A method of plasma welding a leaf spring mounting sleeve

Abstract

The present application relates to the technical field of welding, in particular to a kind of plasma welding method of plate spring installation sleeve, comprising: plate spring installation sleeve is positioned with frame longitudinal beam inner plate clamping output to be welded component, and to be welded component is carried out welding operation test.Get the assembly coaxiality deviation of plate spring installation sleeve and plate spring shaft pipe hole to be sleeved determines welding current;Maximum impact kinetic energy of detecting solder splashing is generated, and the wire feed speed of solder is adjusted;Get the filling rate of change of weld, determine the ion gas flow of plasma welding equipment;Respectively control torch nozzle and plasma generator, according to adjusted welding current, wire feed speed and ion gas flow, carry out actual melting connection, output high-quality welding finished product.Solve the problem that the welding spatter of plate spring installation sleeve and the molten pool melt through caused by the assembly coaxiality deviation of plate spring installation sleeve and plate spring in the welding process of plate spring installation sleeve in prior art, improve the welding quality and consistency of plate spring installation sleeve.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a plasma welding method for a leaf spring mounting sleeve. Background Technology

[0002] The leaf spring mounting sleeve is a key structural component on the longitudinal beam of an automobile frame. It fits into the leaf spring shaft tube to position and install the leaf spring on the longitudinal beam. In existing technologies, the welding method for the leaf spring mounting sleeve typically employs manual arc welding or gas shielded welding, directly welding the cylindrical surface of the sleeve to the inner plate of the longitudinal beam, and then completing the overall welding of the inner and outer plates. However, the above-mentioned existing technologies have the following shortcomings: First, welding parameters rely on manual experience for setting, lacking a systematic parameter adjustment method. In the current welding process, process parameters such as welding current, wire feed speed, and ion gas flow rate are usually roughly selected by the operator based on experience, without establishing an adjustment mechanism between parameters and clamping status and dynamic response during the welding process. Due to the assembly coaxiality deviation and gap fluctuation at the joint between the leaf spring mounting sleeve and the leaf spring shaft tube, fixed welding parameters are difficult to adapt to changes in clamping errors, easily resulting in welding defects such as undercut, incomplete fusion, or burn-through, thus affecting the fitting accuracy and load-bearing reliability of the sleeve and leaf spring. Second, existing technologies lack effective means to control welding spatter. As an elastic element bearing alternating loads in vehicles, the surface quality of leaf springs directly affects their fatigue life. Furthermore, existing technologies lack the ability to compensate for the molten pool filling condition. Differences in thickness between the leaf spring mounting sleeve and the leaf spring itself, as well as variations in assembly gaps, lead to fluctuations in the volume of welding wire required to fill a unit length of weld. If the ion gas flow rate does not match the molten pool filling requirements, the impact force of the ion gas flow on the molten pool can cause quality problems such as burn-through or poor weld formation. Current welding methods lack the technical means to adaptively adjust the ion gas flow rate based on the molten pool filling requirements, making it difficult to guarantee the stability and consistency of weld quality.

[0003] Chinese Patent Publication No. CN103056571B discloses a welding method and positioning fixture for a leaf spring mounting sleeve, including welding and fixing the inner and outer plates of the frame longitudinal beam; correcting the frame longitudinal beam assembly to eliminate welding deformation; and welding and fixing the leaf spring mounting sleeve to the inner plate. The welding method and positioning fixture for the leaf spring mounting sleeve provided by this invention improves the welding dimensional accuracy of the frame longitudinal beam and reduces welding deformation by changing the welding process sequence and adding correction and positioning steps.

[0004] Therefore, the existing technologies mentioned above still do not offer an adaptive adjustment scheme for the welding parameter mismatch caused by assembly coaxiality deviation. They cannot solve the problems of large welding spatter caused by coaxiality deviation, melt penetration or poor forming caused by mismatch between molten pool filling and ion gas flow rate. There is still room for improvement in the stability of welding quality. Summary of the Invention

[0005] Therefore, the present invention provides a plasma welding method for leaf spring mounting sleeves to overcome the problems of welding spatter and melt pool penetration caused by the misalignment of the assembly coaxiality between the leaf spring mounting sleeve and the inner plate of the frame longitudinal beam during the welding process of the leaf spring mounting sleeve and the leaf spring in the prior art.

