JP6794559B2 - Immersion heater for molten non-ferrous metal - Google Patents

Description

The present invention relates to a dipping heater for a non-ferrous metal molten metal that is put into a non-ferrous metal molten metal such as aluminum and zinc to heat the molten metal. It relates to an immersion heater.

As shown in FIGS. 5 and 6, the non-ferrous metal molten metal holding furnace used for heating and holding the non-ferrous metal molten metal such as aluminum and zinc is equipped with a heating element in a ceramic refractory protective tube during the molten metal. It is equipped with a mold or horizontal immersion heater. Such a dipping heater has a ceramic tube having a high insulating property in order to protect the heating element heated by energization from the reaction with the molten metal and to insulate the molten metal from the molten metal. Since the ceramic tube is immersed in a high-temperature molten metal, it is manufactured of a material having high mechanical strength, excellent thermal shock resistance and abrasion resistance, and high thermal conductivity. For that purpose, a silicon nitride sintered body (Si ₃ N ₄ ), a boron nitride sintered body (BN) and the like are often used.

On the other hand, as a heating element housed in a ceramic tube, heaters having various shapes such as a rod-shaped heater and a spiral heater are known. As the heater material, materials such as SiC material, nichrome wire, and molybdenum disilicate are used. Recently, there has been a demand for a heating element that has a large calorific value, stable operation, and a long life, which is commensurate with a large molten metal holding furnace. In this respect, the heating element surface temperature can withstand even 1400 to 1600 ° C, and per unit area. A SiC heating element that has a large calorific value, that is, that corresponds to 5 to 10 times that of a nichrome heating element, has been adopted.

Initially, the SiC heating element was also a recrystallized SiC with a high porosity of 20 to 25%, and the maximum heating temperature was limited to about 1400 ° C by the heating element surface temperature in terms of the life due to the oxidation of SiC. A reaction-sintered SiC with a porosity of 10% or less is used to enable the surface temperature of the heating element to be used up to 1600 ° C. Furthermore, since the specific resistance is as low as 0.02 Ωcm, the heating element is spirally processed to increase the total resistance. There is disclosed a prior art that enables it to be used with an existing power source and can be used with a high temperature furnace at 1400 to 1600 ° C. with a three-phase power source.

JP 2001-257056 ([0002-0004], [Fig. 1], [Fig. 4])

The above-mentioned prior art is excellent in that the surface temperature of the heating element of the SiC heating element is raised, but in the case of a dipping heater for non-ferrous metal molten metal, this SiC heating element is installed in a ceramic tube which is a protective tube. The tube is usually filled with air. In this state, when the SiC heating element is energized to generate heat, the reaction of SiC + 2O ₂ = SiO ₂ + CO ₂ occurs with oxygen in the air, and this reaction proceeds rapidly at the initial stage, but it is generated. When the surface is covered with the SiO ₂ coating, the oxidation rate gradually slows down, and the resistance increase due to oxidation also slows down. However, when the amount of SiO ₂ gradually increases with long-term use, the resistance starts to increase from the initial 1.8 to 2 times approach, and further increases rapidly when it reaches 3 to 4 times. It is said that the life of the SiC heating element is exhausted due to the increase in resistance and the resulting increase in temperature coefficient variation. In particular, in the case of a spiral type heating element, there is a problem that a breakage accident of the heating part of the spiral suddenly occurs.

The present invention solves these problems and prevents oxidation of the SiC heating element of the immersion heater during heat generation to extend the life of the heating element and raise the temperature upper limit of the heating element. This makes it possible to extend the life of the SiC heating element and improve / maintain its performance. Overall, it is possible to improve the operating rate of the molten metal holding furnace and the melting furnace in the molten metal that melts non-ferrous metal ingots in the molten metal, and eventually maintain the quality of the molten metal. The purpose is to reduce maintenance costs.

In order to achieve the above object, the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1 of the present invention is a SiC immersion heater used in a non-ferrous metal molten metal holding furnace, and is a straight tubular insulating ceramics protective tube. A dipping heater in which one or more vertical SiC heaters are arranged and the protective tube is filled with nitrogen, and a vent tube communicating with the outside air is provided inside the protective tube, and the vent tube is provided. By connecting to a deoxidizing layer made of Ti or Nb or Si metal, the nitrogen deoxidized from the outside air is replenished so as to supplement the nitrogen inside the protective tube.

