WO2025115921A1 - Heater - Google Patents

Abstract

[Problem] To provide a heater in which sealing performance of a tubular part for housing a heating element is improved in a state where cost is suppressed. [Solution] An immersion heater 1 as an example of the heater comprises: a heating element 4; a first lead wire part 6 and a second lead wire part 8 which are connected to the heating element 4; a tubular part 2 for housing the heating element 4; and a sealing part 10 for sealing the tubular part 2 while allowing the first lead wire part 6 and the second lead wire part 8 to pass through. The sealing part 10 is a cured product obtained from a liquid-like, gel-like, paste-like or powdery raw material.

Description

heater

The present invention relates to heaters, including immersion heaters, that keep molten metal, which is liquid metal, warm and heat it.

As a heater, one described in Japanese Patent Laid-Open No. 2023-84536 (Patent Document 1) is known.
In this heater, a heating element 4 is disposed within the closed tip end of a tubular portion 2. A first lead wire portion 6 and a second lead wire portion 8 are connected to the heating element 4. The open base end of the tubular portion 2 is sealed by a sealing portion with the first lead wire portion 6 and the second lead wire portion 8 passing through.
In addition, the filler, which is a powdered, highly thermally conductive filler material placed between the tubular portion 2 and the heating element 4, prevents air containing oxygen gas from coming into contact with the heating element 4, thereby preventing embrittlement of the heating element 4 due to oxidation in high-temperature environments.

JP 2023-84536 A

The suppression of embrittlement due to oxidation of the heating element 4 by the above-mentioned filler is not necessarily sufficient depending on the environment. Oxidation due to contact with air flowing in from the sealing portion of the heating element 4 progresses over a long period of time, and embrittlement and breakage due to long-term use may result in a relatively short lifespan of the heating element 4. In addition, the higher the heat generation amount of the heating element 4 and the higher the heating temperature by the heating element 4, the more easily the oxidation of the heating element 4 progresses. Therefore, there is a demand for a simple and low-cost method for suppressing oxidation of the heating element 4 in a high-temperature environment.
On the other hand, the details of the sealing portion in the heater described above are unclear, and there is room for improvement in the sealing of the tubular portion 2 by the sealing portion. If the sealing is improved, the deterioration due to oxidation in the tubular portion 2, including the heating element 4, can be further suppressed. Furthermore, since the sealing portion passes through the lead wire and is subjected to high heat, it requires insulation and heat resistance in addition to sealing, and it is required that it be formed easily and at low cost while having these properties. In particular, the heating element 4 made of a material that is less resistant to oxidation in a high-temperature environment is more required to have improved sealing. Furthermore, there may be a limit to the oxidation suppression by the filler alone, especially in a harsher environment than before, such as a high-temperature environment.
A primary object of the present invention is to provide a heater having an improved sealing performance for the tubular portion housing the heating element.
Another main object of the present invention is to provide a heater having improved sealing of a tubular portion in a simple manner and at reduced cost.

This specification discloses a heater. The heater may include a heating element. The heater may include a lead wire portion connected to the heating element. The heater may include a tubular portion that houses the heating element. The heater may include a sealing portion that seals the tubular portion while passing the lead wire portion. The sealing portion may be a cured product obtained from a liquid, gel, paste, or powder raw material.
The cured product may also be made of a siloxane material.
Furthermore, the cured product may contain at least one of quartz and alumina.

The main advantage of the present invention is that a heater is provided in which the tubular portion housing the heating element has improved sealing performance, which prevents the heating element from becoming brittle and breaking due to oxidation in a high-temperature environment, thereby extending the life of the heating element.
Another major advantage of the present invention is that a heater having improved sealing of the tubular portion is provided in a simple manner and at reduced cost.

1 is a schematic diagram of an immersion heater according to the present invention and its surroundings. 1 is a graph showing the analysis results obtained by a thermogravimetric differential thermal analyzer under condition T1 in Example 2. 1 is a graph showing the analysis results obtained by a thermogravimetric differential thermal analyzer under condition T2 in Example 2. 13 is a graph showing the analysis results obtained by a thermogravimetric differential thermal analyzer under condition T3 in Example 2. 2 is a graph showing the temperature of the sealing portion in FIG. 1 for each flow rate of air from the blower in FIG. 1 under conditions R1 to R3. 6 is a graph showing the difference in temperature of the sealing portion for each air flow rate, relative to the temperature of the sealing portion at an air flow rate of 0 L/min in FIG. 5, under conditions R1 to R3.

Hereinafter, an embodiment and modifications of the present invention will be described with reference to the accompanying drawings.
The present invention is not limited to the following embodiments and modified examples.

FIG. 1 is a schematic diagram of an immersion heater 1 as an example of a heater according to this embodiment and its surroundings.
The immersion heater 1 comprises a tubular portion 2, a heating element 4, a first lead wire portion 6, a first connection portion 7, a second lead wire portion 8, a second connection portion 9, a sealing portion 10, an insulating material 11, a filler (not shown), a support portion 12, a joint portion 14, and a blower portion 16.
The immersion heater 1 is intended to heat and keep warm the molten aluminum W, which is molten aluminum. The immersion heater 1 may be one that heats a molten aluminum metal such as zinc. The immersion heater 1 may be one that heats a molten aluminum metal such as iron. The immersion heater 1 may be one that heats other metals including iron. The immersion heater 1 may be one that heats other objects. The heater may be something other than an immersion heater.
The molten aluminum W is for use in aluminum die-cast products. However, the molten aluminum W may be used for other purposes.
When the molten aluminum W is heated, typically, the tip of the immersion heater 1 is immersed in the molten aluminum W from above, and the immersion heater 1 is positioned so that the longitudinal direction of the immersion heater 1 is in the up-down direction and the tip is on the lower side. The immersion heater 1 is immersed in the molten aluminum W through a hole H opened in a lid T of the molten metal tank. The immersion heater 1 may be used in a position other than the up-down position. Also, the molten metal tank does not need to be equipped with a lid T.

The tubular portion 2 is a cylindrical tube made of ceramics.
The tip 2P of the tubular portion 2 is closed and serves as a closed end, i.e., a sealed end, and has a semispherical shape.
The base end 2B of the tubular portion 2 is open and serves as an open end.
The material of the tubular portion 2 is not limited to ceramics. The shape of the tubular portion 2 is not limited to having a closed end and an open end, and may be, for example, a shape in which both ends are open. Furthermore, the shape of the tip portion 2P of the tubular portion 2 is not limited to a hemispherical shape.

The heating element 4 has a single coil shape as a whole, and generates heat when electricity is passed through it.
The heating element 4 is placed inside the tubular portion 2. The heating element 4 is disposed on the tip portion 2P side inside the tubular portion 2. The tubular portion 2 is disposed outside the heating element 4 and covers the heating element 4. The tubular portion 2 houses the heating element 4. The tubular portion 2 protects the heating element 4.
The heating element 4 is made of molybdenum or a molybdenum alloy. Hereinafter, the two will not be distinguished from each other and will be referred to as being made of molybdenum.
The melting point of molybdenum is about 2500° C., which is higher than the melting point of nichrome wire, which is about 1400° C., and the heat-resistant temperature of nichrome wire, which is 1150° C. Therefore, a higher heating temperature and a larger output can be obtained compared to a heating element made of nichrome wire.
The heating element 4 may be in the form of multiple coils or a plurality of coils, etc. The material of the heating element 4 may be other than molybdenum.

