A high temperature resistance furnace electric heating element structure and arrangement method thereof

Abstract

The present invention provides an electric heating element structure and arrangement method for a high-temperature resistance furnace, including an electric heating element, wherein the electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires, and the measurement and control mechanism is used to measure and adjust the temperature. The heating element is arranged at the top of the furnace, and the furnace temperature of the heating furnace is made uniform through zone arrangement and control. The electric heating element is hung on the furnace top through a suspension rod, which is convenient to install and avoids direct contact with the conductive wire after the electric heating element is deformed. Compared with a trolley-type resistance furnace, the electric heating element is easy to replace. When a fuse or a broken wire is caused and the furnace is stopped, it does not need to be replaced as a whole. It only needs to cut off the broken wire part and replace it or directly connect the wire; the maintenance and processing are convenient, simple and versatile. The diameter of the lead-out electrode of the electric heating element is 3 times greater than the diameter of the electric heating element, and the lead-out electrode material is consistent with the material of the electric heating element, which can reduce the temperature of the lead-out electrode and the wiring connection.

Description

Technical Field

[0001] The invention belongs to the technical field of resistance heating furnaces, and in particular relates to an electric heating element structure for a high-temperature resistance furnace and an arrangement method thereof. Background Art

[0002] Resistance furnace is an industrial furnace that uses electric current to heat the electric heating element or heating medium in the furnace, thereby heating the workpiece or material. The electric heating element is a resistance wire, carbon silicon rod, etc. According to the temperature, it is divided into low-temperature, medium-temperature and high-temperature resistance furnaces. The working temperature is below 650℃ for low-temperature furnaces, 650-1000℃ for medium-temperature furnaces, and above 1000℃ for high-temperature furnaces. In high-temperature and medium-temperature furnaces, heating is mainly carried out by radiation. In low-temperature furnaces, heating is carried out by convection heat transfer. The electric heating element is installed in the air duct, and the fan forces the gas in the furnace to circulate to enhance convection heat transfer.

[0003] The existing general resistance furnace is a trolley-type resistance furnace. The electric heating elements are arranged on both sides of the furnace and in the grooves at the bottom of the furnace. The circulation fan and the guide cover provided outside the tempering fan are used to circulate the hot air in the furnace, so as to achieve a uniform processing temperature for the workpiece. The end wall and furnace door of the large trolley-type resistance furnace are also equipped with electric heating elements. The advantages are simple structure, good versatility, and low purchase cost. The disadvantage is that this type of furnace is only suitable for heat treatment and heating of small and medium-sized workpieces. When the furnace bottom is removed, the heat loss in the furnace is large and the furnace temperature drops quickly. If the heating wire is fused or broken, it is troublesome to handle, repair and replace.

[0004] At present, the installation of electric heating elements is to insert ceramic nails into the fiber folding blocks of the furnace lining for fixing. As a result, when the resistance furnace is working at a high temperature of 1100℃, obvious cracks will appear on the furnace wall and the outer wall will overheat, resulting in poor performance and short service life. In addition, the installation of electric heating elements is mostly fixed with ceramic nails. Since ceramic nails are heavier than hooks and occupy a large space, it is easy to cause the electric heating elements to deform and directly touch the conductive surface. At the same time, there is no reasonable partition, resulting in uneven heating of the thin slab by the electric heating elements. Summary of the invention

[0005] The purpose of the present invention is to provide an electric heating element structure for a high-temperature resistance furnace to overcome the technical problems existing in the prior art.

[0006] Another object of the present invention is to provide a method for arranging the structure of electric heating elements for a high-temperature resistance furnace, which is partitioned and controlled to effectively solve the problem of uniformity of heating of thin slabs by the electric heating elements.

[0007] To this end, the technical solution provided by the present invention is as follows:

[0008] A high-temperature resistance furnace electric heating element structure includes a plurality of electric heating elements arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes a plurality of heating wires, and the measurement and control mechanism is used to measure and adjust the temperature.

[0009] The electric heating element of each zone is formed into a serpentine shape by connecting multiple heating wires end to end. The diameter of the lead-out electrode of the electric heating element is greater than 3 times the diameter of the electric heating element, and the lead-out electrode material is the same as that of the electric heating element.

