A magnetic control narrow gap welding method based on segmented tangent complex waveforms

Abstract

The application discloses a magnetic control narrow-gap welding method based on a segmented tangent complex waveform, and comprises the following steps: generating a periodic complex magnetic field waveform signal; outputting the complex magnetic field waveform signal to an excitation coil, so that the excitation coil generates a complex magnetic field acting on a welding arc; a single period of the complex magnetic field waveform signal comprises a constant amplitude segment and a tangent function transition segment; the constant amplitude segment is used for biasing the welding arc on the sidewall of a narrow-gap groove for fixed-point preheating; and the tangent function transition segment is used for making the welding arc smoothly swing between the sidewalls of the two sides of the narrow-gap groove without mutation.

Description

Technical Field

[0001] This invention belongs to the field of magnetic field control technology and relates to a magnetically controlled narrow gap welding method based on segmented tangential composite waveform. Background Technology

[0002] Narrow gap welding is a highly efficient process for plate components with a thickness of 20mm and above, used in steel structures, pressure vessels, and titanium alloys. This process controls the bevel gap to 8-14mm (i.e., narrow gap), employing multi-layer single-pass filling, and offers advantages such as low heat input, minimal deformation, and low energy consumption. Mainstream processes include narrow gap tungsten inert gas welding (TIG), narrow gap metal inert gas welding (MIG), and narrow gap submerged arc welding (SAW).

[0003] like Figure 1 As shown, narrow-gap bevels include I-type and U-type bevels. Due to the narrow bevel, the arc heat source is concentrated in the center of the bevel, making it difficult to heat the sidewalls. Furthermore, the single-layer penetration depth is small, leading to a common defect: incomplete fusion of the sidewalls. This defect stems from the deep and narrow bevel, with the arc axis nearly parallel to the sidewalls. Insufficient heat input to the sidewalls results in the deposited metal merely adhering to the sidewalls, forming an insulated layer without metallurgical bonding. Low heat input exacerbates insufficient temperature rise, and increasing the current easily burns through the bottom. The high surface tension of the liquid metal prevents it from spreading on steep sidewalls, easily forming gap-type incomplete fusion, reducing the joint's fatigue performance and load-bearing capacity.

[0004] like Figure 2 As shown, an external alternating magnetic field drives the electric arc under Lorentz force, causing it to periodically deflect towards the left and right sidewalls of the bevel, distributing heat to the sidewalls and providing an effective solution to incomplete fusion. The core of this solution is the excitation current waveform, which determines the arc speed and heat input distribution. Commonly used waveforms include DC, sine, square wave, and pulse waveforms. DC magnetic fields have a fixed direction, lack stirring, result in poor grain refinement, and are difficult to adapt to bevel width fluctuations. Sine waves offer a uniform transition, but their effect is gradual near the peak, with limited oscillation amplitude, weak low-frequency stirring, and easy high-frequency coupling interference. Square waves have steep edges and strong instantaneous force, but are prone to arc jitter and spatter, and the weld center receives insufficient heating. Pulse waves allow for segmented heat input control, but parameter matching is complex, improper switching can lead to heat input imbalance, discontinuous low-frequency stirring, and difficulty in high-frequency control.

[0005] Therefore, there is an urgent need to propose a new narrow-gap welding method to solve the above problems. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention proposes a magnetically controlled narrow gap welding method based on segmented tangential composite waveforms.

[0007] The first aspect of the present invention provides a magnetically controlled narrow-gap welding method based on a segmented tangential composite waveform, applied to welding control equipment, comprising: Generate a periodic composite magnetic field waveform signal; The composite magnetic field waveform signal is output to the excitation coil to generate a composite magnetic field that acts on the welding arc. The composite magnetic field waveform signal contains a constant amplitude segment and a tangent function transition segment within a single cycle. The constant amplitude segment is used to bias the welding arc to the sidewall of the narrow gap bevel for fixed-point preheating. The tangent function transition segment is used to make the welding arc oscillate smoothly between the two sidewalls of the narrow gap bevel without abrupt changes.

