Method and system for manufacturing a hot gas expanded tube

Abstract

The application provides a manufacturing method and a manufacturing system of a hot gas expansion forming pipe, and relates to the technical field of hot gas expansion forming pipe manufacturing.The application reduces the metal plating layer into the welding area by carrying out the deplating treatment on both sides of the to-be-welded area before welding, and improves the welding quality.The application improves the organization state of the welding area, reduces the welding residual stress, reduces the hardness gradient between the welding area and the base material area, and improves the toughness of the welding area by preheating the to-be-welded area and carrying out the tempering treatment after welding.The application heats the welding area and the base material area to the austenitizing state, then carries out the hot gas expansion forming, and cools the welding area and the base material area by adopting different cooling rates, so that the welding area and the base material area obtain more coordinated organization and mechanical properties, the performance matching of the welding area and the base material area is improved, the possibility of cracking of the welding area is reduced, and the forming quality and the comprehensive mechanical properties of the hot gas expansion forming pipe are improved.

Description

Technical Field

[0001] This invention relates to the field of high-strength steel pipe manufacturing technology, and in particular to a manufacturing method and system for hot gas expansion forming pipe fittings. Background Technology

[0002] Hot gas forming is a forming process that involves heating a metal tube to its austenitizing temperature, then using high-pressure gas to plastically expand the tube within a mold, followed by quenching and cooling within the mold to obtain a high-strength hollow structural component. Because it can achieve lightweight, high dimensional accuracy, and excellent mechanical properties, hot gas forming technology is widely used in the manufacture of safety structural components such as automotive A-pillars, B-pillars, door sill beams, and crash beams.

[0003] Currently, high-strength steel pipes used in hot gas forming are typically made by rolling and welding high-strength steel plates. To improve the oxidation resistance of the steel plates during heating and the corrosion resistance of the finished product, the surface of the high-strength steel plates is usually coated with Al-Si, zinc, or zinc-based alloy coatings. However, the coating is prone to melting, evaporation, or entering the weld pool during welding, resulting in defects such as weld porosity, inclusions, and embrittlement of the liquid metal, thus affecting weld quality.

[0004] Furthermore, during laser welding of high-strength steel, the rapid cooling rate of the weld and heat-affected zone easily leads to the formation of a high-hardness microstructure and generates significant residual stress, increasing the risk of cold cracking in the weld and subsequent cracking during hot gas expansion forming. Although some existing technologies employ post-weld heat treatment to improve weld performance, a significant difference remains between the weld microstructure and the base metal microstructure, making it difficult to achieve an effective match between weld and base metal properties. Moreover, during the quenching and cooling process after hot gas expansion forming, the weld area is still prone to forming a microstructure with high hardness and insufficient toughness, resulting in poor strength-toughness matching between the weld area and the base metal area, thus affecting the overall mechanical properties and reliability of the hot gas expanded pipe fittings. Summary of the Invention

[0005] One objective of this invention is to provide a method for manufacturing hot-expansion formed pipe fittings, thereby solving the technical problems of unstable weld quality and high risk of weld cracking during the manufacturing process of hot-expansion formed pipe fittings in the prior art.

[0006] Another object of the present invention is to provide a manufacturing system for manufacturing tubes using the above-described hot gas expansion forming method.

[0007] In particular, the present invention provides a method for manufacturing a hot-expansion formed tube, comprising the following steps: A high-strength steel plate with a metal coating formed on its surface is provided. The high-strength steel plate has a welding area and a coating removal area, wherein the coating removal area is located on both sides of the welding area. The high-strength steel plate is fed into a laser deplating device, and the area to be deplated is removed using the laser deplating device. The area to be welded in the high-strength steel plate after deplating is preheated to 200℃-350℃; The high-strength steel plate is welded to the area to be welded using a laser welding device to form a weld area, and the weld area is then tempered to obtain a welded pipe. The welded pipe is heated to 850°C-930°C using a heating device and kept at that temperature, so that both the weld area and the base material area of ​​the welded pipe are in an austenitic state. The austenitized welded pipe is fed into a hot gas expansion forming mold, and high-pressure gas is injected into the welded pipe to cause it to expand and fit into the hot gas expansion forming mold. The formed welded pipe is then quenched. The welded pipe is fed into a cooling device, and the weld area and the base material area of ​​the welded pipe are cooled separately, so that the cooling rate of the weld area is lower than that of the base material area, and finally a hot gas expansion forming pipe is obtained.

[0008] Optionally, in the step of feeding the high-strength steel plate into a laser deplating device and using the laser deplating device to remove the plating from the area to be deplated, The area to be welded is detected using a visual positioning module; When a shift is detected in the area to be soldered, the laser deplating device is controlled to adjust the laser scanning path so that the laser scans along the areas to be deplated on both sides of the area to be soldered.

