JP2017079149A - Immersion heater - Google Patents

Abstract

Provided is an immersion heater that is safe and durable and has good heat generation efficiency. An immersion heater 10 is immersed in a molten metal to heat or keep the molten metal. The heater main body 12 is immersed in the molten metal, and the heater main body 12 is bent via a bent portion 15. The upper part 14b is provided with the power transmission part 14 which is extended in the direction which cross | intersects and is exposed on the hot metal surface ML of a molten metal. The heater body 12 is made of a conductive ceramic material and generates heat when energized via the power transmission unit 14. The heater main body 12 houses the heat generator 16 and protects the heat generator 16 from molten metal. And a protective tube 18. The power transmission unit 14 is provided with an electrode unit for connection with an external power source in an upper part 14b located outside the molten metal, and a power transmission unit 20 made of a conductive ceramic material connected in series to the heating element 16 in the lower part 14b. And a second protective tube 24 that houses the power transmission body 20 and protects the power transmission body 20 from molten metal. [Selection] Figure 2

Description

  The present invention relates to an immersion heater that is immersed in a molten metal in a holding furnace to heat or keep the molten metal.

  Conventionally, radiant heating using oil or gas combustion burners has been the mainstream as a technique for heating or keeping molten metal such as aluminum, zinc, brass, etc. In recent years, from the viewpoint of thermal efficiency, ceramics, etc. It is becoming common to immerse an immersion heater equipped with a heating element in a refractory protective tube (heater tube) in a molten metal holding furnace and heat it directly.

  As such an immersion heater, one that is used by penetrating the side wall of the molten metal container of the holding furnace and extending horizontally near the bottom of the container, or the upper part is suspended from the upper lid of the molten metal container and the lower part is melted. A straight cylindrical heater used by being immersed therein is known.

  However, in the type of immersion heater that is installed by penetrating the side wall of the molten metal container of the holding furnace, since the hole for inserting the immersion heater is formed in the side wall, the heat insulation characteristic of the molten metal container is lowered, and the immersion heater is added later. It is also difficult to do. In addition, in the case of a straight cylindrical heater, the protective tube near the hot water surface of the heater is also exposed to high temperature, and the molten metal adhering to the outer peripheral surface is oxidized and solidified (for example, corundum), and the difference in thermal expansion coefficient from this solidified layer Since the protective tube is easily broken, the heater life is short, and the installation location is limited to the vicinity of the furnace wall, so that the heat transfer efficiency to the molten metal is inferior.

  On the other hand, in order to overcome the above-mentioned problems of the immersion heater, in Patent Document 1 and Patent Document 2, a heating element is built in the horizontal portion of the L-shaped protective tube and is sent to the vertical portion of the protective tube. An immersion heater has been proposed in which an electric wire is housed and the power transmission line is connected to an electrode at the rear end of the heating element. With such an L-shaped immersion heater, it is possible to add a heater without making a hole in the side wall of the molten metal container. In addition, since the heat generating part (horizontal part) is completely immersed in the molten metal, it is possible to prevent damage to the protective tube and to achieve good heat transfer efficiency.

JP 2014-70890 A JP 2012-9230 A

  However, in the case of the prior art described in Patent Document 1, there is a risk that the electrode part connecting the power transmission line and the heating element becomes hot and deteriorates. In addition, since the metal electrode portion has a larger thermal expansion than the ceramics constituting the heating element, there is a risk of contact failure due to loosening or the like in the electrode portion, and there is concern about stable operation. In order to cope with these problems, Patent Document 2 proposes a technique of circulating a refrigerant inside a vertical portion (power transmission tube) of a protective tube to cool an electrode portion. However, in such a technique, not only the electrode part but also the power transmission tube is cooled by the refrigerant, and there is a problem that the molten metal temperature is lowered and heat loss is caused.

  Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide an immersion heater that is safe and excellent in durability and excellent in heat transfer efficiency.