[0010] The electric heating elements are arranged in zones along the direction of the furnace inlet and outlet, wherein the power of the electric heating elements close to the furnace outlet is greater than the power of the electric heating elements arranged in other zones.

[0011] The electric heating element is hung below the furnace top.

[0012] The measurement and control mechanism includes a thermocouple and a temperature controller. The thermocouple is electrically connected to the temperature controller, which is electrically connected to a transformer. The temperature controller is used to collect temperature data of the thermocouple and adjust the transformer voltage after comparing it with a set value.

[0013] The power of the electric heating elements near the furnace mouth is 15-20% greater than the power of the electric heating elements arranged in other areas.

[0014] The furnace top includes a rectangular tube frame and a refractory layer, the refractory layer is fixed to a fixed plate of the rectangular tube frame through a suspension rod, there are multiple suspension rods and a hanging structure is provided at the lower end, and the electric heating element is hung under the furnace top through the hanging structure.

[0015] The electric heating element is a tungsten wire or a molybdenum wire.

[0016] A method for arranging an electric heating element structure for a high-temperature resistance furnace comprises the following steps: Step 1) determining the material of the electric heating element according to the maximum use temperature of the high-temperature resistance furnace;

[0017] Step 2) Determine the installed power of the electric heating element according to the volume of the heating resistance furnace P , then determine the installed power of each zone, and determine the number of heating wires in each zone based on the installed power, voltage, and resistance of a single heating wire;

[0018]

[0019] In the formula, P is the heating furnace power, KW; K It is the comprehensive correction coefficient, which increases with the increase of furnace temperature and takes the value of 100-300; V is the volume of the heating resistance furnace;

[0020] Step 3) Connect the multiple heating wires in each zone end to end to form a snake shape, hang them on the top of the furnace in sections along the inlet and outlet direction of the furnace, and arrange the measurement and control mechanism in sections to complete the arrangement of the electric heating element structure.

[0021] The volume of the heating resistance furnace is the sum of the furnace volume and the furnace neck volume, and the furnace neck volume is the volume between the furnace mouth and the furnace.

[0022] The beneficial effects of the present invention are:

[0023] The electric heating element structure for the high-temperature resistance furnace provided by the present invention has heating elements arranged on the top of the furnace, and the furnace temperature of the heating furnace is made uniform through zoning arrangement and control.

[0024] The electric heating element is hung on the furnace top through a suspension rod, which is convenient for installation and prevents the electric heating element from directly touching the conductive material after deformation.

[0025] Compared with the trolley-type resistance furnace, the electric heating element is easy to replace. When the equipment is used improperly and causes a fuse or broken wire, there is no need to replace the entire part after the furnace is stopped. You only need to cut off the broken wire part and replace it or directly connect the wire. The maintenance and processing is convenient, simple and versatile.

[0026] The diameter of the lead-out electrode of the electric heating element is 3 times greater than the diameter of the electric heating element, and the material of the lead-out electrode is consistent with that of the electric heating element, which can reduce the temperature of the connection between the lead-out electrode and the wiring.

[0027] In order to make the above contents of the present invention more clearly understood, preferred embodiments are given below and described in detail in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the arrangement of the electric heating element of the present invention;

[0029] Figure 2 It is a schematic diagram of the lead-out electrodes of the electric heating element;

[0030] Figure 3 It is a schematic diagram of the boom structure;

[0031] Figure 4 This is a schematic diagram of the top of the furnace.

[0032] In the figure:

[0033] Description of reference numerals:

[0034] 1. Heating wire; 2. Hanging rod; 3. Furnace top; 4. Rectangular tube frame; 5. Nut; 6. Refractory layer; 7. Lead-out electrode; 8. Hanging structure; 9. Pull rod. DETAILED DESCRIPTION

[0035] The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0036] It should be noted that, in the present invention, the top, bottom, left and right in the figure are regarded as the top, bottom, left and right of the electric heating element structure for the high-temperature resistance furnace described in this specification.

[0037] The exemplary embodiments of the present invention are now described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0038] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0039] Embodiment 1:

[0040] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0041] The electric heating element structure for the high-temperature resistance furnace provided by the present invention has heating elements arranged on the top of the furnace, and the furnace temperature of the heating furnace is made uniform through zoning arrangement and control.

