Electric heating element

Abstract

The invention discloses an electric heating element, and belongs to the technical field of heating elements, the electric heating element comprises a ceramic liner, a ceramic sleeve, an electric heating alloy part, a metal tube shell, a lead-out rod and an insulation sealing plug, solid ceramic parts are arranged on the inner side and the outer side of the electric heating alloy part, and low-melting-point high-fluidity liquid metal is arranged between the electric heating alloy and a ceramic material to serve as a gap filler. Through the solid ceramic liner and the ceramic sleeve, the thermal conductivity is improved, the assembly difficulty is greatly reduced, the assembly efficiency is improved, the low-melting-point and high-fluidity liquid metal is used as a gap filler between different materials, the interface thermal resistance between the different materials can be effectively reduced, the thermal conductivity of the electric heating element is improved, the boiling point of the liquid metal is high, and the electric heating element has good heat conduction performance. The volume change rate of the electric heating element is far smaller than that of gas at high temperature, the pressure in the electric heating element can be maintained within a reasonable range at high temperature, the reliability, stability and safety of the electric heating element are improved, and the service life of the electric heating element is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of heating elements, in particular to an electric heating element. Background Art

[0002] Metal tubular electric heating elements can heat air, solid metal media and various liquid media, and are widely used in energy, chemical industry and other fields. In the current tubular electric heating elements, the insulating material in the metal tube is usually a powdered substance with low thermal conductivity. There is interfacial thermal resistance between the metal tube and the insulating material, and between the insulating material and the heating wire. Under the condition of high surface heat load, due to the low thermal conductivity of the insulating material and the interfacial thermal resistance between the insulating material and the metal tube and the heating wire, the temperature of the heating wire will be too high, which will cause the insulation performance of the insulating material to decrease on the one hand, and the failure of the heating wire on the other hand, affecting the reliability and stability of the electric heating element.

[0003] At present, the technical means are through surface modification or increasing the density of powdered insulating materials, but the above two methods do not fundamentally solve the interfacial thermal resistance between the particles of powdered insulating materials, which leads to the problem of too low thermal conductivity. There is also a method of filling the interface gap with soft thermal interface materials with high thermal conductivity such as thermal conductive silicone grease, but the temperature near the heating wire is as high as 900℃ or more, and the thermal conductivity of the soft material will drop sharply at this temperature, thereby adding new thermal resistance between the heating wire and the insulating filling material, causing the temperature of the heating wire to further increase. Summary of the invention

[0004] In order to overcome at least one of the above disadvantages, the present invention provides an electric heating element. The object of the present invention can be achieved by adopting the following technical solution:

[0005] The present invention provides an electric heating element, comprising:

[0006] Ceramic liner;

[0007] A ceramic sleeve, wherein the ceramic liner is arranged in the inner cavity of the ceramic sleeve;

[0008] An electrothermal alloy member, the electrothermal alloy member being arranged between the ceramic liner and the ceramic sleeve;

[0009] A metal tube shell, wherein the metal tube shell is sleeved on the ceramic sleeve;

[0010] A lead-out rod, which is disposed in the inner cavity of the electrothermal alloy member and located at the end of the ceramic liner, and the electrothermal alloy member is electrically connected to the lead-out rod;

[0011] An insulating sealing plug, the insulating sealing plug is arranged between the metal tube shell and the lead-out rod and is located at the end of the ceramic sleeve;

[0012] The gaps between the ceramic liner and the electric heating alloy part, between the electric heating alloy part and the ceramic sleeve, and between the ceramic sleeve and the metal tube shell are all provided with a filler, and the filler is a low-melting-point and high-fluidity liquid metal.

[0013] In one embodiment, the ceramic liner includes a solid tubular body or a solid columnar body made of at least one of magnesium oxide, boron nitride, and silicon carbide, and the ceramic sleeve includes a solid tubular body made of at least one of magnesium oxide, boron nitride, and silicon carbide.

[0014] In one possible implementation, the lengths of the metal tube shell, the ceramic sleeve and the ceramic liner decrease in sequence;

[0015] The axes of the metal tube shell, the ceramic sleeve and the ceramic liner coincide with each other.

