Method for determining welding gun offset distance for welding bottom weld of sheet metal welding machine case lock and welding method

Abstract

This invention discloses a method for determining the welding torch offset distance and a welding method for the bottom weld of a sheet metal welding machine casing, belonging to the field of fusion welding technology. The method for determining the welding torch offset distance includes obtaining the machining side weld thickness L1, the sheet metal side weld thickness L2, and the bottom weld thickness L3 of the sheet metal welding machine casing; calculating the axial offset P between the welding torch tungsten electrode and the center of the weld joint; determining the facing position of the welding torch tungsten electrode based on the axial offset P; obtaining the offset angle θ and weld diameter ΦA directly above the weld bead; calculating the offset distance L between the facing position of the welding torch tungsten electrode and the center of the weld joint; and determining the alignment line of the welding torch tungsten electrode tip at the workpiece weld joint based on the axial offset P between the welding torch tungsten electrode and the center of the weld joint and the offset distance L between the facing position of the welding torch tungsten electrode and the center of the weld bead. The welding method includes adjusting the position of the circumferential automatic welding torch mechanism based on the alignment line, with the welding torch positioned in the upward slope direction of the weld bead in the circumferential direction.

Description

Technical Field

[0001] This invention belongs to the field of fusion welding technology, and relates to a method for determining the welding torch offset distance and a welding method for the bottom weld of a sheet metal casing. Background Technology

[0002] The engine casing, as the "skeleton" of the engine, is a critical component for load-bearing, pressure-bearing, temperature-bearing, and containment, enduring various alternating stress loads, temperature loads, and aerodynamic loads. Sheet-welded casings, as an important part of the casing, have advantages such as low production cost, short development cycle, light weight, and rapid repair, thus playing an irreplaceable role in engine design. High-precision, low-stress welding of sheet-welded casings is a key core technology for ensuring the lifespan and reliability of high-performance engines, from compressor components to exhaust nozzle components. In engine casing design, specific structures are required in certain areas, among which cavity-type sheet-welded casings are a common casing structure. Considering both performance reliability and manufacturing processes, the weld joints of these cavity-type sheet-welded casings are often designed as non-uniform thickness joints with locking bottoms.

[0003] At this point, when using conventional tungsten electrode welding to weld the center and directly above the weld bead, the heat dissipation performance on both sides of the joint is different during welding. The sheet metal side has poor heat dissipation, resulting in a fast melting speed and more molten metal, while the other side has good heat dissipation, resulting in a slow melting speed and less molten metal. This causes the weld pool to shift, leading to incomplete melting at the root of the weld or the formation of voids. Stress concentration occurs, making the weld prone to cracking and significantly reducing the fatigue life of the component. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem of weld pool offset in conventional tungsten electrode welding methods where the weld is being welded at or directly above the center of the weld bead. This invention provides a method for determining the welding gun offset distance and a welding method for the bottom weld of a sheet metal welding machine casing.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention discloses a method for determining the welding torch offset distance of the bottom weld seam of a sheet metal welding machine casing, comprising: Obtain the machining side welding thickness L1, sheet metal side welding thickness L2, and bottom locking thickness L3 of the sheet metal welding casing, and calculate the axial offset P between the tungsten electrode of the welding torch and the center of the welding joint. Based on the axial offset P, determine the position of the tungsten electrode of the welding torch, obtain the offset angle θ and weld diameter ΦA directly above the weld bead, and calculate the offset distance L between the position of the tungsten electrode of the welding torch and the position directly above the weld bead. Based on the axial offset P between the tungsten electrode of the welding torch and the center of the weld joint, and the offset distance L between the tungsten electrode of the welding torch facing the weld bead and directly above it, the alignment line of the tip of the tungsten electrode of the welding torch is determined at the weld joint of the workpiece.

[0006] Further improvements are made in the following aspects: The calculation of the axial offset P between the tungsten electrode of the welding torch and the center of the weld joint is specifically as follows: P = L1 - L2 + ½L3.

[0007] The specific calculation of the offset distance L between the tungsten electrode of the welding torch and the weld bead is as follows: L = ΦA × sin(½θ).

[0008] The empirical value of the offset angle θ between the tungsten electrode of the welding torch and the weld bead is 5° to 7°, which is positively correlated with the height h of the weld bead protruding from the base surface.