[0006] To achieve the above objectives, the present invention provides a plasma welding method for a leaf spring mounting sleeve, comprising: The pre-treated leaf spring mounting sleeve is positioned and clamped with the inner plate of the frame longitudinal beam to output the component to be welded. The components to be welded, which are being positioned and clamped in the welding station, are fused together using plasma welding equipment for welding operation testing. Obtain the coaxiality deviation value of the assembly hole between the leaf spring mounting sleeve and the leaf spring shaft tube during the welding operation test. The welding current of the plasma welding equipment for the components to be welded is determined based on the assembly coaxiality deviation value. The maximum impact kinetic energy of the solder splashing on the molten pool during the welding process is obtained at the moment when the preset coaxiality deviation condition is met, and the wire feed speed of the solder is determined based on the maximum impact kinetic energy. The rate of change of weld fill at the moment when the preset impact kinetic energy condition is met is obtained, and the ion gas flow rate of the plasma welding equipment is determined based on the rate of change of weld fill. The welding torch nozzle and plasma generator of the plasma welding equipment are controlled respectively according to the welding current adjustment method, the wire feeding speed and the ion gas flow rate to actually melt and connect the components to be welded, so as to weld the leaf spring mounting sleeve to the inner plate of the longitudinal beam of the vehicle frame.

[0007] Further, the welding current adjustment method of the plasma welding equipment for the components to be welded is determined based on the assembly coaxiality deviation value, including: The assembly coaxiality deviation value is compared with the preset assembly coaxiality deviation value; If the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value, it is determined that the arc heat during the welding process meets the requirements, and it is determined that the reference current is maintained during the welding process. If the assembly coaxiality deviation value is greater than or equal to the preset assembly coaxiality deviation value, it is determined that the arc heat during welding does not meet the requirements, and it is determined that a compensation current should be added on the basis of the reference current during welding.

[0008] Furthermore, it is determined based on the maximum radial deviation between the axis of the leaf spring mounting sleeve and the axis of the hole to be fitted on the leaf spring shaft tube, in order to determine the assembly alignment accuracy of the leaf spring mounting sleeve and the hole to be welded on the leaf spring shaft tube.

[0009] Furthermore, the increase in the compensation current is positively correlated with the difference between the assembly coaxiality deviation value and the preset assembly coaxiality deviation value.

[0010] Further, determining the solder wire feed speed based on the maximum impact kinetic energy includes, The maximum impact kinetic energy is compared with the preset maximum impact kinetic energy; If the maximum impact kinetic energy is greater than or equal to the preset maximum impact kinetic energy, it is determined that the risk of breakage of the leaf spring mounting sleeve caused by welding spatter does not meet the requirements, and the wire feeding speed of the solder is reduced according to the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy.

[0011] Furthermore, the maximum impact kinetic energy is the maximum kinetic energy of the spatter particles generated after the welding arc of the solder acts on the molten pool at the moment when the preset coaxiality deviation condition is met. The condition for satisfying the preset coaxiality deviation is that the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value.

[0012] Furthermore, the reduction in the wire feed speed of the solder is positively correlated with the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy.

[0013] Further, the ion gas flow rate of the plasma welding equipment is determined based on the weld filler change rate, including: The weld fill change rate is compared with the preset weld fill change rate; If the weld fill rate is greater than or equal to the preset weld fill rate, the risk of melt-through at the welded part is determined to be unacceptable, and the ion gas flow rate of the plasma welding equipment is reduced based on the difference between the weld fill rate and the preset weld fill rate.

[0014] Furthermore, the weld fill rate is the rate of change of the weld filler wire per unit length per unit time. The weld filler change rate is determined by the welding current that satisfies the preset coaxiality deviation condition and the wire feeding speed of the solder at the moment that satisfies the preset impact kinetic energy condition. The preset impact kinetic energy condition is that the maximum impact kinetic energy is less than the preset maximum impact kinetic energy.