[0016] In one possible implementation, there are two lead-out rods, which are disposed at both ends of the ceramic inner liner, one end of the electrothermal alloy part is connected to one of the lead-out rods, and the other end of the electrothermal alloy part is connected to the other lead-out rod.

[0017] In one possible implementation, the electrothermal alloy piece is tubular, and the electrothermal alloy piece is sleeved on the ceramic liner; or,

[0018] The electrothermal alloy piece is in a wire or strip shape and is wound around the ceramic inner container.

[0019] In one possible implementation manner, the ceramic sleeve and the metal tube shell are matched with each other with a small gap. When the electrothermal alloy part is tubular, the ceramic sleeve and the electrothermal alloy part are matched with each other with a small gap.

[0020] In one possible implementation manner, the ceramic sleeve and the metal tube shell are matched with each other with a small gap. When the electric heating alloy piece is in the form of a wire or a strip, the ceramic sleeve and the ceramic liner are matched with each other with a small gap.

[0021] In one embodiment, the gap filler includes at least one of tin-bismuth liquid metal and indium-tin liquid metal.

[0022] In one possible implementation manner, the electrothermal alloy part comprises a Fe-Cr-Al alloy electrothermal wire subjected to surface oxidation treatment.

[0023] In one possible implementation manner, the insulating sealing plug is a flexible annular member made of insulating material, and the insulating sealing plug abuts against the lead-out rod, the metal tube shell and the ceramic sleeve.

[0024] Beneficial technical effects of the present invention: According to the content of the present disclosure, the electric heating element includes a ceramic liner, a ceramic sleeve, an electric heating alloy part, a metal tube shell, a lead-out rod and an insulating sealing plug. By arranging high-thermal conductivity and high-insulation solid ceramic parts on the inside and outside of the electric heating alloy part, namely, a ceramic liner and a ceramic sleeve, the problems of low thermal conductivity and great assembly difficulty of traditional insulating powder are solved, the thermal conductivity is improved, the assembly difficulty is greatly reduced, and the assembly efficiency is improved. The low-melting-point and high-fluidity liquid metal is used as a filler between different materials, which can effectively reduce the interface thermal resistance between different materials and improve the thermal conductivity of the electric heating element. The boiling point of the liquid metal is relatively high, and its volume change rate at high temperature is much smaller than that of the gas. The pressure inside the electric heating element can be maintained within a reasonable range at high temperature, which improves the reliability, stability and safety of the electric heating element and extends the service life of the electric heating element. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the accompanying drawings, the following are given by way of example and not limitation:

[0026] Figure 1 A cross-sectional view of the structure of a first electric heating element of the present invention is shown;

[0027] Figure 2 A cross-sectional view of the structure of a second electric heating element of the present invention is shown;

[0028] Figure 3 A schematic diagram of the internal temperature distribution of an electric heating element without a caulking agent is shown;

[0029] Figure 4 A schematic diagram of the temperature distribution inside an electric heating element in which the gap filler is tin-bismuth liquid metal is shown;

[0030] Figure 5 A schematic diagram of the temperature distribution inside an electric heating element whose gap filler is indium tin liquid metal is shown.

[0031] In the figure: 1. Metal tube shell; 2. Ceramic liner; 3. Ceramic sleeve; 4. Electric heating alloy part; 5. Lead rod; 6. Insulating sealing plug. DETAILED DESCRIPTION

[0032] In the following detailed disclosure, these embodiments are fully described with reference to the accompanying drawings. In order to make the technical scheme of the present invention more clear and specific to those skilled in the art, the implementation methods described below are not limited to this. The present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings.

[0033] In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0035] like Figure 1 and Figure 2 As shown, the present invention provides an electric heating element, including a ceramic liner 2, a ceramic sleeve 3, an electric heating alloy member 4, a metal tube shell 1, a lead-out rod 5 and an insulating sealing plug 6, the ceramic liner 2 is arranged in the inner cavity of the ceramic sleeve 3, the electric heating alloy member 4 is arranged between the ceramic liner 2 and the ceramic sleeve 3, the metal tube shell 1 is sleeved on the ceramic sleeve 3, the lead-out rod 5 is arranged in the inner cavity of the electric heating alloy member 4 and is located at the end of the ceramic liner 2, the electric heating alloy member 4 is electrically connected to the lead-out rod 5, and the insulating seal is arranged between the metal tube shell 1 and the lead-out rod 5 and is located at the end of the ceramic sleeve 3; the gaps between the ceramic liner 2 and the electric heating alloy member 4, between the electric heating alloy member 4 and the ceramic sleeve 3, and between the ceramic sleeve 3 and the metal tube shell 1 are all provided with a filler, and the filler is a low-melting-point and high-fluidity liquid metal.