The first lead wire portion 6 supplies power to the heating element 4 .
The first connection portion 7 is made of metal, for example, stainless steel, and connects the heating element 4 and the first lead wire portion 6. The first connection portion 7 is interposed between the heating element 4 and the first lead wire portion 6.
The first connection portion 7 is connected to the upper end portion of the heating element 4 .
The first lead wire portion 6 is disposed outside the heating element 4. The first lead wire portion 6 and the heating element 4 are aligned in the longitudinal direction.

The second lead wire portion 8 supplies power to the heating element 4. The second lead wire portion 8 has a single-wire group portion 8G and a stranded wire portion 8B. The single-wire group portion 8G is a collection of multiple single wires. The stranded wire portion 8B is disposed on the base end side of the single-wire group portion 8G and is connected to the single-wire group portion 8G.
The second connection portion 9 is made of metal, for example, stainless steel, and connects the heating element 4 and the single-wire group portion 8G of the second lead wire portion 8. The second connection portion 9 is interposed between the heating element 4 and the second lead wire portion 8.
The second connection portion 9 is connected to the lower end portion of the heating element 4 .
The single-wire group portion 8G on the tip side of the second lead wire portion 8 passes radially inward of the heating element 4. The second lead wire portion 8 passes inside the heating element 4.

The center of the first lead wire portion 6 and the center of the second lead wire portion 8 pass through the sealing portion 10, exit upward from the upper end of the tubular portion 2, enter the support portion 12, and pass through the support portion 12.

Of the materials of the first lead wire portion 6 and the second lead wire portion 8, the material of the single-wire group portion 8G in the second lead wire portion 8 is molybdenum, and the material of the other portions is steel. The single-wire group portion 8G is a collection of multiple single wires made of molybdenum. The stranded wire portion 8B of the first lead wire portion 6 and the second lead wire portion 8 is a strand of multiple steel single wires.
The material of the first lead wire portion 6 and the material of the second lead wire portion 8 may be all molybdenum or may be all other than molybdenum. The material of the portion inside the heating element 4 may be steel and the material of the portion other than the inside of the heating element 4 may be molybdenum, or three or more materials may be combined. A part or all of the first lead wire portion 6 and the second lead wire portion 8 may be covered with an insulating coating. Furthermore, the single wire group portion 8G may be omitted and the second lead wire portion 8 may be a series of single wires, or the entire second lead wire portion 8 may be a series of single wires. The first lead wire portion 6 may have a single wire group portion, or the first lead wire portion 6 may be a series of single wires. At least one of the first lead wire portion 6 and the second lead wire portion 8 may include a rod-shaped portion that is a rod-shaped portion. Furthermore, the number of lead wire portions may be one or two or more.

The sealing portion 10 is disposed at the proximal end 2B of the tubular portion 2, and closes and seals the proximal end 2B.
The stranded wire portion 8B of the first lead wire portion 6 and the second lead wire portion 8 pass through the sealing portion 10.

Insulation 11 is disposed within tubular portion 2 adjacent seal portion 10 .
The heat insulating material 11 suppresses the transfer of heat from the molten aluminum W and the heating element 4 to the sealing portion 10 side and the support portion 12 side.
The heat insulating material 11 is, for example, at least one of ceramic fiber and glass fiber wool. The shape of the heat insulating material 11 may be a bracket shape or a fiber shape.
The heat insulating material 11 may be omitted.

The filler is filled into the tubular portion 2 .
The main component of the filler is magnesium oxide (magnesia, MgO). The main component is a component that is the majority by weight or volume. Here, the filler has 90% or more MgO by volume. MgO is a highly thermally conductive filler with excellent thermal conductivity. The thermal conductivity of MgO is about 60 W/m·K (watts per meter per Kelvin). The thermal conductivity of the filler is close to that of MgO.
The filler covers the heating element 4. The filler is in contact with the inner surface of the tip 2P of the tubular portion 2. The filler is disposed around the heating element 4 and holds the heating element 4. The filler is disposed between the tubular portion 2 and the heating element 4. The filler is filled in the area including the first connection portion 7 and further towards the tip side. The filler also enters between adjacent loop portions of the coil-shaped heating element 4. Since the filler holds the heating element 4 and enters the gaps in the heating element 4, adjacent portions of the heating element 4 are prevented from coming into contact with each other due to expansion during heat generation, etc., and the heating element 4 is protected from electric leakage.
The filler prevents oxygen from coming into contact with the heating element 4 made of molybdenum, and thus prevents the heating element 4 from being oxidized in a high-temperature environment, thereby preventing embrittlement due to oxidation.
The main component of the filler may be other than magnesium oxide. The material of the filler may be only MgO. The filler may be in a form other than powder, such as a spherical shape. Furthermore, the filler may be filled further forward than the tip of the first lead wire portion 6 and the tip of the second lead wire portion 8, or may be filled further forward than the sealing portion.

The support portion 12 is made of metal and is connected to the base end portion 2 B of the tubular portion 2 .
The support portion 12 has a connection portion 20 , a wire guide portion 22 , and a plurality of bolts 24 .
The connection portion 20 has a cylindrical portion 20T and a flange portion 20F. The cylindrical portion 20T is tubular and extends vertically. The flange portion 20F is ring-shaped and is fixed to the upper end of the cylindrical portion 20T and extends laterally.
The wire guide portion 22 has a cylindrical portion 22T and a flange portion 22F. The cylindrical portion 22T is tubular and extends vertically. The flange portion 22F is ring-shaped and is fixed to a lower end of the cylindrical portion 22T and extends laterally.
The connection portion 20 and the wire guide portion 22 are connected to each other by inserting bolts 24 in the vertical direction into the flange portions 20F, 22F that are stacked one on top of the other.

A support SP is interposed between the lower surface of the flange portion 20F and the upper surface of the lid T.
The support SP supports the immersion heater 1 .
The support SP is extendable and retractable in the vertical direction. By adjusting the vertical length of the support SP, the position of the tubular portion 2 with respect to the molten aluminum W can be adjusted.
The support SP may be omitted, and the immersion heater 1 may be supported by the hole H of the lid T. The support SP may be a component of the immersion heater 1.

The base end of the first lead wire portion 6 and the base end of the second lead wire portion 8 are connected to corresponding terminals (not shown) in the wire lead-out portion 22, and each terminal (not shown) is connected to a lead-out wire. Each lead-out wire is drawn out from the wire lead-out portion 22 to the outside and connected to a power source (not shown) via a control device (not shown). Note that the wire lead-out portion 22 does not need to accommodate each terminal, and the base end of the first lead wire portion 6 and the base end of the second lead wire portion 8 may be drawn out directly from the wire lead-out portion 22 to the outside.
The power supply here is single phase AC.
The control device controls the power from the power source to the heating element 4 to control the heat generation in the heating element 4 .
The power supply may be DC, three-phase AC, or other. The voltage of the power supply may be selected appropriately.

The joint portion 14 joins the tubular portion 2 and the support portion 12 by brazing.
The joint portion 14 is disposed between a groove portion formed on the outer surface of the base end portion 2B of the tubular portion 2 and a step portion formed on the inner surface of the tube portion 20T of the connection portion 20 of the support portion 12.
Incidentally, the tubular portion 2 and the support portion 12 may be joined by a method other than brazing.