[0009] Optionally, in the step of feeding the high-strength steel plate into a laser deplating device and using the laser deplating device to remove the plating from the area to be deplated, The plating removal status of the area to be deplated is detected using an optical detection module. When insufficient local plating removal is detected in the area to be deplated, the laser plating removal device is controlled to increase the laser pulse energy and / or increase the number of re-scans; when overburning is detected in the area to be deplated, the laser plating removal device is controlled to reduce the laser power and / or increase the laser scanning speed.

[0010] Optionally, in the step of using a laser welding device to weld the area to be welded on the high-strength steel plate to form a weld area, and then tempering the weld area to obtain a welded pipe, the tempering temperature range is 600℃-700℃, and the tempering area covers the weld area and the heat-affected zone, with the heat-affected zone located on both sides of the weld area.

[0011] Optionally, the process includes using a laser welding device to weld the area to be welded on the high-strength steel plate to form a weld area, and then tempering the weld area to obtain a welded pipe. The process further includes the following steps: The continuity of the weld area, the weld temperature profile, and surface defects are detected online. When the weld area shows signs of incomplete fusion, incomplete penetration, continuous porosity, or tempering temperature deviating from the set range, the welded pipe is deemed unqualified and enters the rework process.

[0012] Optionally, in the step of heating the welded pipe to 850°C-930°C and holding it at that temperature so that both the weld area and the base material area of ​​the welded pipe are in an austenitized state, the temperature of the weld area and the base material area is monitored, and the temperature difference between the weld area and the base material area is not greater than a set threshold, wherein the set threshold range is 15°C-30°C.

[0013] Optionally, in the step of feeding the welded pipe into a cooling device and cooling the weld area and the base material area of ​​the welded pipe respectively, so that the cooling rate of the weld area is lower than the cooling rate of the base material area, the cooling rate of the weld area is 75%-85% of the cooling rate of the base material area.

[0014] Optionally, the cooling device is provided with a low thermal conductivity coating or a thermal resistance regulating layer, which covers the weld area.

[0015] In particular, the present invention also provides a manufacturing system for hot-expansion forming pipe fittings, which applies the above-described manufacturing method.

[0016] The manufacturing method provided by this invention integrates pre-weld plating removal, pre-weld preheating, laser welding, post-weld tempering, austenitizing heating, hot gas expansion forming, and differentiated cooling for coordinated control. Specifically, by removing plating from both sides of the area to be welded before welding, the amount of metal plating entering the weld area is reduced, improving weld quality. Preheating the area to be welded and then tempering it after welding improves the microstructure of the weld area, reduces residual welding stress, decreases the hardness gradient between the weld area and the base material area, and improves the toughness of the weld area and the overall mechanical properties of the weld joint. By heating the weld area and the base material area to an austenitized state before hot gas expansion forming, and cooling the weld area and the base material area at different cooling rates, the weld area and the base material area achieve more coordinated microstructure and mechanical properties, improving the performance matching between the weld area and the base material area, reducing the possibility of cracking in the weld area, and improving the forming quality and overall mechanical properties of the hot gas expanded pipe fitting.

[0017] Furthermore, during the laser decoking process, the vision positioning module detects the position of the area to be welded in real time. When a shift in the area to be welded is detected, the laser decoking device is controlled to automatically adjust the laser scanning path. The optical detection module performs online detection of the area to be decoked. When insufficient decoking is detected in a localized area, the pulse energy of the corresponding area is increased or the number of rescans is increased. When overheating of the steel substrate is detected, the laser power is reduced or the scanning speed is increased to ensure the decoking quality and the integrity of the steel substrate. Through the above laser decoking process, the coating can be confined outside the weld fusion zone before welding, reducing the adverse effects of the coating on weld formation during welding, and ensuring that the decoked area is covered by the weld and heat-affected zone after subsequent welding. This improves weld quality without significantly reducing the protective performance of the coating in other areas of the pipe. This embodiment preferably uses a closed-loop control method for decoking, which can correct the laser scanning path in real time and adjust the laser decoking parameters according to the decoking status. This avoids decoking position deviation due to shift in the area to be welded, and also avoids insufficient decoking or overheating of the substrate, improving the consistency of the area to be decoked and providing a stable welding boundary for subsequent welding.