  The present invention has been made to solve the above-mentioned problems, and the present invention is an immersion heater that is immersed in a molten metal to heat or keep the molten metal, and is a heater that is immersed in the molten metal. The heater includes a main body and a power transmission section that extends in a direction intersecting the heater main body via a bent portion and has an upper portion exposed on the surface of the molten metal. The heater main body is made of a conductive ceramic material. A heating element that generates heat when energized through the power transmission unit; and a first protective tube that houses the heating element and protects the heating element from the molten metal. An electrode part for connection to an external power source is provided in the upper part located outside, and a power transmission body made of a conductive ceramic material is connected to the heating element in the lower part, and the metal is housed in the power transmission body. Protect the power transmission body from the molten metal It is characterized in that a second protective tube, a.

  In the immersion heater according to the present invention, it is preferable that the power transmission body is joined to the heating element via a joint portion.

  In the immersion heater according to the present invention, it is preferable that the joint between the power transmission body and the heating element is inclined at a predetermined inclination with respect to the axial direction of the heater body. The inclination is preferably in the range of 30 to 60 degrees.

  Furthermore, in the immersion heater according to the present invention, the heating element includes a high heating part and a low heating part having a smaller heating value than the high heating part, and the low heating part includes the power transmission body and It is preferable that it is disposed adjacent to the joint with the heating element. In this case, it is preferable that a heat shield member is provided between the low heat generating portion and the first protective tube.

  Furthermore, in the immersion heater according to the present invention, it is preferable that the joint between the power transmission body and the heating element is a sintered joint.

  Furthermore, in the immersion heater according to the present invention, the power transmission body includes a pair of power transmission body portions extending in parallel with each other in an insulated state, and the pair of power transmission body portions includes the axial direction of the heater main body portion and the It is preferable that they are juxtaposed in a direction orthogonal to both the axial directions of the power transmission unit.

  Furthermore, in the immersion heater according to the present invention, it is preferable that the power transmission body is formed of a ceramic material having a specific resistance smaller than that of the heating element.

  In addition, in the immersion heater according to the present invention, the heating element preferably has a double spiral portion.

  According to the immersion heater of the present invention, the electrode portion connected to the external power source of the immersion heater is disposed above the surface of the molten metal and is isolated from the heat of the molten metal and the heat of the heating element. It is possible to prevent thermal deterioration of the electrode part and to prevent poor contact due to a difference in thermal expansion. Furthermore, unlike the above-mentioned Patent Document 2, it is not necessary to cool the electrode portion with a refrigerant, and heat transfer efficiency can be improved. Furthermore, since it is a single terminal type in which a connection with an external power source is formed in the upper part of the power transmission unit, it can be installed from the ceiling or side wall of the holding furnace, and expansion and maintenance are easy.

It is the schematic which shows the use condition by which the immersion heater of one Embodiment of this invention was immersed in the molten metal in the molten metal container of a holding furnace. It is a side view which shows the immersion heater of the said embodiment in a partial cross section. The immersion heater of the said embodiment is shown in the state except a protective tube, (a) is a top view, (b) is a side view. The immersion heater of the said embodiment is shown in the state except a protective tube, (a) is a rear view, (b) is an expanded sectional view which follows the AA line in Fig.4 (a). It is a partial side view of an immersion heater which shows the modification of arrangement | positioning of a pair of power transmission body part. (A), (b) is a partial side view of an immersion heater which shows the modification of the junction part of a power transmission body and a heat generating body, respectively.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is a schematic view showing a use state in which the immersion heater according to one embodiment of the present invention is immersed in the molten metal in the molten metal container of the holding furnace, and FIG. 2 shows a part of this immersion heater. FIG. 3 and FIG. 4 show the immersion heater with the protective tube removed, FIG. 3 (a) is a top view, and FIG. 3 (b) is a side view. 4A is a rear view, and FIG. 4B is an enlarged cross-sectional view taken along the line AA in FIG. 4A. In the following description, “up” refers to the direction from the end where the heater main body is connected to the end where the heater main body is not connected in the relationship between the one end and the other end of the power transmission unit. The opposite is the opposite. In addition, “front” refers to the direction from the end where the power transmission unit is connected to the end where the power transmission unit is not connected in the relationship between the one end and the other end of the heater body, and “back” is the opposite. It is. “Left” and “right” are defined based on “front” and “rear” defined above.