The sealing portion 10 is disposed within the cylindrical portion 20T of the connecting portion 20. The connecting portion 20 surrounds the sealing portion 10.
The joint 14 can maintain the bond between the ceramic tubular portion 2 and the metal connecting portion 20, particularly in high-temperature environments such as when the molten aluminum W is heated, and in environments where heated and unheated states are repeatedly switched between. However, the joint 14 allows the inflow of air containing oxygen gas from the outside.

If the hermeticity is lost, the heating element 4 is oxidized and deteriorated by air that flows into the tubular portion 2 and penetrates into the gaps in the filler. In particular, in the case of a heating element 4 made of molybdenum, the loss of hermeticity of the sealing portion 10 causes rapid oxidation in a high-temperature oxygen atmosphere, shortening the lifespan.
In addition, in the immersion heater 1, the first lead wire portion 6 and the second lead wire portion 8 expand when the molten aluminum W is heated or when it is close to the molten aluminum W, and contract when it is not heated or when it is not close to the molten aluminum W, repeating expansion and contraction. The internal pressure of the sealed tubular portion 2 is greater than the outside, i.e., positive pressure, when the molten aluminum W is heated or when it is close to the molten aluminum W. On the other hand, the internal pressure of the tubular portion 2 is smaller than the outside, i.e., negative pressure, when it is not heated or when it is not close to the molten aluminum W, repeating changes between positive and negative pressure. Due to such repeated expansion and contraction of the first lead wire portion 6 and the second lead wire portion 8 and repeated changes between positive and negative pressure in the tubular portion 2, depending on the material, deterioration of the sealed portion 10 progresses, a gap is formed between the first lead wire portion 6 and the second lead wire portion 8, i.e., a lead wire gap, or a gap is generated between the tubular portion 2, i.e., a tubular portion gap. Furthermore, depending on the material, the sealing portion 10 itself may deteriorate due to repeated temperature increases when heated and decreases when not heated, causing at least one of lead wire gaps and tubular portion gaps to occur, resulting in loss of hermeticity.
Therefore, it is preferable that the sealing portion 10 be able to withstand the heat from the generated heating element 4 and the molten aluminum W, i.e., the heat during use, while maintaining its airtightness even over a long total usage time.

Therefore, various materials and physical properties were tested for the sealing portion 10 so as to withstand the heat during use, to maintain adhesion and airtightness to the first lead wire portion 6, the second lead wire portion 8, and the tubular portion 2 even over a long total usage time, and to maintain the airtightness of the tubular portion 2 without causing gaps in the lead wires or in the tubular portion.
As a result, it was found that if the sealing portion 10 has at least one of the materials and physical properties listed below, the airtightness of the tubular portion 2 can be maintained even over a long total usage time.

That is, first, the sealing portion 10 may be a cured product obtained from a liquid, gel, paste, or powder raw material. An example of the environmental temperature before curing is 25° C. That is, the sealing portion 10 may be a cured product obtained from a liquid, gel, paste, or powder raw material at 25° C.
The cured product is solid or rubbery.
Such materials include, for example, at least one of silicone and heat-resistant adhesives. Here, silicone includes silicone resin and silicone rubber. Silicon also includes organopolysiloxanes.
In this case, the liquid, gel, paste or powder raw material is hardened at 25° C. in a state where it is inserted between the single wires of the first lead wire portion 6 and the stranded wire portion 8B of the second lead wire portion 8, which are stranded wires, to form the sealing portion 10. Thus, the sealing portion 10 adheres closely to the first lead wire portion 6 and the second lead wire portion 8 without any gaps. The sealing portion 10 also adheres sufficiently to the tubular portion 2, and particularly adheres well to the ceramic tubular portion 2. Thus, the sealing portion 10 suppresses the occurrence of lead wire gaps and tubular portion gaps, and suppresses the intrusion of air into the tubular portion 2. Even if the stranded wire portion 8B of the first lead wire portion 6 and the second lead wire portion 8 is a single wire assembly portion that is an assembly of multiple single wires that are not twisted, the raw material penetrates into the gaps between the single wires, and the effect of having adhesion is exhibited, as in the case of a stranded wire.
Although natural drying may be used for hardening, heat hardening is preferred from the viewpoint of good properties and speed of formation when the sealing portion 10 is formed. The raw material may be one type of substance that is liquid, gel, paste, or powder (one-liquid type). The raw material may be two types of substances that are originally liquid, gel, paste, or powder (two-liquid type), in which case these two types of substances may be mixed to become liquid, gel, paste, or powder. The raw material may be three or more types of substances that are originally liquid, gel, paste, or powder, in which case these three or more types of substances may be mixed to become liquid, gel, paste, or powder.

Furthermore, even if the first lead wire portion 6 and the second lead wire portion 8 passing through the sealing portion 10 are rod-shaped, if the sealing portion 10 is of the above-mentioned type, oxidation of the heating element 4 due to damage to the sealing portion 10 is suppressed.
That is, the raw material of the sealing portion 10 is distributed over the surfaces of the rod-shaped first lead wire portion 6 and second lead wire portion 8, so that the occurrence of gaps in the lead wires is suppressed by the hardened sealing portion 10. Therefore, even if the rod-shaped first lead wire portion 6 and second lead wire portion 8 expand and contract in the longitudinal direction due to repeated heating and non-heating, the occurrence of gaps in the lead wires is suppressed, and the inflow of air containing oxygen gas into the tubular portion 2 is suppressed, thereby suppressing oxidation of the heating element 4.

The configuration of the sealing portion 10 may be considered to be determined by the manufacturing method, in which the sealing portion 10 is formed by hardening a raw material that is a liquid, gel, paste, or powder before hardening. Even if this is the case, it is considered that such a determination is permissible because of the existence of so-called impossible or impractical circumstances.
That is, there are a wide variety of such objects, and it is virtually impractical to directly specify the sealing portion 10 by its structure or characteristics by listing specific examples in order to distinguish it from other objects.
Moreover, the specific structure of such a cured product is currently unknown, and it is considered to be impossible or impractical to explore all kinds of such structures, since it would require a great deal of equipment and time.
Therefore, even if the sealing portion 10 is considered to be specified by the manufacturing method of being formed by hardening the above-mentioned raw material, such specification should be permitted.

Furthermore, the sealing portion 10 may be a heat-resistant insulator that can withstand heat of at least 250° C. after hardening. If the sealing portion 10 has heat resistance capable of withstanding heat of at least 250° C. during heating due to heat generated by the heating element 4, including heating of the molten aluminum W, damage to the sealing portion 10 during heating is suppressed, and damage to the immersion heater 1, including oxidation of the heating element 4, is suppressed.
Furthermore, if the sealing portion 10 is an insulator, leakage of electricity from at least one of the first lead wire portion 6 and the second lead wire portion 8 to the sealing portion 10 is suppressed, and the occurrence of a short circuit between the first lead wire portion 6 and the second lead wire portion 8 is suppressed.
In addition, if the sealing portion 10 does not expand or does not expand easily, i.e., barely expands, in an environment of 250°C or higher after curing, the occurrence of cracks due to deterioration caused by expansion or repeated expansion during heating and contraction during non-heating is suppressed. Therefore, oxidation of the heating element 4 due to air flowing in from the cracked portion is suppressed. Strictly speaking, no expansion means that the volume remains the same or decreases. On the other hand, in the present invention, no expansion includes slight expansion. However, even if slight expansion occurs in the sealing portion 10, the airtightness of the tubular portion 2 is maintained. Similarly, even if slight contraction occurs in the sealing portion 10, the airtightness of the tubular portion 2 is maintained. If the airtightness of the tubular portion 2 is maintained, the flow of air into the tubular portion 2 is suppressed, and oxidation of the heating element 4 is suppressed.

