Multi-electrode partition heating method and device for pipes with different wall thicknesses

Abstract

According to the multi-electrode partition heating method and device for the pipes with the unequal wall thicknesses, a mold is divided into different heating areas according to the wall thicknesses and structural characteristics of different positions, corresponding heating sequences are distributed, and the pipes are progressively heated through fixed and movable heating electrodes. The heating electrode is made of an electrode material with the characteristic that the resistivity is exponentially increased along with the temperature rise, and the resistance of a heating conductive loop is subjected to feedback regulation by utilizing the temperature difference between different areas in the heating process, so that the heating uniformity of the pipe can be effectively improved; and all parts of the final pipe product can reach preset mechanical properties, forming precision and durability in long-term use.

Description

Technical Field

[0001] The invention belongs to the technical field of hot forming technology for metal pipes, and in particular relates to a multi-electrode zone heating method and device for pipes of unequal wall thickness. Background Art

[0002] With the development of high-end equipment manufacturing technologies such as aerospace and automobile manufacturing, the demand for special-shaped parts with both high strength and light weight in related fields has increased significantly, and higher requirements have been put forward for the forming indicators of unequal wall thickness tubes used in the processing of such parts. In the hot forming process (such as hot bending and hot stamping) of unequal wall thickness tubes, there are still a series of heating control problems to be solved, including plastic flow instability, lack of dynamic phase change control, and mold thermal interaction interference. Due to the obvious difference in the local heat conduction efficiency of different wall thicknesses, it is easy to cause uneven temperature field distribution in various regions of the tube. Severe oxidation will occur at locations where the temperature is too high, affecting the surface quality and subsequent processing performance of the material; at locations where the temperature is too low, insufficient softening of the material and high hardness will occur, thereby reducing the forming adaptability and increasing the difficulty of processing; at the same time, the influence of inconsistent quenching effects in different regions of the component on the final mechanical properties cannot be ignored. Although some existing technologies use heating electrodes to heat different regions separately to improve the heating uniformity, the heating method heats up very quickly, resulting in the accuracy and timeliness of heating power adjustment being difficult to meet the requirements. Therefore, how to improve the heating method during the forming process of tubes with unequal wall thicknesses to improve temperature uniformity and reduce the possibility of process defects is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0003] In view of this, in order to solve the technical problems existing in the art, the present invention provides a multi-electrode zone heating method for pipes of unequal wall thickness, which specifically includes the following steps:

[0004] Step 1: Divide the mold into different heating areas based on the wall thickness and shape structure of each local area, and assign a corresponding heating sequence to each heating area;

[0005] Step 2: a heating electrode is provided at each end of the mold, and at least one movable heating electrode is provided in the middle of the mold, and each heating electrode is electrically connected to an external heating power source; a corresponding temperature sensor is provided for each heating area to measure the temperature during the heating process; the heating electrode used has the characteristic that the resistivity increases exponentially with the increase of temperature;

[0006] Step 3: adjust the position of the movable heating electrode and turn on the external heating power supply, and heat the first area in sequence through the heating electrode and the movable electrode at one end of the mold; during the heating process, use the temperature sensor to monitor the temperature of the first area, and when it reaches the predetermined temperature range, adjust the position of the movable heating electrode to heat the second area in sequence; after the second area reaches the predetermined temperature range, continue to move the movable heating electrode to the third area; and so on;

[0007] During the heating process, the temperature of different areas is monitored by temperature sensors, and the heating power is feedback-regulated according to the temperature difference of adjacent areas where the movable electrode is located, so that the resistance of the heating conductive loop remains constant;

[0008] Step 4: Continue in sequence until the penultimate area is heated by electricity, then remove the movable electrode, use the heating electrodes at both ends of the mold to heat, and simultaneously perform the resistance feedback adjustment process based on the temperature difference until the entire mold reaches the predetermined temperature.

[0009] Furthermore, during the heating process of step three, cold and hot gas spraying, non-contact radiation heaters, etc. are used to adjust and optimize the real-time temperature field distribution in the mold.

[0010] Furthermore, the heating electrode is specifically made of a material whose resistivity doubles with every increase of 150°C.

[0011] Correspondingly, the present invention also provides a multi-electrode zoned heating device for pipes of unequal wall thickness for executing the above method, comprising: a mold, a fixed heating electrode, a movable heating electrode, a temperature sensor and a heating control unit;

[0012] Among them, fixed heating electrodes are arranged at both ends of the mold, and at least one movable heating electrode is arranged between the two ends of the mold and can change its position, so as to cooperate with each other to form a conductive connection with an external heating power source to heat different mold areas; the fixed heating electrode and the movable heating electrode adopt electrode materials with the characteristic that the resistivity increases exponentially with the increase of temperature; the temperature sensor is used to monitor the temperature of each area and provide the monitoring signal to the heating control unit; the heating control unit adjusts the heating current based on the temperature difference between adjacent areas at the movable heating electrode measured by the temperature sensor, and implements feedback adjustment on the heating loop resistance formed by the heating electrode to keep it constant.