[0009] Secondly, this invention discloses a welding method for the bottom lock weld of a sheet metal welding machine casing based on the above-mentioned welding torch offset distance determination method, comprising: Based on the position adjustment of the circumferential automatic welding torch mechanism according to the alignment line, the welding torch is in the uphill direction of the weld bead in the circumferential direction. Based on the principle of magnetic field contraction arc generated by high-frequency pulses, the parameters of high-frequency pulses and precision pulse combinations are determined. The welding process is completed in four steps: uniform positioning welding, denser welding points, root pass welding, and cover pass welding.

[0010] The specific steps for determining the combination parameters of high-frequency pulses and precision pulses are as follows: The operating mode is a high-frequency pulse superposition precision pulse mode; the high-frequency pulse frequency is set to the maximum frequency of the equipment; the peak time and base time of the precision pulse are set to be the same; the peak current, base current and high-frequency pulse current are set to preset ratios.

[0011] The preset ratio of the peak current, base current, and high-frequency pulse current is 5:2:3.

[0012] Argon is used as the shielding gas in the welding process. The shielding gas flow rate is 8-12 L / min when the welding points are evenly distributed and densely packed, and the shielding gas flow rate is increased to 15-20 L / min when the welding is root pass and cover pass.

[0013] After the root pass welding is completed, the root of the weld is inspected for defects using a penetrant testing method. The inspection pass criteria are: the diameter of a single pore does not exceed 0.3 mm, and the number of pores in a 100 mm weld length does not exceed 3. After passing the inspection, the cover pass welding is performed.

[0014] The root pass welding adopts a narrow pass welding method, with the weld width controlled at 4-6mm. The weld width of the cover pass welding is 1.5-2 times the width of the root pass weld, and a 0.5-1mm excess height is reserved during the cover pass welding.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for determining the welding torch offset distance of the bottom weld seam in sheet metal welding casings. It precisely matches the non-uniform thickness structural characteristics of the bottom weld seam joint. By quantifying the machining side welding thickness L1, the sheet metal side welding thickness L2, and the bottom weld seam thickness L3, the axial offset P is scientifically calculated. This fundamentally solves the problem of molten pool offset caused by the difference in heat dissipation on both sides of the joint in conventional centering welding, ensuring that the root of the bottom weld seam can be fully melted, effectively avoiding welding defects such as incomplete fusion and voids, and significantly improving the weld seam formation quality. The offset distance L is calculated by combining the offset angle θ directly above the weld bead and the weld bead diameter ΦA, achieving multi-dimensional precise positioning of the welding torch tungsten electrode, rather than a single-dimensional offset adjustment. This allows the tungsten electrode tip to be precisely aligned with the critical fusion area of ​​the bottom weld seam, ensuring uniform distribution of weld metal at the bottom weld structure, reducing stress concentration, lowering the risk of crack formation, and thus improving the fatigue life and structural reliability of the sheet metal welding casing. By co-calculating the axial offset P and offset distance L, the alignment line of the tungsten electrode tip of the welding torch is clearly defined, providing a precise positioning basis for subsequent automated welding. This avoids subjective errors caused by manual adjustment and ensures the consistency and stability of the welding torch position during welding. It is particularly suitable for mass production scenarios of circumferential automatic welding, improving the repeatability and controllability of the welding process. This determination method is directly derived from the structural parameters of the bottom weld of the sheet metal welding casing, without relying on complex trial and error or empirical value estimation. This simplifies the adjustment process of the welding torch offset distance, shortens the process preparation cycle, and reduces the dependence on the skill level of operators. It achieves a dual improvement in production efficiency and welding quality, providing technical support for the efficient and high-quality manufacturing of sheet metal welding casings. This method constructs a standardized welding torch positioning logic through quantitative parameters. The offset and offset distance can be flexibly adjusted according to structural parameters such as the bottom thickness and weld thickness of different specifications of sheet metal welding casings. It adapts to the welding needs of various types of cavity-type sheet metal welding casings, improving the versatility and adaptability of the technical solution and reducing the process switching costs when producing multi-specification products.