The hardened sealing portion 10 may be an elastic body, may be a non-elastic solid that does not exhibit elasticity, or may be a mixture of elastic and non-elastic portions.
An example of a mixture of elastic and non-elastic parts is an elastic body, such as silicone containing aluminum oxide (alumina), in which a part of the elastic body is made non-elastic. In the sealing part 10, which is an elastic body, the silicone component for elasticity is gradually removed from the tubular part 2 side part including the heating element 4 due to heat from the molten aluminum W and the heating element 4, and the alumina remains and becomes non-elastic. In this case, although the non-elasticity often occurs unevenly, the sealing part 10 mainly in the tubular part 2 side part becomes the non-elastic part, and the sealing part 10 mainly in the upper side (outside air side) part becomes the elastic part.

Also, the sealing portion 10 may be made of a siloxane material. Even in this case, the sealing portion 10 penetrates into the gaps in the stranded wire or adheres closely to the surface of the rod-shaped solid wire. This prevents the occurrence of gaps in the lead wire and inhibits oxidation of the heating element 4. Also, the sealing portion 10 in this case has heat resistance capable of withstanding heat of at least 250°C and is insulating.
The siloxane material is a material having a siloxane structure and used to form silicone, such as a silicone rubber material, an organohydrogenpolysiloxane material, or a reactive cyclic siloxane material, or a combination of any two or more of these.
The siloxane material is not particularly limited, but is preferably a reactive cyclic siloxane material, since it has adhesion, heat resistance, and insulating properties, and is non-expandable.
The reactive cyclic siloxane material is a material that has a cyclic siloxane structure as the main skeleton and has a plurality of reactive functional groups in one molecule.
The number of -Si-O- in the cyclic siloxane structure is not particularly limited, but from the viewpoints of ease of production and handling of the material itself, and good reactivity of the material, it is preferably 3 (trimer) or more and 10 (decamer) or less, and more preferably 3 or more and 5 or less.
The reactive functional group is not particularly limited, but from the viewpoints of ease of production and handling of the material itself, as well as good reactivity of the material and good properties when cured to form the sealing portion 10, it is preferably an organic functional group, more preferably an unsaturated hydrocarbon group, and even more preferably a vinyl group.
Moreover, each Si in the cyclic siloxane structure can bond to two groups in addition to the bonds with the adjacent O on both sides in the main skeleton. Therefore, from the viewpoint of good reactivity of the material and good properties when cured to form the sealing part 10, it is preferable that all Si in the cyclic siloxane structure have one reactive functional group.
The reactive cyclic siloxane material is, for example, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane represented by the following formula (1). The reactive cyclic siloxane material of formula (1) is a tetramer. Each of the four Si in the reactive cyclic siloxane material of formula (1) has one vinyl group, -CH= _CH2 , as a reactive functional group.

The configuration of the sealing portion 10 may be considered to be specified by the manufacturing method of forming it using a siloxane material, and even if this is the case, it is considered that such a specification is permissible because there are so-called impossible or impractical circumstances.
That is, there are a wide variety of siloxane materials that have a siloxane structure but differ in the number of --Si--O- groups and the type and arrangement of reactive functional groups, and it is therefore not practical to directly specify the sealing portion 10 by its structure or characteristics by listing specific examples in order to distinguish it from other polymers.
Furthermore, the specific structure of the product after reaction of such siloxane materials is a polymer structure and differs with each cure, and it is believed that exploring all types of such structures would be impossible or impractical, as it would require a great deal of equipment and time.
Therefore, even if the sealing portion 10 is considered to be specified by a manufacturing method using a siloxane material, such a specification should be permitted.

The sealing portion 10 may be formed only from a siloxane material, but from the viewpoint of good characteristics when it becomes the sealing portion 10, it may be formed by adding at least one of alumina, quartz, zinc oxide, and carbon black. Alternatively, the sealing portion 10 may be formed from at least one of a siloxane material, alumina, quartz, zinc oxide, and carbon black. The sealing portion 10 has the effect of preventing the inflow of air into the tubular portion 2, which causes the acceleration of oxidation of the heating element 4, even when exposed to high temperatures.
Furthermore, the amounts of these materials, in other words the composition of the composite material, are not particularly limited, but from the viewpoint of ease of formation and good properties when it becomes the sealing part 10, it may preferably be a composition related to the following two liquids (agent A and agent B) that are mixed and cured. Here, "x to y" represents x or more and y or less, and the same applies below. At least one of the agents A and B may be adjusted so that the total parts by mass is 100 parts by mass.
Agent A: 40-50 parts by weight of alumina, 30-40 parts by weight of quartz, 0.25-1 part by weight of zinc oxide, 0.1-1 part by weight of carbon black Agent B: 30-40 parts by weight of alumina, 30-40 parts by weight of quartz, 0.3-1.0 part by weight of reactive cyclic siloxane material

The siloxane material can be cured in any manner, including natural drying, but is preferably cured by heat from the standpoint of good properties when it becomes the sealing portion 10 and the speed of formation.

Furthermore, the sealing portion 10 may be formed from a material containing organohydrogenpolysiloxane. Examples of materials containing organohydrogenpolysiloxane include those described in International Publication No. 2019/021824. In this case, as with reactive cyclic siloxane materials, a sealing portion 10 is formed that has excellent gas inflow prevention properties, heat resistance, insulation properties, and non-expansion properties.

The blower 16 blows air N toward the sealing portion 10 .
The blower 16 is a single fan.
The air blowing section 16 is capable of air-cooling the sealing section 10 .
The blower 16 may be a plurality of fans, a blower duct, or a combination of a fan and a blower duct. Also, the blower 16 may be omitted.

In order to expose the sealing portion 10 to the outside air, one or more openings 20P are provided in the cylindrical portion 20T from the outside to the inside in the radial direction. Therefore, a part of the outer surface of the sealing portion 10 on the outside in the radial direction is exposed to the outside air through the openings 20P. The support SP is arranged so as not to block the openings 20P. The openings 20P are arranged above the joint portion 14.
Opening 20P allows outside air to come into contact with sealing portion 10, thereby cooling sealing portion 10.
The opening 20P may be provided commonly to the tubular portion 2 and the cylindrical portion 20T as long as it can expose the sealing portion 10. Also, the opening 20P may be omitted.

An example of a method for manufacturing the immersion heater 1 will now be described.
First, the first connection portion 7 is connected to the tip end of the first lead wire portion 6 , and the first connection portion 7 is connected to the base end of the heating element 4 .
Further, a second connection portion 9 is connected to the tip portion of the second lead wire portion 8 , and the second connection portion 9 is connected to the tip portion of the heating element 4 .
Next, the integrated heating element 4 , first lead wire portion 6 , first connection portion 7 , second lead wire portion 8 , and second connection portion 9 are placed inside the tubular portion 2 .

Next, filler and insulating material 11 are placed inside the tubular portion 2 .
Furthermore, a support portion 12 is disposed outside the base end portion of the first lead wire portion 6 and outside the base end portion of the second lead wire portion 8 .
Subsequently, the tubular portion 2 and the support portion 12 are joined by forming a joint 14 .
In addition, the base end of the first lead wire portion 6 and the base end of the second lead wire portion 8 are connected to a terminal.

