Lower cover up-dragging type welding gas protection tool

Abstract

The invention relates to a lower cover up-dragging type welding gas protection tool, belongs to the technical field of welding tools, and is used for solving the technical problem that existing magnesium alloy is prone to violent oxidation during high-temperature welding. The tool comprises a gas protection lower cover, a gas protection upper support and an argon supply tank, the argon supply tank is communicated with the gas protection lower cover and the gas protection upper support to supply argon, and the gas protection lower cover ensures that the root of a welding seam is formed and air is isolated; the gas protection upper support is used for expanding the protection range and covering a molten pool and a high-temperature heat affected zone in the whole process. The gas protection lower cover and the gas protection upper support are combined to realize active protection of a welding seam area, so that a high-quality welding seam which is good in forming and less in oxide skin is obtained; and a local argon environment is arranged, so that the technical problem that the magnesium alloy is prone to severe oxidation during high-temperature welding is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding tooling, in particular to a lower cover upper drag type welding gas protection tooling. BACKGROUND

[0002] At present, in the magnesium alloy tungsten inert gas welding process, the nozzle of the welding gun is usually used for local argon protection, and the protection range is mainly concentrated in the molten pool area directly below the arc, which is difficult to cover the front surface of the weld in the high-temperature oxidation sensitive interval which has left the arc but is still in the high-temperature oxidation sensitive interval, resulting in easy oxidation and discoloration in this area. For the completely penetrated weld, the back surface is directly exposed to the air, and it is almost impossible to obtain effective protection, which causes the back weld to be severely oxidized, poorly formed, and prone to porosity, slag inclusion and other defects. In addition, the protection gas is often immediately interrupted after welding, and the high-temperature weld will be obviously oxidized during the cooling process in the air, and a loose oxide skin will be formed on the surface.

[0003] The root cause of these problems lies in the fact that the existing protection tooling fails to achieve argon coverage in the whole process and the whole area of welding, especially in the high-temperature area of the weld front surface, the back surface and the post-weld cooling stage. There is a significant gas protection blind area. It is because it is impossible to provide all-round gas protection that magnesium alloy is prone to severe oxidation during high-temperature welding, which in turn leads to joint quality decline, unstable performance and poor process adaptability, becoming a key bottleneck restricting the development of magnesium alloy welding technology. SUMMARY

[0004] The purpose of the present application is to provide a lower cover upper drag type welding gas protection tooling to solve one of the following technical problems existing in the prior art: the magnesium alloy is prone to severe oxidation during high-temperature welding, the pressure loss along the way and uneven flow distribution due to single gas supply point, the lower argon inlet is blocked due to the sinking of the molten pool, and the protection blind area and local oxidation caused by uneven gas flow field and turbulent interference on the front surface of the welding.

[0005] The purpose of the present application is mainly realized by the following technical scheme:

[0006] In a first aspect, the present application provides a lower cover upper drag type welding gas protection tooling, which comprises a gas protection lower cover, a gas protection upper drag and an argon supply tank. The argon supply tank is connected to the gas protection lower cover and the gas protection upper drag to supply argon. The gas protection lower cover is used to support and fix the to-be-welded test piece and provide argon to the back surface of the weld. The gas protection upper drag is connected to the argon arc welding gun to move with the argon arc welding gun. The gas protection upper drag is used to provide argon to the front surface of the weld and the heat affected zone.

[0007] Further, the gas protection lower cover comprises a lower argon inlet, and the outlet end of the lower argon inlet is connected to the back surface of the weld to provide argon to the back surface of the weld.

[0008] Further, the gas protection upper cover comprises an upper argon inlet configured to provide argon to the front of the weld and the heat affected zone.

[0009] Further, the gas protection upper cover is provided with a welding gun surrounding wall configured to embed the argon arc welding gun and a binding ring configured to bind the argon arc welding gun in the welding gun surrounding wall.

[0010] Further, the gas protection lower cover comprises a base platform provided with a receiving groove configured to receive the back of the weld.

[0011] Further, the lower argon inlets are uniformly arranged on the receiving groove.

[0012] Further, the tool further comprises a communication pipe communicated between the lower argon inlets and the argon supply tank.

[0013] Further, the gas protection lower cover further comprises a cooling pipe embedded in the base platform and close to the receiving groove to cool the receiving groove, wherein the cooling pipe is filled with a cooling medium.

[0014] Further, the cooling pipe is communicated with a cooling medium circulating pump.

[0015] In the second aspect, the application further provides a welding method, which uses the protection tool to weld a to-be-welded sample.

[0016] The application can achieve at least one of the following advantages.

[0017] (1) In the technical scheme of the lower cover upper cover type welding gas protection tool, the argon supply tank is used as a stable and pure gas source to build a reliable local argon environment, the gas protection lower cover ensures the root of the weld to be formed and isolated from air, and the gas protection upper cover expands the protection range to cover the molten pool and the high-temperature heat affected zone throughout the whole process, thereby solving the problem of easy severe oxidation of magnesium alloy during high-temperature welding, and the gas protection lower cover and the gas protection upper cover work cooperatively under the support of continuous, controllable pressure and flow argon to achieve active protection of the weld area on the front and back surfaces throughout the whole period, thereby stably obtaining a high-quality weld with good forming and less oxide skin, which reduces defects such as pores and slag inclusion, improves the joint density and mechanical properties, and greatly reduces the workload and cost of post-weld cleaning.

