., resulting in excessively thick scale. Furthermore, in condition 12, the first heating step was not performed, and the second heating step was performed at a second heating temperature of 1200° C. using only an electric heating furnace. In this case, the scale thickness of the heated material was too thin, and when the heated steel material was rolled using a laboratory rolling mill, surface defects were generated on the surface of the steel material.

[0125] From the above, it was found that this embodiment makes it possible to reduce carbon dioxide emissions by using hydrogen or ammonia as the fuel gas for the heating furnace, and also makes it possible to control the amount of scale generation within an appropriate range, thereby reducing the occurrence of surface defects in the metal material and suppressing a deterioration in product yield.

[0126] [Table 1] [Explanation of symbols]

[0127] 100 Heating equipment 101 Control computer S steel material D Steel conveying direction A Combustion air G Fuel gas CG Coal Gas HG Hydrogen Gas NAG Inert Gas 1 1st heating furnace 2 Second heating furnace 3 Pre-tropical zone 4 Heating Zone 5. Average temperature 6 Burner 6a Upper burner 6b Lower burner 7 Burner nozzle 8. First Charging Section 9 First Unloading Section 10 First conveying device 10a Fixed Skid 10b Moving skid 13, 29 Exhaust duct 14 Transfer device 21 Non-oxidizing heating zone 22 Electric heating section 23 Inert gas supply section 24 Inert gas flow meter 25 Inert gas flow control valve 26 Second Loading Section 27 Second Unloading Section 28 Second conveying device 28a Fixed Skid 28b Moving Skid 30 Inert gas supply system 31 Fuel gas supply system 32 Combustion air supply system 33 Fuel gas flow control valve 34 Fuel gas flow meter 35 Combustion air flow control valve 36 Combustion air flow meter 37, 54 Furnace wall 40 Mixing section 41 Hydrogen gas flow control valve 42 Hydrogen gas flow meter 43 Coal gas flow control valve 44 Coal Gas Flow Meter 45 Hydrogen gas supply system 46 Coal Gas Supply System 47 Flow rate setting section 48 Water vapor amount control section 49 Dew point meter 51 Resistance heating element 52 Heat resistant tube 53 Power Cable 55 Insulator 56 Support stand 60 Burner equipment 70, 71 Hydrogen burner equipment

Claims

1. a first heating step of heating the metal material by burner heating using a hydrogen-based gas containing either or both of hydrogen and ammonia as a fuel gas; A second heating step of heating the metal material heated in the first heating step by electric heating in an inert gas atmosphere inside the furnace. A method for heating metal materials.

2. 2. The method for heating a metallic material according to claim 1, wherein a first heating step comprises heating the metallic material by burner heating using, as a fuel gas, a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas.

3. The first heating step includes controlling the amount of water vapor in the furnace to a preset range based on the flow rate of the fuel gas used for the burner heating.

3. A method for heating a metallic material according to claim 1 or 2.

4. The first heating step is performed based on at least one operation parameter selected from a heating time, a heating temperature, and a flow rate of a fuel gas used for the burner heating in the first heating step, The thickness of the oxide layer formed on the surface of the metal material is within a predetermined range. Controlling the amount of steam in the furnace 3. A method for heating a metallic material according to claim 1 or 2.

5. The metal material is a steel material, The first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050° C., The second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250° C.

3. A method for heating a metallic material according to claim 1 or 2.

6. The metal material is a steel material, The first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050° C., The second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250° C. The method for heating a metallic material according to claim 3.

7. The metal material is a steel material, The first heating step heats the metal material so that the surface temperature of the metal material is 850 to 1050° C., The second heating step heats the metal material so that the surface temperature of the metal material is 1050 to 1250° C. The method for heating a metallic material according to claim 4.

8. In the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %. The method for heating a metallic material according to claim 5.

9. In the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %. The method for heating a metallic material according to claim 6.

10. In the first heating step, the amount of water vapor in the furnace is controlled to 20 to 35 volume %. The method for heating a metallic material according to claim 7.

11. a first heating furnace for heating a metal material by burner heating using a hydrogen-based gas containing either or both of hydrogen and ammonia as a fuel gas; a second heating furnace into which the metal material discharged from the first heating furnace is charged, and which heats the metal material by electrical heating while maintaining an inert gas atmosphere inside the furnace; Equipped with Heating equipment for metal materials.

12. 12. The heating equipment for metal materials according to claim 11, wherein a first heating furnace heats the metal material by burner heating using, as a fuel gas, a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas.

13. The first heating furnace is a flow rate setting unit that sets a flow rate of the fuel gas used for heating the burner; a steam amount control unit that controls the amount of steam in the first heating furnace within a preset range; having 13. Heating equipment for metallic materials according to claim 11 or 12.

14. A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material according to claim 5.

15. A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material according to claim 6.

16. A method for operating a heating furnace in which a steel material is heated using the method for heating a metallic material according to claim 7.

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