Here, the sealing portion 10 is formed by pouring a liquid, gel, paste or powder material into the base end of the tubular portion 2 and allowing it to dry naturally or harden by heating.
In forming the sealing portion 10, the raw material sealing portion 10 before hardening may be subjected to an external force such as compression in a state where it is inserted into the base end of the tubular portion 2 and arranged around the first lead wire portion 6 and the second lead wire portion 8. When such an external force application process is performed, the sealing portion 10 penetrates further into the gap between the stranded first lead wire portion 6 and the second lead wire portion 8, or adheres more closely to the surfaces of the rod-shaped first lead wire portion 6 and the second lead wire portion 8.

Additionally, the seal 10 is preferably fabricated from at least one of a reactive cyclic siloxane material and a material containing an organohydrogenpolysiloxane.
In particular, when the sealing portion 10 is manufactured from the above-mentioned components A and B, the gel-like mixture of components A and B is placed at the base end of the tubular portion 2 and placed in an environment at a predetermined temperature, for example 100° C. or higher, for a predetermined period of time, for example 30 minutes, or longer, and is thermally cured.

An example of the operation of such an immersion heater 1 will now be described.
A user turns on the power to generate heat from the heating element 4 of the immersion heater 1. The heat from the heating element 4 is efficiently transferred to the tubular portion 2 by the filler. Also, the heat insulating material 11 suppresses the transfer of heat to the base end side.
The user can heat the molten aluminum W by immersing the tip of the tubular portion 2 from above into the molten aluminum W in the molten metal tank, through heat transfer from the heating element 4 through the filler and the tubular portion 2.
The amount of heat generated by the heating element 4 is controlled by a control device. Here, a temperature sensor (not shown) electrically connected to the control device detects the temperature of the molten aluminum W and transmits a temperature signal indicating that temperature to the control device, and the control device controls the amount of heat generated by the heating element 4 according to the temperature associated with the received temperature signal. Note that the heating element 4 may be driven at a constant output without temperature control.
The maximum heat generation (maximum output) of the heating element 4 can be made larger by using a heating element 4 made of molybdenum than by using a heating element made of nichrome. The oxidation of molybdenum, which leads to embrittlement of the heating element 4, is suppressed by disposing a filler around the heating element 4.

Furthermore, the above-mentioned sealing portion 10 suppresses the occurrence of at least one of gaps in the lead wire and gaps in the tubular portion even if the immersion heater 1 is repeatedly turned on and off and moved close to and away from the molten aluminum W. This prevents air containing oxygen gas from flowing into the tubular portion 2, and suppresses oxidation of the heating element 4.
Furthermore, if the sealing portion 10 is air-cooled by the air blowing portion 16, deterioration of the sealing portion 10 due to heat is further suppressed, and the life of the sealing portion 10 is further extended.

The above-described immersion heater 1 provides the following functions and effects.
That is, the immersion heater 1 comprises a heating element 4, a first lead wire portion 6 and a second lead wire portion 8 connected to the heating element 4, a tubular portion 2 that houses the heating element 4, and a sealing portion 10 that seals the tubular portion 2 while allowing the first lead wire portion 6 and the second lead wire portion 8 to pass through. The sealing portion 10 is a hardened product obtained from a liquid, gel, paste, or powder raw material.
Therefore, an immersion heater 1 having improved sealing performance of the tubular portion 2 housing the heating element 4 can be provided more simply and at reduced cost.

Moreover, the sealing portion 10 is a heat-resistant insulator that can withstand heat of at least 250° C. Therefore, the sealing and insulating properties of the sealing portion 10 are maintained in a high-temperature environment, and the first lead wire portion 6 and the second lead wire portion 8 are insulated while oxidation of the heating element 4 is suppressed.
Furthermore, the sealing portion 10 does not expand in an environment of 250° C. or higher. Therefore, the occurrence of cracks in the sealing portion 10 in a high-temperature environment is suppressed, and oxidation of the heating element 4 due to air flowing in through cracks is suppressed.
Furthermore, the sealing portion 10 prevents air from flowing into the tubular portion 2. Thus, the immersion heater 1 is provided with improved sealing performance of the tubular portion 2 housing the heating element 4.
Furthermore, the sealing portion 10 is made of at least one of a siloxane material, alumina, quartz, zinc oxide, and carbon black, so that the immersion heater 1 can be provided with improved sealing performance of the tubular portion 2 housing the heating element 4 in a simpler manner and at a reduced cost.

In addition, the immersion heater 1 includes a heating element 4, a first lead wire portion 6 and a second lead wire portion 8 connected to the heating element 4, a tubular portion 2 that houses the heating element 4, and a sealing portion 10 formed of a siloxane material that seals the tubular portion 2 while allowing the first lead wire portion 6 and the second lead wire portion 8 to pass through.
Therefore, an immersion heater 1 having improved sealing performance of the tubular portion 2 housing the heating element 4 can be provided more simply and at reduced cost.

In addition, the siloxane material is a reactive cyclic siloxane material. Therefore, the immersion heater 1 having the tubular portion 2 housing the heating element 4 and having improved sealing performance can be provided more simply and at a reduced cost.
Furthermore, the reactive cyclic siloxane material is 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane. Therefore, the immersion heater 1 having the tubular portion 2 housing the heating element 4 and having improved sealing performance can be provided more simply and at reduced cost.
Furthermore, the sealing portion 10 is formed from a siloxane material and at least one of alumina, quartz, zinc oxide, and carbon black, thereby providing the immersion heater 1 with improved sealing performance of the tubular portion 2 housing the heating element 4 in a simpler manner and at reduced cost.

In addition, the immersion heater 1 includes a heating element 4, a first lead wire portion 6 and a second lead wire portion 8 connected to the heating element 4, a tubular portion 2 that houses the heating element 4, and a sealing portion 10 including at least one of quartz and alumina that seals the tubular portion 2 while allowing the first lead wire portion 6 and the second lead wire portion 8 to pass through.
Therefore, an immersion heater 1 having improved sealing performance of the tubular portion 2 housing the heating element 4 can be provided more simply and at reduced cost.

Moreover, the heating element 4 and at least one of the first lead wire portion 6 and the second lead wire portion 8 are made of molybdenum. Therefore, the sealing performance of the tubular portion 2 housing the heating element 4 made of molybdenum, which is more susceptible to oxidation and embrittlement in high-temperature environments than other materials, is improved more simply and at reduced cost.
Furthermore, the first lead wire portion 6 and the second lead wire portion 8 include a stranded wire portion 8B. Thus, the sealing portion 10 is formed with the liquid, gel, paste or powdery raw material entering the stranded wire portion 8B, and the sealing property of the tubular portion 2 housing the heating element 4 is improved more simply and at a reduced cost. Even if the first lead wire portion 6 and the second lead wire portion 8 include a single wire assembly portion which is an assembly of a plurality of single wires, the same effect as in the case of the stranded wire portion 8B can be achieved.
Furthermore, even if the first lead wire portion 6 and the second lead wire portion 8 include a rod-shaped portion, the sealing portion 10 is formed in a state where the liquid, gel, paste or powdery raw material is in close contact with the surface of the rod-shaped portion. This improves the airtightness of the tubular portion 2 that houses the heating element 4 more simply and at reduced cost.

Furthermore, the immersion heater 1 is provided with a blower 16 that blows air N to the sealing portion 10 .
Additionally, the tubular portion 2 has an opening 20P for exposing the sealing portion 10 to the outside air.
Therefore, the life of the sealing portion 10 is further extended by cooling.