[0018] (2) In the technical solution of the lower cover upper drag welding gas protection tool of the present invention, the forming defects caused by the molten pool falling or the irregular solidification shrinkage are reduced by the forced forming constraint, which enhances the stability of the welding process and reduces the workload of subsequent grinding and finishing; at the same time, the uniform coverage of the protective gas is achieved by the distributed lower argon gas inlet, which effectively prevents back oxidation or porosity defects caused by insufficient local protection, thereby comprehensively improving the forming quality of the back weld.

[0019] (3) In the technical solution of the lower cover upper drag welding gas protection fixture of the present invention, the gas flow state (flow rate and velocity) of all lower argon gas inlets and outlets within the entire length range of the containment tank can be basically consistent through the gas equalization component. This allows argon gas to cover the entire weld back forming area in a uniform "gas curtain" form, eliminating protection dead corners or weak areas, and solving the problem of pressure loss and uneven flow distribution along the path caused by a single gas supply point.

[0020] (4) In the technical solution of the lower cover upper drag welding gas protection fixture of the present invention, the pre-homogenization treatment of the airflow buffer homogenization component ensures that the gas flowing out from the upper argon inlet can cover the entire protection area below the drag cover in a uniform and stable laminar flow state, reducing the weak points of protection caused by uneven gas supply, so that the weld front and heat-affected zone can obtain a uniform silver-white high-quality surface and reduce local oxidation color difference.

[0021] (5) In the technical solution of the welding method of the present invention, the pre-welding cleaning in S1 provides a clean base material for welding, and the double-sided dynamic protection in S2 and S3 during welding maintains the clean state and controls the thermal process. On the one hand, it solves the surface oxidation problem by reducing oxygen contact, and on the other hand, it effectively suppresses the generation of surface microcracks, mainly hot cracks, by purifying the molten pool and optimizing the thermal cycle, thereby realizing high-quality magnesium alloy welding, solving the technical problems of surface oxidation and surface microcracks in magnesium alloy welding, and thus being able to stably obtain high-quality welds with beautiful shape (silver white), few internal defects, and reliable mechanical properties, thereby improving the process reliability, quality consistency and pass rate of magnesium alloy argon arc welding.

[0022] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0023] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0024] Figure 1 This is a schematic diagram of the structure of the gas protective lower cover in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the gas-protected upper tractor structure in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the gas equalization component in an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the sealing nail structure in an embodiment of the present invention;

[0028] Figure 5 This is a schematic flowchart of the welding method in an embodiment of the present invention.

[0029] Figure label:

[0030] 1-Gas protection lower cover, 11-Base platform, 12-Containing tank, 121-Lower argon inlet, 14-Gas equalization assembly, 141-Primary gas equalization chamber, 142-Inter-chamber connecting hole, 143-Secondary gas equalization chamber, 15-Pressure plate, 16-Fastener, 17-Cooling pipe, 18-Sealing nail, 181-Nailing nail body, 182-First channel, 183-Second channel, 184-Claw, 185-Side flow channel, 2-Gas protection upper trailer, 21-Welding torch enclosure, 22-Binding ring, 23-Upper trailer body, 24-Gas duct assembly, 241-Gas duct main pipe, 242-Gas duct branch pipe, 25-Airflow buffer and equalization assembly, 251-Primary screen, 252-Secondary screen, 26-Upper argon inlet, 3-Connecting pipe, 4-Argon arc welding torch. Detailed Implementation

[0031] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0032] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0033] Example 1

[0034] like Figure 1 and Figure 2As shown, Embodiment 1 of the present invention provides a lower cover and upper drag type welding gas protection fixture, which aims to solve the technical problem of severe oxidation during high-temperature welding of magnesium alloys.

[0035] The fixture includes a lower gas shield 1, an upper gas shield 2, and an argon supply tank. The argon supply tank is connected to the lower gas shield 1 and the upper gas shield 2 to supply argon. The lower gas shield 1 is used to support and fix the test piece to be welded and to supply argon to the back of the weld. The upper gas shield 2 is connected to the argon arc welding torch 4 to move with the argon arc welding torch 4. The upper gas shield 2 is used to supply argon to the front of the weld and the heat-affected zone.

