Silicon carbide rod heating body and production process

Abstract

The invention belongs to the technical field of production of silicon carbide electric heating elements, and particularly relates to a silicon carbide rod heating body and a production process. The production process of the silicon carbide rod heating element comprises the following steps: (1) pretreatment of a silicon carbide raw material: mixing the silicon carbide raw material with an additive, and pre-sintering; (2) mixing and molding: mixing a silicon carbide raw material with the pretreated silicon carbide, graphite electrode powder, carbon black and a binder, and carrying out extrusion molding to obtain a bar blank; (3) drying: drying the bar billet; (4) primary firing: firing in a carbon tube furnace or a vacuum furnace; and (5) secondary firing: firing in a carbon tube furnace or a vacuum furnace to obtain the silicon carbide rod heating body. The production process of the silicon carbide rod heating body is environment-friendly, and the produced heating body is high in density and adjustable in resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of production of silicon carbide electric heating elements, and in particular relates to a silicon carbon rod heating element and a production process. Background Art

[0002] Silicon carbon rod is a non-metallic electric heating element mainly composed of high-purity silicon carbide, consisting of a heating part and a cold end. The performance of the heating part is crucial. When the silicon carbon rod is in use, the heating part is in the furnace, generating heat (converting electrical energy into thermal energy), and its resistance conforms to JB / T3890-2017. The cold end is in the furnace hole and has a smaller resistance value. In the production process of the heating part of the silicon carbon rod, there are currently two different preparation processes, A and B, each of which has unique advantages and limitations.

[0003] The A-type process uses asphalt as a binder, mixes raw materials such as silicon carbide and graphite electrode powder evenly, and then forms a rod blank by hot extrusion. The formed rod blank needs to be cooled by cold water to fix its shape and structure. Subsequently, it is necessary to carry out biscuit firing at a high temperature of about 1000°C, and subsequent firing or roasting treatment to ensure that the density and strength of the rod blank meet the use requirements. This process can produce silicon carbon rods with a density of more than 2.55g / cm³, which have high mechanical strength and good thermal conductivity. However, the A-type process will produce a large amount of polluting gases during the production process, such as smoke and harmful gases produced by the combustion of asphalt, which causes serious pollution to the environment and does not meet the current increasingly stringent environmental protection requirements. In addition, the resistance value adjustment range of the A-type process is relatively limited, and it is difficult to produce high-resistance products. For example, the patent CN116041077A discloses that although this process can improve the density to a certain extent, it still cannot completely break through the limitations of the A-type process itself.

[0004] Compared with the Type A process, the Type B process uses a more environmentally friendly preparation method. It uses a small amount of cellulose and PVA as temporary binders, and uses silicon carbide as the main raw material for cold extrusion to form a rod blank. The rod blank only needs to be dried at a low temperature not exceeding 200°C to remove moisture and volatiles. Subsequently, a recrystallization sintering is carried out at a high temperature to combine the particles of the rod blank and further improve the strength. The Type B process not only avoids the pollution problems caused by the Type A process, but also improves the controllability of the resistance and red heat uniformity of the prepared silicon carbon rod. CN105837217A discloses a silicon carbon rod and a preparation method thereof, including a heating element, which is made of the following raw materials by mass fraction: 97% to 98.7% silicon carbide, 1% to 3% binder, and 0.1% to 0.3% boron nitride. The heating part is formed by extrusion molding, but because silicon carbide accounts for more than 97% of the ratio, there is a problem of large friction between the blank and the mold barrel and the die nozzle and mold needle. If the pressure is increased to make the density reach 2.55g / cm 3 If the above conditions are met, the blank will have no fluidity and will be difficult to extrude. Even when the pressure is too high, the mold and equipment will be damaged, and a high-density heating element cannot be produced. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies in the prior art and provide a production process for a silicon carbon rod heating element, which is environmentally friendly and produces a heating element with high density and adjustable resistance.

[0006] The production process of the silicon carbon rod heating element of the present invention comprises the following steps: (1) Pretreatment of silicon carbide raw materials: Mix the silicon carbide raw materials with additives and pre-sinter them; (2) Mixing and molding: Mix the untreated silicon carbide raw material with the pretreated silicon carbide, graphite electrode powder, carbon black, and binder, and extrude them to obtain a rod blank; (3) Drying: Drying the rod blank; (4) Primary firing: firing in a carbon tube furnace or vacuum furnace; (5) Secondary firing: Firing in a carbon tube furnace or vacuum furnace to obtain a silicon carbon rod heating element.