Furthermore, the immersion heater 1 includes a heating element 4, a first lead wire portion 6 and a second lead wire portion 8 connected to the heating element 4, a tubular portion 2 that houses the heating element 4, a sealing portion 10 that seals the tubular portion 2 while allowing the first lead wire portion 6 and the second lead wire portion 8 to pass through, and a blower portion 16 that blows air toward the sealing portion 10.
Therefore, the sealing portion 10 is cooled by the air blown therethrough, which further extends the life of the sealing portion 10.

The immersion heater 1 also comprises a heating element 4, a first lead wire portion 6 and a second lead wire portion 8 connected to the heating element 4, a tubular portion 2 that houses the heating element 4, a sealing portion 10 that seals the tubular portion 2 while allowing the first lead wire portion 6 and the second lead wire portion 8 to pass through, and a connection portion 20 that surrounds the sealing portion 10. The connection portion 20 has an opening 20P for exposing the sealing portion 10 to the outside air, and thus the sealing portion 10 is cooled by the outside air through the opening 20P. This further extends the life of the sealing portion 10.

Hereinafter, more specific examples according to the above-described embodiment of the present invention will be described.
However, the present invention is not limited to the following examples.

In Example 1, a one-component heat-resistant silicone was used as the sealing portion 10, which was formed by hardening one gel-like raw material. More specifically, the gel-like raw material was filled into the base end of the tubular portion 2, and was heated and hardened by being placed in an environment of 100° C. for 60 minutes.
As Example 2, a sealing portion 10 was produced that was a two-liquid type heat-resistant silicone formed from the above-mentioned components A and B. More specifically, the above-mentioned components A and B were mixed together to form a paste-like raw material, which was then filled into the base end of the tubular portion 2 and placed in an environment of 100° C. for 60 minutes to be heat-cured.

The sealing portions 10 according to both Examples 1 and 2 were excellent in gas inflow prevention properties, heat resistance, insulation properties, and non-expansion properties after curing.
Comparing these, the sealing portion 10 of Example 2 was more excellent in preventing the inflow of gas than the sealing portion 10 of Example 1, and furthermore, exhibited better durability in the durability test.

Composition analysis and hardness measurements were performed under various conditions on samples of the sealing portion 10 of Examples 1 and 2, which were smaller in size than the actual sealing portion 10 but formed in the same manner as the actual sealing portion 10 and had the same composition.
The results of the composition analysis of Example 1 are shown in Table 1 below, and the results of the composition analysis of Example 2 are shown in Table 2 below. Note that the units of values in Tables 1 and 2 are mass %, and when the total is less than 100 mass %, the remainder may be considered to be carbon atoms.
Condition A is when heating is performed for 41 hours in a temperature environment of 250°C. Condition B is when heating is performed for 8 hours in a temperature environment of 400°C. Condition C is when heating is performed for 8 hours in a temperature environment of 400°C, followed as soon as possible by heating for 1 hour in a temperature environment of 700°C. Condition D is when a temperature environment of 1000°C is created over 4 hours and heating is performed in that environment for 4 hours. Condition E is when 8 hours of heating in a temperature environment of 250°C is performed as one set, one set per day for three consecutive days, for a total of three sets. Condition F is when heating is performed for 8 hours in a temperature environment of 600°C.
The results of the hardness measurement in Example 1 are shown in Table 3 below, and the results of the hardness measurement in Example 2 are shown in Table 4 below. The larger the hardness value, the harder the material is. The letter "A" before the value indicates that the shape of the probe used in the measurement was type A.

As shown in Table 1, the main composition of Example 1 was 34 mass% oxygen atoms (O), 61 mass% silicon atoms (Si), and 4 mass% aluminum atoms (Al) before exposure to heat (unheated). After heating under condition A, the main composition of Example 1 was 30 mass% O, 62 mass% Si, and 7 mass% Al. After heating under condition B, the main composition of Example 1 was 42 mass% O, 51 mass% Si, and 6 mass% Al. After heating under condition C, the main composition of Example 1 was 48 mass% O, 40 mass% Si, and 11 mass% Al. After heating under condition D, the main composition of Example 1 was 49 mass% O, 44 mass% Si, and 6 mass% Al.
According to the main composition of Example 1, as the thermal conditions become severer, the mass ratio of oxygen atoms increases and the mass ratio of silicon atoms relatively decreases. On the other hand, the oxygen atoms are limited to 49 mass% at the upper limit and the silicon atoms are limited to 40 mass% at the lower limit. Thus, the sealing portion 10 of Example 1 allows oxidation and partial inelasticity due to heating, but the oxidation and partial inelasticity are limited to a predetermined level. Conventionally, the cross-sectional area of the heating element 4 of a predetermined material was reduced by about 50% in some places due to oxidation based on long-term use, even if a filler was added. In contrast, in Example 1, the cross-sectional area of the heating element 4 of the same material as the conventional one is expected to be reduced by a maximum of about 10% during the same period of use. Therefore, the sealing portion 10 of Example 1 can maintain a seal that suppresses oxidation of the heating element 4.

As shown in Table 2, the main composition of Example 2 was 53% by mass of O, 32% by mass of Si, and 15% by mass of Al before heating. After heating under condition E, the main composition of Example 2 was 51% by mass of O, 33% by mass of Si, and 16% by mass of Al. After heating under condition B, the main composition of Example 2 was 58% by mass of O, 24% by mass of Si, and 18% by mass of Al. After heating under condition F, the main composition of Example 2 was 61% by mass of O, 25% by mass of Si, and 14% by mass of Al. After heating under condition D, the main composition of Example 2 was 61% by mass of O, 23% by mass of Si, and 16% by mass of Al.
According to the main composition of Example 2, as the thermal conditions become severer, the mass ratio of oxygen atoms increases, and the mass ratio of silicon atoms decreases relatively. On the other hand, the oxygen atoms are limited to 61 mass% at the upper limit and the silicon atoms are limited to 23 mass% at the lower limit. Therefore, although the sealing portion 10 of Example 2 allows oxidation and partial inelasticity due to heating, the oxidation and partial inelasticity are limited to a predetermined level. Furthermore, the sealing portion 10 of Example 2 has a larger mass ratio of aluminum atoms than the sealing portion 10 of Example 1. Conventionally, the cross-sectional area of the heating element 4 of a predetermined material was reduced by about 50% in some places due to oxidation based on long-term use, even if a filler was added. In contrast, in Example 2, the cross-sectional area of the heating element 4 of the same material as the conventional one is expected to be reduced by a maximum of about 5% when used for the same period of time. Therefore, the sealing portion 10 of Example 2 can maintain a seal that suppresses oxidation of the heating element 4.

Moreover, as shown in Table 3, the hardness of Example 1 was A35 as the average (average hardness) of five measurements when not heated. After heating under condition A, the average hardness of Example 1 was A22. After heating under conditions B, C, and D, the hardness of Example 1 could not be measured because the sample was in a powder form during hardness measurement. *1 in Tables 3 and 4 indicates that the hardness could not be measured because the sample was in a powder form.
According to the hardness of Example 1, as the thermal conditions become severer, the sealing portion 10 of Example 1 becomes softer. Therefore, it can be said that the sealing portion 10 of Example 1 gradually softens to maintain the sealing.