[0042] Embodiment 2:

[0043] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0044] The electric heating element of each zone is formed into a serpentine shape by connecting multiple heating wires 1 end to end. The diameter of the lead-out electrode 7 of the electric heating element is greater than 3 times the diameter of the electric heating element, and the material of the lead-out electrode 7 is the same as that of the electric heating element. Figure 1 and Figure 2 shown.

[0045] The diameter of the lead-out electrode 7 of the electric heating element is 3 times greater than the diameter of the electric heating element, and the material of the lead-out electrode 7 is consistent with that of the electric heating element, which can reduce the temperature of the connection between the lead-out electrode 7 and the wiring.

[0046] Embodiment 3:

[0047] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0048] The electric heating elements are arranged in zones along the direction of the furnace inlet and outlet, wherein the power of the electric heating elements close to the furnace outlet is greater than the power of the electric heating elements arranged in other zones.

[0049] In the area near the furnace mouth, the heat loss during the furnace door opening process is too large, so the surface power per unit area near the furnace mouth needs to be increased. In this embodiment, the power of the electric heating element near the furnace mouth is 15-20% greater than the power of the electric heating element arranged in other areas.

[0050] Embodiment 4:

[0051] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0052] The electric heating element is hung below the furnace top 3 .

[0053] The electric heating element is hung on the furnace top 3 through the suspension rod 2, which is convenient for installation and prevents the electric heating element from directly touching the conductive material after deformation.

[0054] Compared with the trolley-type resistance furnace, the electric heating element is easy to replace. When the equipment is used improperly and causes a fuse or broken wire, there is no need to replace the entire part after the furnace is stopped. You only need to cut off the broken wire part and replace it or directly connect the wire. The maintenance and processing is convenient, simple and versatile.

[0055] Embodiment 5:

[0056] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0057] The measurement and control mechanism includes a thermocouple and a temperature controller. The thermocouple is electrically connected to the temperature controller, which is electrically connected to a transformer. The temperature controller is used to collect temperature data of the thermocouple and adjust the transformer voltage after comparing it with a set value.

[0058] In this embodiment, if Figure 1 As shown in the figure, the electric heating elements are arranged in three zones. The temperature control system uses a three-channel temperature controller (model 2604) to control the temperature in the furnace. The temperature is collected through three thermocouples, and the collected data is sent to their respective channels to control the temperature of the three zones of the furnace respectively. When the temperature of a certain zone is too low or too high, the temperature controller controls the current and voltage of the transformer through the built-in PID adjustment controller to make the furnace temperature reach the set temperature value.

[0059] Embodiment 6:

[0060] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0061] The electric heating element is hung below the furnace top 3 .

[0062] Among them, the furnace top 3 includes a rectangular tube frame 4 and a refractory layer 6, and the refractory layer 6 is fixed to the fixed plate of the rectangular tube frame 4 through a hanger 2. The hanger 2 is multiple and has a hanging structure 8 at the lower end. The electric heating element is hung under the furnace top 3 through the hanging structure 8.

[0063] like Figure 3 As shown, the suspension rod 2 includes three parts, the upper part is made of stainless steel, the middle part is made of molybdenum, and the lower part is made of tungsten. The bottom end of the lower part is provided with a suspension structure 8. The upper part, the middle part and the lower part are connected by threads.

[0064] The main functions of the suspension rod 2 are to connect and fix the refractory fiberboard and to fix the heating wire 1 through the suspension structure 8. The suspension rod 2 is arranged in the middle of the multi-layer refractory layer 6.

[0065] like Figure 4 As shown, the end of the furnace roof 3 is fixed by nuts 5 after passing through the multi-layer refractory layer 6 through the tie rod 9. The tie rod 9 includes an upper half and a lower half, which are connected by threads. The upper half is made of stainless steel and the lower half is made of molybdenum. The function of the tie rod 9 is to connect and fix the refractory layer 6. The lower half is made of high-temperature molybdenum material for fire resistance.

[0066] Embodiment 7:

[0067] The present embodiment provides an electric heating element structure for a high-temperature resistance furnace, including an electric heating element. The electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element includes multiple heating wires 1, and the measurement and control mechanism is used to measure and adjust the temperature.

[0068] The electric heating element is a tungsten wire or a molybdenum wire.