[0007] The additive in step (1) is boron nitride or boron carbide, and its added mass is 0.5-6‰ of the pretreated silicon carbide raw material, and the purity of the silicon carbide is above 99%.

[0008] The pre-sintering in step (1) is carried out in a vacuum furnace at 1900-1950° C. for 1 h-1.5 h, or in a carbon tube furnace at 2000-2100° C. for 1.0 h-1.5 h in an Ar gas atmosphere.

[0009] The mass percentages of the unpretreated silicon carbide raw material and the pretreated silicon carbide, graphite electrode powder, carbon black, and binder in step (2) are 80% to 90% silicon carbide, 6% to 15% graphite electrode powder, 0.5% to 1.0% carbon black, and 3.5% to 4% binder.

[0010] The mass percentage of the unpretreated silicon carbide raw material and the pretreated silicon carbide in step (2) is 55%-65%:35%-45%.

[0011] The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 7:3 to 5:5.

[0012] The particle size of graphite electrode powder is 1.5μm~3.5μm, and the carbon content is ≥99.9%; the specific surface area of ​​carbon black is 1000~2000m 2 / g, specific gravity is 1.9~2.0g / cm³, and carbon content is ≥99%.

[0013] The drying temperature of step (3) is 170-190°C and the drying time is 8-10 hours.

[0014] The carbon tube furnace firing temperature of step (4) is 2150-2200°C, and the firing time is 2-3 hours; or the vacuum furnace firing temperature is 1650-1700°C, and the firing time is 8-10 hours.

[0015] The carbon tube furnace firing temperature of step (5) is 2460-2480°C, and the firing time is 2.5-3.0 hours; or the vacuum furnace firing temperature is 2180-2200°C, and the firing time is 2.0-2.5 hours.

[0016] Specifically, the production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: Mix 35%~45% silicon carbide raw materials with 0.5~6‰ boron nitride or boron carbide, and treat them in a vacuum furnace at 1900~1950℃ for 1h~1.5h, or in an Ar gas atmosphere carbon tube furnace at 2000~2100℃ for 1.0h~1.5h.

[0017] (2) Mixing and forming: 80% to 90% of the remaining untreated 55% to 65% silicon carbide raw material and 35% to 45% silicon carbide pretreated in step (1), 6% to 15% graphite electrode powder, 0.5% to 1.0% carbon black, and 3.5% to 4% binder are mixed, and water is added. The mixture is cold extruded by a hydraulic press to form a rod blank. The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 7:3 to 5:5.

[0018] (3) Drying: Dry the rod blank at 170-190℃ for 8-10h.

[0019] (4) Primary firing: The dried rod blank is covered with silicon particles for silicification (the mass ratio of the rod blank to silicon particles is 100:43~100:66), and fired in a carbon tube furnace protected by an atmosphere (Ar or N2) at a temperature of 2150~2200℃ for 2~3h; or fired in a vacuum furnace at a temperature of 1650~1700℃ for 8~10h. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0020] (5) Secondary firing: After the primary firing in step (4), the rod blank is covered with graphite electrode powder of 10% to 15% of the rod blank mass, and is further fired in a carbon tube furnace at a temperature of 2460 to 2480°C for 2.5 to 3.0 h; or in a vacuum furnace at a temperature of 2180 to 2200°C for 2.0 to 2.5 h to obtain a silicon carbon rod heating element, which meets the requirements of Appendix C of JB / T3890-2017.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The production process of the silicon carbon rod heating element of the present invention adopts cellulose / PVA environmentally friendly binder to replace asphalt, eliminates high-temperature pollution emissions, reduces drying energy consumption, and has no harmful gases in the production process, which meets environmental protection requirements.

[0022] (2) The production process of the silicon carbon rod heating element of the present invention changes the conductive properties of the silicon carbide material through pretreatment, thereby increasing the resistance of this part of silicon carbide, and combining it with the gradient ratio of the untreated material to achieve wide range control of the resistivity of the heating element (meeting Annex C of JB / T3890-2017).

[0023] (3) The production process of the silicon carbon rod heating element of the present invention converts the carbon in the blank into new silicon carbide in the first firing process to increase the total content of silicon carbide, and further purifies the composition of the product through the second firing process to improve the recrystallization process. The double firing constructs a high-density skeleton of the product with high density and good stability. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments.