[0036] The electric heating element comprises a ceramic liner 2, a ceramic sleeve 3, an electric heating alloy part 4, a metal tube shell 1, a lead rod 5 and an insulating sealing plug 6. By arranging high thermal conductivity and high insulation solid ceramic parts both inside and outside the electric heating alloy part 4, namely, the ceramic liner 2 arranged on the inside of the electric heating alloy part 4 and the ceramic sleeve 3 arranged on the outside of the electric heating alloy part 4, the problems of low thermal conductivity and great assembly difficulty of traditional filling insulating powder are solved. The solid ceramic liner 2 and ceramic sleeve 3 improve the thermal conductivity of the electric heating element, greatly reduce the assembly difficulty, and improve the assembly efficiency.

[0037] The electric heating element uses low-melting-point and high-fluidity liquid metal as a filler between different materials, which can effectively reduce the interfacial thermal resistance between different materials and improve the thermal conductivity of the electric heating element. The liquid metal has a high boiling point and its volume change rate is much smaller than that of the gas at high temperatures. The pressure inside the electric heating element can be maintained within a reasonable range at high temperatures.

[0038] Under the same metal tube shell 1 and surface heat load conditions, the electric heating element can effectively reduce the temperature of the heating wire and the insulating material, greatly reduce the risk of failure of the insulating material and the heating wire, improve the reliability, stability and safety of the electric heating element, and extend the service life of the electric heating element.

[0039] In one embodiment, the ceramic liner 2 includes a solid tubular body or a solid columnar body made of at least one of magnesium oxide, boron nitride, and silicon carbide, and the ceramic sleeve 3 includes a solid tubular body made of at least one of magnesium oxide, boron nitride, and silicon carbide.

[0040] The ceramic liner 2 and the ceramic sleeve 3 may be made of the same material, and may be a solid ceramic component made of one or more of magnesium oxide, boron nitride, and silicon carbide.

[0041] In one possible implementation, Figure 1 and Figure 2 As shown, the lengths of the metal tube shell 1, the ceramic sleeve 3 and the ceramic liner 2 decrease in sequence, and the axes of the metal tube shell 1, the ceramic sleeve 3 and the ceramic liner 2 coincide with each other.

[0042] Among them, the ceramic inner liner 2, the electric heating alloy part 4, the ceramic sleeve 3, and the metal tube shell 1 are arranged in sequence from the inside to the outside, the electric heating alloy lead-out rod 5 is connected to the electric heating alloy part 4 and extends out of the metal tube shell 1, and the insulation and sealing functions are realized between the lead-out rod 5 and the metal tube shell 1 through an insulating sealing plug 6.

[0043] In one embodiment, there are two lead-out rods 5 , which are disposed at both ends of the ceramic inner liner 2 , one end of the electrothermal alloy part 4 is connected to one lead-out rod 5 , and the other end of the electrothermal alloy part 4 is connected to the other lead-out rod 5 .

[0044] Among them, the electric heating element can be a double-end lead-out electric heating element, two lead-out rods 5 are relatively arranged at the two ends of the metal tube shell 1, the two lead-out rods 5 are respectively connected to the two ends of the electric heating alloy part 4, the lead-out rod 5 can be welded together with the electric heating alloy part 4 to lead out the current. In order to ensure that the material in the metal tube shell 1 does not leak and to insulate the lead-out rod 5 from the metal tube shell 1, an insulating sealing plug 6 is used to fill the lead-out rod 5 and the metal tube shell 1.

[0045] In one possible implementation, Figure 1As shown, the electrothermal alloy member 4 is tubular, and the electrothermal alloy member 4 is sleeved on the ceramic liner 2; or, as shown Figure 2 As shown, the electrothermal alloy member 4 is in a wire or ribbon shape, and the electrothermal alloy member 4 is wound around the ceramic inner container 2 .