On the other hand, as shown in Table 4, the hardness of Example 2 was A62 as an average (average hardness) of five measurements without heating. After heating under condition E, the hardness of Example 2 was A65 as an average hardness. After heating under condition B, the hardness of Example 2 was A82 as an average hardness. However, in two of the five hardness measurements of Example 2 after heating under condition B, the hardness could not be measured because the durometer needle penetrated the sample surface. Therefore, the average hardness of Example 2 after heating under condition B is the average value of three measurements. After heating under conditions F and D, the hardness of Example 2 could not be measured because the sample was powdery in the hardness measurement. *2 in Table 4 indicates that the hardness could not be measured because the durometer needle penetrated the sample surface in the hardness measurement.
According to the hardness of Example 2, as the thermal conditions become severer, the sealing portion 10 of Example 2 becomes harder. Therefore, it can be said that the sealing portion 10 of Example 2 gradually hardens to maintain the sealing.

The above samples of Example 2, which had not been subjected to any tests including the composition analysis and hardness measurement, were analyzed by a thermogravimetric differential thermal analyzer (TG-GTA) after heating under the following conditions. The weight of each sample was about 10 mg. Each sample was placed in an open alumina container.
Condition T1 is when the temperature is increased from 40° C. to 300° C. in air, and then the heating is maintained in a temperature environment of 300° C. for 8 hours. Condition T2 is when the temperature is increased from 40° C. to 350° C. in air, and then the heating is maintained in a temperature environment of 350° C. for 8 hours. Condition T3 is when the temperature is increased from 40° C. to 500° C. in air, and then the heating is maintained in a temperature environment of 500° C. for 8 hours.
In all of the conditions T1 to T3, the temperature rise rate was 5° C./min. In addition, in all of the conditions T1 to T3, air was introduced into the heating furnace at a flow rate of 200 mL/min during heating.

Fig. 2 is a graph showing the results of the thermogravimetric differential thermal analysis under condition T1, Fig. 3 is a graph showing the results of the thermogravimetric differential thermal analysis under condition T2, and Fig. 4 is a graph showing the results of the thermogravimetric differential thermal analysis under condition T3.
2 to 4, the horizontal axis represents the elapsed time (min) from the start of heating the sample, and the vertical axis represents temperature (° C.), TG (%), and DTA (μV). TG is the rate of decrease in thermal mass from the initial value, and DTA is differential thermal.
2 to 4, the solid line indicates temperature, the dashed line indicates TG, and the broken line indicates DTA.

First, the behavior of the weight change temperature obtained from the results of differential thermal analysis will be explained.
Under condition T1, the DTA curve shows a small peak immediately after the start of the analysis, and then continues to decrease uniformly until about 60 minutes later when the temperature reaches 300° C. Thereafter, the DTA curve remains flat until the end of the measurement, and no peak is observed.
In condition T2, the DTA curve shows a small peak just after the start of the analysis, similar to condition T1, and then shows one large peak at 70 to 75 min, which corresponds to between 300°C and 350°C. The temperature CR at the time indicated by the intersection of the extrapolated line U1 of the DTA curve before the minimum value of the DTA curve just before the peak and the extrapolated line U2 of the DTA curve after the minimum value was 329°C. Here, looking at the TG curve of condition T2, weight loss is observed at approximately the same temperature as the temperature CR. Therefore, it can be said that the weight change temperature in Example 2 is 329°C. In addition, in condition T2, after reaching 350°C, the DTA curve remains flat until the end of the measurement, and no peak is observed.
In condition T3, the DTA curve showed a small exothermic peak immediately after the start of the analysis, similar to conditions T1 and T2, and then showed a large broad peak on the high temperature side at 70 to 75 min, which corresponds to between 300°C and 350°C. This peak is considered to be the same as the peak observed in condition T2, and the temperature CS at the time when the two extrapolated lines V1 and V2 intersect is 329°C, the same as the temperature CR in condition T2. Furthermore, the DTA curve in condition T3 showed multiple peaks from 90 to 100 min, which corresponds to between about 450°C and 500°C. The temperature CT at the time indicated by the intersection of the extrapolated line W1 of the DTA curve before the immediately previous minimum value and the extrapolated line W2 of the DTA curve after the minimum value, which corresponds to the first peak among the multiple peaks of the DTA curve, was 450°C. Looking at the TG curve in condition T3, a weight loss is observed at the time corresponding to the temperature CT. Therefore, it can be said that there are at least two weight change temperatures in Example 2, with the first stage weight change temperature being 329°C, which corresponds to temperature CS, and the second stage weight change temperature being 450°C, which corresponds to temperature CT.
The weight change temperatures under conditions T1 to T3 are summarized in Table 5 below.

According to such weight change temperature behavior, it can be said that Example 2 undergoes the first comprehensive composition change at 329°C, which is higher than 250°C.
Therefore, Example 2 can withstand heat of at least 250° C. Furthermore, Example 2 does not expand in an environment of 250° C. or higher.

Next, the behavior of the TG reduction rate obtained from the thermal mass differential thermal analysis results will be explained.
For the average value of the DTA in the period starting from 420 minutes after the holding temperature was reached and ending from 480 minutes after the holding temperature was reached under condition T1, i.e., the stable DTA average value, the point at which the DTA first enters the range from the lower limit value corresponding to 99% of the stable DTA average value to the upper limit value corresponding to 101% of the stable DTA average value is set as the baseline stabilization start time BS1 under condition T1. Similarly, for the stable DTA average value under condition T2, the point at which the stable DTA first enters the range is set as the baseline stabilization start time BS2 under condition T2. Also, for the stable DTA average value under condition T3, the point at which the stable DTA first enters the range is set as the baseline stabilization start time BS3 under condition T3.
The TG reduction rates (%) at the following three time points are summarized in Table 6 below. The three time points are, for condition T1, time point TA1 when the holding temperature is reached, time point BS1 when the baseline stabilization starts, and time point 8 hours after the holding temperature is reached. The three time points are, for condition T2, time point TA2 when the holding temperature is reached, time point BS2 when the baseline stabilization starts, and time point 8 hours after the holding temperature is reached. The three time points are, for condition T3, time point TA3 when the holding temperature is reached, time point BS3 when the baseline stabilization starts, and time point 8 hours after the holding temperature is reached.

According to such behavior of the decrease rate of TG, Example 2 has a low decrease rate at 300° C., which is higher than 250° C., and it can be said that no deterioration such as global combustion, sublimation, or evaporation occurs in Example 2 under condition T1, which is related to a holding temperature of 300° C. Furthermore, it can be said that deterioration such as global combustion, sublimation, or evaporation occurs gradually in Example 2 after the holding temperature reaches 350° C. under condition T2, which is related to a holding temperature of 350° C. Furthermore, it can be said that deterioration due to global combustion, sublimation, evaporation, or the like occurs relatively early in Example 2 after the holding temperature reaches 500° C. under condition T1, which is related to a holding temperature of 500° C.
Therefore, Example 2 can withstand heat of at least 250° C. Furthermore, Example 2 does not expand in an environment of 250° C. or higher.

Meanwhile, the temperature of the sealed portion 10 of the immersion heater 1 in which the sealed portion 10 was actually formed according to Example 2 was measured under specific conditions.
Such temperature measurements were performed under roughly four different conditions depending on the presence or absence of the opening 20P communicating with the sealing portion 10 and the presence or absence of the lid T.
The temperature was measured for each type of condition with the output of the immersion heater 1 set to five levels: 0 kW (i.e., not lit), 1 kW, 2 kW, 3 kW, and 4 kW.
Furthermore, the temperature was measured one hour after the storage of the molten aluminum W was completed.