  First, as shown in FIG. 1, the molten metal container 1 has a heat insulation wall structure of a plurality of layers, in the illustrated example, three layers, rising from the bottom wall 2 and the periphery of the bottom wall 2, aluminum, zinc, It consists of a plurality of (usually four) side walls 3 that define and form a holding region S for molten metal such as brass. Although not shown, the molten metal container 1 may have a support for supporting and fixing the immersion heater 10 to the molten metal container 1.

  As shown in FIG. 1, the immersion heater 10 according to one embodiment of the present invention penetrates the heater main body 12 that may be installed substantially horizontally along the bottom wall 2 of the molten metal container 1 and the molten metal surface ML. The power transmission unit 14 that may be installed substantially vertically is provided with a bent portion 15 and has a substantially L shape in a side view, and the power transmission unit 14 has at least a lower part 14a immersed in the molten metal. The upper part 14b is exposed on the molten metal surface ML of the molten metal and has a length that allows the heater body 12 to be completely immersed in the molten metal.

  The angle of the bent portion 15, that is, the angle formed by the axial direction (extending direction) C 1 of the heater main body 12 and the axial direction (extending direction) C 2 of the power transmission unit 14 is substantially perpendicular as shown in the illustrated example. However, the present invention is not limited to this, and any angle in the range of 45 degrees to 135 degrees may be used. By making the angle between the heater main body 12 and the power transmission unit 14 less than 90 degrees or more than 90 degrees, it is possible to adapt to the molten metal containers 1 having different shapes.

  The specific configuration of the immersion heater 10 is shown in FIG. As shown in FIG. 2, the heater main body 12 of the immersion heater 10 is made of a conductive ceramic material such as silicon carbide (SiC) or SiC—Si composite material, and generates heat when energized. And a first protective tube 18 made of insulating ceramics for protecting the heating element 16 from a high-temperature molten metal. The space between the first protective tube 18 and the heating element 16 may be filled with a ceramic filler (not shown) that promotes heat transfer.

  Insulating ceramics with high insulation resistance used for the first protective tube 18 not only have high strength, high hardness, and high corrosion resistance at high temperatures, but also exhibit good thermal conductivity at high temperatures, and are good at high temperatures. Those exhibiting excellent electrical insulation can be employed. In the present invention, for example, silicon nitride, sialon, boron nitride or composite ceramics thereof can be used. In particular, silicon nitride has a small decrease in insulation resistance even at a high temperature of 800 ° C. or higher, has excellent corrosion resistance against non-ferrous metal melts such as aluminum and zinc, and has excellent thermal shock resistance, and can be suitably used.

  The power transmission unit 14 of the immersion heater 10 includes a long power transmission body 20 made of a conductive ceramic material such as silicon carbide (SiC) or a SiC-Si composite material, and a metal melt containing the power transmission body 20 therein. And the second protective tube 24 made of the same insulating ceramic material as the first protective tube 18 for protecting the power transmission body 20 from the first protective tube 18. An electrode portion 22 for connection to an external power source (not shown) is provided on an upper portion of the power transmission body 20 located outside the molten metal.

  In addition, the immersion heater 10 connects the first protective tube 18 in the heater main body 12 and the second protective tube 24 in the power transmission unit 14 in a state of crossing each other (orthogonal in the illustrated example). A bending member 26 made of an insulating ceramic material similar to the protective tube 18 and the second protective tube 24 is provided. The first protective tube 18 and the bending member 26, and the second protective tube 24 and the bending member 26 are respectively screw-bonded to each other and bonded by a heat-resistant ceramic adhesive, whereby the bonding strength and the sealing property Has been increased.