[0036] The lower gas shield shroud 1 provides a support platform for the magnesium alloy specimen to be welded and fixes it in place by a clamping mechanism (such as a clamp). This ensures that the specimen does not shift or deform during welding. By using argon gas (usually argon), oxygen is isolated, reducing the contact between the back of the magnesium alloy and air, thus preventing a violent oxidation reaction (forming MgO oxide scale); and reducing defects such as porosity and slag inclusions caused by oxygen intrusion. The upper gas shield shroud 2 is rigidly connected to the welding torch and moves synchronously. By continuously and stably covering the weld face, molten pool, and surrounding heat-affected zone with argon gas, the protection area is expanded. The upper gas shield shroud 2, with its larger cavity, extends the protection range and effectively protects the weld. To protect the heat-affected zone (HAZ) of the weld face, which is highly susceptible to oxidation even at high temperatures, the gas shielding device moves with the welding torch during welding. It provides continuous argon gas protection to the weld area (including the newly solidified metal and the HAZ) that is still very hot after leaving the arc, preventing oxidation during cooling. The argon supply tank is the gas source and pressure center of this protective tooling system. Its function is to continuously and stably provide high-purity argon gas throughout the welding process, ensuring that it has the required pressure and flow rate. The outlet of the argon supply tank is equipped with a pressure regulating valve to control and regulate the gas pressure delivered to the tooling, ensuring a stable gas flow and adjustable parameters. For example, the argon supply tank can be a high-pressure gas cylinder with a pressure reducing valve.

[0037] In summary, by using an argon supply tank as a stable and pure gas source, a reliable local argon environment was constructed. The lower gas shield 1 ensures the weld root is formed and isolates it from air; the upper gas shield 2 expands the protection range, covering the molten pool and high-temperature heat-affected zone throughout the process. This solves the technical problem of severe oxidation during high-temperature welding of magnesium alloys. The lower gas shield 1 and the upper gas shield 2 work together under continuous, pressure- and flow-controlled argon support to achieve active protection of the weld area on both the front and back sides at all times. This results in a stable and high-quality weld with good formation and less oxide scale, which reduces defects such as porosity and slag inclusions, improves the joint density and mechanical properties, and significantly reduces the workload and cost of post-weld cleaning.

[0038] Furthermore, such as Figure 1As shown, the gas protective cover 1 includes a lower argon inlet 121, and the outlet end of the lower argon inlet 121 is connected to the back side of the weld to provide argon to the back side of the weld.

[0039] The lower argon inlet 121 is used to directionally and centrally deliver argon gas to the back area of ​​the weld, forming a local argon environment below the molten pool to isolate it from air. This prevents the back of the weld from oxidizing and nitriding at high temperatures, ensuring that the back weld is uniform in shape and free of oxidation color, reducing back porosity and slag inclusion defects, thereby guaranteeing the quality of both sides of the weld and its overall mechanical properties.

[0040] Furthermore, such as Figure 2 As shown, the gas-protected upper trailer 2 includes an upper argon inlet 26, which is used to supply argon to the weld face and heat-affected zone.

[0041] The upper argon inlet 26 is the core of the gas delivery for the front drag shield, which evenly distributes and covers the entire drag shield cavity with argon gas, thereby forming a moving, wide-area gas protective layer in front of and behind the welding torch. As a result, the protective gas can continuously and stably cover the weld pool and high-temperature heat-affected zone on the front of the weld, effectively preventing oxidation and contamination in these areas, thus obtaining a silvery-white, high-quality front weld and improving the stability and reliability of the welding process.

[0042] Furthermore, such as Figure 2 As shown, the gas-protected upper trailer 2 is provided with a welding torch enclosure 21 and a binding ring 22. The welding torch enclosure 21 is used for embedding the argon arc welding torch 4, and the binding ring 22 is used to bind the argon arc welding torch 4 inside the welding torch enclosure 21.

[0043] The welding torch enclosure 21 provides a positioning and support base for the welding torch, ensuring that the drag shield is aligned with the welding torch axis; the binding ring 22 applies a fastening force, rigidly connecting the two into a whole, achieving synchronous movement; thus, the protective drag shield moves seamlessly in coordination with the welding torch during the welding process, ensuring that the argon gas protection area always accurately covers the molten pool, eliminating protection failure caused by the relative displacement of the two, and improving the stability of welding quality and the controllability of operation.

[0044] Furthermore, the gas protective cover 1 includes a base platform 11, such as... Figure 1 As shown, the base platform 11 is provided with a receiving groove 12 for accommodating the back of the weld. The receiving groove 12 is provided with a lower argon gas inlet 121 evenly distributed on the receiving groove 12. The lower argon gas inlet 121 is connected to the connecting pipe 3 to obtain argon gas.

[0045] The receiving groove 12 serves as the forming reference and constraint structure for the back side of the weld. Its function is to apply precise geometric constraints to the molten metal. During the welding process, the molten pool penetrating the workpiece solidifies in this groove. Its width, depth, and groove edge radius directly control the reinforcement height, width, and surface morphology of the back weld, thereby achieving controlled and precise forming of the back weld. In addition, the groove itself (for example, using copper material with good thermal conductivity) can act as a heat sink to help regulate the cooling rate of the weld area. The lower argon inlet 121 is a series of micropores distributed on the receiving groove, forming a distributed output network of argon gas on the back side. Its main function is to diffuse and equalize the input argon gas, so as to cover the entire groove cavity with a stable and uniform laminar flow, so that the back side of the high-temperature weld is always in an argon atmosphere, achieving comprehensive anti-oxidation protection.