Conventionally, the inside of the insulating ceramic protective tube containing the vertical heater is filled with air communicating with the outside air, so that the SiC heating element is oxidized at about 800 ° C. or higher, whereas the SiC of the present invention is used. The immersion heater is a protective tube filled with nitrogen to prevent the SiC heating element from being oxidized at 800 ° C. or higher. Further, when the temperature of the SiC heating element rises or falls, the gas in the protective tube expands or contracts and the gas enters and exits. However, in the present invention, the gas can enter and exit through the ventilation pipe communicating with the outside air, and the outside air. When inhaled from, oxygen is absorbed and removed by the Ti or Nb or Si metal through the Ti or Nb or Si deoxidizing layer, and only nitrogen is replenished.

By adopting the configuration of claim 1 of the present invention, it is possible to prevent the SiC heating element from oxidizing from SiC to SiO ₂ at 800 ° C. or higher by using only nitrogen as the atmosphere in the protective tube, so that the characteristics of the SiC heating element are maintained. It is also possible to raise the temperature of the heating element, improving the heating capacity of the heating element and extending its life.

The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 2 is the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1, wherein the SiC heater has a heating element having a double spiral shape. To do.

With this configuration, since the SiC heater has a long double spiral current flow path, a large Joule heat can be generated even if the SiC has a low resistance, a SiC immersion heater having a large heat output can be obtained, and the SiC can be obtained. Since it is possible to avoid making the heater SiO ₂ , it contributes to the improvement of heat output and the extension of life.

Further, in the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 3, in the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1, the upper limit of the operating heating temperature of the heating element of the SiC heater is 1300 ° C. It is characterized by being.

When the operating heating temperature of the SiC heating element of the SiC heater becomes 1400 ° C. or higher, the SiC reacts with the N ₂ gas in the protective tube to generate the nitride of SiC ₃ N ₄ , and the life of the SiC heater is impaired. In order to prevent this, a configuration in which 1300 ° C. is the upper limit of the operating temperature can be adopted to extend the life while maintaining the performance of the SiC heater.

Further, the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 4 is the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1 or 2 or 3, wherein the Ti or Nb or Si deoxidizing layer is granular. It is characterized in that it is filled with Ti or Nb or Si metal which is either powdery or fibrous or a mixture thereof.

With this configuration, it is possible to improve the air permeability of the deoxidizing layer and increase the total surface area contributing to the deoxidizing reaction of the metal to increase the deoxidizing ability, and the oxygen content is removed into the protective tube. Nitrogen gas can be reliably supplied.

The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5 is the SiC immersion heater for heating a non-ferrous metal molten metal according to any one of claims 1 to 4, wherein the Ti or Nb or Si deoxidizing layer is the same. It is characterized in that it is provided in a hemispherical portion at the tip of a protective tube and in a room partitioned by a partition wall that supports the tip of a heating element of a SiC heater and has a plurality of ventilation holes at corners.

By adopting this configuration, a sufficient capacity of the oxygen scavenger layer can be secured, so that nitrogen can be reliably and evenly supplied into the protective tube from the outside air, and the temperature of the oxygen scavenger layer is defined as the temperature of the heater heating element. It can be made to the same degree, and the deoxygenation reaction from the outside air can be surely promoted.

The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 6 is the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Ti deoxidizing layer is in the temperature range of 800 to 1300 ° C. It is characterized by being.

When the operating temperature of the Ti deoxidizing layer is 800 ° C. or lower, deoxidation by the Ti metal is insufficient, and when the temperature is 1400 ° C. or higher, the Ti metal selectively reacts with nitrogen rather than oxygen to reduce the deoxidizing ability. .. Therefore, by taking a temperature range that avoids this problem, that is, the temperature of the SiC heating element that is the heat source is set to an upper limit of 1300 ° C. or less so that the operating temperature of the Ti deoxidizing layer is in the temperature range of 800 to 1300 ° C. The Ti deoxidized layer can maintain an appropriate deoxidizing capacity by adjusting the temperature to at least 800 degrees or higher.

The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 7 is the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Nb deoxidizing layer is in the temperature range of 200 to 1000 ° C. It is characterized by being.