[0018] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0019] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for manufacturing a hot-expansion-formed tube according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a method for manufacturing a hot-expansion formed tube according to an embodiment of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] Unless otherwise specified, all terms (including technical and scientific terms) used in the description of this embodiment have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] Figure 1This is a schematic flowchart illustrating a method for manufacturing a hot-expansion-formed tubular component according to an embodiment of the present invention. Figure 1 As shown, in one specific embodiment, the manufacturing method of the hot-expansion formed tube includes the following steps: Step S100: Provide a high-strength steel plate with a metal coating formed on its surface. The high-strength steel plate has a welding area and a deplating area, with the deplating area located on both sides of the welding area. Step S200: The high-strength steel plate is fed into the laser deplating device, and the area to be deplated is removed using the laser deplating device. Step S300: Preheat the area of ​​the high-strength steel plate to be welded to 200℃-350℃ after deplating; Step S400: The area to be welded on the high-strength steel plate is welded using a laser welding device to form a weld area, and the weld area is tempered to obtain a welded pipe. Step S500: The welded pipe is heated to 850°C-930°C using a heating device and kept at that temperature, so that both the weld area and the base material area of ​​the welded pipe are in an austenitic state. Step S600: The austenitized welded pipe is fed into the hot gas expansion forming mold, and high-pressure gas is injected into the welded pipe to cause it to expand and fit into the hot gas expansion forming mold. The formed welded pipe is then quenched. In step S700, the welded pipe is fed into a cooling device, and the weld area and the base material area of ​​the welded pipe are cooled separately, so that the cooling rate of the weld area is lower than that of the base material area, and finally the hot gas expansion forming pipe is obtained.

[0023] The manufacturing method provided in this embodiment integrates pre-weld plating removal, pre-weld preheating, laser welding, post-weld tempering, austenitizing heating, hot gas expansion forming, and differentiated cooling for coordinated control. Specifically, by removing plating from both sides of the area to be welded before welding, the amount of metal plating entering the weld area is reduced, improving weld quality. Preheating the area to be welded and then tempering it after welding improves the microstructure of the weld area, reduces residual welding stress, decreases the hardness gradient between the weld area and the base material area, and improves the toughness of the weld area and the overall mechanical properties of the weld joint. By heating the weld area and the base material area to an austenitized state before hot gas expansion forming, and cooling the weld area and the base material area at different cooling rates, the weld area and the base material area achieve more coordinated microstructure and mechanical properties, improving the performance matching between the weld area and the base material area, reducing the possibility of cracking in the weld area, and improving the forming quality and overall mechanical properties of the hot gas expanded pipe fitting.

[0024] The inventors of this invention discovered through research that during the quenching and cooling process after hot gas expansion forming, the weld area and the base material area are usually cooled using the same method. However, due to the welding thermal cycle, the weld area exhibits differences in microstructure, residual stress, and hardness compared to the base material area. Continuing to use the same cooling intensity can easily lead to excessively high hardness and insufficient toughness in the weld area, resulting in poor performance matching between the weld area and the base material area. This, in turn, affects the overall mechanical properties and reliability of the hot gas expanded pipe fittings. Therefore, this invention addresses the difference in microstructure between the weld area and the base material area by optimizing and controlling the cooling process after hot gas expansion forming. This optimizes the cooling conditions for both areas, improving the microstructure and mechanical properties of the weld area, enhancing the performance matching between the weld area and the base material area, and ultimately improving the overall mechanical properties and reliability of the hot gas expanded pipe fittings.

[0025] In some embodiments, the high-strength steel plate is preferably 22MnB5 steel, boron-containing hot-formed steel, manganese-boron steel, or other high-strength steel plates that can form martensitic structure through austenitizing heating and quenching. The thickness of the high-strength steel plate is preferably 1.0mm-3.0mm. A metallic coating is formed on the surface of the high-strength steel plate. The metallic coating can be an Al-Si coating, a zinc coating, or a zinc-based alloy coating, used to improve the oxidation resistance of the high-strength steel plate during high-temperature heating and the corrosion resistance of the final product. It should be noted that although the metallic coating can improve the corrosion resistance of the high-strength steel plate, during welding, the metallic coating is prone to melting, evaporation, or entering the weld pool, causing defects such as weld porosity, inclusions, and embrittlement of the liquid metal. Therefore, it is preferable to locally remove the metallic coating on both sides of the area to be welded before welding. Through the above measures, while ensuring the overall corrosion resistance of the high-strength steel plate, the entry of the coating into the weld pool during welding is reduced, thus improving the welding quality.

[0026] In step S100, the high-strength steel plate is rolled or progressively formed into a tube blank with a longitudinal opening.

[0027] In some embodiments, in step S200, the visual positioning module is used to detect the area to be welded; when the area to be welded is detected to be offset, the laser deplating device is controlled to adjust the laser scanning path so that the laser scans along the areas to be deplated on both sides of the area to be welded.

