Graphite heating tube for uniform heating inside vacuum furnace

Abstract

The utility model discloses a graphite heating tube for vacuum furnace inside even heating, including graphite heating tube, both sides of graphite heating tube all have the joint of fixed communication, the inner wall of graphite heating tube is equipped with spiral flow guide groove, the outer wall of graphite heating tube is fixed with a plurality of reinforcing rings, the inner wall of graphite heating tube is fixed with two variable power density pipe body structures symmetrically, the utility model discloses the organic combination of variable power density pipe body structure, compound type heat field regulation and control structure and integrated high -strength support and deformation -resistant structure's mode of system in pure mechanical has solved the core pain point such as vacuum furnace graphite heating pipe temperature uneven, easy deformation, short life, has the rational structure, the superior performance, safe and reliable, long service life etc. Prominent advantages.

Description

Technical Field

[0001] This utility model relates to the field of heating tube technology in vacuum furnaces, specifically to a graphite heating tube for uniform heating inside a vacuum furnace. Background Technology

[0002] Vacuum heat treatment furnaces are key equipment widely used in processes such as material sintering, annealing, and brazing. The performance of their core component, the heating tube, directly determines the uniformity of the temperature field within the furnace, process stability, and energy consumption. Graphite, due to its high temperature resistance, low coefficient of thermal expansion, and ease of processing, is often the preferred material for heating tubes. However, existing graphite heating tubes still have several significant problems in practical applications: First, traditional graphite tubes with uniform diameter and wall thickness exhibit uneven axial temperature distribution during electric heating due to end effects (rapid heat loss through electrode connectors) and central overheating effects (heat concentration), making it difficult to meet the stringent requirements of high-end manufacturing for furnace temperature uniformity. Second, the thermal radiation efficiency and directional control capability of ordinary smooth tube walls are limited, easily causing radial and circumferential temperature gradients within the furnace, affecting the consistency of workpiece processing. Furthermore, the strength of graphite decreases at high temperatures, and long heating tubes are prone to bending, deformation, or even breakage due to their own weight and thermal stress during long-term high-temperature service, not only shortening their service life but also potentially causing safety accidents such as equipment short circuits. Utility Model Content

[0003] The purpose of this invention is to provide a graphite heating tube for uniform heating inside a vacuum furnace, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a graphite heating tube for uniform heating inside a vacuum furnace, comprising a graphite heating tube, with connectors fixedly connected to both sides of the graphite heating tube, a spiral guide groove formed on the inner wall of the graphite heating tube, multiple reinforcing rings fixedly assembled on the outer wall of the graphite heating tube, and two variable power density tube structures symmetrically fixedly assembled on the inner wall of the graphite heating tube.

[0005] Preferably, each of the variable power density tube structures includes a first tube wall, a second tube wall, and a third tube wall. The first tube wall is connected to the third tube wall through the second tube wall. The inner diameter of the first tube wall is smaller than the inner diameter of the second tube wall, and the inner diameter of the second tube wall is smaller than the inner diameter of the third tube wall. The second tube wall is located near the outer end of the graphite heating tube.

[0006] Preferably, the inner walls of the first pipe wall, the second pipe wall, and the third pipe wall are all fixedly fitted with support rings corresponding to their inner diameters.

[0007] Preferably, the reinforcing ring and the graphite heating tube are integrally formed.

[0008] Compared with the prior art, the beneficial effects of this utility model are: Excellent axial temperature uniformity is achieved: The variable power density tube structure changes the cross-sectional area of ​​the heating tube along the axial direction by designing the tube wall as a stepped variable inner diameter consisting of a first tube wall, a second tube wall, and a third tube wall. According to the principle of resistance heating, under constant current, resistance is inversely proportional to cross-sectional area. By reducing the cross-sectional area in the end region where the temperature is low (corresponding to the third tube wall, where the inner diameter is the largest), the resistance and heating power are increased to compensate for the heat loss at the end. In the middle region where the temperature is high (corresponding to the first tube wall, where the inner diameter is the smallest), the cross-sectional area is increased to reduce the resistance and heating power and suppress central overheating.