[0016] This invention discloses a welding method for the bottom weld of a sheet metal casing. The method adjusts the welding torch position based on the alignment line, ensuring the torch is circumferentially positioned on the upslope of the weld bead. This precise configuration accurately matches the heat dissipation differences inherent in the non-uniform thickness structure of the bottom weld joint. Compared to the weld pool offset problem caused by conventional centering welding, this positioning method guides the arc energy to be precisely distributed to the side with better heat dissipation and slower melting speed, ensuring sufficient fusion energy at the root of the bottom weld. This effectively avoids fatal defects such as incomplete fusion and root voids, while also reducing stress concentration and lowering the tendency for crack initiation from the welding source. This significantly improves the mechanical properties and fatigue life of the weld, providing a core guarantee for the pressure-bearing and load-bearing stability of the sheet metal casing. The method is based on the principle of high-frequency sub-pulse magnetic field contraction arc, employing a combination of high-frequency sub-pulse and precision pulse parameter modes, which has significant advantages over single-pulse or conventional DC welding. The magnetic field generated by high-frequency pulses can effectively contract the electric arc, improve its stiffness and energy density, and make the energy distribution of the arc more uniform on non-uniform thickness joints, avoiding problems such as over-melting and weld beads due to poor heat dissipation on the sheet metal side. Precision pulses can precisely control the heating and cooling rhythm of the molten pool, promote the full escape of gas in the molten pool, reduce porosity defects, and refine the weld grains, improving the density and toughness of the weld. The synergistic effect of the two pulses makes the weld formation more aesthetically pleasing and dimensionally accurate, meeting the technical requirements of high-precision welding of sheet metal casings. The method adopts a four-pass welding process of "uniformly distributed tack welding - denser weld points - root pass welding - cap pass welding", forming a systematic guarantee system from temporary fixation to permanent formation. Uniformly distributed tack welding precisely fixes each component of the sheet metal casing, preventing positional shifts caused by thermal deformation during welding. Increasing the density of weld points further strengthens the temporary connection, providing a stable structural foundation for subsequent continuous welding and reducing welding deformation. The root pass weld, acting as the "skeleton" of the weld, relies on precise welding torch positioning and optimized pulse parameters to ensure complete fusion at the root, building a reliable load-bearing foundation. The cover pass weld compensates for minor defects on the root pass surface, improving weld surface quality and corrosion resistance. These four interconnected steps ensure the weld's connection strength and sealing meet all standards, adapting to the harsh operating conditions of alternating stress and high temperatures in engines. The method explicitly employs a circular automatic welding torch mechanism, using a precise alignment line as the adjustment benchmark, eliminating reliance on manual welding experience and making torch position adjustment more standardized. Automated operation not only significantly improves welding efficiency, reducing single-piece welding time by more than 30% compared to manual welding, but also ensures high consistency in torch position and welding parameters for each weld in mass production, avoiding individual differences caused by manual operation. Meanwhile, the standardized pulse parameter settings and welding process facilitate integration into the automated control system of the production line, realizing full automation from welding torch positioning to welding completion, reducing the skill threshold and labor intensity of operators, and providing a feasible path for the mass and efficient production of sheet metal welding casings.In summary, this invention actively aligns the tungsten electrode of the welding torch axially by adjusting the P value, which can offset the heat dissipation difference on both sides of the joint, eliminate weld misalignment, ensure bottom-locking melting, avoid stress concentration, and extend fatigue life. Aligning the tungsten electrode of the welding torch with the weld bead's upward slope increases the fluidity of the molten pool metal along the weld direction, reduces the weld face width, and increases the weld's protrusion height relative to the base surface. Active control of the weld face height is achieved by adjusting the θ value. Through the design of reasonable high-frequency pulse and precision pulse combination parameters and welding process flow, heat input can be reduced, weld penetration increased, welding deformation reduced, porosity residue in titanium alloy welds eliminated, and the weld's appearance, dimensions, and morphological uniformity improved.

[0017] Furthermore, the preset ratio of peak current, base current, and high-frequency pulse current is defined as 5:2:3. This ratio has been specifically optimized to achieve a precise match of "sufficient penetration depth - stable arc - uniform energy": the peak current has the highest proportion, which can ensure full fusion at the root of the weld; the base current has a moderate proportion, which can prevent the arc from extinguishing during the welding process; and the high-frequency pulse current has a reasonable proportion, which can effectively shrink the arc and optimize the molten pool morphology.

[0018] Furthermore, argon is used as a protective gas. Argon has stable chemical properties and can form a dense protective atmosphere in the weld area, effectively isolating impurities such as oxygen and nitrogen in the air, avoiding defects such as oxidation and nitriding in the weld, ensuring the purity and corrosion resistance of the weld, and making it suitable for the high temperature and high pressure working environment of the engine.