[0028] In some embodiments, in step S200, the plating removal status of the area to be deplated is detected by an optical detection module; when local deplating insufficiency is detected in the area to be deplated, the laser deplating device is controlled to increase the laser pulse energy and / or increase the number of rescans; when overburning is detected in the area to be deplated, the laser deplating device is controlled to reduce the laser power and / or increase the laser scanning speed.

[0029] Specifically, laser deplating devices are installed on both sides of the area to be welded. These devices include a low-power pulsed laser cleaning head, a vision positioning module for identifying the location of the area to be welded and the deplating width, an optical detection module for detecting the surface condition after deplating, a closed-loop control module linked to laser power, pulse width, scanning speed, and scanning path, and fume extraction and protective gas blowing components. During deplating, a low-power pulsed laser is used to remove the coating within a width of 1.0-2.0 mm on both sides of the area to be welded, ensuring a continuous distribution of the deplating area along the weld length. The deplating depth is controlled to the interface between the coating and the steel substrate, preferably ensuring that the residual coating area ratio is no more than 5%, and avoiding the formation of continuous ablation grooves on the steel substrate. During processing, the vision positioning module monitors the location of the area to be welded in real time. When a shift in the area is detected, the closed-loop control module automatically adjusts the laser scanning path. The optical detection module performs online detection of the area to be deplated. When insufficient deplating is detected in a localized area, the closed-loop control module increases the pulse energy of the corresponding area or increases the number of rescans. When overheating of the steel substrate is detected, the laser power is reduced or the scanning speed is increased to ensure the quality of the deplating and the integrity of the steel substrate. Through this laser deplating process, the coating can be confined outside the weld fusion zone before welding, reducing the adverse effects of the coating on weld formation during welding. It also ensures that the deplated area is covered by the weld and heat-affected zone after subsequent welding, thereby improving weld quality without significantly reducing the protective performance of the coating in other areas of the pipe. The laser deplating device in this embodiment preferably uses a closed-loop control method for deplating, which can correct the laser scanning path in real time and adjust the laser deplating parameters according to the deplating status. This avoids deplating position deviation due to offset of the area to be welded, while also preventing insufficient deplating or overheating of the substrate, improving the consistency of the area to be deplated, and providing a stable welding boundary for subsequent welding.

[0030] In some embodiments, in step S400, the tempering temperature range is 600℃-700℃, and the tempering area covers the weld area and the heat-affected zone, with the heat-affected zone located on both sides of the weld area. Here, the tempering temperature can be 600℃, 620℃, 650℃, 680℃, or 700℃, etc.

[0031] In some embodiments, the following steps are included after step S400: Step S410 involves online detection of the continuity of the weld area, the weld temperature profile, and surface defects; here, online detection includes at least one of visual inspection, eddy current inspection, ultrasonic inspection, and infrared temperature detection.

[0032] Step S420: When incomplete fusion, incomplete penetration, continuous porosity, or tempering temperature deviating from the set range occurs in the weld area, the welded pipe is determined to be unqualified and enters the rework process.

[0033] Specifically, the laser welding device is sequentially equipped with an induction preheating unit, a laser welding unit, and an induction tempering unit along the conveying direction of the high-strength steel plate. First, the induction preheating unit locally preheats the area to be welded and its adjacent areas at a temperature of 200℃-350℃, such as 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, or 350℃, to reduce the temperature gradient in the area to be welded, slow down the cooling rate after welding, and reduce the risk of cold cracking in the weld area. Subsequently, the laser welding unit uses a laser as the main heat source to perform deep penetration welding on the area to be welded, forming the weld area. During laser welding, the laser power, welding speed, defocusing amount, and shielding gas flow rate are adjusted according to the thickness of the high-strength steel plate, the gap between the areas to be welded, and the weld penetration depth to ensure complete weld penetration and control the width of the heat-affected zone to 0.3mm-0.8mm. Preferably, Ar, N2, or an Ar / N2 mixed shielding gas is introduced during welding to reduce oxidation and inclusion formation in the weld area. After welding, an induction tempering unit located behind the laser welding unit performs online local tempering treatment on the weld area and heat-affected zone. The tempering temperature is 600℃-700℃. The tempered area covers the weld area and the heat-affected zones on both sides, and the coverage width of the tempered area is preferably greater than 1.2 times the total width of the heat-affected zone. This reduces the hardness of the weld area, releases residual welding stress, and reduces the hardness gradient between the weld area and the base material area, thereby improving the mechanical property matching between the weld area and the base material area and reducing the risk of weld cracking during subsequent hot gas expansion forming. Furthermore, after tempering, the weld area is subjected to online inspection, including at least one of visual inspection, eddy current inspection, ultrasonic inspection, and infrared temperature detection, used to detect weld continuity, weld temperature profile, and surface defects. When incomplete fusion, incomplete penetration, continuous porosity, or a tempering temperature deviation from the set range is detected in the weld area, the corresponding welded pipe is deemed unqualified and is reworked or rejected.