  As shown in detail in FIG. 3 and FIG. 4, the heating element 16 and the power transmission body 20 are formed in a hollow cylindrical shape as a whole, and the axial line extends from the rear end (base end) at two upper and lower positions. A pair of semi-cylindrical straight portions 30a and 30b divided into right and left by two straight slits 28a and 28b extending along the direction C1, and forward from the two straight slits 28a and 28b. And double spiral portions 34a and 34b formed by two spiral slits 32a and 32b, which are continuous with each other on the front end side of the heating element 16. doing.

  The double spiral portions 34a and 34b of the heating element 16 constitute a high heat generating portion 36 having a relatively large resistance, and the straight portions 30a and 30b constitute a low heat generating portion 38 having a relatively small resistance. The high heat generating portion 36 and the low heat generating portion 38 may be formed to have different specific resistances (specific resistance at 1000 ° C.) in addition to the difference in structure. For example, the specific resistance of the low heat generating portion 38 may be 10% or less of the specific resistance of the high heat generating portion 36. Such a specific resistance adjustment can be performed, for example, by making the ratio of Si and C different between the high heat generating portion and the low heat generating portion. Specifically, a method of impregnating the straight portions 30a and 30b with Si, or a method of joining the straight portions 30a and 30b to the SiC spiral portions 34a and 34b via the joining surface 39 using a SiC-Si composite material. Etc. As a method of joining the spiral portions 34a, 34b made of SiC and the straight portions 30a, 30b made of a SiC-Si composite material at the joining surface 39, an adhesive containing SiC, C, and a binder is used as the joining surface 39. There is a reactive sintering bonding method in which the coating is heated to a high temperature (1900 to 2100 ° C.) in a nitrogen atmosphere and reacted with molten Si and C in the adhesive. In addition, an adhesive containing SiC, C, and a binder is applied to the joint surface 39 between the spiral portions 34a and 34b made of SiC and the linear portions 30a and 30b made of a composite material of SiC-Si, and these are fixed. There is a method of bonding by heating (1450 ° C. to 1600 ° C.) under control of reduced pressure (150-1500 Pa). The straight portions 30a and 30b and the spiral portions 34a and 34b may have the same specific resistance value. Also in this case, since the spiral portions 34a and 34b have a spiral shape, the resistance absolute value of the spiral portions 34a and 34b can be made larger than the resistance absolute value of the linear portions 30a and 30b.

  The power transmission body 20 has a pair of power transmission body portions 20a and 20b that are semi-cylindrical in cross section and extend in the vertical direction, and each of the power transmission body portions 20a and 20b is made of silicon carbide (SiC) or SiC-Si. Made of a conductive ceramic material such as a composite material. It is preferable that the specific resistance in each power transmission body part 20a, 20b is made smaller than the specific resistance in the spiral parts 34a, 34b (high heat generation part 36) of the heating element 16, specifically, each power transmission body part 20a, 20b. The specific resistance at is preferably 10% or less of the specific resistance at the spiral portions 34a and 34b. In addition, the specific resistance in each power transmission body part 20a, 20b is good also as the same value as the specific resistance in the linear part 30a, 30b (low heat generation part 38) of the heat generating body 16, or substantially the same value.

  Between the pair of power transmission parts 20a and 20b, gaps 40a and 40b having a width equivalent to the width of the linear slits 28a and 28b are provided at two positions on the front and rear sides. In these gaps 40a and 40b, insulating spacers 41 and 42 made of alumina, for example, are inserted in two places on the upper and lower sides of the power transmission body 20, respectively.

