Radiant tube heaters and heat treatment furnaces

Abstract

We provide a radiant tube heater that can be used not only in heating processes but also in cooling processes as needed. [Solution] The radiant tube heater 20 comprises a tube 22 with openings at both ends, a first cover body 45A and a second cover body 45B that close the openings at both ends, at least one electrical resistance heating element 30 provided inside the tube 22, a support member 35 provided inside the tube 22 to support the electrical resistance heating element 30, a gas inlet 47A for introducing furnace cooling gas into the tube 22, and a gas outlet 47B for discharging the furnace cooling gas introduced into the tube 22.

Description

Technical Field

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[0001] The present invention relates to a radiant tube heater used as a heating means for heating an object to be treated such as steel material, and a heat treatment furnace provided with the radiant tube heater.

Background Art

[0002] In a heat treatment furnace for heat-treating an object to be treated such as steel material, a radiant tube heater is used as a heating means (see, for example, Patent Document 1 below). Such a radiant tube heater has an electric resistance heating element housed inside a straight protective tube (tube). The radiant tube heater configured as described above is particularly suitable for use in an atmosphere heating furnace that performs heat treatment under various atmospheres because the inside of the protective tube in which the electric resistance heating element is housed is isolated from the furnace atmosphere. <00,00011> However, such a radiant tube heater does not have a cooling function and can be used in heating processes such as heating up and soaking of the object to be treated, but a separate cooling device was required in the cooling (temperature drop) process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made for the purpose of providing a radiant tube heater that can be used not only in the heating process but also in the cooling process as needed, and a heat treatment furnace using the same, based on the above circumstances

Means for Solving the Problems

[0006] Thus, the radiant tube heater in the first aspect of this invention is defined as follows: A tube with openings at both ends, A first cover body and a second cover body that close the openings at both ends, The tube contains at least one electrical resistance heating element, A support member provided inside the tube for supporting the electrical resistance heating element, The tube includes a gas inlet for introducing furnace cooling gas, A gas outlet for discharging the furnace cooling gas introduced into the tube, It is equipped with.

[0007] According to the first aspect of the radiant tube heater defined in this way, when placed inside a heat treatment furnace, it is possible to heat the workpiece inside the furnace by supplying power to the electrical resistance heating element to generate heat, and, if necessary, to introduce a furnace cooling gas into the tube through a gas inlet and circulate it through the tube to cool the workpiece inside the furnace.

[0008] Here, the tube may have a curved portion, and the openings at both ends may be open in the same direction (second aspect). U-shaped or W-shaped tubes that have been conventionally used in radiant tube burners can be used as the tubes in the radiant tube heater of this invention.

[0009] Furthermore, in this radiant tube heater, the gas inlet can be provided on the first cover body that closes one opening of the tube, and the gas outlet can be provided on the second cover body that closes the other opening of the tube (third aspect). In this way, gas inlet and outlet ports can be easily added externally while reusing the tubing of a conventional radiant tube burner.

[0010] The fourth aspect of this invention is defined as follows: The support member, when disposed within the tube, has a protruding portion facing the inner wall surface of the tube, and the outer circumference of the protruding portion has a plurality of convex portions spaced apart in the circumferential direction, and recessed portions that constitute part of the flow path for the furnace cooling gas circulating within the tube. According to this defined fourth aspect, the position of the electrical resistance heating element supported by the support member within the tube can be defined by the contact between the protrusion and the inner wall surface of the tube, while the furnace cooling gas can be circulated in a manner that allows it to come into contact with the inner wall surface of the tube, thereby increasing the furnace cooling capacity.

[0011] Furthermore, in this invention, the furnace heating capacity can be enhanced by providing a first electrical resistance heating element provided on one end of the tube and a second electrical resistance heating element provided on the other end of the tube (fifth aspect).

[0012] The heat treatment furnace in the sixth aspect of this invention is defined as follows: A heat treatment furnace for performing heat treatment on an object to be treated, A radiant tube heater according to claim 1 is provided as a heating means for heating the object to be processed contained in the furnace. According to the heat treatment furnace of the sixth phase as defined in this way, the same effect as that of the first phase is achieved. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram shows the schematic overall configuration of a radiant tube heater according to one embodiment of the present invention. [Figure 2] Figure 1 shows the support member, where (A) is a front view and (B) is a cross-sectional view of (A) BB. [Figure 3] Figure 1 shows a schematic overall configuration of an atmospheric heat treatment furnace using a radiant tube heater. [Figure 4] Figure 3 shows the elements involved in controlling the internal temperature of an atmospheric heat treatment furnace.