[0009] The radial heat field distribution is optimized and the thermal efficiency is improved: This utility model adopts a composite heat field control structure, specifically, a spiral guide groove is opened on the inner wall of the graphite heating tube. This structure can guide and balance the internal heat flow. At the same time, multiple reinforcing rings are set on the outer wall. These reinforcing rings not only play a supporting role, but also act as dense annular heat dissipation turbulence ribs, which greatly increases the effective radiation surface area of ​​the heating tube. This design changes the path and direction of heat radiation, turning the radiation in a single direction into a complex radiation field with multiple angles, effectively filling the heating blind zone, significantly improving the radial and circumferential temperature uniformity of the workpiece area in the furnace, and improving the thermal energy utilization efficiency.

[0010] The overall structural strength and deformation resistance are significantly enhanced, extending the service life. The integrated high-strength support and deformation-resistant structure of this utility model is reflected in two aspects: First, the reinforcing ring and the graphite heating tube are manufactured using an integrated molding process, forming a robust overall frame that greatly enhances the tube's resistance to bending and sagging, effectively preventing deformation at high temperatures. Second, the variable power density tube structure itself reduces thermal stress concentration caused by large temperature differences by balancing axial temperature. These two factors work together to ensure the structural integrity of the heating tube under rapid heating and cooling conditions, thereby significantly extending its service life.

[0011] Improved support stability and installation convenience: The support ring set on the inner wall of the variable power density tube structure provides a stable and precise support point for auxiliary components (such as guide tubes) that may be installed inside, enhancing the rigidity of the entire heating system and facilitating installation and positioning.

[0012] This invention systematically solves the core problems of uneven temperature, easy deformation, and short lifespan of graphite heating tubes in vacuum furnaces through the organic combination of variable power density tube structure, composite thermal field control structure, and integrated high-strength support and anti-deformation structure in a purely mechanical manner. It has outstanding advantages such as reasonable structure, superior performance, safety and reliability, and long service life, and can make the hardness uniformity and deformation effect of product heat treatment better. Attached Figure Description

[0013] Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a partial structural cross-sectional view of the present invention; Figure 3 This is a planar sectional view of the present invention; Figure 4 This is a three-dimensional schematic diagram of the support ring.

[0014] In the figure: 1-graphite heating tube, 2-joint, 3-spiral guide groove, 4-reinforcing ring, 5-support ring, 6-variable power density tube structure, 61-first tube wall, 62-second tube wall, 63-third tube wall. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] Please see Figure 1-4 This utility model provides a graphite heating tube for uniform heating inside a vacuum furnace, including a graphite heating tube 1, with connectors 2 fixedly connected to both sides of the graphite heating tube 1, a spiral guide groove 3 opened on the inner wall of the graphite heating tube 1, multiple reinforcing rings 4 fixedly assembled on the outer wall of the graphite heating tube 1, and two variable power density tube structures 6 symmetrically fixedly assembled on the inner wall of the graphite heating tube 1.

[0017] This graphite heating tube, used for uniform heating inside a vacuum furnace, has a core component of graphite heating tube 1. This tube body is preferably made of high-purity, high-density isostatic graphite material through precision machining to ensure excellent conductivity, heat resistance, and thermal stability. At each of the axial ends of the graphite heating tube 1, a connector 2 is fixedly connected. These connectors 2 are typically made of metal (such as stainless steel) and achieve reliable electrical connection and vacuum sealing with the graphite tube body through a special threading or crimping process. This connection is used to connect to an external power source, providing operating current for the entire heating tube. This symmetrical design facilitates the parallel or series arrangement of multiple heating tubes within the vacuum furnace, forming a uniform heating zone. To achieve effective control of the thermal field, this invention incorporates continuous spiral guide grooves 3 machined on the inner wall of the graphite heating tube 1. The helix angle, groove depth, and groove width need to be precisely calculated and optimized through fluid dynamics simulation. Its main function is to guide the airflow along a predetermined helical path when there is residual gas or process atmosphere inside the tube, thereby prolonging the heat exchange time and promoting the uniform distribution of heat inside the tube, avoiding local overheating. At the same time, multiple reinforcing rings 4 are integrally formed on the outer wall of the graphite heating tube 1 and are evenly distributed along the axial direction. These reinforcing rings 4 not only serve as part of the composite thermal field control structure, enhancing the uniformity of thermal radiation by increasing the outer surface area, but are also key to the integrated high-strength support and anti-deformation structure. They greatly enhance the radial and axial stiffness of the tube body, effectively resisting the bending and deformation tendencies caused by self-weight and thermal stress under long-term high-temperature operation, and ensuring the stability of the relative position between the heating tube and the furnace insulation screen and workpiece.