[0015] Furthermore, the reduction in the ion gas flow rate of the plasma welding equipment is positively correlated with the difference between the weld filling rate and the preset weld filling rate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Firstly, the present invention measures the coaxiality deviation of the mounting sleeve and the spring shaft tube to be fitted through welding operation testing. Based on the coaxiality deviation, it determines whether the arc heat during welding meets the requirements. If the requirements are not met, the welding current of the plasma welding equipment is adjusted. When the coaxiality deviation between the two components is large, increasing the current solves the problem of poor local contact caused by misalignment: increasing the current improves the arc energy density, making the arc heat more concentrated, thus ensuring proper alignment even under non-ideal alignment conditions. It can quickly melt through the oxide film, break through the micro gaps, and stably ignite the main arc; the strong thermal radiation and convection generated by the high-temperature arc cause the metal surface in the contact area to soften rapidly or even melt locally, so that the molten metal flows and fills the gap depressions under the synergistic effect of electromagnetic force and surface tension, partially compensating for geometric eccentricity; at the same time, the increased current strengthens the thermal inertia and plasma stability of the arc column, suppresses arc drift, arc jumping or arc breakage caused by coaxiality deviation, ensures that heat is continuously and evenly input to the actual contact zone, and improves the stability of the welding process and the finished product qualification rate of the leaf spring mounting sleeve.

[0017] Furthermore, when the welding current of the ion welding equipment is increased, the maximum impact kinetic energy of the solder splashing on the molten pool during the welding process will also increase accordingly. The maximum impact kinetic energy of the solder splashing on the molten pool at the moment when the preset coaxiality deviation condition is met is obtained. Based on this maximum impact kinetic energy, it is determined that the risk of leaf spring breakage caused by welding spatter in the leaf spring mounting sleeve does not meet the requirements, and the wire feed speed of the solder is adjusted for non-compliance. When the solder spatter kinetic energy exceeds the critical threshold, excessive molten droplets impact the edge of the molten pool or the semi-solidified heat-affected zone at high speed, causing severe local stress mutations: the high kinetic energy impact of the spatter leads to a sudden increase in transient pressure on the surface of the molten pool, which in turn causes microcracks to appear at the grain boundaries near the weld zone of the leaf spring shaft tube; the impact disturbance disrupts the surface tension balance and temperature gradient field stability of the molten pool, causing non-uniform dendritic segregation and abnormal coarsening of columnar crystals at the solidification front, significantly reducing the grain boundary bonding strength; simultaneously, the oxide inclusions carried by the spatter droplets form stress concentration sources during the impact embedding process, which, combined with the residual tensile stress induced by the thermal cycle, further exacerbate the stress concentration. High hydrogen concentrations can lead to delayed cracking. In addition, repeated impacts of high-frequency, high-energy spatter on the same area cause fatigue accumulation due to alternating hot and cold temperatures in the surface metal, inducing micro-plastic deformation and dislocation pile-up, which weakens the fatigue crack propagation resistance of the leaf spring material under service loads. By reducing the wire feed speed of the solder, the frequency of droplet generation per unit time and the mass of a single droplet can be effectively reduced, thereby suppressing the initial velocity and impact kinetic energy of the spatter, ensuring a regular molten pool shape, controllable solidification path, and uniform thermal stress distribution, ultimately eliminating the hidden danger of micro-cracking induced by spatter, and improving the structural integrity and service reliability of the leaf spring mounting sleeve under high dynamic load conditions.

[0018] Furthermore, by reducing the wire feed speed of the solder, the weld fill rate during the welding process will change relatively. The weld fill rate at the moment when the preset impact kinetic energy condition is met is obtained. Based on the weld fill rate, it is determined whether the risk of melt-through at the welded part meets the requirements, and the ion gas flow rate of the plasma welding equipment is adjusted if the requirements are not met. When the rate of change of weld filler is significantly higher than the preset safety threshold, the increase in ion gas flow rate effectively suppresses weld penetration: the increase in ion gas flow rate enhances the compression effect and straightness of the plasma arc, making the arc energy distribution more concentrated on the weld centerline, reducing the lateral diffusion intensity of the arc on the heat-affected zone of the base material, thereby slowing down the excessive melting rate of the metal at the bottom of the molten pool; at the same time, the increased ion gas flow rate exerts a continuous and uniform mechanical scouring effect on the surface of the molten pool, suppressing violent boiling and splashing of the molten pool, and delaying the instantaneous collapse trend in the depth direction of the molten pool; the enhanced gas flow rate also accelerates the discharge of high-temperature metal vapor and oxidation products above the molten pool, improves the optical transparency and heat radiation dissipation conditions of the molten pool, promotes the early formation and stable expansion of the solidification front at the top of the molten pool, improves the controllability of the molten pool, and ensures the stability of the welding process. Attached Figure Description

[0019] Figure 1 This is a flowchart of the plasma welding method for the leaf spring mounting sleeve according to an embodiment of the present invention; Figure 2 The following is a flowchart of the welding current of the plasma welding equipment for the components to be welded, as specified in the embodiments of the present invention; Figure 3 A flowchart for determining the wire feed speed of solder in an embodiment of the present invention; Figure 4 A flow chart of ion gas flow rate for plasma welding equipment is provided for embodiments of the present invention. Detailed Implementation

[0020] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0022] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0023] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 this invention according to the specific circumstances.