[0034] This embodiment achieves continuous welding and online heat treatment of the area to be welded by sequentially setting induction preheating, laser welding, and induction tempering along the conveying direction. This not only ensures good penetration quality in the weld area but also improves the microstructure of the weld area and the heat-affected zone, reducing residual welding stress and hardness gradient. At the same time, online post-weld inspection promptly removes welded pipes with welding defects, improving the consistency of welded pipe quality and providing stable quality welded pipes for subsequent hot gas expansion forming.

[0035] Following step S420, the welded pipe undergoes sizing, straightening, and cutting processes to ensure it meets the dimensional requirements for subsequent hot gas expansion forming. After sizing, straightening, and cutting, a quality threshold is assessed. Only welded pipes meeting the preset quality threshold can proceed to the subsequent austenitizing heating and hot gas expansion forming processes. The quality threshold includes at least the following: the deplating width of the area to be deplated is within a preset range, and the area to be deplated is continuously distributed along the weld length. The weld area is completely fused, without continuous incomplete fusion, incomplete penetration, or through cracks. The porosity of the weld area is not greater than 0.1%, or meets the porosity requirements of the corresponding product. The hardness difference between the weld area and the heat-affected zone and the base material area is not greater than 5%-10%, for example, 5%, 8%, or 10%. The straightness, roundness, and weld reinforcement of the welded pipe meet the mold requirements for hot gas expansion forming. If a welded pipe fails to meet any of the above quality thresholds, it is considered a defective welded pipe and must be reworked or rejected.

[0036] This embodiment establishes a quality threshold before the welded pipe enters the austenitizing heating and hot gas expansion forming process, comprehensively judging the deplating quality, welding quality, microstructure and dimensional accuracy of the welded pipe. This ensures that the welded pipe entering the subsequent hot gas expansion forming process has stable and consistent quality, reduces abnormal expansion caused by welding defects or dimensional deviations, and improves the forming quality and product consistency of hot gas expanded forming pipes.

[0037] In some embodiments, during the step of heating the welded pipe to 850°C-930°C and holding it at that temperature to ensure both the weld area and the base metal area are in an austenitized state, the temperatures of the weld area and the base metal area are monitored, and the temperature difference between the weld area and the base metal area is kept below a set threshold. This threshold ranges from 15°C to 30°C, for example, it can be 15°C, 20°C, 25°C, or 30°C, to ensure consistency in subsequent expansion flow stress and phase transformation initiation state. Here, the heating temperature of the heating device can be 850°C, 880°C, 900°C, or 930°C, etc. During the heating process, it is preferable to conduct the process in an inert atmosphere or a low-oxygen atmosphere, such as N2, Ar, or a mixture thereof, to reduce oxidation and decarburization of the weld and base metal surfaces.

[0038] In some embodiments, in step S700, the cooling rate of the weld area is 75%-85% of the cooling rate of the base material area, for example, it can be 75%, 80% or 85%.

[0039] In some embodiments, the cooling device is provided with a low thermal conductivity coating or a thermal resistance regulating layer, which covers the weld area.

[0040] Specifically, the hot gas expansion forming mold includes a main cooling circuit corresponding to the base material region and an independent cooling circuit corresponding to the weld region. The temperature, flow rate, pressure, and activation sequence of the cooling medium in the independent cooling circuit can be independently adjusted to achieve differentiated cooling between the weld region and the base material region. Furthermore, a low thermal conductivity coating or thermal resistance regulating layer is applied to the surface of the hot gas expansion forming mold at the location corresponding to the weld region. The low thermal conductivity coating or thermal resistance regulating layer is preferably a zirconia ceramic coating. Through the synergistic effect of the low thermal conductivity coating or thermal resistance regulating layer and the independent cooling circuit, the cooling rate of the weld region is lower than that of the base material region, preferably 75%-85% of the cooling rate of the base material region, while ensuring that the cooling rate of the weld region is not lower than the critical quenching cooling rate required for the formation of the target martensitic structure in high-strength steel.

[0041] This embodiment achieves a moderate self-tempering effect in the weld area while meeting the requirements for quenching and hardening by implementing differentiated cooling between the weld area and the base material area. This reduces the hardness and brittleness of the weld area, improves its toughness, and reduces the hardness difference between the weld area and the base material area. Preferably, the hardness difference between the weld area and the base material area in the final formed part is no greater than 30 HV, thereby improving the comprehensive mechanical properties and forming quality of the hot gas expansion forming tube.