When the operating temperature of the Nb deoxidizing layer is 200 ° C. or lower, deoxygenation by the Nb metal is insufficient, and when the temperature is 1000 ° C. or higher, the Nb metal selectively reacts with nitrogen rather than oxygen to reduce the deoxidizing ability. .. Therefore, by taking a temperature range to avoid this defect, that is, the temperature of the SiC heating element as a heat source is set to an upper limit of 1000 ° C. or less so that the operating temperature of the Nb deoxidizing layer is in the temperature range of 200 to 1000 ° C. By adjusting the temperature to at least 200 degrees or higher, the Nb deoxidizing layer can maintain an appropriate deoxidizing capacity. Therefore, it is necessary to deoxidize the gas passing through the ventilation pipe when the temperature of the SiC heating element is in the temperature range of 200 to 1000 ° C.

The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 8 is the SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Si deoxidizing layer is in the temperature range of 800 to 1300 ° C. It is characterized by being.

When the operating temperature of the Si deoxidizing layer is 800 ° C. or lower, deoxygenation by the Si metal is insufficient, and when it is 1400 ° C. or higher, the Si metal is softened and melted to reduce the deoxidizing ability. Therefore, by taking a temperature range that avoids this problem, that is, the temperature of the SiC heating element that is the heat source is set to an upper limit of 1300 ° C. or less so that the operating temperature of the Si deoxidizing layer is in the temperature range of 800 to 1300 ° C. The Si deoxidizing layer can maintain an appropriate deoxidizing capacity by adjusting the temperature to at least 800 degrees or higher.

According to the SiC immersion heater for heating a non-ferrous metal molten metal according to claims 1 to 8 according to the present invention, when the SiC heating element of the immersion heater generates heat, oxidation by air in the protective tube can be prevented and deterioration of the heating element can be prevented. As a result, the upper limit of the temperature of the heating element can be raised, and the life of the heating element can be extended. As a result, the life of the SiC heating element can be extended and the performance can be improved / maintained. As a whole, the operating rate of the molten metal holding furnace and the molten metal melting furnace can be maintained and improved, and the quality of the molten metal in the molten metal holding furnace and the molten metal melting furnace can be maintained. In addition, the replacement of the immersion heater is reduced, the damage caused by cooling and heating of the molten metal holding furnace and the melting furnace in the molten metal is reduced, and the maintenance cost can be reduced. Further, the SiC immersion heater for heating a non-ferrous metal molten metal of the present invention can be widely applied as a stable heat source for melting non-ferrous metal ingots and chips, so that the range of application in the field of non-ferrous metals can be expanded. it can.

FIG. 1 is a schematic perspective sectional view of a immersion heater of a non-ferrous metal molten metal according to a mode for carrying out the present invention. FIG. 2 is a schematic plan view of a immersion heater for a molten nonferrous metal according to a mode for carrying out the present invention. FIG. 3 is a schematic side sectional view taken along the line AA in FIG. FIG. 4 is a schematic side sectional view taken along the line BB in FIG. 5A and 5B are immersion heaters of another non-ferrous metal molten metal according to the embodiment of the present invention, in which FIG. 5A is a schematic plan view, and FIG. 5B is a schematic view of arrow AA in FIG. A side sectional view (c) is a schematic side sectional view taken along the line BB in (a). FIG. 6 is an example of a layout drawing of a vertical immersion heater in a non-ferrous metal molten metal holding furnace. FIG. 7 is an example of a layout drawing of a horizontal immersion heater in a non-ferrous metal molten metal holding furnace.

The SiC immersion heater 1 for heating a non-ferrous metal molten metal (hereinafter, referred to as a SiC immersion heater 1) according to the present invention will be described with reference to FIGS. 1, 2, 3 and 4. The SiC immersion heater 1 has three SiC heater main bodies 2 evenly separated from the inner wall surface of the protective tube 3 in the longitudinal direction of the protective tube 3 in the protective tube 3 of straight tubular insulating ceramics, and has a central angle of about 120. Arranged in degrees. As insulating ceramics, since they are immersed in a high-temperature molten metal to transfer heat, they must be manufactured of a material with high mechanical strength, excellent thermal shock resistance and abrasion resistance, and high thermal conductivity. Therefore, silicon nitride sintered body (Si) ₃N₄) And boron nitride sintered body (BN) can be used.