[0025] The raw materials and additives used in the following examples and comparative examples are all commercially available products. The particle size of the graphite electrode powder is 1.5 μm to 3.5 μm, and the carbon content is ≥ 99.9%; the specific surface area of ​​the carbon black is 1000 to 2000 m 2 / g, specific gravity is 1.9~2.0g / cm³, carbon content is ≥99%, and silicon carbide raw material content is ≥99%.

[0026] Example 1 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 40% silicon carbide raw materials were mixed with 2‰ boron nitride and treated in a vacuum furnace at 1900°C for 1.5 h.

[0027] (2) Mixing and molding: The remaining 60% of the untreated silicon carbide raw material is mixed with 80% of the silicon carbide pretreated in step (1), 15% of graphite electrode powder (particle size 2.50 μm), 1.0% of carbon black, and 4.0% of a binder. The mixture is mixed with 15% water in a mixer for 30 minutes. The uniformly mixed material is placed in a hydraulic press die and extruded to form a rod blank. The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 6:4.

[0028] (3) Drying: Dry the rod blank at 180℃ for 9h.

[0029] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh, and then sintered (the mass ratio of the rod blank to the silicon particles is 100:66). The rod blank is then fired in a vacuum furnace at a temperature of 1700°C for 8 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0030] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 12% of the rod blank mass of graphite electrode powder, and is further sintered in a vacuum furnace at a temperature of 2200°C for 2.0 h to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 1.0 Ω / 1000 mm at 1050°C±50°C, and a density of 2.95 g / cm 3 .

[0031] Example 2 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: Mix 40% silicon carbide raw materials with 4‰ boron carbide and treat them in a vacuum furnace at 1950℃ for 1h.

[0032] (2) Mixing and molding: The remaining 60% of the untreated silicon carbide raw material is mixed with 90% of the silicon carbide pretreated in step (1), 6% of graphite electrode powder (particle size 2.90 μm), 0.5% of carbon black, and 3.5% of a binder. 10% of the weight of the above raw material powder and water are added. The mixture is mixed in a mixer for 30 minutes. The uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank. The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 6:4.

[0033] (3) Drying: Dry the rod blank at 170℃ for 10h.

[0034] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:43), and then fired in a vacuum furnace at a temperature of 1650°C for 10 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0035] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 15% of the mass of the rod blank with graphite electrode powder, and is further sintered in a vacuum furnace at a temperature of 2180°C for 2.5 hours to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 2.0 Ω / 1000 mm at 1050°C±50°C, and a density of 2.66 g / cm 3 .

[0036] Example 3 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 45% silicon carbide raw materials were mixed with 6‰ boron carbide and treated at 2000°C in an Ar gas atmosphere carbon tube furnace for 1.5 h.

[0037] (2) Mixing and molding: The remaining 55% of untreated silicon carbide raw materials are mixed with 85% of silicon carbide pretreated in step (1), 10.5% of graphite electrode powder (particle size 2.90 μm), 0.8% of carbon black, and 3.7% of binder, and 12.5% ​​of water by weight of the above raw material powders are added. The mixture is mixed in a mixer for 30 minutes, and the uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank; The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 7:3.

[0038] (3) Drying: Dry the rod blank at 190℃ for 8h.

[0039] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:54), and is placed in a carbon tube furnace protected by Ar atmosphere for firing at a temperature of 2150°C for 3 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0040] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 10% of the mass of the rod blank with graphite electrode powder, and is further sintered in a carbon tube furnace at a temperature of 2460°C for 3.0 h to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 2.5 Ω / 1000 mm at 1050°C±50°C, and a density of 2.72 g / cm 3 .

[0041] Example 4 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 35% silicon carbide raw materials were mixed with 2‰ boron nitride and treated at 2100°C in an Ar gas atmosphere carbon tube furnace for 1.0 h.

[0042] (2) Mixing and molding: The remaining 65% of untreated silicon carbide raw materials are mixed with 83% of silicon carbide pretreated in step (1), 13% of graphite electrode powder (particle size 2.90 μm), 0.5% of carbon black, and 3.5% of binder, and 13.5% of water in the same mass as the above raw material powders are added. The mixture is mixed in a mixer for 30 minutes, and the uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank; The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 5:5.

[0043] (3) Drying: Dry the rod blank at 190℃ for 8h.