[0046] In summary, the mechanical constraint of the accommodating groove 12 effectively suppresses shape defects caused by molten pool sag and solidification shrinkage, improves welding stability, and reduces subsequent grinding workload. At the same time, the uniformly arranged argon micropores achieve full coverage of the back side of the weld with protective gas, avoiding oxidation or porosity problems caused by local gas deficiency, thereby improving the overall forming quality and metallurgical quality of the back side weld.

[0047] Furthermore, such as Figure 1 and Figure 3 As shown, the gas protection lower cover 1 includes a cooling pipe 17, which is embedded in the base platform 11 and close to the receiving tank 12 to cool the receiving tank 12. The cooling pipe 17 is filled with a cooling medium.

[0048] The cooling pipe 17 actively dissipates heat and cools the metal of the receiving groove 12, which is in direct contact with the back of the weld, through the cooling medium (usually circulating water or other coolant) filled inside it. Its "close" design ensures the shortest heat conduction path, thereby quickly transferring and removing a large amount of welding heat accumulated in the forming groove area during the welding process. Active cooling makes the solidification and cooling process of the weld metal (especially the root) controllable. By adjusting the flow rate or temperature of the cooling medium, coarse grains and overheated structure caused by slow cooling of magnesium alloy can be avoided, as well as residual stress and cold cracking tendency caused by excessively rapid cooling. This helps to obtain a finer and more uniform weld microstructure, thereby improving the mechanical properties of the joint.

[0049] Furthermore, a cooling medium circulation pump is connected to the cooling pipe 17.

[0050] The introduction of the cooling medium circulation pump upgrades the static cooling chamber into a dynamic and controllable active circulation cooling system. Through forced circulation, the cooling medium that has absorbed heat is continuously removed and replaced with a low-temperature medium, thereby greatly improving cooling efficiency and stability. This allows the tooling to maintain the temperature of the forced forming groove within the set range during long-term, high-heat-input welding processes, ensuring the ultra-consistency of the back weld forming dimensions and the repeatability of the process.

[0051] Embodiment 1 of the present invention provides another welding method, which applies the aforementioned protective tooling to solve the technical problems of surface oxidation and surface microcracks in magnesium alloy welding.

[0052] like Figure 5 As shown, the welding method includes:

[0053] S1. Dry the magnesium alloy test piece to be welded and mechanically scrape the surface of the area to be welded to remove the oxide layer;

[0054] S2. Clamp the treated test piece onto the gas shield 1 and press it tightly; before welding, introduce argon gas into the gas shield 1 to create an argon gas environment on the back of the test piece.

[0055] S3. Install the welding torch on the gas shielded upper cable 2; before welding, introduce argon gas into the gas shielded upper cable 2 to create an argon gas environment on the front side of the test piece; perform argon arc welding while the argon gas is continuously supplied.

[0056] S1 aims to eliminate two major sources of pollution at the source. Drying removes moisture adsorbed on the test piece, preventing hydrogen porosity during welding. Mechanical scraping removes the surface oxide layer of the area to be welded, ensuring a clean welding interface and creating conditions for a pure metallurgical bond. For example, the magnesium alloy test piece is a cast test piece made of high-performance rare-earth magnesium alloy material (material grade VK100Z). Argon arc welding is performed using this cast test piece (material grade VK100Z). The test piece uses a 2.5mm thick butt joint, and the welding wire is filled with the same material. During mechanical scraping, a scraper is used to scrape the front and back sides of the test piece to be welded and the butt joint surface in the same direction. The scraping width on both sides is 10mm-15mm to ensure the metallic luster is exposed and the surface oxide layer is removed.

[0057] S2 achieves stable fixation of the test piece and pre-replacement of the back environment. The clamping ensures the geometric accuracy and stability of the welding process. The pre-introduction of back protective gas removes the air in the back cavity and pre-establishes an argon environment, ensuring that once the arc is ignited, the back of the molten pool is immediately protected. For example, forming an argon environment on the back of the test piece specifically means that the argon concentration reaches 99.99% or higher.

[0058] In S3, the installation of the gas-shielded upper trailer 2 integrates the protection device with the heat source; pre-supply of gas establishes the initial protective atmosphere on the front; during welding, the gas-shielded upper trailer 2 moves synchronously with the welding torch, providing continuous and dynamic gas protection for the molten pool, arc, and high-temperature heat-affected zone to prevent them from reacting with air. Specifically, the gas-shielded upper trailer 2 is installed on the ceramic tube of the welding torch nozzle, and the height is adjusted to ensure that the distance between the gas-shielded upper trailer and the surface of the test piece is no more than 2mm; before formal welding, the interior of the gas-shielded upper trailer 2 is pre-filled with gas to ensure an argon atmosphere environment; after setting the welding process parameters, formal welding begins.