The SiC heater main body 2 has a cylindrical shape and is composed of a non-heating element 2-2 having no resistance connected to an electric terminal portion 2-3 to which a power supply is connected and a high-resistance heating element 2-1. -2 is vertically divided into two to form a conductive path for supplying electricity to the heating element 2-1. On the other hand, as shown in FIG. 1, the heating element 2-1 is a heating element having a spiral groove cut, and is a length of the main body from a place where it is connected to a non-heating element 2-2 in a hollow cylindrical main body made of SiC. Two grooves are cut along the direction so that the portion up to the other end side forms a spiral shape, and are connected by the tip portion. Even if the main body of the heating element 2-1 is SiC with low resistance, it has a shape in which two long spiral current paths are connected, so that resistance can be secured and a large Joule heat can be generated.

Further, in the SiC heater main body 2, the tip portion is the heater tip support portion of the partition wall 7 at the hemispherical portion 3-1 at the tip of the protection tube 3, and the root portion is the heater root support portion 6 at the root portion of the protection tube 3. It is fixed. The SiC heater main body 2 is appropriately positioned in the protective tube 3 by the support portions at the tips and roots thereof, and the heat generation energy of the three SiC heater main bodies 2 is transferred to the tubular portion 3-2 of the protective tube 3. On the other hand, heat is appropriately transferred by radiant heat transfer.

Further, in order to control the surface temperature of the heating element 2-1 of the SiC heater main body 2, the thermocouple tubes 5 are installed in parallel with the three SiC heater main bodies 2 and at substantially the center positions of the three, and the temperature. It is preferable that the thermocouple tip portion 5-1 to be measured is installed substantially in the center of the heating element 2-1 of the SiC heater main body 2, and it is assumed that this measurement temperature indicates the surface temperature of the heating element 2-1. A temperature signal is guided to a temperature setting adjusting device (not shown) via a thermocouple compensating lead wire 5-2, and an external current is adjusted to the electric terminal portion 2-3 in order to bring the surface temperature (for example, 1200 ° C.). And apply.

In the SiC immersion heater 1 of the present invention, the protective tube 3 is filled with nitrogen, and if the heating element 2-1 of the SiC heater main body 2 is the conventional air, the SiC is oxidized at about 800 ° C. or higher. It is possible to prevent the change to SiO ₂ and maintain the state of SiC. Further, when the nitrogen in the protective tube 3 expands or contracts as the SiC heating element 2-1 rises or falls in temperature, the nitrogen in the protective tube 3 becomes the ventilation hole 4-2, the deoxidizing layer 4-1 and the ventilation pipe. Although it enters and exits via 4, in the present invention, only nitrogen can enter and exit through the ventilation pipe 4 that communicates with the outside air. That is, when inhaling from the outside air using the deoxidizing layer of Ti metal, it passes through the deoxidizing layer 4-1 of Ti metal heated to a temperature range of 800 to 1300 ° C. via the ventilation pipe 4. Sometimes oxygen reacts with Ti and is removed by the reaction of Ti + O ₂ = TiO ₂ and only nitrogen is inhaled. When the Nb metal deoxidizing layer is used and sucked from the outside air, it passes through the Nb metal deoxidizing layer 4-1 heated to a temperature range of 200 to 1000 ° C. via the ventilation pipe 4. Sometimes oxygen reacts with Nb and is removed by the reaction of 2Nb + O ₂ = 2NbO, resulting in inhalation of only nitrogen. When the Si metal deoxidizing layer is used and sucked from the outside air, it passes through the Si metal deoxidizing layer 4-1 heated to a temperature range of 800 to 1000 ° C. via the ventilation pipe 4. Occasionally, oxygen reacts with Si and is removed by the reaction of Si + O ₂ = SiO ₂ , and only nitrogen is inhaled. Incidentally, an embolic portion 2-4 is formed at the root portion of the SiC heater main body 2 of the present invention, whereby the inside of the SiC heater main body 2 and the protective tube 3 of the SiC immersion heater 1 is separated from the outside air only by the ventilation pipe 4. It will be connected.

An embodiment of the SiC immersion heater 1 of the present invention having an output of 34 kW, when composed of three SiC heaters 2, the protective tube 3 has an outer diameter of 170 mm and a length of 900 mm, and the SiC heater 2 is outside. It has a diameter of 40 mm and a length of 900 mm. The Ti metal forming the deoxidizing layer 4-1 is made of sponge Ti, which can be processed into granular, powdery, or fibrous form, and the filling weight is about 600 to 700 gr. The outer diameter of the ventilation pipe 4 is about 20 mm. The heat transfer pair is a normal one and can be used through an alumina protective tube of 4 × 6 mm.