[0019] Furthermore, by adding a penetration test after the root pass welding is completed, potential defects such as lack of fusion and porosity at the weld root can be detected in time, preventing defects from being covered up after the cover pass welding, which would make subsequent repairs difficult. This controls weld quality from the source and reduces rework costs and usage risks. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the locking bottom weld joint and weld seam in a welding method for locking bottom weld seam of a sheet metal welding machine casing according to an embodiment of the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 This is a schematic diagram of the weld pool and morphology control in a welding method for the bottom lock weld of a sheet metal welding machine casing according to an embodiment of the present invention. Figure 4 This is a schematic diagram of arc contraction in a welding method for the bottom lock weld of a sheet metal welding machine casing according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the weld seam and heat-affected zone width in a welding method for the bottom lock weld of a sheet metal casing according to an embodiment of the present invention.

[0022] Wherein: 1-Main body of the casing; 2-Sheet metal forming part; 3-Weld; 4-Heat affected zone; 5-Circumferential weld bead; 6-Tungsten electrode of the welding torch; 11-Filling station; 12-Joint lock bottom; 13-Root of the joint lock bottom; P-Axial offset between the tungsten electrode and the center of the joint; h-Height of the weld bead relative to the surface of the base material; L-Offset distance between the tungsten electrode facing position and the weld bead; θ-Offset angle between the tungsten electrode facing position and the weld bead; I-Welding current; ΦA-Weld bead diameter; B-Magnetic field generated by high-frequency pulse; H1-Weld width; H2-Width of the heat affected zone; L1-Weld thickness on the machined side; L2-Weld thickness on the sheet metal side; L3-Locking bottom thickness. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 , Figure 2 and Figure 3 This invention discloses a method for determining the welding torch offset distance of the bottom weld seam in a sheet metal welding machine casing, comprising: Step 1: Obtain the welding thickness L1 on the machining side, the welding thickness L2 on the sheet metal side, and the bottom locking thickness L3 of the sheet metal welding machine housing, and calculate the axial offset P between the tungsten electrode of the welding torch and the center of the welding joint. The calculation of the axial offset P between the tungsten electrode of the welding torch and the center of the weld joint is specifically as follows: P = L1 - L2 + ½L3.

[0030] The specific calculation of the offset distance L between the tungsten electrode of the welding torch and the weld bead is as follows: L = ΦA × sin(½θ).

[0031] The empirical value of the offset angle θ between the tungsten electrode of the welding torch and the weld bead is 5° to 7°, which is positively correlated with the height h of the weld bead protruding from the base surface.

[0032] Step 2: Determine the position of the tungsten electrode of the welding torch based on the axial offset P, and obtain the offset angle θ and weld diameter ΦA directly above the weld bead. Calculate the offset distance L between the position of the tungsten electrode of the welding torch and the position directly above the weld bead. Step 3: Based on the axial offset P between the welding torch tungsten electrode and the center of the weld joint and the offset distance L between the welding torch tungsten electrode facing the weld bead and directly above it, determine the alignment line of the tip of the welding torch tungsten electrode at the weld joint of the workpiece.

[0033] This invention discloses a method for determining the welding torch offset distance of the bottom weld seam in sheet metal welding casings. It precisely matches the non-uniform thickness structural characteristics of the bottom weld seam joint. By quantifying the machining side welding thickness L1, the sheet metal side welding thickness L2, and the bottom weld seam thickness L3, the axial offset P is scientifically calculated. This fundamentally solves the problem of molten pool offset caused by the difference in heat dissipation on both sides of the joint in conventional centering welding, ensuring that the root of the bottom weld seam can be fully melted, effectively avoiding welding defects such as incomplete fusion and voids, and significantly improving the weld seam formation quality. The offset distance L is calculated by combining the offset angle θ directly above the weld bead and the weld bead diameter ΦA, achieving multi-dimensional precise positioning of the welding torch tungsten electrode, rather than a single-dimensional offset adjustment. This allows the tungsten electrode tip to be precisely aligned with the critical fusion area of ​​the bottom weld seam, ensuring uniform distribution of weld metal at the bottom weld structure, reducing stress concentration, lowering the risk of crack formation, and thus improving the fatigue life and structural reliability of the sheet metal welding casing. By co-calculating the axial offset P and offset distance L, the alignment line of the tungsten electrode tip of the welding torch is clearly defined, providing a precise positioning basis for subsequent automated welding. This avoids subjective errors caused by manual adjustment and ensures the consistency and stability of the welding torch position during welding. It is particularly suitable for mass production scenarios of circumferential automatic welding, improving the repeatability and controllability of the welding process. This determination method is directly derived from the structural parameters of the bottom weld of the sheet metal welding casing, without relying on complex trial and error or empirical value estimation. This simplifies the adjustment process of the welding torch offset distance, shortens the process preparation cycle, and reduces the dependence on the skill level of operators. It achieves a dual improvement in production efficiency and welding quality, providing technical support for the efficient and high-quality manufacturing of sheet metal welding casings. This method constructs a standardized welding torch positioning logic through quantitative parameters. The offset and offset distance can be flexibly adjusted according to structural parameters such as the bottom thickness and weld thickness of different specifications of sheet metal welding casings. It adapts to the welding needs of various types of cavity-type sheet metal welding casings, improving the versatility and adaptability of the technical solution and reducing the process switching costs when producing multi-specification products.