[0069] In this embodiment, the heating furnace is a hydrogen resistance heating furnace, and the electric heating element material is selected from tungsten or molybdenum. Since the temperature of the heating furnace is 1650°C, the temperature of the electric heating element should be between 1700°C and 1800°C. The melting point of molybdenum is 2610°C. Molybdenum has the characteristics of high strength, high hardness, and excellent mechanical properties, and can still maintain high strength and high hardness at high temperatures, so molybdenum wire is selected as the electric heating element.

[0070] Embodiment 8:

[0071] This embodiment provides a method for arranging an electric heating element structure for a high-temperature resistance furnace, comprising the following steps: Step 1) determining the material of the electric heating element according to the maximum operating temperature of the high-temperature resistance furnace;

[0072] Step 2) Determine the installed power of the electric heating element according to the volume of the heating resistance furnace P , and then determine the installed power of each zone, and determine the number of heating wires 1 in each zone according to the installed power, voltage, and resistance of a single heating wire 1;

[0073]

[0074] In the formula, P is the heating furnace power, KW; K It is the comprehensive correction coefficient, which increases with the increase of furnace temperature and takes the value of 100-300; V is the volume of the heating resistance furnace;

[0075] Step 3) Connect the multiple heating wires 1 in each zone end to end to form a snake shape, hang them on the top of the furnace in sections along the furnace inlet and outlet direction, and arrange the measurement and control mechanism in sections to complete the arrangement of the electric heating element structure.

[0076] The volume of the heating resistance furnace is the sum of the furnace volume and the furnace neck volume, and the furnace neck volume is the volume between the furnace mouth and the furnace.

[0077] In this embodiment, the heating furnace is a hydrogen resistance heating furnace (furnace size 4350×3280×610), and the electric heating element material is selected from tungsten or molybdenum. Since the temperature of the heating furnace is 1650°C, the temperature of the electric heating element should be between 1700°C and 1800°C. The melting point of molybdenum is 2610°C. Molybdenum has the characteristics of high strength, high hardness, and excellent mechanical properties, and can still maintain high strength and high hardness at high temperatures, so molybdenum wire is selected as the electric heating element.

[0078] like Figure 1 As shown, the power of the heating furnace is distributed in three areas. The installed power of the electric heating element is determined according to the volume of the heating resistance furnace. P , and then determine the installed power of each zone, and determine the number of heating wires 1 in each zone according to the installed power, voltage, and resistance of a single heating wire 1;

[0079]

[0080] In the formula, P is the heating furnace power, KW; K It is the comprehensive correction coefficient, which increases with the increase of furnace temperature and takes the value of 100-300; V is the volume of the heating resistance furnace.

[0081] in, K It is related to the furnace temperature, the type of heat shield, the length of heating time, and the operation mode. At 1400℃, K=150~200, at 1600℃, K=200~250, and at 1800℃, K=250~300. Because the furnace has a large volume, a lot of charge, and a large heat loss and heat storage, K The maximum value is 300.

[0082] The relationship between the volume, installed power and power per unit furnace surface area of ​​the heating resistance furnace is shown in Table 1.

[0083] Table 1 Relationship between the volume, installed power and power per unit furnace surface area of ​​the heating resistance furnace

[0084]

[0085] According to the size of the furnace, the length of each zone of the three-zone heating wire 1 is preliminarily arranged, and the molybdenum wire with a diameter of φ3 is selected. The resistance value of a single molybdenum wire is calculated:

[0086] Where: R 0 is the resistance value of a single wire (Ω); is the resistivity of molybdenum at 1800℃ =0.556Ω·mm 2 / m; S is the cross-sectional area of ​​the heating wire 1 mm 2 ;L is the length of a single heating wire 1.

[0087] Voltage selection: The working voltage of the electric heating element should not be too high, because the insulation resistance of the refractory material drops sharply at high temperature, and the evaporation of the electric heating element increases. The conductivity of the insulator surface increases, and arc discharge is easy to occur between the electrodes, which increases the danger at work. If the voltage is too high, the electric heating element will be thin and long, making installation difficult and shortening the service life; if the voltage is too low, the electric heating element will be thick and short, the amount of components will increase, and the cost will be increased. Usually the voltage is controlled below 100V.

[0088] Based on the heating furnace power calculated previously, the power distribution in the three zones is preliminarily determined, and the current I and resistivity R in each zone are calculated. , Where: I is the current, A; P i is the power per zone, W; R is the resistance value of each zone (Ω).