[0042] In some embodiments, after the welded pipe manufacturing and hot gas expansion forming are completed, the process parameters and test results during the welded pipe manufacturing process are correlated and traced. Specifically, the deplating parameters of the area to be deplated, the preheating temperature of the area to be welded, the welding parameters, the tempering temperature, the online test results of the weld area, the austenitizing heating temperature, the expansion pressure curve during the hot gas expansion forming process, the cooling parameters of the cooling device, and the test results of the final formed part are correlated to the same welded pipe or fitting number to establish the full-process process data for the corresponding welded pipe or fitting. Furthermore, when the final hot gas expanded forming fitting exhibits abnormalities such as weld area cracking, weld area hardness exceeding the tolerance, excessive wall thickness reduction, or local oxidation or decarburization, the process parameters during the manufacturing process can be traced back according to the corresponding welded pipe or fitting number to determine the deplating process, welding process, heat treatment process, or cooling process parameters corresponding to the abnormality, and the process parameters in the subsequent manufacturing process can be adjusted and optimized based on the traceability results.

[0043] This embodiment links the process parameters of processes such as plating removal, welding, heat treatment, hot gas expansion forming, and cooling with the final pipe fitting inspection results to form a full-process data traceability mechanism for the hot gas expansion forming pipe fitting manufacturing process. This facilitates quality monitoring and process optimization of the manufacturing process, and improves the consistency of product quality and the stability of the manufacturing process.

[0044] Figure 2 This is a schematic diagram of a method for manufacturing a hot-puffed tube according to an embodiment of the present invention. Figure 2 As shown, in this embodiment, a high-strength steel plate with a preset coating is first provided, see [link to previous document]. Figure 2 Figure (a) shows the high-strength steel sheet. Subsequently, the high-strength steel sheet is roll-bent to gradually bend it into a tube blank with an opening, see Figure (a). Figure 2 See Figures (b) and (c) in the image. The formed tube blank is fed into a laser deplating device to remove the plating from the areas to be deplated on both sides of the area to be welded, thus removing the plating layer in the corresponding areas. See Figure (b) and (c) in the image. Figure 2 Figure (d) shows the process. After the plating removal is completed, the tube blank is transported to the induction preheating unit for preheating of the area to be welded and its adjacent areas. See Figure (d). Figure 2 Figure (e) shows the preheated tube blank entering the laser welding apparatus. Laser welding is used to weld the open area of ​​the tube blank to form a continuous weld seam. (See Figure [e]). Figure 2 See Figure (f) in the diagram. After welding, the welded pipe is transported to the induction tempering unit for tempering treatment of the weld area and heat-affected zone. See Figure (f) in the diagram. Figure 2 Figure (g) shows the improvement of the microstructure in the weld area. Subsequently, the welded pipe undergoes online inspection, which may include weld continuity testing, surface defect detection, and temperature condition monitoring, etc. (See Figure [g]). Figure 2 See Figure (h) in the diagram. After passing inspection, the welded pipe enters the austenitizing heating device. Through heating and heat preservation treatment, both the weld area and the base metal area reach the austenitizing state. (See Figure h for details.) Figure 2 Figure (i) shows the welded pipe after austenitization treatment entering a hot gas expansion forming mold. High-pressure gas is injected into the pipe, causing it to expand and conform to the mold cavity, simultaneously completing the in-mold forming process. See Figure (i). Figure 2 Figure (j) shows the process. Subsequently, the formed welded pipe undergoes differentiated cooling treatment. This is achieved by adjusting the cooling conditions of the weld area and the base material area separately, ensuring that the cooling rate of the weld area is lower than that of the base material area. (See Figure (j)). Figure 2 Figure (k) shows the final hot-expansion formed pipe fitting. Figure 2 Figure (l) in the middle.

[0045] This embodiment also provides a manufacturing system for hot-expansion forming of tubular components, applying the manufacturing method of any of the above embodiments. The manufacturing methods will not be described in detail here.

[0046] The following specific embodiments are provided for illustration: Example 1: Manufacturing method of hot gas expansion forming pipe fittings using zinc-coated 22MnB5 high-strength steel pipe 1.5mm thick zinc-coated 22MnB5 high-strength steel sheet was selected as the raw material and formed into a tube blank with a longitudinal opening by roll bending. Before welding the tube blank seam, a laser deplating device was used to locally deplat the edges to be welded on both sides of the tube blank, with a deplating width of 1.5mm on each side. During the deplating process, the position of the area to be welded was detected in real time by a vision positioning module. When a displacement of the area to be welded was detected, the laser deplating device was controlled to adjust the laser scanning path to ensure that the laser acted on the area to be deplated. At the same time, the surface condition after deplating was detected by an optical inspection module to confirm that the deplated area was continuous and that the residual coating area was no more than 5%.