[0034] See Figure 4 and Figure 5 The present invention also discloses a welding method for the bottom lock weld of a sheet metal casing, comprising: Step 1: Adjust the position of the circumferential automatic welding torch mechanism based on the alignment line, so that the welding torch is in the uphill direction of the weld bead in the circumferential direction; Step 2: Based on the principle of magnetic field contraction arc generated by high-frequency pulses, determine the combination parameters of high-frequency pulses and precision pulses; The operating mode is a high-frequency pulse superimposed with a precision pulse mode; the high-frequency pulse frequency is set to the maximum frequency of the device; the peak time and base time of the precision pulse are set to be the same; the peak current, base current, and high-frequency pulse current are set to a preset ratio. The preset ratio of the peak current, base current, and high-frequency pulse current is 5:2:3.

[0035] Step 3: Complete the welding process in 4 passes, following the steps of evenly distributed positioning welding, denser welding points, root pass welding, and cover pass welding.

[0036] Argon is used as the shielding gas during the welding process. The shielding gas flow rate is 8-12 L / min for uniformly distributed tack welding and denser weld joints, and increased to 15-20 L / min for root pass and cover pass welding. After the root pass welding is completed, the weld root is inspected for defects using penetrant testing. The acceptance criteria are: the diameter of a single pore does not exceed 0.3 mm, and the number of pores in a 100 mm weld length does not exceed 3. After passing the inspection, the cover pass welding is performed. The root pass welding uses a narrow-pass welding method, with the weld width controlled at 4-6 mm. The width of the cover pass weld is 1.5-2 times the width of the root pass weld, and a 0.5-1 mm allowance is reserved during the cover pass welding.

[0037] This invention discloses a welding method for the bottom weld of a sheet metal casing. The method adjusts the welding torch position based on the alignment line, ensuring the torch is circumferentially positioned on the upslope of the weld bead. This precise configuration accurately matches the heat dissipation differences inherent in the non-uniform thickness structure of the bottom weld joint. Compared to the weld pool offset problem caused by conventional centering welding, this positioning method guides the arc energy to be precisely distributed to the side with better heat dissipation and slower melting speed, ensuring sufficient fusion energy at the root of the bottom weld. This effectively avoids fatal defects such as incomplete fusion and root voids, while also reducing stress concentration and lowering the tendency for crack initiation from the welding source. This significantly improves the mechanical properties and fatigue life of the weld, providing a core guarantee for the pressure-bearing and load-bearing stability of the sheet metal casing. The method is based on the principle of high-frequency sub-pulse magnetic field contraction arc, employing a combination of high-frequency sub-pulse and precision pulse parameter modes, which has significant advantages over single-pulse or conventional DC welding. The magnetic field generated by high-frequency pulses can effectively contract the electric arc, improve its stiffness and energy density, and make the energy distribution of the arc more uniform on non-uniform thickness joints, avoiding problems such as over-melting and weld beads due to poor heat dissipation on the sheet metal side. Precision pulses can precisely control the heating and cooling rhythm of the molten pool, promote the full escape of gas in the molten pool, reduce porosity defects, and refine the weld grains, improving the density and toughness of the weld. The synergistic effect of the two pulses makes the weld formation more aesthetically pleasing and dimensionally accurate, meeting the technical requirements of high-precision welding of sheet metal casings. The method adopts a four-pass welding process of "uniformly distributed tack welding - denser weld points - root pass welding - cap pass welding", forming a systematic guarantee system from temporary fixation to permanent formation. Uniformly distributed tack welding precisely fixes each component of the sheet metal casing, preventing positional shifts caused by thermal deformation during welding. Increasing the density of weld points further strengthens the temporary connection, providing a stable structural foundation for subsequent continuous welding and reducing welding deformation. The root pass weld, acting as the "skeleton" of the weld, relies on precise welding torch positioning and optimized pulse parameters to ensure complete fusion at the root, building a reliable load-bearing foundation. The cover pass weld compensates for minor defects on the root pass surface, improving weld surface quality and corrosion resistance. These four interconnected steps ensure the weld's connection strength and sealing meet all standards, adapting to the harsh operating conditions of alternating stress and high temperatures in engines. The method explicitly employs a circular automatic welding torch mechanism, using a precise alignment line as the adjustment benchmark, eliminating reliance on manual welding experience and making torch position adjustment more standardized. Automated operation not only significantly improves welding efficiency, reducing single-piece welding time by more than 30% compared to manual welding, but also ensures high consistency in torch position and welding parameters for each weld in mass production, avoiding individual differences caused by manual operation. Meanwhile, the standardized pulse parameter settings and welding process facilitate integration into the automated control system of the production line, realizing full automation from welding torch positioning to welding completion, reducing the skill threshold and labor intensity of operators, and providing a feasible path for the mass and efficient production of sheet metal welding casings.In summary, this invention actively aligns the tungsten electrode of the welding torch axially by adjusting the P value, which can offset the heat dissipation difference on both sides of the joint, eliminate weld misalignment, ensure bottom-locking melting, avoid stress concentration, and extend fatigue life. Aligning the tungsten electrode of the welding torch with the weld bead's upward slope increases the fluidity of the molten pool metal along the weld direction, reduces the weld face width, and increases the weld's protrusion height relative to the base surface. Active control of the weld face height is achieved by adjusting the θ value. Through the design of reasonable high-frequency pulse and precision pulse combination parameters and welding process flow, heat input can be reduced, weld penetration increased, welding deformation reduced, porosity residue in titanium alloy welds eliminated, and the weld's appearance, dimensions, and morphological uniformity improved.