[0059] Through S1-S3, a double-sided active protection system is formed that runs through the entire process of pre-weld, during-weld, and post-weld (process continuation). Pre-weld cleaning in S1 provides clean base material for welding, and double-sided dynamic protection in S2 and S3 maintains the cleanliness and controls the thermal process. On the one hand, it solves the surface oxidation problem by reducing oxygen contact, and on the other hand, it effectively suppresses the generation of surface microcracks, mainly hot cracks, by purifying the molten pool and optimizing the thermal cycle. This enables high-quality magnesium alloy welding and solves the technical problems of surface oxidation and surface microcracks in magnesium alloy welding. As a result, it can stably obtain high-quality welds with beautiful shape (silver-white), few internal defects, and reliable mechanical properties, and improve the process reliability, quality consistency, and pass rate of magnesium alloy argon arc welding.

[0060] Furthermore, after S3, there is also S4, which is a post-weld slow cooling step to maintain a continuous supply of argon gas to the front and back of the test piece, so that the weld can be cooled in an argon atmosphere.

[0061] In S4, the post-weld slow cooling step serves to maintain double-sided argon gas protection after the welding thermal cycle, allowing the high-temperature weld to cool slowly and uniformly to a safe temperature in a controlled inert atmosphere. This extends the active protection during the welding process, preventing secondary oxidation of the high-temperature metal upon contact with air during the cooling stage, and regulating the post-solidification cooling process of the weld. As a result, the weld and heat-affected zone surfaces maintain a clean metallic color (silver-white), reducing the formation of post-weld oxide scale. At the same time, slow cooling effectively reduces the cooling rate and temperature gradient in the weld zone, helping to reduce residual welding stress, inhibiting the generation of cold cracks, and improving the uniformity of the weld microstructure, thereby enhancing the overall mechanical properties and corrosion resistance of the joint.

[0062] Furthermore, S3 also includes a step of adjusting the gap between the welding torch and the surface of the test piece.

[0063] Adjusting the gap (i.e., arc length) between the welding torch and the test piece surface is an operation to control the transmission of welding energy. This determines the stability of the arc, the concentration of heat input, and the shape and size of the molten pool. Precisely adjusting the gap is a prerequisite for ensuring that the weld penetration and width meet the requirements and for achieving stable welding. Maintaining an optimal and stable welding torch gap can obtain an arc with concentrated energy and stable combustion. This is conducive to forming a molten pool of appropriate size and controllable fluidity, thereby ensuring uniform weld formation and consistent penetration, and effectively preventing defects such as undercut, incomplete penetration, or burn-through caused by arc length fluctuations.

[0064] Furthermore, in S2, the flow rate of argon gas introduced into the gas-protected lower hood 1 is not less than 15 L / min, and the introduction time lasts for at least 1 minute.

[0065] By rapidly replacing the air in the back cavity with a sufficiently large airflow, a uniform and stable argon environment is established, ensuring that the back of the molten pool is protected from the moment the arc is ignited.

[0066] In practical applications, the flow rate and the inlet time are not limited to the above-mentioned flow rate or inlet time. The flow rate and inlet time can be determined based on the actual sample length, the size of the receiving tank, and the given input gas flow rate and inlet time.

[0067] Furthermore, in S3, the flow rate of argon gas introduced into the gas protection upper tractor 2 is 8-12 L / min, and the introduction time is at least 30 seconds.

[0068] This creates a stable and uniform argon atmosphere within the front shield, and maintains a laminar protective gas curtain during welding that is sufficient to cover the molten pool and high-temperature zone without interfering with the stability of the arc and molten pool.

[0069] In practical applications, it is not limited to the above-mentioned traffic volume, nor is it limited to the above-mentioned access time.

[0070] Furthermore, in S4, the weld is cooled in an argon atmosphere for no less than 30 seconds. This provides a controlled, slow cooling environment for the weld, isolating it from air and actively managing its cooling process.

[0071] Example 2

[0072] Embodiment 2 of the present invention is a further improvement based on Embodiment 1, which aims to solve the problems of pressure loss and uneven flow distribution along the pipeline caused by a single gas supply point.

[0073] like Figure 1 and Figure 3 As shown, the lower gas protective cover 1 also includes a gas equalization component 14, which is disposed at the bottom of the receiving tank 12. The inlet end of the gas equalization component 14 is connected to the connecting pipe 3, and the outlet end of the gas equalization component 14 is connected to the lower argon inlet 121, so that the gas introduced from the connecting pipe 3 is evenly distributed in the receiving tank 12.

[0074] The gas equalization component 14, serving as the pressure equalization and flow distribution center for the back-side protective gas flow path, is typically a cavity connecting the main inlet (connecting pipe 3) and multiple dispersed outlets (lower argon inlets 121). Its working principle is as follows: a concentrated gas flow with high velocity and pressure input from a single pipeline is buffered, diffused, and redistributed within its internal cavity, converting the gas dynamic pressure into a uniform static pressure. This provides a consistent pressure and balanced flow source for each downstream lower argon inlet 121, resolving the pressure loss along the flow path caused by a single gas supply point. The problem of uneven flow distribution is solved by the gas equalization component 14, which ensures that the airflow state (flow rate and velocity) of all lower argon inlets 121 and outlets within the entire length of the containment tank 12 is basically consistent. This allows the argon to cover the entire back-side forming area of ​​the weld in a uniform "air curtain" form, eliminating protection dead zones or weak areas. As a result, no matter how long the weld is, a high-quality back-side weld with uniform overall color (all silver-white) and no local oxidation spots can be obtained, improving the reliability and repeatability of the protection process. It is especially suitable for long welds or precision welding applications with high requirements for back-side quality.