[0024] Please see Figure 1 The diagram shown is a flowchart of a plasma welding method for a leaf spring mounting sleeve according to an embodiment of the present invention. The present invention provides a plasma welding method for a leaf spring mounting sleeve, comprising: Step S1: Position and clamp the pre-treated leaf spring mounting sleeve to the inner plate of the frame longitudinal beam to output the component to be welded. Step S2: Use plasma welding equipment to melt and connect the components to be welded that are being positioned and clamped at the welding station, in order to perform welding operation testing. Step S3: Obtain the coaxiality deviation value of the assembly hole of the leaf spring mounting sleeve and the leaf spring shaft tube during the welding operation test. Step S4: Determine the welding current of the plasma welding equipment for the components to be welded based on the assembly coaxiality deviation value. Step S5: Obtain the maximum impact kinetic energy of the solder splashing on the molten pool at the moment when the preset coaxiality deviation condition is met, and determine the wire feeding speed of the solder based on the maximum impact kinetic energy. Step S6: Obtain the weld fill change rate at the moment when the preset impact kinetic energy condition is met, and determine the ion gas flow rate of the plasma welding equipment based on the weld fill change rate. Step S7: Control the welding torch nozzle and plasma generator of the plasma welding equipment according to the welding current adjustment method, the wire feeding speed, and the ion gas flow rate to perform actual melting and connection of the components to be welded, so as to weld the leaf spring mounting sleeve to the inner plate of the longitudinal beam of the vehicle frame; The pretreatment includes removing oil, rust, and oxide layers from the surface of the part to be welded on the leaf spring mounting sleeve. The specific pretreatment method is not limited, as long as the surface cleanliness requirements of the welding part are met. Those skilled in the art can choose grinding, sandblasting, or chemical cleaning to complete the pretreatment according to the actual production conditions.

[0025] Specifically, the assembly coaxiality deviation value is obtained by an industrial camera set up at the welding station. The industrial camera collects the contour of the end face of the leaf spring mounting sleeve and the inner contour of the hole to be fitted on the leaf spring shaft tube respectively. The maximum deviation distance is obtained by comparing the radial offset distance between the centers of the two contours.

[0026] Specifically, the equipment used for positioning and clamping the leaf spring mounting sleeve and the leaf spring to be welded is a combination of a three-jaw self-centering chuck and an axial positioning cylinder. The three-jaw chuck achieves centering by radially clamping the outer circle of the leaf spring mounting sleeve, while the axial positioning cylinder pushes the end face of the leaf spring to fit against the welding reference surface of the sleeve, ensuring the relative positional accuracy of the two in the axial direction.

[0027] Please see Figure 2 The diagram shown is a flowchart illustrating the process of determining the welding current of the plasma welding equipment for the components to be welded according to an embodiment of the present invention. The determination of the welding current of the plasma welding equipment for the components to be welded based on the assembly coaxiality deviation value includes: The assembly coaxiality deviation value is compared with the preset assembly coaxiality deviation value; If the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value, it is determined that the arc heat during the welding process meets the requirements, and it is determined that the reference current is maintained during the welding process. If the assembly coaxiality deviation value is greater than or equal to the preset assembly coaxiality deviation value, it is determined that the arc heat during welding does not meet the requirements, and it is determined that a compensation current should be added on the basis of the reference current during welding.

[0028] Specifically, when measuring the coaxiality deviation of the assembly, a laser displacement sensor array is used for detection. The array has three sets of sensors evenly arranged along the circumference of the hole to be welded on the leaf spring. By synchronously collecting the distance data between the outer surface of the sleeve and the sensor, the data processing system calculates the maximum radial deviation distance between the sleeve axis and the leaf spring hole axis, which is the coaxiality deviation value of the assembly.

[0029] The coaxiality deviation value is determined based on the maximum radial deviation between the axis of the leaf spring mounting sleeve and the axis of the hole to be welded on the leaf spring shaft tube. It is used to determine the alignment accuracy of the assembly between the leaf spring mounting sleeve and the hole to be welded on the leaf spring shaft tube.