The SiC immersion heater 1 of another embodiment of the present invention will be described with reference to FIG. The protective tube 3 of the SiC immersion heater 1 is characterized by the arrangement and configuration of the ventilation tube 4 filled with nitrogen. The SiC heater main body 2 is composed of three, and three ventilation pipes 4 are arranged in the middle of each SiC heater main body between the inside of the protective tube 3 and the outside air. Each ventilation pipe 4 faces the heating element 2-1 of the SiC heater main body 2 and has two ventilations for holding the deoxidizing layer 4-1 filled with the deoxidizing material and the deoxidizing layer 4-1. It is composed of plugs 4-3. As the deoxidizing layer 4-1, a Ti metal, Nb metal, or Si metal that exhibits a deoxidizing effect can be used in the form of granules, powder, or fibers. Further, in order to hold the deoxidizing layer 4-1, porous ceramic vent plugs 4-3 are provided at two upper and lower positions. Since the oxygen scavenger layer 4-1 is provided in each of the three ventilation pipes 4 and is sandwiched between the two ventilation plugs 4-3, the oxygen scavenger is made of Ti, Nb, or Si metal. There are few restrictions on the amount of material that can be stored. Since the gas flowing into the protection pipe 3 always passes through the three ventilation pipes 4, the inflowing outside air is built in, and the deoxidizing layer 4-1 heated to a high temperature by the radiation of the SiC heater main body 2 is used. Since it is deoxidized and flows in when it passes through, the inside of the protective tube 3 can be maintained in a state without oxygen, so that the performance of the SiC heater main body 2 can be sufficiently exhibited and the life of the heater can be extended.

The SiC immersion heater 1 of the present invention is mainly composed of a SiC heater main body 2 and a protective tube 3, and is usually in the molten metal M of the molten metal holding furnace 10 shown in FIGS. 6 and 7 in the vertical direction (FIG. 6) or in the horizontal direction (FIG. 6). It is installed by immersing it in 7). As for the heat output of the SiC immersion heater 1, the heat generated by the SiC heater main body 2 is transferred to the molten metal M via the protective tube 3, and the heat energy raises the temperature of the molten metal M or keeps it at a constant temperature. In the SiC immersion heater 1, the thermal energy of the temperature of the SiC heater main body 2 (usually 900 to 1300 ° C.) is transmitted to the inner wall of the protective tube 3 by heat transfer mainly by radiation, and the tubular portion of the protective tube 3 is mainly transmitted. Although the inner wall of 3-2 is heated, since the protective tube 3 is immersed in the molten metal, it is presumed that the temperature of the protective tube 3 is slightly higher than the molten metal temperature (for example, 650 to 720 ° C. in the molten aluminum). ..

Therefore, the higher the surface temperature of the SiC heater main body 2, the higher the thermal energy for heating the inner wall of the protective tube 3, and the higher the temperature of the molten metal M in contact with the protective tube 3 is. However, if the surface temperature of the SiC heater main body 2 is in the air, oxidation of SiC to SiO 2 occurs, so that the limit is 1000 ° C., and the performance of the SiC heater main body 2 is limited. On the other hand, in the SiC heating element 2-1 of the immersion heater 1 of the present invention, the oxidation of SiC to SiO ₂ can be prevented in nitrogen, so that the surface temperature can be up to 1300 ° C. However, when the surface temperature of the SiC heating element 2-1 becomes 1400 ° C. or higher, the SiC reacts with nitrogen to become Si ₃ N ₄ , and the SiC deteriorates. Therefore, in the present invention, if the surface temperature of the SiC heating element 2-1 is in the air by heating the SiC heater main body 2 in a nitrogen atmosphere, 1000 ° C. is the maximum from the viewpoint of SiC oxidation. On the other hand, in nitrogen, the surface temperature can be maxed out at 1300 ° C. to increase the amount of heat transferred to the molten metal M, and it is possible to prevent the oxidation of SiC and extend the life of the SiC heating element 2-1. I made it.