[0018] Each variable power density tube structure 6 includes a first tube wall 61, a second tube wall 62, and a third tube wall 63. The first tube wall 61 is connected to the third tube wall 63 through the second tube wall 62. The inner diameter of the first tube wall 61 is smaller than the inner diameter of the second tube wall 62, and the inner diameter of the second tube wall 62 is smaller than the inner diameter of the third tube wall 63. The second tube wall 62 is located near the outer end of the graphite heating tube 1.

[0019] Variable power density tube structure 6, such as Figure 2 and Figure 3As clearly shown in the cross-sectional view, the structure is symmetrically arranged at both ends of the tube (i.e., the part near connector 2), with one set at each end. Each set consists of three sections of tube walls with different inner diameters that transition continuously: namely, the first tube wall 61, the second tube wall 62, and the third tube wall 63. The first tube wall 61 has the smallest inner diameter and is located closest to the middle of the tube; the second tube wall 62 has the middle inner diameter; and the third tube wall 63 has the largest inner diameter and is located at the outermost end. This stepped diameter design causes the conductive cross-sectional area of ​​the heating tube to change continuously from the end to the middle. According to electrical principles, when the same current is applied, the part with a smaller cross-sectional area (such as the first tube wall 61) has a larger resistance and generates more heat (power) per unit time; while the part with a larger cross-sectional area (such as the third tube wall 63) has a smaller resistance and generates relatively less heat. This design cleverly compensates for the low temperature caused by the rapid heat dissipation at the end, realizing the heating tube itself to heat up as needed along the axial direction, and fundamentally improving temperature uniformity.

[0020] The inner walls of the first pipe wall 61, the second pipe wall 62, and the third pipe wall 63 are all fixedly fitted with support rings 5 ​​corresponding to their inner diameters.

[0021] To further enhance the mechanical stability of the variable power density tube structure 6 and provide support for any components that may be installed inside, corresponding support rings 5 ​​are fixedly fitted onto the inner walls of each step change point in the first tube wall 61, the second tube wall 62, and the third tube wall 63, such as... Figure 4 As shown, these support rings 5 ​​are also made of graphite material and can be integrally formed with the tube wall or fixed by high-precision assembly. Their main function is to serve as the mounting base for auxiliary components such as internal guide tubes and workpiece supports, ensuring accurate center positioning and avoiding collisions or friction with the inner wall of the heating tube; they also play a local reinforcing role for the variable diameter structure, smoothing stress distribution and reducing potential risks caused by abrupt changes in cross-section.

[0022] The reinforcing ring 4 and the graphite heating tube 1 are integrally formed.

[0023] The reinforcing ring 4 and the graphite heating tube 1 are manufactured using an integrated molding process. This manufacturing method eliminates the connection interface, resulting in extremely high bonding strength and heat conduction efficiency between the reinforcing ring 4 and the tube body 1. This avoids cracking problems caused by differences in thermal expansion coefficients or poor connections. This integrated design ensures that the entire component can expand and contract as a whole in a vacuum high-temperature environment, greatly improving the reliability and service life of the product.

[0024] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A graphite heating tube for uniform heating inside a vacuum furnace, characterized in that: It includes a graphite heating tube (1), with connectors (2) fixedly connected to both sides of the graphite heating tube (1), a spiral guide groove (3) opened on the inner wall of the graphite heating tube (1), multiple reinforcing rings (4) fixedly assembled on the outer wall of the graphite heating tube (1), and two variable power density tube structures (6) symmetrically fixedly assembled on the inner wall of the graphite heating tube (1).

2. A graphite heating tube for uniform heating inside a vacuum furnace according to claim 1, characterized in that: Each of the variable power density tube structures (6) includes a first tube wall (61), a second tube wall (62), and a third tube wall (63). The first tube wall (61) is connected to the third tube wall (63) through the second tube wall (62). The inner diameter of the first tube wall (61) is smaller than the inner diameter of the second tube wall (62). The inner diameter of the second tube wall (62) is smaller than the inner diameter of the third tube wall (63). The second tube wall (62) is close to the outer end of the graphite heating tube (1).

3. A graphite heating tube for uniform heating inside a vacuum furnace according to claim 2, characterized in that: The inner walls of the first pipe wall (61), the second pipe wall (62) and the third pipe wall (63) are all fixedly fitted with support rings (5) corresponding to their inner diameters.

4. A graphite heating tube for uniform heating inside a vacuum furnace according to claim 1, characterized in that: The reinforcing ring (4) and the graphite heating tube (1) are integrally formed.

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