Mode for Carrying Out the Invention

[0014] Next, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 shows a radiant tube heater 20 according to an embodiment of the present invention, and more specifically, shows a state of being attached to a furnace wall 1a of a heat treatment furnace 1. The radiant tube heater 20 includes a tubular tube 22 that penetrates the furnace wall 1a inside and outside, an electric resistance heating element 30 provided in the tube 22, a support member 35 that supports the electric resistance heating element 30, and first and second cover bodies 45A and 45B that close openings 24 and 25 at both ends of the tube 22.

[0015] The tube 22 is a metal pipe made of a heat-resistant alloy such as stainless steel with a circular cross-section, and in this embodiment, the whole of it forms a U shape. The tube 22 has one end side portion 22a and the other end side portion 22b that penetrate the furnace wall 1a in parallel along the furnace interior and exterior directions, a curved portion 22c that protrudes in a semi-circular shape toward the heat treatment chamber 3 side (inside the furnace), and a hollow portion 23 that continuously penetrates the inside thereof. Note that the shape of the tube 22 can be appropriately adopted as a W shape or the like other than the U shape as needed. Further, the tube 22 is not limited to being made of metal, and in some cases, it may be made of a non-oxide ceramic having excellent heat resistance such as SiC.

[0016] The electric resistance heating element 30 generates heat at a predetermined temperature (for example, 800°C) by passing an electric current. As the electric resistance heating element 30, a metal heating element or a non-metal heating element can be used. The electric resistance heating element 30 of this embodiment is supported by a plurality of support members 35 connected in the axial direction, and is housed in the hollow portion 23 of the tube 22 (specifically, the linearly extending portion of the hollow portion 23) while being folded back at a predetermined length. Electrode bars 32, 32 connected to both ends of the electric resistance heating element 30 penetrate heat insulating materials 52 and lid portions 50 disposed near the openings 24 and 25 of the tube 22 and protrude to the outside (left side in the figure), and are connected to a power source (not shown). In the radiant tube heater 20 of the present embodiment, as the electric resistance heating element 30, a first electric resistance heating element 30A disposed on one end side portion 22a of the tube 22 and a second electric resistance heating element 30B disposed on the other end side portion 22b of the tube 22 are provided.

[0017] Between the first electric resistance heating element 30A and the opening 24 of the tube 22, and between the second electric resistance heating element 30B and the opening 25 of the tube 22, a heat insulating material 52 is disposed. The heat insulating material 52 is formed by laminating graphite fiber or ceramic fiber, and prevents the heat of the electric resistance heating element 30 from escaping to the outside. In the present embodiment, a through hole 53 for allowing the gas for cooling inside the furnace to flow through the central portion thereof is formed.

[0018] FIG. 2 is a view showing a support member 35 disposed inside the tube 22. The support member 35 is made of a ceramic having non-conductivity and fire resistance, and is a member integrally formed with a shaft-like portion 36 extending in the axial direction (longitudinal direction) of the tube 22 as shown in FIG. 2(B) and an overhanging portion 38 extending in a direction orthogonal to the axis from one end of the shaft-like portion 36. The overhanging portion 38 is a disk-shaped portion having a predetermined thickness. On the outer peripheral portion thereof facing the inner wall surface 26 of the tube 22, as shown in FIG. 2(A), a plurality of convex portions 39 provided at intervals of 90° in the circumferential direction and contacting or approaching the inner wall surface 26 of the tube 22 and recessed portions 40 located between adjacent convex portions 39, 39 are formed. Such recessed portions 40 constitute a part of the flow path of the gas for cooling inside the furnace flowing through the tube 22. In FIG. 2(B), the flow of the gas for cooling inside the furnace at one end side portion 22a of the tube 22 is indicated by an arrow. As shown in the figure, the gas for cooling inside the furnace can flow through the tube 22 in contact with the inner wall surface 26 of the tube 22 by passing through the recessed portions 40. At a position radially inner than the recessed portion 40 of the overhanging portion 38, a plurality of through holes 43 for inserting the electric resistance heating element 30 are formed at equal intervals in the circumferential direction.

[0019] As shown in Figure 2(B), an engaging recess 42 is formed in the center of the side surface 38a of the protruding portion 38 opposite to the axial portion 36, which engages with the tip 36a of the axial portion 36 of the adjacent support member 35, so that multiple support members 35 can be connected at equal intervals along the longitudinal direction of the tube 22.