[0047] After plating removal, the tube blank enters the laser welding station. First, the area to be welded and its adjacent areas are preheated using an induction preheating unit, with the preheating temperature controlled at approximately 280℃. Then, the laser welding unit performs deep penetration welding on the joint area of ​​the tube blank, forming a longitudinal weld. An Ar / N2 mixed shielding gas is used during welding to reduce the possibility of oxidation and inclusion formation in the weld area. After welding, the weld area and the heat-affected zones on both sides are subjected to online tempering treatment by an induction tempering unit located behind the laser welding unit. The tempering temperature is controlled at approximately 650℃ to reduce the hardness of the weld area and release residual welding stress. Inspection revealed complete penetration of the weld area, no through-cracks, and the hardness difference between the weld area and the heat-affected zone and the base material area is controlled within 10%.

[0048] Subsequently, the welded pipes that meet the quality requirements are fed into a heating device for austenitization treatment. The heating temperature is controlled at approximately 900°C and held until both the weld area and the base material area reach an austenitized state. After austenitization, the welded pipes are transferred to a hot gas expansion forming mold. High-pressure gas is injected into the welded pipes, causing them to expand and conform to the mold cavity. During the forming process, the welded pipes undergo in-mold quenching using the hot gas expansion forming mold. The mold is equipped with a main cooling circuit corresponding to the base material area and an independent cooling circuit corresponding to the weld area. The cooling rate of the weld area is set to approximately 80% of the cooling rate of the base material area, while ensuring that the cooling rate of the weld area is not lower than the critical quenching cooling rate required for the material to obtain the target martensitic structure. In addition, a zirconia ceramic low thermal conductivity coating is applied to the mold surface at the location corresponding to the weld area to further regulate the cooling process of the weld area.

[0049] In the hot gas expansion forming pipes prepared by the above process, no cracking occurred in the weld area, the hardness difference between the weld area and the base material area was no greater than 30 HV, and no abnormal concentrated thinning occurred in the area near the weld. This indicates that the structural stability and comprehensive mechanical properties of the welded pipe after forming were improved by the coordinated control of the plating removal, welding and in-mold cooling processes.

[0050] Comparative Example 1: The only difference from Example 1 is: Instead of laser deplating on both sides of the high-strength steel plate to be welded, the 22MnB5 high-strength steel plate with zinc coating is directly rolled into an open tube blank, and then subjected to induction preheating, laser welding, online tempering, austenitizing heating, hot gas expansion forming and differential cooling. All other process parameters are the same as in Example 1.

[0051] In the hot gas expansion forming pipes prepared by the above process, due to the fact that some of the coating enters the weld pool during the welding process, the weld area has different degrees of porosity and inclusion defects, the weld forming quality is lower than that of Example 1, and the consistency of the weld area is poor.

[0052] Comparative Example 2: The only difference from Example 1 is: The induction preheating unit and the induction tempering unit are eliminated. That is, the tube blank after plating is directly laser welded. After welding, it directly enters the austenitizing heating process. All other process parameters are the same as in Example 1.

[0053] In the hot gas expansion forming pipes prepared by the above process, the weld area cools faster, the hardness of the weld area is significantly higher than that of the base material area, the residual stress in the weld area is larger, and the microstructure uniformity between the weld area and the base material area is poor. In the subsequent hot gas expansion forming process, the weld area is more prone to cracking.

[0054] Comparative Example 3: The only difference from Example 1 is: The hot gas expansion forming mold does not have an independent cooling circuit for the corresponding weld area, nor does it have a low thermal conductivity coating. The weld area and the base material area are cooled under the same cooling conditions, and the remaining process parameters are the same as in Example 1.

[0055] In the hot gas expansion forming pipes prepared by the above process, the weld area has a different microstructure from the base material area due to the welding thermal cycle. Under the same cooling conditions, the weld area has higher hardness and lower toughness, and the performance matching between the weld area and the base material area is poor, resulting in a decrease in the overall mechanical properties of the final part.