[0013] The heating method and device provided by the present invention for forming pipes of unequal wall thickness divides the mold into different heating areas according to the wall thickness and structural characteristics at different positions and assigns corresponding heating sequences, and progressively heats the pipe using fixed and movable heating electrodes. The heating electrode uses an electrode material with the characteristic that the resistivity increases exponentially with the increase of temperature. During the heating process, the temperature difference between different areas is used to feedback-regulate the resistance of the heating conductive circuit, which can effectively improve the uniformity of pipe heating, so that each part of the final pipe product can achieve the predetermined mechanical properties, forming accuracy and durability in long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of an optional progressive heating process based on the method provided by the present invention. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The present invention provides a multi-electrode zone heating method for pipes of unequal wall thickness, such as Figure 1 As shown, the specific steps include:

[0017] Step 1: Divide the mold into three different heating areas based on the wall thickness and shape structure of each local area, and assign a heating order from left to right to each heating area;

[0018] Step 2: a heating electrode is provided at each end of the mold, and at least one movable heating electrode is provided in the middle of the mold, and each heating electrode is electrically connected to an external heating power source; a corresponding temperature sensor is provided for each heating area to measure the temperature during the heating process; the heating electrode used has the characteristic that the resistivity increases exponentially with the increase of temperature;

[0019] Step 3: adjust the position of the movable heating electrode and turn on the external heating power supply, and heat the first area in sequence through the heating electrode and the movable electrode at one end of the mold; during the heating process, use the temperature sensor to monitor the temperature of the first area, and when it reaches the predetermined temperature range, move the movable heating electrode to the right to heat the second area; after the second area reaches the predetermined temperature range, move the movable heating electrode to the right to the third area;

[0020] During the heating process, the temperature of different areas is monitored by temperature sensors, and the heating power is feedback-regulated according to the temperature difference of adjacent areas where the movable electrode is located, so that the resistance of the heating conductive loop remains constant;

[0021] Step 4: Continue in sequence until the penultimate area is heated by electricity, then remove the movable electrode, use the heating electrodes at both ends of the mold to heat, and simultaneously perform the resistance feedback adjustment process based on the temperature difference until the entire mold reaches the predetermined temperature.

[0022] In a preferred embodiment of the present invention, during the heating process of step three, hot and cold gas spraying, non-contact radiation heaters, etc. are used to adjust and optimize the real-time temperature field distribution in the mold.

[0023] In a preferred embodiment of the present invention, the heating electrode is specifically made of a material whose resistivity doubles with every increase of 150°C.

[0024] Correspondingly, the present invention also provides a multi-electrode zoned heating device for pipes of unequal wall thickness for executing the above method, comprising: a mold, a fixed heating electrode, a movable heating electrode, a temperature sensor and a heating control unit;

[0025] Among them, fixed heating electrodes are arranged at both ends of the mold, and at least one movable heating electrode is arranged between the two ends of the mold and can change its position, so as to cooperate with each other to form a conductive connection with an external heating power source to heat different mold areas; the fixed heating electrode and the movable heating electrode adopt electrode materials with the characteristic that the resistivity increases exponentially with the increase of temperature; the temperature sensor is used to monitor the temperature of each area and provide the monitoring signal to the heating control unit; the heating control unit adjusts the heating current based on the temperature difference between adjacent areas at the movable heating electrode measured by the temperature sensor, and implements feedback adjustment on the heating loop resistance formed by the heating electrode to keep it constant.

[0026] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0027] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-electrode zone heating method for pipes of unequal wall thickness, characterized in that: The specific steps include: Step 1: Divide the mold into different heating areas based on the wall thickness and shape structure of each local area, and assign a corresponding heating sequence to each heating area; Step 2: a heating electrode is provided at each end of the mold, and at least one movable heating electrode is provided in the middle of the mold, and each heating electrode is electrically connected to an external heating power source; a corresponding temperature sensor is provided for each heating area to measure the temperature during the heating process; the heating electrode used has the characteristic that the resistivity increases exponentially with the increase of temperature; Step 3: adjust the position of the movable heating electrode and turn on the external heating power supply, and heat the first area in sequence through the heating electrode and the movable electrode at one end of the mold; during the heating process, use the temperature sensor to monitor the temperature of the first area, and when it reaches the predetermined temperature range, adjust the position of the movable heating electrode to heat the second area in sequence; after the second area reaches the predetermined temperature range, continue to move the movable heating electrode to the third area; and so on; During the heating process, the temperature of different areas is monitored by temperature sensors, and the heating power is feedback-regulated according to the temperature difference of adjacent areas where the movable electrode is located, so that the resistance of the heating conductive loop remains constant; Step 4: Continue in sequence until the penultimate area is heated by electricity, then remove the movable electrode, use the heating electrodes at both ends of the mold to heat, and simultaneously perform the resistance feedback adjustment process based on the temperature difference until the entire mold reaches the predetermined temperature.

2. The method according to claim 1, characterized in that: During the heating process of step three, hot and cold gas spraying and / or non-contact radiation heaters are used to adjust and optimize the real-time temperature field distribution in the mold.

3. The method according to claim 1, characterized in that: The heating electrode is specifically made of a material whose resistivity doubles with every increase in temperature of 150°C.

4. A multi-electrode zoned heating device for pipes of unequal wall thickness for executing the method as claimed in any one of claims 1 to 3, characterized in that: It includes a mold, a fixed heating electrode, a movable heating electrode, a temperature sensor and a heating control unit; Among them, fixed heating electrodes are arranged at both ends of the mold, and at least one movable heating electrode is arranged between the two ends of the mold and can change its position, so as to cooperate with each other to form a conductive connection with an external heating power source to heat different mold areas; the fixed heating electrode and the movable heating electrode adopt electrode materials with the characteristic that the resistivity increases exponentially with the increase of temperature; the temperature sensor is used to monitor the temperature of each area and provide the monitoring signal to the heating control unit; the heating control unit adjusts the heating current based on the temperature difference between adjacent areas at the movable heating electrode measured by the temperature sensor, and implements feedback adjustment on the heating loop resistance formed by the heating electrode to keep it constant.

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