[0075] Based on this, such as Figure 3 As shown, the gas equalization assembly 14 includes a primary gas equalization chamber 141, a secondary gas equalization chamber 143, and an inter-chamber communication hole 142 connecting the primary gas equalization chamber 141 and the secondary gas equalization chamber 143. The primary gas equalization chamber 141 is opened on the base platform 11 and is connected to the connecting pipe 3. The secondary gas equalization chamber 143 is opened at the bottom of the receiving groove 12, and the lower argon gas inlet 121 passes through the receiving groove 12 and communicates with the secondary gas equalization chamber 143. The inter-chamber communication hole 142 is opened on the base platform 11.

[0076] The primary equalization chamber 141, serving as the primary pressure stabilization and distribution chamber for gas entry, directly receives the concentrated high-speed airflow from the connecting pipe 3. Utilizing its relatively large cavity volume, it causes a sudden drop in gas velocity and initial dissipation of kinetic energy, transforming the unstable pipe flow into a relatively stable static pressure field within the chamber. The secondary equalization chamber 143, located close to the bottom of the receiving groove 12, serves as a secondary pressure stabilization and equalization chamber, collecting and further homogenizing the gas from the primary equalization chamber 141. Through the secondary equalization chamber 143, the gas pressure is further homogenized along the entire length and width of the receiving groove 12. The step balance ensures that the inlet pressure of each lower argon inlet 121 covering the bottom of the forming tank is consistent; the inter-chamber connecting hole 142 serves as a flow limiting and guiding channel connecting the two-stage buffer chambers. Its function is to control the flow rate and velocity of gas from the primary equalization chamber 141 to the secondary equalization chamber 143. Through its specific hole diameter and number design, it can not only ensure sufficient ventilation, but also further suppress the pulsation and disturbance of gas flow, prevent gas from being directly injected into the secondary equalization chamber 143, and achieve a smooth pressure transition, reduce gas flow short circuit or local overshoot. Through the synergistic effect of the two-stage buffer chamber and the flow-limiting connecting hole structure, a precise gas pressure equalization and distribution structure is formed. By performing two buffer pressure reductions and one steady flow transition on the inlet gas, it is ensured that the gas flowing out of all the lower argon inlets 121 on the containment tank 12 has a highly consistent flow rate and velocity. This achieves uniform laminar flow coverage of the back protective gas, reduces defects such as oxidation color difference and porosity caused by uneven local protection, and effectively buffers the fluctuation of input gas pressure, thereby improving the stability, reliability and process repeatability of the back weld protection effect, which is especially suitable for welding high-quality long welds.

[0077] Furthermore, such as Figure 1 As shown, the gas protection lower cover 1 also includes a pressure plate 15, which is detachably and movably mounted on the base platform 11 by fasteners 16 to press and fix the test piece to be welded.

[0078] The pressure plate 15 and fastener 16 are used for mechanical fixation and clamping of the test piece, providing adjustable and reliable downward pressure. The test piece to be welded is tightly attached to the base platform 11 (and receiving groove 12) by the pressure plate 15. Its detachable and movable design realizes flexible adjustment of the clamping position to adapt to test pieces of different sizes or weld positions, and ensures the absolute rigid fixation of the test piece during the welding process, preventing displacement caused by thermal deformation or arc force. The fastener 16 can be a screw.

[0079] Example 3

[0080] Embodiment 3 of the present invention is a further improvement based on Embodiment 1 or Embodiment 2, and aims to solve the technical problems of protective blind spots and local oxidation caused by uneven gas flow field and turbulence interference on the welding front.

[0081] likeFigure 2 As shown, the gas-protected upper trailer 2 also includes: an upper trailer body 23 having a bottom surface parallel to the welding plane; a gas guide pipe assembly 24 for connecting to an external argon gas source, disposed on the upper trailer body 23, and having an outlet facing the top of the upper trailer body 23; and a gas flow buffer and homogenization assembly 25 disposed inside the upper trailer body 23, covering the upper argon gas inlet 26, for making the incoming protective gas pass through the upper argon gas inlet 26 smoothly and evenly to cover the weld surface.

[0082] The upper drag body 23 provides a structural body and a flat bottom surface parallel to the welding plane to define and maintain a constant protective space, ensuring a stable distance between the drag cover and the test piece surface. The gas guide pipe assembly 24 serves as the inlet for delivering protective gas, efficiently introducing high-pressure, high-speed airflow from an external gas source into the upper drag body 23. Through its top-facing outlet design, it reduces the direct impact of airflow on the workpiece or molten pool below, guiding the airflow to diffuse upwards first. The airflow buffer and homogenization assembly 25 acts as a primary gas distributor and rectifier, receiving the concentrated airflow from the gas guide pipe assembly 24 and discharging it through its porous structure. The barrier or cavity structure reduces the gas flow rate, converts dynamic pressure into static pressure, and allows the gas to be fully mixed and homogenized inside, thereby providing a premixed gas source with balanced pressure and uniform flow for the dense upper argon inlet 26. Through the pre-homogenization treatment of the airflow buffer homogenization component 25, it is ensured that the gas flowing out from the upper argon inlet 26 (such as a screen or flow equalization plate) can cover the entire protection area below the hood in a uniform and stable laminar flow state, reducing the weak points in protection caused by uneven gas supply, so that the weld front and heat-affected zone can obtain a uniform silver-white high-quality surface and reduce local oxidation color difference.