  A plurality of arcuate (four in the illustrated example) fastening collars 43 made of an insulating material such as alumina are attached to the upper end portion of the power transmission body 20 located above the molten metal surface ML of the molten metal, A metal fastening band 44 is wound around the fastening collar 43. Thereby, a pair of power transmission part 20a, 20b is shape-maintained by the cylindrical shape in the upper part. Further, a pair of terminals 22a and 22b constituting the electrode unit 22 are interposed between the tightening collar 43 and the outer surfaces of the pair of power transmission units 20a and 20b.

  The lower ends of the power transmission body portions 20a and 20b are joined to the rear ends (base ends) of the linear portions 30a and 30b of the heating element 16 via the joint portion 45, respectively. That is, the lower end of one power transmission body part 20 a is joined to the rear end of one straight line part 30 a via one joint part 45, and the lower end of the other power transmission part 20 b is joined via the other joint part 45. It is joined to the rear end of the other straight part 30b. The power transmission body 20 and the heating element 16 may be an integral sintered body without the joint portion 45.

  The joining of the lower ends of the power transmission units 20a and 20b and the rear ends of the straight portions 30a and 30b of the heating element 16 is, for example, after the lower end surfaces of the power transmission units 20a and 20b and the straight portions 30a and 30b of the heating unit 16. Applying an adhesive containing SiC, C, and a binder to the end face, heating to high temperature (1900-2100 ° C.) in a nitrogen atmosphere, and reacting with molten Si and C in the adhesive, Then, an adhesive containing SiC, C, and a binder is applied to the lower end surfaces of the power transmission units 20a and 20b and the rear end surfaces of the linear portions 30a and 30b of the heating element 16, and these are subjected to a certain reduced pressure (150 to 1500 Pa). Controlled, heated (1450 ° C to 1600 ° C) bonding method, brazing using a metal material such as silver or titanium and an inorganic material such as glass or silicon, bonding using an adhesive, electron beam or laser beam It can be carried out by fusion welding. Or you may use not only these but mechanical coupling methods, such as insertion and shrink fitting.

  Further, the joint portion 45 between the power transmitting body portions 20a, 20b and the straight portions 30a, 30b is inclined at a predetermined inclination θ with respect to the axial direction C1 of the heater main body portion 12 in a side view shown in FIG. It is preferable to make it. The slope θ is more preferably in the range of 30 to 60 degrees, and more preferably in the range of 40 to 50 degrees. If it does in this way, the junction area of power transmission parts 20a and 20b and straight parts 30a and 30b can be increased, and junction strength can be raised. Further, when the heating element 16 and the power transmission body 20 are thermally expanded, a force that presses each other acts on the joint portion 45, so that the reliability of the joint portion 45 can be improved and the heat generation body 16 and the power transmission body 20 can be improved. Excessive elongation can be suppressed.

  By the way, in this embodiment, as shown in FIG. 4, a pair of power transmission body parts 20a and 20b is a direction orthogonal to both the axial direction C1 of the heater main body part 12 and the axial direction C2 of the power transmission part 14, that is, left and right Juxtaposed in the direction. According to such an arrangement, as can be seen from a comparison with the modified example shown in FIG. 5, the lengths of the pair of power transmitting body portions 20a and 20b can be made equal, and thus between the power transmitting body portions 20a and 20b. Thus, the degree of elongation due to heat can be made substantially equal, and shear stress can be prevented from occurring at the joint 45 between the heating element 16 and the power transmission parts 20a and 20b. However, in the present invention, as in the modification shown in FIG. 5, the pair of power transmitting body portions 20 a and 20 b are juxtaposed in the front-rear direction, and the linear portions 30 a and 30 b of the heating element 16 are opposed to each other in the vertical direction. It is good also as a structure where the one junction part 45 is located in a line up and down.

  In addition, when joining the heat generating body 16 and the power transmission body 20 in the junction part 45, it is not necessary to abut on each other in the L-shaped corner | angular part diagonally, and the heater main-body part 12 like the modification shown to Fig.6 (a). The joint portion 45 may be formed in parallel to the axial direction C1 of the heater, or the joint portion 45 may be formed perpendicular to the axial direction of the heater main body portion 12 as in the modification shown in FIG. Also good.