[0038] Example 1 (1) with Figure 1 For example, measure the actual dimensions of the workpieces L1, L2, and L3 to be welded, and calculate the axial offset P between the tungsten electrode and the center of the joint based on these three dimensions. The empirical value is P = L1 - L2 + ½L3.

[0039] (2) Figure 2 As shown, the arrow points in the direction of the weld bead's upward slope. Measure the weld bead diameter ΦA. Based on ΦA and the value of θ, calculate the offset distance L between the tungsten electrode's facing position and the top of the weld bead: L = ΦA × sin(½θ), where θ is the offset angle between the tungsten electrode's facing position and the top of the weld bead. The empirical value is 5° to 7°. The greater the required height h of the weld bead relative to the base surface, the larger θ will be.

[0040] (3) Based on the axial offset P between the tungsten electrode and the joint center calculated in steps (1) and (2), and the offset distance L between the tungsten electrode facing position and the weld bead directly above, mark the alignment line of the tungsten electrode tip of the welding gun at the weld joint of the assembled workpiece.

[0041] (4) Adjust the circumferential automatic welding torch mechanism and align the tungsten electrode of the welding torch according to the workpiece joint marking position in step (3). In the circumferential direction, the welding torch is in the uphill direction of the weld bead.

[0042] (5) Design the combination parameters of high-frequency pulse and precision pulse. The working mode is high-frequency pulse superimposed with precision pulse. The frequency of high-frequency pulse is 20000Hz, and the peak time and base time of precision pulse are both 0.5s. The frequency of precision pulse is 1Hz. Main current (peak): auxiliary current (base): high-frequency pulse current = 3:2:1.

[0043] (6) Weld in four passes according to the process of uniformly distributed positioning welding → dense welding points → root pass welding → cover pass welding, and check the appearance and size of the weld, such as the height of the weld protrusion.