[0030] In this embodiment, the larger the coaxiality deviation value of the assembly, the greater the coaxiality error between the two workpieces to be welded, the smaller the actual contact area, and the more likely it is to cause problems such as insufficient local arc energy and poor welding fusion.

[0031] The preset assembly coaxiality deviation value is used to determine whether the arc heat during welding meets the requirements by judging the alignment accuracy deviation between the leaf spring mounting sleeve and the welding hole of the leaf spring shaft tube. Under different leaf spring mounting sleeve specifications, different base material thicknesses, and different fitting clearances between the sleeve and the leaf spring, the preset assembly coaxiality deviation value can be adaptively adjusted. Those skilled in the art can set specific values ​​based on the statistical results of batch welding tests and the finished product qualification requirements.

[0032] It should be noted that the preset coaxiality deviation value is selected within this range to balance the stability of the welding process and energy utilization efficiency: if the deviation threshold is set too small, current compensation will be triggered frequently, causing unnecessary energy waste and additional heat input, resulting in excessive welding deformation; if the deviation threshold is set too large, current compensation for out-of-tolerance coaxiality cannot be performed in time, which can easily lead to welding defects such as poor fusion and reduce the yield of finished products.

[0033] Specifically, the solution to the problem of insufficient arc heat during welding when the assembly coaxiality deviation exceeds the preset coaxiality deviation value is to increase the compensation current based on the reference current. This is because the increased current improves the arc energy density, making the arc heat more concentrated. This allows for rapid melting through the oxide film, breaking through the micro-gap, and stably igniting the main arc even under non-ideal alignment conditions. The intense thermal radiation and convection generated by the high-temperature arc cause the metal surface in the contact area to soften rapidly or even partially melt. This allows the molten metal to flow and fill the gap depressions under the combined action of electromagnetic force and surface tension, partially compensating for geometric eccentricity. The increased current strengthens the thermal inertia and plasma stability of the arc column, suppressing arc drift, arc jumping, or arc breakage caused by coaxiality deviation, and ensuring that heat is continuously and evenly input to the actual contact zone.

[0034] Specifically, the increase in the compensation current is directly related to the difference between the assembly coaxiality deviation value and the preset assembly coaxiality deviation value. That is, the larger the assembly coaxiality deviation value, the larger the increment of the compensation current. This is because a larger coaxiality deviation corresponds to a smaller actual contact area, requiring a higher arc energy density to ensure fusion quality. Therefore, the current increment increases synchronously with the increase of the deviation value, matching the heat input requirements of actual welding.

[0035] It should be noted that increasing the welding current of the ion welding equipment on the components to be welded will correspondingly increase the maximum impact kinetic energy of the solder spatter on the molten pool during the welding process. When the kinetic energy of the solder spatter exceeds the critical threshold, the high kinetic energy impact of the spatter will cause a sudden increase in transient pressure on the surface of the molten pool, which in turn will cause microcracks to appear at the grain boundaries near the weld zone of the leaf spring shaft tube. The impact disturbance disrupts the surface tension balance and temperature gradient field stability of the molten pool, causing non-uniform dendritic segregation and abnormal coarsening of columnar crystals at the solidification front, significantly reducing the grain boundary bonding strength. The oxide inclusions carried by the spatter droplets are embedded during the impact. During the process, stress concentration sources are formed, which, combined with the residual tensile stress induced by thermal cycling, exacerbate the tendency for hydrogen-induced delayed cracking. High-frequency, high-kinetic-energy spatter repeatedly impacts the same area, causing fatigue accumulation due to alternating hot and cold temperatures in the surface metal, inducing micro-plastic deformation and dislocation pile-up, and weakening the fatigue crack propagation resistance of the leaf spring material under service loads. By reducing the wire feed speed of the solder, the frequency of droplet generation per unit time and the mass of a single droplet can be effectively reduced, thereby suppressing the initial spatter velocity and impact kinetic energy, ensuring a regular molten pool shape, controllable solidification path, and uniform thermal stress distribution, and eliminating the hidden danger of micro-cracks induced by spatter.

[0036] Please see Figure 3 The diagram shown is a flowchart illustrating the process of determining the solder wire feed speed according to an embodiment of the present invention; the step of determining the solder wire feed speed based on the maximum impact kinetic energy includes, The maximum impact kinetic energy is compared with the preset maximum impact kinetic energy; If the maximum impact kinetic energy is greater than or equal to the preset maximum impact kinetic energy, it is determined that the risk of leaf spring breakage caused by welding spatter in the leaf spring mounting sleeve does not meet the requirements, and the wire feeding speed of the solder is reduced according to the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy.

