Rapid heating hot gas bulging forming method and equipment for pipe blank

Abstract

The invention provides a rapid heating hot gas expansion forming method and equipment for a pipe blank, which considers respective advantages and disadvantages of a traditional self-resistance heating mode or a furnace type heating mode in a hot gas expansion process, organically combines the two heating modes, and designs a method for rapidly heating the pipe blank to a set temperature by firstly carrying out self-resistance heating and then rapidly heating the pipe blank to a set temperature. And then furnace type heat preservation heating is carried out to reduce the temperature difference of all parts of the pipe blank, so that the heating efficiency is improved, the uniformity of temperature distribution is effectively ensured, and the quality and the performance of a final finished product can better meet the design target requirement. And large-scale batch production of tubular beam components with complex shapes, axes and wall thickness changes is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of hot air expansion forming of metal tube blanks, and in particular relates to a method and equipment for rapid heating and hot air expansion forming of tube blanks with complex axes and shapes. Background Art

[0002] At present, the demand for high-strength and lightweight tubular beam components in the field of highway and railway transportation is becoming more and more urgent, and the application of the tubular beam forming process of "hot air expansion + quenching" is becoming more and more widespread. At present, there is an obvious trend that the geometric form of the tubular beam in the design of tubular beams is gradually becoming more complicated, which significantly increases the difficulty of using this expansion process. Before the expansion process of some tubular beam components with complex shapes, it is often necessary to perform a bending operation so that the tube blank can first form a specific complex axis, and then the tube blank can be subjected to a series of processes such as heating-insulation-expansion-quenching in sequence. The heating methods of the tube blank in the prior art mainly include: a self-resistance heating method of passing a direct current through the tube blank and a radiation heating method using a heating furnace. For example, the Chinese patent with the publication number CN114669970A discloses that these two tube blank heating methods can be selected respectively. However, these two heating methods still have some problems, which can easily have a negative impact on the production efficiency and quality of finished products of pipe beam components. For example, although the self-resistance heating method heats up quickly, due to the influence of the current skin effect, there will be a large temperature difference in the thickness direction when the thickness of the tube is thicker, so the heating process is not easy to control. The local wall thickness unevenness that often occurs with the bending operation will further aggravate this temperature unevenness; although the furnace heating method can ensure the uniformity of the tube temperature, it generally takes several hours to heat the tube to a given temperature. The low efficiency obviously cannot meet the requirements of large-scale batch production. It is worth noting that the existing technology has not yet realized the problems and shortcomings of using the above two heating methods alone, and there is no targeted solution. 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 method for rapid heating and hot air expansion forming of a tube blank, which is particularly suitable for processing a tube beam component with a complex axis, shape and varying wall thickness. The method specifically comprises the following steps:

[0004] Step 1: Perform a pipe bending operation on the straight pipe blank to bend it so that its axis meets the design requirements;

[0005] Step 2: Connect the bent tube to the electrode for self-resistance heating, apply high-power low-voltage direct current to the tube for rapid heating, measure the temperature of the tube during the process, and terminate the self-resistance heating when the tube reaches a predetermined temperature at least at the thickest part of the wall;

[0006] Step 3: Transfer the self-resistance heated tube blank to a heating furnace that has been preheated to a predetermined temperature;

[0007] Step 4: Use a heating furnace to heat-insulate the tube billet and measure the temperature of the tube billet at the same time, until the temperature difference between various parts of the tube billet is less than a predetermined value, and then the heat preservation ends;

[0008] Step 5: Place the insulated tube blank into the mold cavity that has been preheated to a predetermined temperature, and seal both ends of the tube blank;

[0009] Step 6: close the mold and fill the tube blank cavity with high-pressure gas, so that the outer surface of the tube blank and the inner surface of the mold can be completely fitted together, thereby achieving the expansion forming of the tube beam component;

[0010] Step seven, rapidly cooling and quenching the formed tube.

[0011] Furthermore, the predetermined value in step 4 is specifically set to 10°C.

[0012] Furthermore, the process of transferring the tube blank after self-resistance heating to the heating furnace and transferring the tube blank after insulation to the mold are both carried out in a sealed and heat-insulating environment.

[0013] Furthermore, the process of transferring the tube blank after self-resistance heating to the heating furnace and the process of transferring the tube blank after heat preservation to the mold are both performed by robots.