[0044] Taking a titanium alloy cavity casing of a certain type of engine as an example, it is a cavity-type welded integral casing. The main body is machined from an α+β titanium alloy TC25 forging and a 1.8mm and 1.5mm thick α titanium alloy TA15 sheet metal curved shell, welded together by four lock-edge argon arc welds. The lock-edge thickness is 1.5mm to 2.0mm, the width is 0.8mm to 1.2mm, and the weld grade is Class I. The product drawing requires that all welds should have a raised portion, with the raised portion between 0.15mm and 0.8mm. Due to the cavity structure of the casing, the assembly gap and misalignment of the joints are difficult to control. The back of the joint has a lock-edge stop, and the weld penetration cannot be observed. A method based on high-frequency sub-pulse superposition of precision pulse current contraction arc and tungsten electrode circumferential and axial misalignment of the weld bead is used to actively control the molten pool and morphology of the lock-edge ring weld of the cavity-type sheet metal welded casing. The steps are as follows: 1. Taking one weld as an example, the actual dimensions of L1, L2, and L3 are 2.5mm, 1.8mm, and 1.4mm respectively. Calculate the axial offset P between the tungsten electrode and the joint center: P = L1 - L2 + ½L3 = 1.4mm. 2. Measure the weld diameter ΦA as 562mm. Assuming θ is 6°, calculate the offset distance L between the tungsten electrode's aligned position and the top of the weld bead: L = ΦA × sin(½θ) = 29.4mm. 3. Based on the axial offset of 1.4mm between the tungsten electrode and the joint center calculated in steps 1 and 2, and the offset distance of 29.4mm between the tungsten electrode's aligned position and the top of the weld bead, mark the alignment line of the tungsten electrode tip on the weld joint of the assembled workpiece. 4. Adjust the circumferential automatic welding torch mechanism, aligning the tungsten electrode with the workpiece joint alignment line from step 3. In the circumferential direction, the welding torch should be positioned on the uphill side of the weld bead. 5. Design the combination parameters for high-frequency and precision pulses. The working mode is a high-frequency pulse superposition precision pulse mode. The high-frequency pulse frequency is designed to be 20000Hz, and the peak time and base time of the precision pulse are both 0.5s. The main current (peak value), auxiliary current (base value), and high-frequency pulse current are tested at a ratio of 3:2:1, with values ​​of 120A, 80A, and 40A respectively. 6. Weld in four passes: uniformly distributed tack welding → denser weld joints → root pass welding → cover pass welding. After welding, check whether the weld protrusion height meets the requirement of 0.15mm~0.8mm, and perform other conformity checks on appearance and dimensions according to relevant standards.

[0045] This method, by actively adjusting the P value to offset the heat dissipation difference on both sides of the joint, eliminates weld offset, ensures bottom-locking melting, and avoids stress concentration; by aligning the tungsten electrode of the welding torch with the upslope direction of the weld bead, the fluidity of the molten pool metal along the weld direction is increased, the width of the weld face is reduced, and the height of the weld relative to the base surface is increased; by designing reasonable high-frequency pulse and precision pulse combination parameters and welding process flow, heat input is reduced, weld penetration is increased, welding deformation is reduced, porosity residue in titanium alloy welds is eliminated, and the appearance, size, and morphological uniformity of the weld are improved.

[0046] The working process of this invention is as follows: The purpose of this invention is to provide a method for actively controlling the weld pool and morphology of the bottom ring weld of a cavity-type sheet metal welding machine casing by using a high-frequency sub-pulse superimposed precision pulsed current to contract the arc and perform circumferential and axial deflection of the weld bead with a tungsten electrode. This method achieves its purpose through the following steps: (1) with Figure 1 and Figure 2 For example, measure the actual dimensions of the workpieces L1, L2, and L3 to be welded, and calculate the axial offset P between the tungsten electrode and the center of the joint based on these three dimensions. The empirical value is P = L1 - L2 + ½L3.

[0047] (2) Figure 3 As shown, the arrow points in the direction of the weld bead's upward slope. Measure the weld bead diameter ΦA. Based on ΦA and the value of θ, calculate the offset distance L between the tungsten electrode's facing position and the top of the weld bead: L = ΦA × sin(½θ), where θ is the offset angle between the tungsten electrode's facing position and the top of the weld bead. The empirical value is 5° to 7°. The greater the required height h of the weld bead relative to the base surface, the larger θ will be.

[0048] (3) Based on the axial offset P between the tungsten electrode and the joint center calculated in steps (1) and (2), and the offset distance L between the tungsten electrode facing position and the weld bead directly above, mark the alignment line of the tungsten electrode tip of the welding gun at the weld joint of the assembled workpiece.

[0049] (4) Adjust the circumferential automatic welding torch mechanism and align the tungsten electrode of the welding torch according to the workpiece joint marking position in step (3). In the circumferential direction, the welding torch is in the uphill direction of the weld bead.

[0050] (5) Utilizing the principle of magnetic field contraction of electric arc generated by high-frequency pulses, design the combination parameters of high-frequency pulses and precision pulses. The working mode is high-frequency pulse superposition precision pulse mode. The frequency of high-frequency pulses is designed to be the maximum frequency of the equipment, and the peak time and base time of precision pulses are designed to be the same. The main current (peak value), auxiliary current (base value), and high-frequency pulse current are designed according to a certain ratio.

[0051] (6) Weld in four passes according to the process of uniformly distributed positioning welding → dense welding points → root pass welding → cover pass welding, and check the appearance and size of the weld, such as the height of the weld protrusion.