[0037] Specifically, when measuring the maximum impact kinetic energy during the welding process, a combination of high-speed photography and image recognition technology is used. A high-speed camera is set up on the side of the welding area to capture the trajectory of the spatter particles. The velocity and direction of the spatter particles are extracted by the image recognition algorithm. Combined with the particle density, the kinetic energy of the spatter particles impacting the leaf spring per unit time is calculated, thereby obtaining the maximum impact kinetic energy.

[0038] Maximum impact kinetic energy is the maximum kinetic energy of the spatter particles generated after the welding arc of the solder acts on the molten pool at the moment when the preset coaxiality deviation condition is met. It is used to determine the degree of impact damage caused by the spatter particles to the sleeve surface. The condition for satisfying the preset coaxiality deviation is that the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value.

[0039] In this embodiment, the greater the maximum impact kinetic energy, the higher the velocity and mass of the splashed particles, and the easier it is to form microcracks or stress concentration points on the sleeve surface, thereby causing the leaf spring to have the risk of fatigue fracture during service.

[0040] The preset maximum impact kinetic energy is used to determine whether the risk of breakage of the sleeve leaf spring meets the requirements by the impact intensity of welding spatter. The preset maximum impact kinetic energy can be adaptively adjusted under different welding current, welding speed, shielding gas flow rate and welding wire diameter. Those skilled in the art can set specific values ​​based on the statistical results of batch welding tests and the finished product qualification requirements.

[0041] It should be noted that the maximum impact energy is set within this range to balance welding quality and production efficiency: if the threshold is set too low, it will frequently trigger a reduction in wire feeding speed, resulting in insufficient solder supply, poor weld formation, or a decrease in deposition rate; if the threshold is set too high, it will be impossible to adjust the wire feeding in time to handle high impact energy splashes, increasing the risk of leaf spring breakage and reducing fatigue life.

[0042] Specifically, the solution to the problem of leaf spring fracture risk due to maximum impact kinetic energy exceeding the preset maximum impact kinetic energy is to reduce the wire feed speed of the solder based on the difference. This is because a lower wire feed speed reduces the flow velocity and sputtering tendency of the liquid metal in the molten pool, thereby reducing the number of large-sized, high-speed spatter particles generated. At the same time, a lower wire feed speed prolongs the transition time of the molten droplets in the arc, allowing the droplets to fully melt and smoothly transition to the molten pool, suppressing violent spatter caused by short-circuit transition or large droplet transition, thus ensuring the structural integrity of the leaf spring mounting sleeve.

[0043] Specifically, the reduction in the wire feed speed of the solder is directly related to the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy. That is, the greater the maximum impact kinetic energy, the greater the reduction in wire feed speed. This is because a larger impact kinetic energy corresponds to larger or higher-velocity spatter particles, requiring a greater adjustment in wire feed to suppress spatter generation and reduce its impact energy, thereby effectively controlling the risk of leaf spring breakage and matching the performance requirements of actual welding spatter control.

[0044] It should be noted that reducing the wire feed speed of the solder will relatively change the rate of change of weld filler during the welding process. When the rate of change of weld filler exceeds the preset safety threshold, the risk of weld pool burn-through is suppressed by increasing the ion gas flow rate. Specifically, the increased ion gas flow rate enhances the compression effect and straightness of the plasma arc, making the arc energy distribution more concentrated on the weld centerline, reducing the lateral diffusion intensity of the arc on the heat-affected zone of the base material, thereby slowing down the excessive melting rate of the metal at the bottom of the weld pool. The increased ion gas flow exerts a continuous and uniform mechanical scouring effect on the surface of the weld pool, suppressing violent boiling and splashing of the weld pool, and delaying the instantaneous collapse trend in the depth direction of the weld pool. The enhanced gas flow also accelerates the discharge of high-temperature metal vapor and oxidation products above the weld pool, improves the optical transparency and heat radiation dissipation conditions of the weld pool, and promotes the earlier formation of the solidification front at the top of the weld pool.