[0046] Among them, Figure 1 As shown, the electrothermal alloy part 4 is tubular, a ceramic liner 2 is mounted on the inner side of the electrothermal alloy tube, a ceramic sleeve 3 is mounted on the outer side of the electrothermal alloy tube, a metal tube shell 1 is mounted on the outer side of the ceramic sleeve 3, a caulking agent is filled between the ceramic sleeve 3 and the metal tube shell 1, insulating sealing plugs 6 are arranged at both ends of the metal tube shell 1, and a lead rod 5 is arranged on the electrothermal alloy tube, extending outward to the insulating sealing plugs 6 extending out of the two ends of the metal tube shell 1. The outer diameter of the ceramic liner 2 is slightly smaller than the inner diameter of the electrothermal alloy tube, the outer diameter of the electrothermal alloy tube is slightly smaller than the inner diameter of the ceramic sleeve 3, and the outer diameter of the ceramic sleeve 3 is slightly smaller than the inner diameter of the metal tube shell 1.

[0047] Among them, Figure 2 As shown, the electric heating alloy member 4 is in the form of a wire or a strip, the electric heating alloy wire or the electric heating alloy strip is wound on the ceramic inner liner 2, a ceramic sleeve 3 is installed on the outer side of the electric heating alloy wire or the electric heating alloy strip, a metal tube shell 1 is installed on the outer side of the ceramic sleeve 3, a caulking agent is filled between the electric heating alloy wire / strip and the ceramic inner liner 2, between the electric heating alloy wire / strip and the ceramic sleeve 3, and between the ceramic sleeve 3 and the metal tube shell 1, an insulating sealing plug 6 is arranged at both ends of the metal tube shell 1, and a lead rod 5 is arranged on the electric heating alloy wire / strip, extending outward to the insulating sealing plug 6 extending out of the two ends of the metal tube shell 1. The outer diameter of the ceramic inner liner 2 is smaller than the inner diameter of the ceramic sleeve 3, a gap for accommodating the electric heating alloy wire or the electric heating alloy strip is formed between the ceramic inner liner 2 and the ceramic sleeve 3, and the outer diameter of the ceramic sleeve 3 is slightly smaller than the inner diameter of the metal tube shell 1.

[0048] During the operation of the electric heating element, the temperature near the electric heating alloy part 4 is relatively high, usually above 900°C. The electric heating alloy and ceramic, ceramic and metal tube shell 1 are two different materials. Due to the inconsistency of their expansion coefficients, a gap will be formed at high temperature, thereby forming a layer of surface thermal resistance between the two materials.

[0049] In one possible implementation, Figure 1 As shown, the ceramic sleeve 3 and the metal tube shell 1 are matched with each other with a small gap. When the electric heating alloy member 4 is tubular, the ceramic sleeve 3 and the electric heating alloy member 4 are matched with each other with a small gap.

[0050] At the operating temperature of the electric heating element, gaps will be formed between the ceramic sleeve 3 and the metal tube shell 1, and between the ceramic sleeve 3 and the electric heating alloy part 4. Filling the gaps with liquid metal with good fluidity can reduce the interface thermal resistance and improve the overall thermal conductivity of the electric heating element.

[0051] In one possible implementation, Figure 2 As shown, the ceramic sleeve 3 and the metal tube shell 1 are matched with each other with a small gap. When the electric heating alloy member 4 is in the shape of a wire or a strip, the ceramic sleeve 3 and the ceramic liner 2 are matched with each other with a small gap.

[0052] A gap for accommodating the electric heating alloy wire or the electric heating alloy strip is formed between the ceramic inner liner 2 and the ceramic sleeve 3. At the operating temperature of the electric heating element, a gap is formed between the ceramic sleeve 3 and the metal tube shell 1. The gap is filled with liquid metal with good fluidity, which can reduce the interface thermal resistance and improve the overall thermal conductivity of the electric heating element.

[0053] In one embodiment, the gap filler includes at least one of tin-bismuth liquid metal and indium-tin liquid metal.