[0044] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:60), and is placed in a carbon tube furnace protected by N2 atmosphere for firing at a temperature of 2200°C for 2 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0045] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 10% to 15% of the mass of the rod blank with graphite electrode powder, and is further sintered in a carbon tube furnace at a temperature of 2480°C for 2.5 hours to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 0.8 Ω / 1000 mm at 1050°C ± 50°C, and a density of 2.90 g / cm 3 .

[0046] Example 5 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 40% silicon carbide raw materials were mixed with 3.5‰ boron nitride and treated in a vacuum furnace at 1900℃ for 1.5h.

[0047] (2) Mixing and molding: The remaining 60% of untreated silicon carbide raw materials are mixed with 86% of silicon carbide pretreated in step (1), 9.4% of graphite electrode powder (particle size 2.90 μm), 1.0% of carbon black, and 3.6% of binder, and 13% of water by weight of the above raw material powders are added. The mixture is mixed in a mixer for 30 minutes, and the uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank; The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 6:4.

[0048] (3) Drying: Dry the rod blank at 180℃ for 9h.

[0049] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:60), and then fired in a vacuum furnace at a temperature of 1700°C for 8 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0050] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 12% of the rod blank mass of graphite electrode powder, and is further sintered in a vacuum furnace at a temperature of 2200°C for 2.0 h to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 1.8 Ω / 1000 mm at 1050°C±50°C, and a density of 2.79 g / cm 3 .

[0051] Example 6 The production process of the silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 45% silicon carbide raw materials were mixed with 0.5‰ boron nitride and treated in a vacuum furnace at 1900℃ for 1.5h.

[0052] (2) Mixing and molding: The remaining 55% of untreated silicon carbide raw materials are mixed with 90% of silicon carbide pretreated in step (1), 5.5% of graphite electrode powder (particle size 2.90 μm), 0.8% of carbon black, and 3.7% of binder, and 10.8% of water by weight of the above raw material powders are added. The mixture is mixed in a mixer for 30 minutes, and the uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank; The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 6:4.

[0053] (3) Drying: Dry the rod blank at 180℃ for 9h.

[0054] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:45), and then placed in a vacuum furnace for firing at a temperature of 1700°C for 8 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0055] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 15% of the rod blank mass of graphite electrode powder, and is further sintered in a vacuum furnace at a temperature of 2200°C for 2.0 h to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 1.3 Ω / 1000 mm at 1050°C±50°C, and a density of 2.67 g / cm 3 .

[0056] Comparative Example 1 A production process of a silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 40% silicon carbide raw materials were mixed with 2‰ boron nitride and treated in a vacuum furnace at 1900°C for 1.5 h.

[0057] (2) Mixing and molding: The remaining 60% of the untreated silicon carbide raw material is mixed with 97% of the silicon carbide pretreated in step (1), 0.7% of graphite electrode powder (particle size 2.50 μm), 0.5% of carbon black, and 1.8% of a binder. The mixture is mixed with 8.5% water in a mixer for 30 minutes. The uniformly mixed material is placed in a hydraulic press die and extruded to form a rod blank. The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 6:4.

[0058] (3) Drying: Dry the rod blank at 180℃ for 9h.

[0059] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh, and then sintered (the mass ratio of the rod blank to the silicon particles is 100:12). The rod blank is then fired in a vacuum furnace at a temperature of 1700°C for 8 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0060] (5) Secondary sintering: After the primary sintering in step (4), the rod blank is covered with 12% of the rod blank mass of graphite electrode powder, and is further sintered in a vacuum furnace at a temperature of 2200°C for 2.0 h to obtain a silicon carbon rod heating element with a diameter of 30 mm, a unit length resistance of 2.9 Ω / 1000 mm at 1050°C±50°C, and a density of 2.52 g / cm 3 .

[0061] Comparative Example 2 This comparative example is the same as Example 1, but the binder is all polyvinyl alcohol, and the cellulose is removed, and the preparation is the same as Example 1. When the vertical forming exceeds 2000mm, the rod blank breaks more than 15%. However, when the present invention adds cellulose to the binder, there is no rod blank breakage.

[0062] Comparative Example 3 A production process of a silicon carbon rod heating element comprises the following steps: (1) Pretreatment of silicon carbide raw materials: 45% silicon carbide raw materials were mixed with 6‰ boron carbide and treated at 2000°C in an Ar gas atmosphere carbon tube furnace for 1.5 h.