[0014] Accordingly, the present invention also provides a tube blank rapid heating hot air bulging forming device, which is used to perform the method provided by the present invention. The device is composed of a tube bending machine, a self-resistance heater, a heating furnace, a temperature measuring device, a tube blank transfer device, a forming die and a high-pressure gas source.

[0015] Among them, the pipe bending machine is used to bend the straight pipe billet before heating the billet so that its axis meets the design requirements;

[0016] The self-resistance heater is used to be electrically connected to the tube billet after bending, and high-power low-voltage direct current is applied to the tube billet through the electrode for rapid heating, so that the tube billet reaches a predetermined temperature at least at the thickest part of the wall;

[0017] The tube blank transfer device is used to sequentially transfer the tube blank between the self-resistance heating station, the heating furnace and the mold;

[0018] The heating furnace is used to perform heat preservation heating on the tube billet after self-resistance heating until the temperature difference of each part thereof is less than a predetermined value;

[0019] The temperature measuring device is used to measure the temperature of each part of the tube blank during the heating and insulation process;

[0020] The forming mold is used to provide a clamping force to the tube blank placed in its cavity; the high-pressure gas source is used to provide high-pressure gas to the inner cavity of the tube blank during the clamping process, so that its outer surface is completely fitted with the inner surface of the mold.

[0021] Furthermore, the tube blank rapid heating hot air bulging forming equipment comprises a sealed heat-insulating environment for transferring the tube blank between the self-resistance heating station, the heating furnace and the mold.

[0022] Furthermore, the tube blank transferring device specifically adopts a robot.

[0023] The method and equipment for rapid heating and hot expansion forming of tube blanks provided by the present invention take into account the advantages and disadvantages of traditional self-resistance or furnace heating methods in the hot expansion process, organically combine the two heating methods, and design a method of first performing self-resistance heating to quickly raise the tube blank to a predetermined temperature, and then performing furnace insulation heating to reduce the temperature difference between different parts of the tube blank, thereby improving the heating efficiency while effectively ensuring the uniformity of temperature distribution, so that the quality and performance of the final product can better meet the design target requirements, which is conducive to the large-scale batch production of tube beam components with complex shapes, axes and wall thickness changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flowchart of the method provided by the present invention. DETAILED DESCRIPTION

[0025] 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.

[0026] The tube blank rapid heating hot air bulging forming method provided by the present invention is as follows: Figure 1 As shown, the specific steps include:

[0027] Step 1: Perform a pipe bending operation on the straight pipe blank to bend it so that its axis meets the design requirements;

[0028] Step 2: Connect the bent tube to the electrode for self-resistance heating, apply high-power low-voltage direct current to the tube for rapid heating, measure the temperature of the tube during the process, and terminate the self-resistance heating when the tube reaches a predetermined temperature at least at the thickest part of the wall;

[0029] Step 3: Transfer the self-resistance heated tube blank to a heating furnace that has been preheated to a predetermined temperature;

[0030] Step 4: Use a heating furnace to heat-insulate the tube billet and measure the temperature of the tube billet at the same time, until the temperature difference between various parts of the tube billet is less than a predetermined value, and then the heat preservation ends;

[0031] Step 5: Place the insulated tube blank into the mold cavity that has been preheated to a predetermined temperature, and seal both ends of the tube blank;

[0032] Step 6: close the mold and fill the tube cavity with high-pressure gas, so that the outer surface of the tube is completely fitted with the inner surface of the mold, thereby achieving expansion forming of the tube beam component;

[0033] Step seven, rapidly cooling and quenching the formed tube.

[0034] In a preferred embodiment of the present invention, the predetermined value in step 4 is specifically set to 10°C.

[0035] In a preferred embodiment of the present invention, the process of transferring the tube blank after self-resistance heating to the heating furnace and transferring the tube blank after insulation to the mold are both carried out in a sealed and heat-insulating environment.

[0036] In a preferred embodiment of the present invention, the process of transferring the tube blank after self-resistance heating to the heating furnace and the process of transferring the tube blank after heat preservation to the mold are both performed by robots.

[0037] Accordingly, the present invention also provides a tube blank rapid heating hot air bulging forming device, which is used to perform the method provided by the present invention. The device is composed of a tube bending machine, a self-resistance heater, a heating furnace, a temperature measuring device, a tube blank transfer device, a forming die and a high-pressure gas source.