[0020] Next, the cover body will be described. The first cover body 45A shown in Figure 1 is a member that closes the opening 24 of the tube 22, and is composed of a cylindrical portion 46 and a lid portion 50. The cylindrical portion 46 has a hollow section with approximately the same diameter as the tube 22. The cylindrical portion 46 is attached to the end of the tube 22 on the side where the opening 24 is formed, so as to be in communication with the hollow section 23 of the tube 22. A lid portion 50 is attached to the left end of the cylindrical portion 46 in the figure via an insulating packing 49. In this embodiment, a gas inlet 47A is provided in the cylindrical portion 46, and furnace cooling gas can be introduced into the tube 22 through the gas inlet 47A.

[0021] The second cover body 45B is a component that closes the opening 25 of the tube 22, and, like the first cover body 45A, is composed of a cylindrical portion 46 and a lid portion 50. The cylindrical portion 46 of the second cover body 45B is provided with a gas outlet 47B, and the furnace cooling gas introduced into the tube 22 can be discharged through the gas outlet 47B. The components of the second cover body 45B are basically the same as those of the first cover body 45A, and components common to the first cover body 45A are indicated using the same reference numerals, and their explanations are omitted here.

[0022] In the radiant tube heater 20 of this embodiment, the furnace cooling gas introduced into the tube 22 through the gas inlet 47A flows through the tube 22, in contact with the inner wall surface 26 of the tube 22, to one end side 22a, the curved section 22c, and the other end side 22b, and the heat exchange that takes place during this process can cool the inside of the furnace.

[0023] Next, we will describe the atmospheric heat treatment furnace 1 using a radiant tube heater 20. Figure 3 is a schematic diagram showing the overall configuration of the atmospheric heat treatment furnace 1. The atmospheric heat treatment furnace 1 shown in the figure is a batch-type atmospheric heat treatment furnace used for heat treatment of wire coils, steel bars, etc., and a heat treatment chamber 3 is formed inside a box-shaped furnace body 2. An inlet / outlet 4 is formed on one end of the furnace body 2 in the longitudinal direction, and the workpiece to be treated is loaded into the furnace (heat treatment chamber 3) through the inlet / outlet 4 by a group of rollers 5. The inlet / outlet 4 can be opened and closed by a door 7 connected to a drive device 6.

[0024] The heat treatment chamber 3 is equipped with multiple radiant tube heaters 20 and ceiling fans 10 along the transport direction (longitudinal direction), and is connected to gas introduction pipes 11 for introducing various gases.

[0025] Figure 4 is a schematic diagram showing the elements involved in controlling the internal temperature of the atmospheric heat treatment furnace 1. As shown in the figure, the atmospheric heat treatment furnace 1 is equipped with a temperature detector 60, a plurality of radiant tube heaters 20 as heating means, and a temperature control unit 61.

[0026] The temperature detector 60 detects the temperature inside the furnace and transmits the temperature information to the temperature control unit 61. The type of temperature detector 60 is not particularly limited, but known thermocouples, radiation thermometers, etc. can be used, taking into consideration the measurable range and responsiveness.

[0027] The radiant tube heater 20 is configured to receive power from a commercial power source (not shown) via a thyristor 63, which acts as a power supply control unit, to the electrical resistance heating element 30. Furthermore, a cooling gas supply pipe 64 is connected to the gas inlet 47A of the radiant tube heater 20, allowing the cooling gas (e.g., air) supplied by the blower 65 to be introduced into the tube 22 through the cooling gas supply pipe 64 and the gas inlet 47A. A flow control valve 66 is provided upstream of the cooling gas supply pipe 64.

[0028] The temperature control unit 61 adjusts the control output to the thyristor 63 or flow control valve 66 so that the detected temperature received from the temperature detector 60 approaches a preset operating heat pattern (target temperature). Such a temperature control unit 61 can be implemented, for example, by a PLC (Programmable Logic Controller) or a temperature controller equipped with a data processing unit, a storage unit, and a communication interface unit.

[0029] In the atmospheric heat treatment furnace 1 configured in this way, during the heating process, a control signal from the temperature control unit 61 is sent to the thyristor 63, and the amount of power supplied to the radiant tube heater 20 (specifically, the electrical resistance heating element 30) is adjusted. This makes it possible to perform heat treatment under desired heating conditions. Furthermore, during the cooling process, the power supply to the electrical resistance heating element 30 is stopped, and a control signal from the temperature control unit 61 is sent to the flow rate control valve 66, which adjusts the amount of furnace cooling gas introduced into the radiant tube heater 20 (specifically, the tube 22). This allows the cooling process to be performed under the desired cooling conditions.