  Further, in this embodiment, as shown in FIG. 2, in the annular space between the straight portions 30 a and 30 b (low heat generation portion 38) of the heating element 16 and the first protective tube 18, heat insulation and electrical insulation are provided. A heat shield member 48 made of, for example, ceramics is provided. By providing such a heat shield member 48, loss of heat generation energy can be reduced, and the connection portion 45 between the heating element 16 and the power transmission body 20 and the connection portion between the first protective tube 18 and the bending member 26 can be reduced. The heat load can be reduced, and the reliability of the joint portion 45 and the connecting portion can be improved. In FIG. 2, a member denoted by reference numeral 49 is an insulating plate made of, for example, ceramics that insulates between the tip of the heating element 16 and the inner wall of the tip of the first protective tube 18. The insulating plate 49 also plays a role of centering the heating element 16 with respect to the first protective tube 18.

  In the immersion heater 10 having the above configuration, the substantially L-shaped immersion heater 10 in a side view has a heater main body portion 12 that extends along the bottom wall 2 of the molten metal container 1 of the holding furnace and a power transmission portion 14 that is substantially vertical. When a predetermined external power source is connected between the terminals 22a and 22b of the electrode part 22 and a voltage is applied in a state where the molten metal container 1 is filled with a high-temperature molten metal, one power transmission part 20a, one straight portion 30a, double spiral portions 34a, 34b, the other straight portion 30b, and the other power transmitting body portion 20b flow in this order, and heat is generated in the relatively high resistance spiral portions 34a, 34b. . Then, the generated heat is transmitted to the molten metal via the first protective tube 18, and the molten metal is heated or kept warm.

  At this time, the electrode part 22 of the immersion heater 10 connected to the external power source is disposed above the molten metal surface ML and is isolated from the heat of the molten metal and the heat of the heating element 16. 22 can be prevented from being deteriorated, and contact failure due to a difference in thermal expansion between the metal terminals 22a and 22b and the ceramic power transmission parts 20a and 20b can also be prevented. Further, unlike Patent Document 2, it is not necessary to circulate the refrigerant in the power transmission section (power transmission cylinder) and cool it, and the heat transfer efficiency can be improved.

  Further, according to the immersion heater 10 of the above-described embodiment, the low heat generation portion 38 is interposed between the high heat generation portion 36 of the heat generating body 16 and the joint portion 45 between the power transmission body 20 and the heat generating body 16, so The temperature rise of 45 can be suppressed, and the joining stability of the joining part 45 can be improved.

  Furthermore, according to the immersion heater 10 of the above embodiment, the heat shield member 48 is provided between the low heat generating portion 38 and the first protective tube 18, thereby reducing the loss of heat generation energy, The heat load on the joint 45 between the heating element 16 and the power transmission body 20 and the joint between the first protective tube 18 and the bending member 26 can be reduced, and the stability of the joint 45 and the joint can be further increased. This can be further improved.

  Furthermore, according to the immersion heater 10 of the said embodiment, a pair of power transmission body part 20a, 20b which comprises the power transmission body 20 is orthogonal to both the axial direction C1 of the heater main-body part 12, and the axial direction C2 of the power transmission part 14. Since the power transmission units 20a and 20b are thermally expanded due to heat generation or external heat input, the degree of extension of the two power transmission units 20a and 20b is substantially equal by being juxtaposed in the direction (that is, in the left-right direction). The shear stress at the joint 45 between the power transmission body 20 and the heating element 16 can be reduced or prevented.

  While the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described embodiment, and various modifications and additions can be made within the scope of the claims. For example, the immersion heater of the present invention may have two or more heater main bodies for one power transmission unit, and in this case, the immersion heater may be an inverted T-shape as a whole. In the above-described embodiment, the heater body has a double spiral structure, but it may be a three-phase immersion heater including a heating element having a triple spiral structure.