[0038] Among them, the pipe bending machine is used to bend the straight pipe billet before heating the billet so that its axis meets the design requirements;

[0039] The self-resistance heater is used to be electrically connected to the tube billet after bending, and high-power low-voltage direct current is applied to the tube billet through the electrode for rapid heating, so that the tube billet reaches a predetermined temperature at least at the thickest part of the wall;

[0040] The tube blank transfer device is used to sequentially transfer the tube blank between the self-resistance heating station, the heating furnace and the mold;

[0041] The heating furnace is used to perform heat preservation heating on the tube billet after self-resistance heating until the temperature difference of each part thereof is less than a predetermined value;

[0042] The temperature measuring device is used to measure the temperature of each part of the tube blank during the heating and insulation process;

[0043] The forming mold is used to provide a clamping force to the tube blank placed in its cavity; the high-pressure gas source is used to provide high-pressure gas to the inner cavity of the tube blank during the clamping process, so that its outer surface is completely fitted with the inner surface of the mold.

[0044] In a preferred embodiment of the present invention, the tube blank rapid heating hot air bulging forming equipment comprises a sealed heat-insulating environment for transferring the tube blank between the self-resistance heating station, the heating furnace and the mold.

[0045] In a preferred embodiment of the present invention, the tube blank transferring device is specifically a robot.

[0046] 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.

[0047] 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 method for rapid heating and hot air bulging of a tube blank, characterized in that: The specific steps include: Step 1: Perform a pipe bending operation on the straight pipe blank to bend it so that its axis meets the design requirements; Step 2: Connect the bent tube to the electrode for self-resistance heating, apply direct current to the tube for rapid heating, measure the temperature of the tube during the process, and terminate the self-resistance heating when the tube reaches a predetermined temperature at least at the thickest part of the wall; Step 3: Transfer the self-resistance heated tube blank to a heating furnace that has been preheated to a predetermined temperature; Step 4: Use a heating furnace to heat-insulate the tube billet and measure the temperature of the tube billet at the same time, until the temperature difference between various parts of the tube billet is less than a predetermined value, and then the heat-insulation ends; Step 5: Place the insulated tube blank into the mold cavity that has been preheated to a predetermined temperature, and seal both ends of the tube blank; Step 6: close the mold and fill the tube blank cavity with high-pressure gas, so that the outer surface of the tube blank and the inner surface of the mold can be completely fitted together, thereby achieving the expansion forming of the tube beam component; Step seven, rapidly cooling and quenching the formed tube.

2. The tube blank rapid heating hot air bulging forming method according to claim 1, characterized in that: The predetermined value described in step 4 is specifically set to 10°C.

3. The tube blank rapid heating hot air bulging forming method according to claim 1, characterized in that: The process of transferring the tube blank after self-resistance heating to the heating furnace and transferring the tube blank after insulation to the mold are both carried out in a sealed and heat-insulating environment.

4. The tube blank rapid heating hot air bulging forming method according to claim 1, characterized in that: The process of transferring the tube billet after self-resistance heating to the heating furnace and transferring the tube billet after insulation to the mold are both carried out by robots.

5. A tube blank rapid heating hot air bulging forming device, used to perform the method according to claim 1, characterized in that: The equipment is composed of a tube bending machine, a self-resistance heater, a heating furnace, a temperature measuring device, a tube blank transfer device, a forming die and a high-pressure gas source. Among them, the pipe bending machine is used to bend the straight pipe billet before heating the billet so that its axis meets the design requirements; The self-resistance heater is used to be electrically connected to the tube billet after bending, and high-power low-voltage direct current is applied to the tube billet through the electrode for rapid heating, so that the tube billet reaches a predetermined temperature at least at the thickest part of the wall; The tube blank transfer device is used to sequentially transfer the tube blank between the self-resistance heating station, the heating furnace and the mold; The heating furnace is used to perform heat preservation heating on the tube billet after self-resistance heating until the temperature difference of each part thereof is less than a predetermined value; The temperature measuring device is used to measure the temperature of each part of the tube blank during the heating and insulation process; The forming mold is used to provide a clamping force to the tube blank placed in its cavity; the high-pressure gas source is used to provide high-pressure gas to the inner cavity of the tube blank during the clamping process, so that its outer surface is completely fitted with the inner surface of the mold.

6. The tube blank rapid heating hot air bulging forming equipment according to claim 5, characterized in that: The tube blank rapid heating hot air expansion forming equipment comprises a sealed heat-insulating environment for transferring the tube blank between the self-resistance heating station, the heating furnace and the mold.

7. The tube blank rapid heating hot air bulging forming equipment according to claim 5, characterized in that: The tube blank transfer device specifically adopts a robot.

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