[0045] Please see Figure 4 The diagram shown is a flowchart illustrating the determination of the ion gas flow rate of the plasma welding equipment according to an embodiment of the present invention. Determining the ion gas flow rate of the plasma welding equipment based on the weld filler change rate includes: The weld fill change rate is compared with the preset weld fill change rate; If the weld fill rate is greater than or equal to the preset weld fill rate, the risk of melt-through at the welded part is determined to be unacceptable, and the ion gas flow rate of the plasma welding equipment is reduced based on the difference between the weld fill rate and the preset weld fill rate.

[0046] Specifically, to determine the rate of change of weld filling, three-dimensional data of the thickness difference between the leaf spring mounting sleeve and the leaf spring and the assembly gap are obtained by industrial CT scanning, and the volume of welding wire required to fill the weld per unit length is calculated.

[0047] The weld fill rate is the rate at which the weld fills a unit length of weld per unit time. The weld filler change rate is determined by the welding current that satisfies the preset coaxiality deviation condition and the wire feeding speed of the solder at the moment that satisfies the preset impact kinetic energy condition. The preset impact kinetic energy condition is that the maximum impact kinetic energy is less than the preset maximum impact kinetic energy.

[0048] In this embodiment, the greater the rate of change of weld filling, the faster the welding wire is deposited into the molten pool, the faster the volume of the molten pool expands, the lower the surface tension support capacity, and the more likely the liquid metal in the molten pool is to become unstable and flow or even drip under the action of gravity and plasma flow force, thereby causing defects such as melt-through or weld beads; conversely, the smaller the rate of change of weld filling, the slower the filling process, the faster the heat of the molten pool is dissipated, and the problems of incomplete fusion or incomplete filling may occur.

[0049] The preset weld fill rate is used to determine whether the risk of burn-through during welding is within an acceptable range by observing the rate of change in the molten pool filling process. The preset weld fill rate can be adaptively adjusted under different conditions such as leaf spring mounting sleeve specifications, base material thickness, welding speed, and welding current. Those skilled in the art can set specific values ​​based on statistical results from batch welding tests and the finished product qualification requirements.

[0050] It should be noted that the preset weld filler rate variation range is chosen to balance welding quality and production efficiency: if the threshold is set too low, it will frequently trigger the adjustment of ion gas flow rate, causing fluctuations in the molten pool protection effect, increasing the risk of porosity or slag inclusions, and reducing welding efficiency; if the threshold is set too high, it will be impossible to adjust the ion gas flow rate to reduce the high filler rate in time, and the molten pool will be prone to melt-through due to overheating and overfilling, reducing the finished product qualification rate.

[0051] Specifically, the reason for choosing to reduce the ion gas flow rate of the plasma welding equipment to address the issue of insufficient burn-through risk during welding processes where the weld filler change rate is greater than or equal to the preset weld filler change rate is as follows: Reducing the ion gas flow rate weakens the compression of the plasma arc, decreases arc stiffness, and expands the arc diameter. This leads to a more dispersed distribution of the arc heat source, reducing heat input per unit area. Although the heated area of ​​the molten pool increases, the peak temperature decreases, slowing down the melting rate and fluidity of the molten pool. Simultaneously, the lower ion gas flow rate reduces the impact of the plasma gas flow on the molten pool, decreasing the agitation of the molten metal and making the molten pool surface more stable. This enhances the surface tension of the molten metal, improving the molten pool's resistance to gravity and external forces, effectively reducing the risk of burn-through. Furthermore, appropriately reducing the ion gas flow rate can also reduce disturbance to the protective atmosphere around the molten pool, maintaining better gas protection and preventing welding defects caused by air entrapment due to excessive gas flow.

[0052] Specifically, the reduction in the ion gas flow rate of the plasma welding equipment is directly related to the difference between the weld fill rate and the preset weld fill rate. That is, the greater the difference between the weld fill rate and the preset value, the greater the reduction in ion gas flow rate. This is because a higher fill rate corresponds to a more severe expansion and instability trend in the molten pool, requiring a greater reduction in the arc compression effect and gas flow impact force to bring the heating and stress state of the molten pool back to the stable welding window range, thereby avoiding burn-through.