1 to 4, an immersion heater having the following specifications is immersed in molten aluminum for 3 days, and after immersion, the immersion heater is disassembled. When the state of the joined portion with the heating element was investigated, the electrode portion was not deteriorated by heat and the contactability was good. Also, there was no damage such as cracks at the joint, and good joint was maintained. In addition, an effective output of 2.8 kW was obtained for a rated output of 3 kW.
-Material of power transmission body: SiC-Si composite, specific resistance at 1000 ° C 0.003 Ωcm
-Material of heating element (linear part): SiC, specific resistance at 1000 ° C 0.016 Ωcm
-Material of heating element (helical part): SiC, specific resistance at 1000 ° C 0.016 Ωcm
-Materials of first and second protective tubes and bending members: Si ₃ N ₄
-Joining method between power transmission body and heating element: Reaction sintering joining-Angle between heater body and power transmission section: 90 degrees

  According to the present invention, it is possible to provide a submerged heater that is excellent in safety and durability and has good heat transfer efficiency.

DESCRIPTION OF SYMBOLS 1 Molten container 2 Bottom wall 3 Side wall 10 Immersion heater 12 Heater main-body part 14 Power transmission part 15 Bending part 16 Heating body 18 1st protective tube 20 Power transmission body 20a, 20b Power transmission body part 22 Electrode part 22a, 22b Terminal 24 2nd Protective tube 26 Bending member 28a, 28b Linear slit 30a, 30b Linear portion 32a, 32b Helical slit 34a, 34b Spiral portion 36 High heat generating portion 38 Low heat generating portion 39 Bonding surface 40a, 40b Gap 41, 42 Insulating spacer 43 Tightening collar 44 Tightening band 45 Joining portion 48 Heat shield member 49 Insulating plate C1 Axial direction of heater body C2 Axial direction of power transmission unit ML Hot water surface

Claims (10)

An immersion heater that is immersed in a molten metal to heat or keep the molten metal,
A heater main body immersed in the molten metal, and a power transmission unit that extends in a direction intersecting the heater main body through the bent portion, and whose upper portion is exposed on the molten metal surface of the molten metal,
The heater body is made of a conductive ceramic material and generates heat when energized through the power transmission unit, and a first protective tube that houses the heat generator and protects the heat generator from the molten metal Have
The power transmission unit is provided with an electrode part for connection to an external power source at an upper part located outside the molten metal, and a power transmission body made of a conductive ceramic material connected to the heating element at the lower part, and the power transmission body And a second protective tube for protecting the power transmission body from the molten metal.   The immersion heater according to claim 1, wherein the power transmission body is joined to the heating element via a joint portion.   The immersion heater according to claim 2, wherein a joint portion between the power transmission body and the heating element is inclined at a predetermined inclination with respect to an axial direction of the heater body.   The immersion heater according to claim 3, wherein the inclination is in a range of 30 to 60 degrees.   The heating element includes a high heating part and a low heating part having a smaller heating value than the high heating part, and the low heating part is disposed adjacent to a joint part between the power transmission body and the heating element. The immersion heater according to any one of claims 2 to 4, wherein   The immersion heater according to claim 5, further comprising a heat shield member between the low heat generating portion and the first protective tube.   The immersion heater according to any one of claims 2 to 6, wherein a joint portion between the power transmission body and the heating element is a sintered joint portion.   The power transmission body is composed of a pair of power transmission body portions that extend in parallel with each other in an insulated state, and the pair of power transmission body portions are orthogonal to both the axial direction of the heater main body portion and the axial direction of the power transmission portion. The immersion heater according to any one of claims 1 to 7, which is juxtaposed.   The immersion heater according to any one of claims 1 to 8, wherein the power transmission body is formed of a ceramic material having a specific resistance smaller than that of the heating element.   The said heating element is an immersion heater as described in any one of Claims 1-9 which has a double spiral part.

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