[0054] The filler uses low-melting point and high-fluidity liquid metal, which has the advantages of low melting point and high boiling point, ensuring that filling can be achieved at room temperature. At the same time, it is not easy to boil at high temperature, ensuring the stability of the pressure in the electric heating element. After using low-melting point and high-fluidity liquid metal as a filler between different materials, the temperature difference between the electric heating alloy and the ceramic, and between the ceramic and the metal tube shell 1 is greatly reduced, and the interface thermal resistance is greatly reduced.

[0055] The present invention takes the electrothermal alloy part 4 as Fe-Cr-Al and the ceramic liner 2 and the ceramic sleeve 3 as magnesium oxide as an example, the gap between the electrothermal alloy part 4 and the insulating filling material is 1.5nm, and the interface thermal resistance and interface temperature difference of the electrothermal element are obtained by numerical simulation. The numerical simulation method is used to test the temperature distribution between different liquid metal filling and no liquid metal filling when the center temperature of the electrothermal alloy part 4 is 1060K. The data are as follows Figure 3-Figure 5 shown.

[0056] Among them, Figure 3 The schematic diagram of the internal temperature distribution of the electric heating element without low-melting-point high-fluidity liquid metal as a filler is shown. Before the liquid metal filling is added, a large temperature jump occurs between the two contact surfaces. The characteristics of the temperature jump will first limit the maximum temperature that the insulating material can reach, thereby affecting the heating temperature of the metal tube shell 1; secondly, the temperature jump will make the temperature of the electric heating alloy part 4 much higher than the insulating filling material, and the high temperature will affect the service life of the electric heating alloy part 4.

[0057] Among them, Figure 4The schematic diagram of the temperature distribution inside the electric heating element with tin-bismuth liquid metal as the gap filler is shown. By comparison, it is found that under the same heating power, the interface temperature difference is reduced to about 50% of the original after the liquid metal is filled, from 185K to 95K. The temperature of the insulating filling material is increased from 870K to 968K, an increase of about 100K, and the corresponding heating temperature of the metal tube shell 1 is also increased by about 100K.

[0058] Among them, Figure 5 The schematic diagram of the temperature distribution inside the electric heating element with the filler being indium tin liquid metal is shown. By comparison, it is found that under the same heating power, the interface temperature difference is reduced to about 60% of the original after the liquid metal is filled, from 185K to 110K. The temperature of the insulating filling material is increased from 870K to 945K, an increase of about 75K, and the corresponding heating temperature of the metal tube shell 1 is also increased by about 75K.

[0059] Under the same heating power, after filling with liquid metal with low melting point and high fluidity, the interface temperature difference is greatly reduced, the temperature of the insulating filling material increases, that is, the temperature of the ceramic sleeve 3 increases, and the corresponding heating temperature of the metal tube shell 1 will also increase, reducing the interface thermal resistance and improving the overall thermal conductivity of the electric heating element.

[0060] In one embodiment, the electric heating alloy member 4 includes a Fe-Cr-Al alloy electric heating wire with surface oxidation treatment.

[0061] Among them, the Fe-Cr-Al alloy heating wire that has undergone surface oxidation treatment is used to avoid the corrosion of the alloy heating wire by low-melting-point liquid metal, improve reliability, greatly reduce the risk of failure of insulating materials and heating wire, and increase the service life of the entire heating tube.

[0062] Among them, since the low-melting-point liquid metal is highly corrosive, it is preferred to perform anti-corrosion treatment on Fe-Cr-Al and perform oxidation coating on the surface of the Fe-Cr-Al alloy. On the basis of ensuring the reliability of anti-corrosion, the thickness of the oxide film is reduced as much as possible, and the final thickness of the oxide film is selected to be about 0.2nm to 50nm.

[0063] Specifically, the Fe-Cr-Al alloy is plated using a high-temperature oxidation process, in which a heating temperature of 950 to 1050° C. and an oxidation time of no less than 100 hours are required to achieve an oxide film with a thickness of 0.2 nm to 50 nm.

[0064] In one possible implementation manner, the insulating sealing plug 6 is a flexible annular member made of insulating material, and the insulating sealing plug 6 abuts against the lead-out rod 5 , the metal tube housing 1 and the ceramic sleeve 3 .