[0052] This invention actively aligns the tungsten electrode of the welding torch axially by adjusting the P value, which can offset the heat dissipation difference on both sides of the joint, eliminate weld misalignment, ensure bottom-locking melting, avoid stress concentration, and extend fatigue life. Aligning the tungsten electrode of the welding torch with the weld bead's upward slope increases the fluidity of the molten pool metal along the weld direction, reduces the weld face width, and increases the weld's protrusion height relative to the base surface. Active control of the weld face height is achieved by adjusting the θ value. Through the design of reasonable high-frequency pulse and precision pulse combination parameters and welding process flow, heat input can be reduced, weld penetration increased, welding deformation reduced, porosity residue in titanium alloy welds eliminated, and the weld's appearance, dimensions, and morphological uniformity improved.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the welding torch offset distance of the bottom weld seam in a sheet metal welding machine casing, characterized in that, include: Obtain the machining side welding thickness L1, sheet metal side welding thickness L2, and bottom locking thickness L3 of the sheet metal welding casing, and calculate the axial offset P between the tungsten electrode of the welding torch and the center of the welding joint. Based on the axial offset P, determine the position of the tungsten electrode of the welding torch, obtain the offset angle θ and weld diameter ΦA directly above the weld bead, and calculate the offset distance L between the position of the tungsten electrode of the welding torch and the position directly above the weld bead. Based on the axial offset P between the tungsten electrode of the welding torch and the center of the weld joint and the offset distance L between the tungsten electrode of the welding torch facing the weld bead and directly above it, the axial offset P causes the tungsten electrode of the welding torch to deviate from the center of the weld bead towards the machining side, and the alignment position line of the tip of the tungsten electrode of the welding torch is determined at the weld joint of the workpiece. The calculation of the axial offset P between the tungsten electrode of the welding torch and the center of the weld joint is specifically as follows: P = L1 - L2 + ½L3 The specific calculation of the offset distance L between the tungsten electrode of the welding torch and the weld bead is as follows: L=ΦA×sin(½θ) The empirical value of the offset angle θ between the tungsten electrode of the welding torch and the weld bead is 5° to 7°, which is positively correlated with the height h of the weld bead relative to the substrate surface. The offset distance L causes the tungsten electrode of the welding torch to deviate from the weld bead along the upward slope direction of the welding direction.

2. A welding method for the bottom lock weld of a sheet metal welding machine casing based on the welding torch offset distance determination method of claim 1, characterized in that, include: Based on the position adjustment of the circumferential automatic welding torch mechanism according to the alignment line, the welding torch is in the uphill direction of the weld bead in the circumferential direction. Based on the principle of magnetic field contraction arc generated by high-frequency pulses, the parameters of high-frequency pulses and precision pulse combinations are determined. The welding process is completed in four steps: uniform positioning welding, denser welding points, root pass welding, and cover pass welding.

3. The welding method for the bottom lock weld of the sheet metal casing according to claim 2, characterized in that, The specific steps for determining the combination parameters of high-frequency pulses and precision pulses are as follows: The operating mode is a high-frequency pulse superposition precision pulse mode; the high-frequency pulse frequency is set to the maximum frequency of the equipment; the peak time and base time of the precision pulse are set to be the same. The peak current, base current, and high-frequency pulse current are set to preset ratios.

4. The welding method for the bottom lock weld of the sheet metal casing according to claim 3, characterized in that, The preset ratio of the peak current, base current, and high-frequency pulse current is 5:2:

3.

5. The welding method for the bottom lock weld of the sheet metal casing according to claim 3, characterized in that, Argon is used as the shielding gas during the welding process. The shielding gas flow rate is 8-12 L / min when the welding points are evenly distributed and densely packed, and the shielding gas flow rate is increased to 15-20 L / min when the welding is root pass and cover pass.

6. The welding method for the bottom lock weld of the sheet metal casing according to claim 3, characterized in that, After the root pass welding is completed, the root of the weld is inspected for defects using a penetrant testing method. The inspection pass criteria are: the diameter of a single pore does not exceed 0.3 mm, and the number of pores in a 100 mm weld length does not exceed 3. After passing the inspection, the cover pass welding is performed.

7. The welding method for the bottom lock weld of the sheet metal casing according to claim 3, characterized in that, The root pass welding adopts a narrow pass welding method, with the weld width controlled at 4-6mm. The weld width of the cover pass welding is 1.5-2 times the width of the root pass weld, and a 0.5-1mm excess height is reserved during the cover pass welding.

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