[0063] (2) Mixing and molding: The remaining 55% of untreated silicon carbide raw materials are mixed with 85% of silicon carbide pretreated in step (1), 10.5% of graphite electrode powder (particle size 2.90 μm), 0.8% of carbon black, and 3.7% of binder, and 12.5% ​​of water by weight of the above raw material powders are added. The mixture is mixed in a mixer for 30 minutes, and the uniformly mixed material is placed in a hydraulic press die barrel for extrusion molding to form a rod blank; The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 7:3.

[0064] (3) Drying: Dry the rod blank at 190℃ for 8h.

[0065] (4) Primary firing: The dried rod blank is covered with silicon particles with a particle size of 20-60 mesh for silicification firing (the mass ratio of the rod blank to the silicon particles is 100:54), and is placed in a carbon tube furnace protected by Ar atmosphere for firing at a temperature of 2460°C for 2 hours. After firing, the residue adhering to the rod body is cleaned and eliminated.

[0066] In comparative example 3, after only one firing, the furnace tube shrinkage is serious, the service life is less than 10 days, and the resistance controllability of the heating element is poor. However, the furnace tube of the present invention has a service life extended by more than 2 times, meeting the conditions for mass production.

Claims

1. A production process for a silicon carbon rod heating element, characterized in that: The following steps are involved: (1) Pretreatment of silicon carbide raw materials: Mix the silicon carbide raw materials with additives and pre-sinter them; (2) Mixing and molding: Mix the untreated silicon carbide raw material with the pretreated silicon carbide, graphite electrode powder, carbon black, and binder, and extrude them to obtain a rod blank; (3) Drying: Drying the rod blank; (4) Primary firing: firing in a carbon tube furnace or vacuum furnace; (5) Secondary firing: Firing in a carbon tube furnace or vacuum furnace to obtain a silicon carbon rod heating element.

2. The production process of the silicon carbon rod heating element according to claim 1, characterized in that: The additive in step (1) is boron nitride or boron carbide, and its added mass is 0.5-6‰ of the pretreated silicon carbide raw material, and the purity of the silicon carbide is above 99%.

3. The production process of the silicon carbon rod heating element according to claim 2, characterized in that: The pre-sintering in step (1) is carried out in a vacuum furnace at 1900-1950° C. for 1 h-1.5 h, or in a carbon tube furnace at 2000-2100° C. for 1.0 h-1.5 h in an Ar gas atmosphere.

4. The production process of the silicon carbon rod heating element according to claim 1, characterized in that: The mass percentages of the unpretreated silicon carbide raw material and the pretreated silicon carbide, graphite electrode powder, carbon black, and binder in step (2) are 80% to 90% silicon carbide, 6% to 15% graphite electrode powder, 0.5% to 1.0% carbon black, and 3.5% to 4% binder.

5. The production process of the silicon carbon rod heating element according to claim 4, characterized in that: The mass percentage of the unpretreated silicon carbide raw material and the pretreated silicon carbide in step (2) is 55%-65%:35%-45%.

6. The production process of the silicon carbon rod heating element according to claim 4, characterized in that: The binder is obtained by mixing cellulose and polyvinyl alcohol in a mass ratio of 7:3 to 5:

5.

7. The production process of the silicon carbon rod heating element according to claim 5, characterized in that: The particle size of graphite electrode powder is 1.5μm~3.5μm, and the carbon content is ≥99.9%; the specific surface area of ​​carbon black is 1000~2000m 2 / g, specific gravity is 1.9~2.0g / cm³, and carbon content is ≥99%.

8. The production process of the silicon carbon rod heating element according to claim 1, characterized in that: The drying temperature of step (3) is 170-190°C, and the time is 8-10 hours; the carbon tube furnace firing temperature of step (4) is 2150-2200°C, and the firing time is 2-3 hours; or the vacuum furnace firing temperature is 1650-1700°C, and the firing time is 8-10 hours.

9. The production process of the silicon carbon rod heating element according to claim 1, characterized in that: The carbon tube furnace firing temperature of step (5) is 2460-2480°C, and the firing time is 2.5-3.0 hours; or the vacuum furnace firing temperature is 2180-2200°C, and the firing time is 2.0-2.5 hours.

10. A silicon carbon rod heating element, characterized in that: It is produced by the production process of the silicon carbon rod heating element according to any one of claims 1 to 9.