[0030] As described above, the radiant tube heater 20 of this embodiment can not only heat the workpiece inside the furnace by supplying power to the electrical resistance heating element 30 while it is placed inside the heat treatment furnace 1, thereby heating the electrical resistance heating element 30, but it can also cool the workpiece inside the furnace by introducing furnace cooling gas into the tube 22 through the gas inlet 47A as needed and circulating it through the tube 22.

[0031] Furthermore, since the radiant tube heater 20 of this embodiment uses a tube 22 having a curved portion 22c and openings 24 and 25 at both ends that are open in the same direction, it is possible to use U-shaped or W-shaped tubes that have been used in conventional radiant tube burners.

[0032] Furthermore, in the radiant tube heater 20 of this embodiment, the gas inlet 47A is provided on the first cover body 45A that closes one opening 24 of the tube 22, and the gas outlet 47B is provided on the second cover body 45B that closes the other opening 25 of the tube 22. This configuration allows for the easy addition of gas inlet and gas outlet ports by external attachment while reusing the tube of a conventional radiant tube burner.

[0033] Furthermore, in the radiant tube heater 20 of this embodiment, the protruding portion 38 of the support member 35 that supports the electrical resistance heating element 30 has a plurality of protrusions 39 and a recessed portion 40 that forms part of the flow path for the furnace cooling gas circulating inside the tube 22. This allows the furnace cooling gas to circulate in contact with the inner wall surface 26 of the tube 22 while defining the position of the electrical resistance heating element 30 inside the tube 22, thereby improving the furnace cooling capacity.

[0034] Furthermore, the radiant tube heater 20 of this embodiment is configured to include a first electrical resistance heating element 30A provided on one end side portion 22a of the tube 22 and a second electrical resistance heating element 30B provided on the other end side portion 22b of the tube 22, thereby increasing the furnace heating capacity.

[0035] Although embodiments of the present invention have been described in detail above, these are merely examples. For example, in the above embodiment, the cover body attached to the end of the tube was composed of a cylindrical part and a lid part, and a gas inlet (or gas outlet) was provided in the cylindrical part. However, it is also possible to provide a gas inlet (or gas outlet) in the lid part that constitutes the cover body, or in some cases, a gas inlet (or gas outlet) can be provided directly on the tube. Furthermore, although the above embodiment was an example in which the radiant tube heater of the present invention was used in an atmospheric heat treatment furnace, the radiant tube heater of the present invention can also be used in an air heat treatment furnace or a vacuum heat treatment furnace. In short, the present invention can be implemented in various modified forms without departing from its spirit. [Explanation of Symbols]

[0036] 1. Atmospheric heat treatment furnace 3. Heat treatment chamber (inside the furnace) 20 Radiant Tube Heaters 22 tubes 22a One end side 22b Other end side 22c curved section 24,25 aperture 26 Interior wall surface 30 Electrical resistance heating element 30A First electrical resistance heating element 30B Second electrical resistance heating element 35 Support member 38 Protruding section 39 Convex part 40 Recessed area 45A First Cover Body 45B Second Cover Body 47A Gas Inlet 47B Gas outlet

Claims

1. A tube with openings at both ends, A first cover body and a second cover body that close the openings at both ends, The tube contains at least one electrical resistance heating element, A support member provided inside the tube for supporting the electrical resistance heating element, The tube includes a gas inlet for introducing furnace cooling gas, A gas outlet for discharging the furnace cooling gas introduced into the tube, A radiant tube heater equipped with [a specific feature].

2. The radiant tube heater according to claim 1, wherein the tube has a curved portion and the openings at both ends are open in the same direction.

3. The radiant tube heater according to claim 1, wherein the gas inlet is provided in the first cover body that closes one opening of the tube, and the gas outlet is provided in the second cover body that closes the other opening of the tube.

4. The radiant tube heater according to claim 1, wherein the support member, when disposed within the tube, has a protruding portion facing the inner wall surface of the tube, and the outer circumference of the protruding portion has a plurality of convex portions spaced apart in the circumferential direction and a recessed portion that constitutes part of the flow path for the furnace cooling gas circulating within the tube.

5. The radiant tube heater according to claim 1, comprising a first electrical resistance heating element provided on one end of the tube and a second electrical resistance heating element provided on the other end of the tube.

6. A heat treatment furnace for performing heat treatment on an object to be treated, A heat treatment furnace is provided with a radiant tube heater as described in claim 1 as a heating means for heating the object to be treated contained in the furnace.

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