[0065] In order to ensure that the material in the metal tube shell 1 does not leak, the lead-out rod 5 and the metal tube shell 1 are insulated, and the lead-out rod 5 and the metal tube shell 1 are filled with a flexible annular insulating sealing plug 6 .

[0066] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0068] In view of the above detailed description, these and other changes can be made to these embodiments, and this written description includes the best mode embodiments to disclose the present invention. The scope of the patent obtained by the present invention is defined by the claims, which are not limited by the present disclosure, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field within the scope disclosed by the present invention, according to the technical solution and its conception of the present invention, is equivalent to or changes, and all are within the protection scope of the present invention.

Claims

1. An electric heating element, characterized in that: include: Ceramic liner (2); A ceramic sleeve (3), wherein the ceramic liner (2) is arranged in the inner cavity of the ceramic sleeve (3); An electric heating alloy member (4), wherein the electric heating alloy member (4) is arranged between the ceramic inner liner (2) and the ceramic sleeve (3); A metal tube shell (1), wherein the metal tube shell (1) is sleeved on the ceramic sleeve (3); A lead-out rod (5), the lead-out rod (5) being arranged in the inner cavity of the electrothermal alloy member (4) and located at the end of the ceramic liner (2), the electrothermal alloy member (4) being electrically connected to the lead-out rod (5); An insulating sealing plug (6), the insulating sealing plug being arranged between the metal tube shell (1) and the lead-out rod (5) and located at the end of the ceramic sleeve (3); The gaps between the ceramic liner (2) and the electric heating alloy member (4), between the electric heating alloy member (4) and the ceramic sleeve (3), and between the ceramic sleeve (3) and the metal tube shell (1) are all provided with a filler, and the filler is a low-melting-point high-fluidity liquid metal.

2. The electric heating element according to claim 1, characterized in that: The ceramic liner (2) comprises a solid tubular body or a solid columnar body made of at least one of magnesium oxide, boron nitride and silicon carbide, and the ceramic sleeve (3) comprises a solid tubular body made of at least one of magnesium oxide, boron nitride and silicon carbide.

3. The electric heating element according to claim 1, characterized in that: The lengths of the metal tube shell (1), the ceramic sleeve (3) and the ceramic liner (2) decrease in sequence; The axes of the metal tube shell (1), the ceramic sleeve (3) and the ceramic liner (2) coincide with each other.

4. The electric heating element according to claim 3, characterized in that: The number of the lead-out rods (5) is two, and the two lead-out rods (5) are arranged at the two ends of the ceramic inner liner (2), one end of the electrothermal alloy part (4) is connected to one of the lead-out rods (5), and the other end of the electrothermal alloy part (4) is connected to the other of the lead-out rods (5).

5. The electric heating element according to any one of claims 1 to 4, characterized in that: The electrothermal alloy member (4) is tubular, and the electrothermal alloy member (4) is sleeved on the ceramic inner container (2); or, The electrothermal alloy piece (4) is in the form of a wire or a strip, and the electrothermal alloy piece (4) is wound around the ceramic inner container (2).

6. The electric heating element according to claim 5, characterized in that: The ceramic sleeve (3) and the metal tube shell (1) are matched with each other with a small gap. When the electric heating alloy part (4) is tubular, the ceramic sleeve (3) and the electric heating alloy part (4) are matched with each other with a small gap.

7. The electric heating element according to claim 5, characterized in that: The ceramic sleeve (3) and the metal tube shell (1) are matched with each other with a small gap. When the electric heating alloy part (4) is in the form of a wire or a strip, the ceramic sleeve (3) and the ceramic liner (2) are matched with each other with a small gap.

8. The electric heating element according to claim 7, characterized in that: The gap filler includes at least one of tin-bismuth liquid metal and indium-tin liquid metal.

9. The electric heating element according to claim 1, characterized in that: The electric heating alloy part (4) comprises a Fe-Cr-Al alloy electric heating wire subjected to surface oxidation treatment.

10. The electric heating element according to claim 1, characterized in that: The insulating sealing plug (6) is a flexible annular member made of insulating material, and the insulating sealing plug (6) is in contact with the lead-out rod (5), the metal tube housing (1) and the ceramic sleeve (3).

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