[0089] Determine the number of heating elements per zone .

[0090] Calculate the actual surface power (W / cm 2 )

[0091]

[0092] Where: W b - Actual unit surface power of the component (W / cm 2 ); P i is the power of a single zone (W); n is the number of each electric heating element; d is the diameter of a single wire (cm); L is the length of the single zone wire (cm); Wy is the permissible surface power per unit of the component (W / cm 2 ).

[0093] Calculate the power and number of heating elements in each zone according to the above formula until the values ​​meet the requirements in Table 2.

[0094] Table 2 Permissible unit surface power W of electric heating elements y (W / cm 2 )

[0095]

[0096] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for arranging a structure of electric heating elements for a high-temperature resistance furnace, characterized in that: The following steps are involved: Step 1) determining the material of the electric heating element according to the maximum operating temperature of the high temperature resistance furnace; Step 2) determining the installed power P of the electric heating element according to the volume of the heating resistance furnace, then determining the installed power of each zone, and determining the number of heating wires (1) in each zone according to the installed power, voltage, and resistance of a single heating wire (1); Number of heating elements per zone ,in, , , , power per zone P i The sum is equal to the heating furnace power P ; In the formula, P is the heating furnace power, KW; P i Power per zone, KW ；K It is the comprehensive correction coefficient, which increases with the increase of furnace temperature and takes the value of 100-300; V is the volume of the heating resistance furnace; R 0 is the resistance value of a single wire, Ω; is the resistivity, Ω·mm 2 / m; S is the cross-sectional area of ​​the heating wire, mm 2 ; L is the length of a single heating wire, I is the current; Step 3) multiple heating wires (1) in each zone are connected end to end to form a serpentine shape, and are hung on the top of the furnace in sections along the inlet and outlet direction of the furnace mouth, and measurement and control mechanisms are arranged in sections to complete the arrangement of the electric heating element structure; The electric heating element structure for a high-temperature resistance furnace comprises an electric heating element, wherein the electric heating element is multiple and arranged in zones, each zone is provided with a measurement and control mechanism, the electric heating element is arranged at the top of the furnace, the electric heating element comprises multiple heating wires (1), and the measurement and control mechanism is used to measure and adjust the temperature; The electric heating element is suspended below the furnace top (3); the furnace top (3) comprises a rectangular tube frame (4) and a refractory layer (6); the refractory layer (6) is fixed to a fixed plate of the rectangular tube frame (4) via a suspension rod (2); the suspension rod (2) is multiple and has a suspension structure (8) at its lower end; the electric heating element is suspended below the furnace top (3) via the suspension structure (8).

2. The method for arranging a high-temperature resistance furnace electric heating element structure according to claim 1, characterized in that: The electric heating element of each zone is formed into a serpentine shape by connecting a plurality of heating wires (1) end to end. The diameter of the lead-out electrode (7) of the electric heating element is greater than 3 times the diameter of the electric heating element. The material of the lead-out electrode (7) is the same as that of the electric heating element.

3. The method for arranging a high-temperature resistance furnace electric heating element structure according to claim 1, characterized in that: The electric heating elements are arranged in zones along the direction of the furnace inlet and outlet, wherein the power of the electric heating elements close to the furnace outlet is greater than the power of the electric heating elements arranged in other zones.

4. The method for arranging a high-temperature resistance furnace electric heating element structure according to claim 1, characterized in that: The measurement and control mechanism includes a thermocouple and a temperature controller. The thermocouple is electrically connected to the temperature controller, which is electrically connected to a transformer. The temperature controller is used to collect temperature data of the thermocouple and adjust the transformer voltage after comparing it with a set value.

5. The method for arranging the electric heating element structure for a high temperature resistance furnace according to claim 1, characterized in that: The power of the electric heating elements near the furnace mouth is 15-20% greater than the power of the electric heating elements arranged in other areas.

6. The method for arranging the electric heating element structure for a high temperature resistance furnace according to claim 1, characterized in that: The electric heating element is a tungsten wire or a molybdenum wire.

7. The method for arranging a high-temperature resistance furnace electric heating element structure according to claim 1, characterized in that: The volume of the heating resistance furnace is the sum of the furnace volume and the furnace neck volume, and the furnace neck volume is the volume between the furnace mouth and the furnace.

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