The SiC immersion heater 1 of the present invention is at room temperature before being energized and heated, and only nitrogen gas is sealed in the protective tube 3. When the SiC immersion heater 1 is energized and heated, the nitrogen gas expands and escapes to the outside air via the ventilation pipe 4. When the temperature level of the SiC heater main body 2 (range of 1000 to 1300 ° C.) is settled, the nitrogen gas in the protective tube 3 also has little thermal change and becomes a volumeally stable state. After that, when it becomes necessary to lower the temperature of the SiC immersion heater 1 when the molten metal holding furnace 10 is stopped, the nitrogen gas in the protective pipe 3 contracts and the outside air invades from the ventilation pipe 4. Oxygen in the outside air is combined with Ti or Nb or Si metal to form oxides by the deoxidizing layer 4-1 of Ti or Nb or Si metal connected to the ventilation pipe 4, oxygen is removed from the outside air, and nitrogen is removed. Only is replenished in the protective tube 3. Deoxidation of Ti and Si metals starts at 700 ° C, but the upper limit is preferably 1300 ° C. The upper limit is set to 1300 ° C. When the temperature exceeds 1400 ° C, the Ti metal reacts with nitrogen in the outside air to form a nitride, and the deoxidation becomes insufficient. In the case of Si metal, the temperature is 1400 ° C. If it exceeds, it may soften or melt. On the other hand, deoxidation of Nb metal starts at 200 ° C., but if it exceeds 1000 ° C., it reacts with nitrogen, so that the deoxidizing power may decrease.

Therefore, in order to replenish nitrogen from the outside air, it is preferable to perform it when the temperature of the tip portion 5-1 of the thermocouple 5 indirectly indicating the temperature of the Ti or Si deoxidizing layer 4-1 is 700 to 1300 ° C. .. On the other hand, in the case of the Nb deoxidizing layer 4-1 it is preferable to carry out at 200 to 1000 ° C.

It can be applied not only to holding furnaces for molten non-ferrous metals such as aluminum and zinc and melting furnaces in molten metal, but also in the field of melting treatment of non-ferrous metal ingots and chips.

1: SiC immersion heater 2: SiC heater body 2-1: Heating element 2-2: Non-heating element 2-3: Electric terminal part 2-4: Embolization part 3: Protective tube 3-1: Hemisphere part 3-2: Cylindrical part
4: Ventilation pipe 4-1: Oxygen scavenger layer 4-2: Vent hole 4-3: Ventilation plug 5: Thermocouple 5-1: Thermocouple tip 5-2: Thermocouple compensation lead wire 6: Heater root support
7: Bulkhead (heater tip support)
10: Molten holding furnace M: Molten

Claims (8)

In a SiC immersion heater used in a non-ferrous metal molten metal holding furnace or melting furnace, one or more vertical SiC heaters are arranged in a straight tubular insulating ceramics protective tube, and the protective tube is filled with nitrogen. In the immersion heater, a ventilation pipe that communicates with the outside air is provided inside the protection pipe, and the ventilation pipe is connected to a deoxidizing layer made of Ti, Nb, or Si metal to release nitrogen that has deoxidized the outside air. A SiC immersion heater for heating a non-ferrous metal molten metal, which is replenished so as to supplement the nitrogen inside the protective tube. The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1, wherein the SiC heater has a heating element having a double helix shape. The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 1 or 2, wherein the upper limit of the operating heating temperature of the heating element of the SiC heater is 1300 ° C. Claim 1 is characterized in that the Ti or Nb or Si deoxidizing layer is filled with Ti or Nb or Si metal which is any of granular, powdery, fibrous, or a mixture thereof. Alternatively, the SiC immersion heater for heating a non-ferrous metal molten metal according to 2 or 3. A room in which the Ti or Nb or Si deoxidizing layer is inside the hemisphere at the tip of the protective tube, supports the tip of the heating element of the SiC heater, and is partitioned by a partition wall having a plurality of ventilation holes at the corners. The SiC immersion heater for heating a non-ferrous metal molten metal according to any one of claims 1 to 4, wherein the SiC immersion heater is provided inside. The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Ti deoxygenated layer is in the temperature range of 800 to 1300 ° C. The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Nb deoxidizing layer is in the temperature range of 200 to 1000 ° C. The SiC immersion heater for heating a non-ferrous metal molten metal according to claim 5, wherein the operating temperature of the Si deoxidizing layer is in the temperature range of 800 to 1300 ° C.

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