Specifically, the vertical length of the heating element 4, which corresponds to the arrow LH in FIG. 1, is 200 mm. The vertical length from the lower surface of the heat insulating material 11 to the tip 2P of the tubular portion 2, which corresponds to the arrow LF in FIG. 1, is 550 mm. Filler is filled from the lower surface of the heat insulating material 11 to the tip 2P of the tubular portion 2. The vertical length of the sealing portion 10, which corresponds to the arrow LS in FIG. 1, is 30 mm. The vertical length of the heat insulating material 11, which corresponds to the arrow LI in FIG. 1, is 550 mm. The distance from the lower surface of the lid T to the upper surface of the molten aluminum W, which corresponds to the arrow LP in FIG. 1, is 80 mm. In the absence of the lid T, the arrow LP corresponds to the distance from the upper surface of the wall of the storage portion of the molten aluminum W to the upper surface of the molten aluminum W. The depth from the upper surface of the molten aluminum W to the upper end of the heating element 4, which corresponds to the arrow LD in FIG. 1, is 150 mm.
Furthermore, the temperature of the molten aluminum W is 680°C. The vertical depth of the stored molten aluminum W is 457 mm. The vertical length of the tubular portion 2 is 600 mm. One opening 20P is provided in a circular shape, and its diameter is 5 mm. Furthermore, the temperature of the sealing portion 10 in Example 2 was measured using a thermocouple. The temperature measurement point of the sealing portion 10 in Example 2 was 10 mm below the upper surface of the sealing portion 10, and inside the sealing portion 10.
The temperature measurement results are shown in Table 7 below.

According to Table 7, when the lid T is present, the temperature of the sealing portion 10 when the opening 20P is present is lower than when the opening 20P is not present, at any output, and the difference between the two is about 15° C. Also, when the lid T is not present, the temperature of the sealing portion 10 when the opening 20P is present is lower than when the opening 20P is not present, at any output, and the difference between the two is about 35° C.
In this way, when the opening 20P is provided, the temperature rise of the sealing portion 10 is suppressed compared to when the opening 20P is not provided. This temperature suppression effect is more noticeable when the lid T is not provided.
Moreover, the situation in which the temperature is measured is often seen when handling molten aluminum W. The temperature of the sealing portion 10 is 179° C. when the lid T is provided and the opening 20P is not provided, and is 177° C. when the lid T is not provided and the opening 20P is not provided, even at an output of 4 kW. Therefore, if the sealing portion 10 has a heat resistance capable of withstanding heat of at least 250° C., that is, if the heat-resistant temperature of the sealing portion 10 is 250° C. or higher, then the sealing portion 10 will have sufficient durability.

On the other hand, the relationship between the air volume from the blower 16, i.e., the air flow rate, and the temperature of the sealing portion 10 was measured under the above-mentioned specific conditions. However, in the measurement of the air flow rate, the lid T was provided, but the opening 20P was not provided.
The air flow rate was measured under the following three conditions R1 to R3. That is, first, condition R1 corresponds to the arrow LA in Fig. 1, where the distance from the lid T to the bottom end of the sealing part 10 is 80 mm and the output of the immersion heater 1 is 6 kW. Next, condition R2 corresponds to the distance from the lid T to the bottom end of the sealing part 10 is 80 mm and the voltage of the immersion heater 1 is 200 V. Next, condition R3 corresponds to the distance from the lid T to the bottom end of the sealing part 10 is 5 mm and the voltage of the immersion heater 1 is 200 V.

Fig. 5 is a graph showing the temperature of the sealing portion 10 for each air flow rate under these three conditions R1 to R3. Fig. 6 is a graph showing the temperature difference for each air flow rate with respect to the temperature of the sealing portion 10 when the air flow rate is 0 L/min under these three conditions R1 to R3. An air flow rate of 0 L/min corresponds to no air being blown from the blower 16.
5 and 6, under any of the three conditions R1 to R3, the temperature of the sealing portion 10 decreases more significantly as the air flow rate increases. Under conditions R1 and R2, the temperature decreases by 100° C. or more at an air flow rate of 50 L/min or more. Moreover, under condition R3, the temperature decreases by 150° C. or more at an air flow rate of 60 L/min.
Therefore, the sealing portion 10 is sufficiently cooled by the wind from the blower 16. This further extends the life of the sealing portion 10.

1: Immersion heater (heater), 2: Tubular portion, 4: Heating element, 6: First lead wire portion, 7: First connection portion, 8: Second lead wire portion, 9: Second connection portion, 10: Sealing portion, 11: Insulating material, 12: Support portion, 14: Joint portion, 16: Blowing portion, N: Air, 20P: Opening portion.

Claims (17)

A heating element;
A lead portion connected to the heating element;
A tubular portion that houses the heating element;
a sealing portion that seals the tubular portion while passing the lead wire portion;
Equipped with
The sealing portion is
A heater characterized in that it is a cured product obtained from a liquid, gel, paste or powder raw material. 2. The heater according to claim 1, wherein the cured material is a heat-resistant insulating material that can withstand heat of at least 250°C. 2. The heater according to claim 1, wherein the cured product does not expand in an environment of 250° C. or higher. The heater according to claim 1 , wherein the hardened material prevents air from flowing into the tubular portion. 2. The heater according to claim 1, wherein the cured material is made of at least one of a siloxane material, alumina, quartz, zinc oxide, and carbon black. A heating element;
A lead portion connected to the heating element;
A tubular portion that houses the heating element;
a sealing portion that seals the tubular portion while passing the lead wire portion;
Equipped with
The heater, wherein the sealing portion is made of a siloxane material. 7. The heater of claim 6, wherein the siloxane material is a reactive cyclic siloxane material. 8. The heater of claim 7, wherein the reactive cyclic siloxane material is 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane. 7. The heater according to claim 6, wherein the sealing portion is formed from the siloxane material and at least one of alumina, quartz, zinc oxide, and carbon black. A heating element;
A lead portion connected to the heating element;
A tubular portion that houses the heating element;
a sealing portion that seals the tubular portion while passing the lead wire portion;
Equipped with
The sealing portion is
A heater comprising at least one of quartz and alumina. 11. The heater according to claim 1, 6 or 10, wherein at least one of the heating element and the lead wire portion is made of molybdenum or a molybdenum alloy. 11. The heater according to claim 1, 6 or 10, wherein the lead wire portion includes a stranded wire portion or a single wire assembly portion which is an assembly of a plurality of single wires. 11. The heater according to claim 1, 6 or 10, wherein the lead wire portion includes a rod-shaped portion. 11. The heater according to claim 1, further comprising a blower for blowing air to the sealed portion. Further, a connection portion is provided surrounding the sealing portion,
11. The heater according to claim 1, 6 or 10, wherein the connection portion has an opening for exposing the sealing portion to the outside air. A heating element;
A lead portion connected to the heating element;
A tubular portion that houses the heating element;
a sealing portion that seals the tubular portion while passing the lead wire portion;
A blower unit that blows air to the sealing portion;
A heater comprising: A heating element;
A lead portion connected to the heating element;
A tubular portion that houses the heating element;
a sealing portion that seals the tubular portion while passing the lead wire portion;
A connection portion surrounding the sealing portion;
Equipped with
The heater is characterized in that the connection portion has an opening for exposing the sealing portion to the outside air.

Images