[0053] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A plasma welding method for a leaf spring mounting sleeve, characterized in that, include: The pre-treated leaf spring mounting sleeve is positioned and clamped with the inner plate of the frame longitudinal beam to output the component to be welded. The components to be welded, which are being positioned and clamped in the welding station, are fused together using plasma welding equipment for welding operation testing. Obtain the coaxiality deviation value of the assembly hole between the leaf spring mounting sleeve and the leaf spring shaft tube during the welding operation test. The welding current of the plasma welding equipment for the components to be welded is determined based on the assembly coaxiality deviation value. The maximum impact kinetic energy of the solder splashing on the molten pool during the welding process is obtained at the moment when the preset coaxiality deviation condition is met, and the wire feed speed of the solder is determined based on the maximum impact kinetic energy. The rate of change of weld fill at the moment when the preset impact kinetic energy condition is met is obtained, and the ion gas flow rate of the plasma welding equipment is determined based on the rate of change of weld fill. The welding torch nozzle and plasma generator of the plasma welding equipment are controlled respectively according to the welding current adjustment method, the wire feeding speed and the ion gas flow rate to actually melt and connect the components to be welded, so as to weld the leaf spring mounting sleeve to the inner plate of the longitudinal beam of the vehicle frame.

2. The plasma welding method for the leaf spring mounting sleeve according to claim 1, characterized in that, The method for adjusting the welding current of the plasma welding equipment for the components to be welded is determined based on the assembly coaxiality deviation value, including: The assembly coaxiality deviation value is compared with the preset assembly coaxiality deviation value; If the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value, it is determined that the arc heat during the welding process meets the requirements, and it is determined that the reference current is maintained during the welding process. If the assembly coaxiality deviation value is greater than or equal to the preset assembly coaxiality deviation value, it is determined that the arc heat during welding does not meet the requirements, and it is determined that a compensation current should be added on the basis of the reference current during welding.

3. The plasma welding method for the leaf spring mounting sleeve according to claim 2, characterized in that, It is based on the maximum radial deviation between the axis of the leaf spring mounting sleeve and the axis of the hole to be welded on the leaf spring shaft tube, and is used to determine the assembly alignment accuracy of the leaf spring mounting sleeve and the hole to be welded on the leaf spring shaft tube.

4. The plasma welding method for the leaf spring mounting sleeve according to claim 3, characterized in that, The increase in the compensation current is positively correlated with the difference between the assembly coaxiality deviation value and the preset assembly coaxiality deviation value.

5. The plasma welding method for the leaf spring mounting sleeve according to claim 4, characterized in that, The step of determining the wire feed speed of the solder based on the maximum impact kinetic energy includes, The maximum impact kinetic energy is compared with the preset maximum impact kinetic energy; If the maximum impact kinetic energy is greater than or equal to the preset maximum impact kinetic energy, it is determined that the risk of breakage of the leaf spring mounting sleeve caused by welding spatter does not meet the requirements, and the wire feeding speed of the solder is reduced according to the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy.

6. The plasma welding method for the leaf spring mounting sleeve according to claim 5, characterized in that, The maximum impact kinetic energy is the maximum kinetic energy of the spatter particles generated after the welding arc of the solder acts on the molten pool at the moment when the preset coaxiality deviation condition is met. The condition for satisfying the preset coaxiality deviation is that the assembly coaxiality deviation value is less than the preset assembly coaxiality deviation value.

7. The plasma welding method for the leaf spring mounting sleeve according to claim 6, characterized in that, The reduction in the wire feed speed of the solder is positively correlated with the difference between the maximum impact kinetic energy and the preset maximum impact kinetic energy.

8. The plasma welding method for the leaf spring mounting sleeve according to claim 7, characterized in that, The ion gas flow rate of the plasma welding equipment is determined based on the weld filler change rate, including: The weld fill change rate is compared with the preset weld fill change rate; If the weld fill rate is greater than or equal to the preset weld fill rate, the risk of melt-through at the welded part is determined to be unacceptable, and the ion gas flow rate of the plasma welding equipment is reduced based on the difference between the weld fill rate and the preset weld fill rate.

9. The plasma welding method for the leaf spring mounting sleeve according to claim 8, characterized in that, The weld fill rate is the rate of change of the weld fill rate per unit length per unit time. The weld filler change rate is determined by the welding current that satisfies the preset coaxiality deviation condition and the wire feeding speed of the solder at the moment that satisfies the preset impact kinetic energy condition. The preset impact kinetic energy condition is that the maximum impact kinetic energy is less than the preset maximum impact kinetic energy.

10. The plasma welding method for the leaf spring mounting sleeve according to claim 9, characterized in that, The reduction in the ion flow rate of the plasma welding equipment is positively correlated with the difference between the weld filling rate and the preset weld filling rate.

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