[0083] Furthermore, such as Figure 2 As shown, the airflow buffer homogenization component 25 includes a primary screen 251 and a secondary screen 252. The primary screen 251 is positioned above the secondary screen 252, and the secondary screen 252 is connected to the upper argon inlet 26. The outlet aperture of the primary screen 251 is larger than that of the secondary screen 252.

[0084] The primary screen 251, acting as a primary buffer, primarily dissipates the kinetic energy of the airflow. High-speed, concentrated airflow from the guide pipe impacts this plate, generating a throttling effect and numerous small eddies as it passes through its larger apertures. This reduces the gas velocity and dynamic pressure, and initially disperses the airflow into multiple fine streams, preparing it for the next stage of processing. For example, the aperture of the primary screen 251 is Φ4mm. The secondary screen 252, acting as a secondary refiner, primarily equalizes pressure and establishes laminar flow. It receives the initially diffused airflow from the previous stage and, through its denser, smaller apertures, performs a second throttling and mixing of the gas. This further equalizes the pressure of the airflow at various points, ultimately "combing" the airflow into countless streams with uniform velocity and perpendicular direction. The downward-facing micro-columns of gas lay the foundation for the formation of a stable and uniform laminar protective gas curtain. For example, the aperture of the secondary screen 252 is Φ2mm. Through the two-stage stepped aperture design, the gas is forced to be "uniformed". This reduces local airflow dead zones or high-speed jets caused by air intake impact or cavity shape, ensuring that the gas flowing out from the entire upper argon inlet 26 (i.e., the bottom surface of the secondary screen) is almost uniform in speed, flow rate and direction. As a result, an oxidation-free, overall silver-white weld surface can be obtained. At the same time, it reduces the arc drift, weld pool disturbance or overcooling that may be caused by high-speed airflow blowing directly onto the molten pool. This makes the welding process more stable, the allowable range of process parameters (such as gas flow rate) is wider, and the process robustness is stronger.

[0085] Furthermore, such as Figure 2 As shown, the gas duct assembly 24 includes a gas duct main 241 and a gas duct branch 242. One end of the gas duct main 241 is connected to an argon gas source to obtain argon gas, and the other end of the gas duct main 241 is connected to the gas duct branch 242 to distribute argon gas. The gas outlet on the gas duct branch 242 faces the top of the upper towing body 23.

[0086] The main gas duct 241 serves as the main delivery channel, responsible for steadily and continuously introducing argon gas from an external gas source into the upper carrier body 23 at high pressure and speed. The branch gas duct 242 serves as a transition structure, which diffuses the gas flow from a single point (the port of the main gas duct) through its own tubular volume, reducing the concentration of the gas flow. The gas outlet on the branch gas duct 242, facing upwards, forces a change in the direction of the gas flow, making it spray vertically upwards. This reduces the direct impact of high-pressure gas flow on the workpiece or interference with the molten pool, while guiding the gas flow towards the top space of the carrier, using the top obstruction for secondary rebound diffusion, so that the gas can be more fully and evenly distributed in the carrier before entering the subsequent homogenization components. The upper part of the cavity; through the initial diffusion and upward jet design of the gas guide branch pipe 242, the kinetic energy of the high-speed intake airflow is effectively dissipated and redistributed. This prevents local high-pressure areas caused by direct airflow and ensures that the subsequent airflow buffering and homogenizing component 25 (such as a double-layer mesh plate) can receive a pre-mixed and tamed air source, thereby more efficiently converting it into a uniform laminar flow. This reduces the direct interference of the shielding airflow on the welding process. At the same time, the optimized air intake method and the homogenization system work together to achieve a stable and reliable protection effect within a wide range of air intake flow parameters, broadening the process window and enhancing the adaptability and repeatability of the entire welding system under different working conditions.

[0087] Example 4

[0088] Embodiment 4 of the present invention is a further improvement based on Embodiment 1, Embodiment 2 or Embodiment 3, and aims to solve the technical problem of blocking the lower argon gas inlet due to the molten pool falling.

[0089] like Figure 4 As shown, the lower argon inlet 121 is covered with a sealing nail 18. The sealing nail 18 includes a nail body 181, a first channel 182, a second channel 183, and a claw 184. The first channel 182 and the second channel 183 are both connected to the nail body 181. The inlet end of the first channel 182 is connected to the lower argon inlet 121, and its outlet end is close to the test piece to be welded. The inlet end of the second channel 183 is connected to the first channel 182 and / or the lower argon inlet 121, and its outlet end is located on the side wall of the top of the nail body 181. The claw 184 is fixedly set at the bottom of the nail body 181 to lock the sealing nail 18 onto the lower argon inlet 121.