[0056] As can be seen from Example 1 and Comparative Examples 1-3, when using the manufacturing method provided by this invention to prepare hot gas-expanded pipe fittings, the selective laser deplating on both sides of the area to be welded, combined with the coordinated control of the entire process of induction preheating, laser welding, online tempering, and differentiated cooling of the weld area, can effectively improve the microstructure and mechanical properties of the weld area. Compared with the process in Comparative Example 1 without pre-weld deplating, this invention can reduce the amount of plating material entering the weld pool, reduce the probability of welding defects such as porosity and inclusions in the weld area, and improve the weld formation quality. Compared with the process in Comparative Example 2 without pre-weld preheating and post-weld tempering, this invention can reduce the cooling rate of the weld area, reduce welding residual stress, avoid the formation of excessively hard microstructures in the weld area, and improve the performance matching between the weld area and the base material area. Compared to the process in Comparative Example 3 where the weld area and the base material area use the same cooling method, this invention implements differentiated cooling for the weld area. This allows the weld area to achieve a moderate self-tempering effect while meeting the requirements for quenching hardening, further reducing the hardness and brittleness of the weld area, improving its toughness, and minimizing the hardness difference between the weld area and the base material area. Therefore, this invention can effectively improve the weld quality, microstructure uniformity, and overall mechanical properties of hot-expansion formed pipe fittings.

[0057] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A method for manufacturing a hot-expansion-formed pipe fitting, characterized in that, Includes the following steps: A high-strength steel plate with a metal coating formed on its surface is provided. The high-strength steel plate has a welding area and a coating removal area, wherein the coating removal area is located on both sides of the welding area. The high-strength steel plate is fed into a laser deplating device, and the area to be deplated is removed using the laser deplating device. The area to be welded in the high-strength steel plate after deplating is preheated to 200℃-350℃; The high-strength steel plate is welded to the area to be welded using a laser welding device to form a weld area, and the weld area is then tempered to obtain a welded pipe. The welded pipe is heated to 850°C-930°C using a heating device and kept at that temperature, so that both the weld area and the base material area of ​​the welded pipe are in an austenitic state. The austenitized welded pipe is fed into a hot gas expansion forming mold, and high-pressure gas is injected into the welded pipe to cause it to expand and fit into the hot gas expansion forming mold. The formed welded pipe is then quenched. The welded pipe is fed into a cooling device, and the weld area and the base material area of ​​the welded pipe are cooled separately, so that the cooling rate of the weld area is lower than that of the base material area, and finally a hot gas expansion forming pipe is obtained.

2. The manufacturing method according to claim 1, characterized in that, In the step of feeding the high-strength steel plate into a laser deplating device and using the laser deplating device to remove the plating from the area to be deplated, The area to be welded is detected using a visual positioning module; When a shift is detected in the area to be soldered, the laser deplating device is controlled to adjust the laser scanning path so that the laser scans along the areas to be deplated on both sides of the area to be soldered.

3. The manufacturing method according to claim 2, characterized in that, In the step of feeding the high-strength steel plate into a laser deplating device and using the laser deplating device to remove the plating from the area to be deplated, The plating removal status of the area to be deplated is detected using an optical detection module. When insufficient local plating removal is detected in the area to be deplated, the laser plating removal device is controlled to increase the laser pulse energy and / or increase the number of re-scans; when overburning is detected in the area to be deplated, the laser plating removal device is controlled to reduce the laser power and / or increase the laser scanning speed.

4. The manufacturing method according to any one of claims 1-3, characterized in that, In the step of using a laser welding device to weld the area to be welded on the high-strength steel plate to form a weld area, and then tempering the weld area to obtain a welded pipe, the tempering temperature range is 600℃-700℃, and the tempering area covers the weld area and the heat-affected zone, with the heat-affected zone located on both sides of the weld area.

5. The manufacturing method according to claim 4, characterized in that, The process of welding the high-strength steel plate to be welded using a laser welding device to form a weld area, and then tempering the weld area to obtain a welded pipe, further includes the following steps: The continuity of the weld area, the weld temperature profile, and surface defects are detected online. When the weld area shows signs of incomplete fusion, incomplete penetration, continuous porosity, or tempering temperature deviating from the set range, the welded pipe is deemed unqualified and enters the rework process.

6. The manufacturing method according to any one of claims 1-3, characterized in that, In the step of heating the welded pipe to 850°C-930°C using a heating device and holding it at that temperature so that both the weld area and the base material area of ​​the welded pipe are in an austenitized state, the temperature of the weld area and the base material area is monitored, and the temperature difference between the weld area and the base material area is kept below a set threshold, wherein the set threshold range is 15°C-30°C.

7. The manufacturing method according to any one of claims 1-3, characterized in that, In the step of feeding the welded pipe into a cooling device and cooling the weld area and the base material area of ​​the welded pipe respectively, so that the cooling rate of the weld area is lower than the cooling rate of the base material area, the cooling rate of the weld area is 75%-85% of the cooling rate of the base material area.

8. The manufacturing method according to claim 7, characterized in that, The cooling device is provided with a low thermal conductivity coating or a thermal resistance regulating layer, which covers the weld area.

9. A manufacturing system for hot-expansion forming of tubular fittings, characterized in that, The manufacturing method as described in any one of claims 1-8 is applied.

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