[0090] As an integrated gas path conversion and physical protection component, the sealing nail 18 has its constituent parts working together to allow the normal output of protective gas while physically preventing molten metal from entering and blocking the lower argon inlet 121. Specifically, the nail body 181 serves as the main structure, supporting the internal flow channels and providing an installation base; the first channel 182 serves as the main gas flow path, guiding the argon gas from the inlet to a position close to the test piece, forming direct bottom gas protection; the second channel 183 serves as an auxiliary or diversion path, and its lateral outlet end can form an upward gas curtain around the top of the nail body, further isolating the molten pool; the claws 184 are used for mechanical locking, ensuring that the sealing nail is protected from welding vibration and heat effects. The positioning is stable; by introducing the sealing pin 18, the risk of molten metal falling and blocking the pores is solved. The technical effects are as follows: First, it reduces the failure mode of sudden interruption of back protection due to blockage of the air inlet, ensuring a continuous and stable supply of protective gas; Second, by combining the vertical air outlet of the first channel 182 and the side air outlet of the second channel 183, the local flow field in the receiving groove 12 is optimized, enhancing the gas's encapsulation effect on the high-temperature metal; Third, it improves the reliability and service life of the tooling, preventing frequent cleaning or maintenance due to pore blockage; thereby enhancing the robustness of the back protection system and providing additional assurance for obtaining high-quality, oxidation-free, and stable back weld formation.

[0091] Furthermore, such as Figure 4 As shown, the sealing nail 18 also includes a lateral flow channel 185, which is formed on the nail body 181. Its inlet end is connected to the first channel 182, and its outlet end is formed on the side wall of the nail body 181.

[0092] The lateral flow channel 185, as a branch of the first channel 182, directs part of the main protective gas from the side wall of the nail body 181 at a specific angle. This lateral airflow can form a surrounding gas curtain around the nail body. Its mechanical effect can lift or push away the molten metal that tries to approach the nail body. At the same time, it forms a local argon microenvironment on the side of the nail body, further enhancing the protection against oxidation and adhesion of the nail body structure itself. This enhances the reliability of preventing the molten pool metal from sticking or blocking the gas inlet, especially in the case of high metal fluidity such as large melting depth or oscillating welding. At the same time, it reduces the protection dead angle that may be caused by the nail body, making the high temperature metal surface more tightly and uniformly wrapped with argon gas, providing additional protection for the reliability of the back weld quality.

[0093] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A bottom-cover, top-draft type welding gas protection fixture, characterized in that, It includes a lower gas shield (1), an upper gas shield (2), and an argon supply tank. The argon supply tank is connected to the lower gas shield (1) and the upper gas shield (2) to supply argon. The lower gas shield (1) is used to support and fix the test piece to be welded and to supply argon to the back of the weld. The upper gas shield (2) is connected to the argon arc welding torch (4) to move with the argon arc welding torch (4). The upper gas shield (2) is used to supply argon to the front of the weld and the heat-affected zone.

2. The lower cover upper drag type welding gas protection fixture according to claim 1, characterized in that, The gas protective cover (1) includes a lower argon inlet (121), the outlet of which is connected to the back of the weld to provide argon to the back of the weld.

3. The lower cover upper drag type welding gas protection fixture according to claim 1, characterized in that, The gas-protected upper tractor (2) includes an upper argon inlet (26), which is used to supply argon to the weld face and the heat-affected zone.

4. The lower cover upper drag type welding gas protection fixture according to claim 1, characterized in that, The gas-protected upper trailer (2) is provided with a welding torch enclosure (21) and a binding ring (22). The welding torch enclosure (21) is used for embedding the argon arc welding torch (4), and the binding ring (22) is used to bind the argon arc welding torch (4) inside the welding torch enclosure (21).

5. The lower cover upper drag type welding gas protection fixture according to claim 2, characterized in that, The gas protective cover (1) includes a base platform (11).

6. The lower cover upper drag type welding gas protection fixture according to claim 5, characterized in that, The base platform (11) is provided with a receiving groove (12) for accommodating the back of the weld, and the lower argon gas inlet (121) is evenly distributed on the receiving groove (12).

7. The lower cover upper drag type welding gas protection fixture according to claim 5, characterized in that, It also includes a connecting pipe (3) that connects the lower argon inlet (121) and the argon supply tank.

8. The lower cover upper drag type welding gas protection fixture according to claim 5, characterized in that, The gas protection lower cover (1) also includes a cooling pipe (17), which is embedded in the base platform (11) and is close to the receiving groove (12) to cool the receiving groove (12). The cooling pipe (17) is filled with a cooling medium.

9. The lower cover upper drag type welding gas protection fixture according to claim 8, characterized in that, A cooling medium circulation pump is connected to the cooling pipe (17).

10. A welding method, characterized in that, Welding is performed on the test piece using the protective fixture described in any one of claims 1-9.

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