[0008] Optionally, within the single period, the constant amplitude segment includes a negative constant segment and a positive constant segment, and the tangent function transition segment includes a rising transition segment and a falling transition segment; The individual cycles are, in sequence: the negative constant segment, the rising transition segment, the positive constant segment, and the falling transition segment; The negative constant segment is used to bias the welding arc onto the first sidewall, the rising transition segment is used to make the welding arc swing smoothly from the first sidewall to the second sidewall, the positive constant segment is used to bias the welding arc onto the second sidewall, and the falling transition segment is used to make the welding arc swing smoothly back from the second sidewall to the first sidewall.

[0009] Optionally, the magnetic flux density variation curves of the rising transition segment and the falling transition segment are tangent function curves; the amplitudes of the rising transition segment and the falling transition segment at their respective starting and ending points are continuously connected with the amplitudes of the adjacent constant amplitude segments, so that the composite magnetic field waveform signal has no abrupt changes throughout the entire cycle.

[0010] Optionally, the descent transition section and the rise transition section allow the molten pool to release air and slag during the oscillation process, so that the welding wire can be fully melted and effectively bonded to the sidewall.

[0011] Optionally, the slope of the tangent function transition segment is set according to the opening angle of the narrow gap bevel.

[0012] Optionally, the normalized magnetic induction intensity y represented by the composite magnetic field waveform signal changes with time t within a single period according to the following piecewise function: Let the single period be T, t∈[0,T]; when When y = -1; when hour, ; when When y=1; when hour, ; Where m is the tangent scaling factor, used to control the slope of the rising transition segment and the falling transition segment; k is the amplitude calibration factor. This is used to ensure that the function values ​​of each segment at the connection point are equal to ±1.

[0013] Optionally, the period T and the tangent scaling factor m are determined according to the welding speed. The higher the welding speed, the smaller the period T and the larger the tangent scaling factor m.

[0014] Optionally, the frequency of the composite magnetic field waveform signal may be adjusted according to the welding stage: The first frequency is used in the root pass welding stage, the second frequency is used in the fill pass welding stage, and the third frequency is used in the cover pass welding stage. The first frequency is the second frequency The third frequency is the second frequency. .

[0015] Optionally, generating a periodic composite current waveform signal specifically includes: A low-voltage reference electrical signal is generated by an arbitrary waveform generator based on preset waveform data; The low-voltage reference electrical signal is amplified to the required excitation current and then output to the excitation coil.

[0016] A second aspect of the present invention provides a magnetically controlled narrow-gap welding method based on a segmented tangential composite waveform, applied to an excitation coil, comprising: Receives the composite magnetic field waveform signal output by the welding control equipment; A composite waveform magnetic field is generated based on the composite current waveform signal, and the composite waveform magnetic field acts on the welding arc; The variation law of magnetic induction intensity of the composite magnetic field in a single cycle includes: a constant magnetic induction intensity range and a tangent function transition magnetic induction intensity range; Within the range of constant magnetic induction intensity, the composite magnetic field causes the welding arc to be continuously biased to one side wall of the narrow gap bevel. Within the range of the transition magnetic induction intensity of the tangent function, the composite magnetic field causes the welding arc to oscillate smoothly between the two sidewalls of the narrow gap bevel.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention, through the inclusion of negative and positive constant segments within a single cycle, allows the welding arc to be periodically biased towards the left and right sidewalls of a narrow-gap groove for targeted preheating. This provides sufficient heat input to the sidewall base material, enabling the sidewall temperature to reach melting point and form a good metallurgical bond with the deposited metal, fundamentally eliminating sidewall incomplete fusion defects. Simultaneously, the rising and falling transition segments employ tangent function curves to achieve a continuous and smooth change in magnetic induction intensity. This allows the arc to sweep rapidly between the two sidewalls while maintaining sufficient heat input to the weld, further enhancing the sidewall fusion effect. As a result, welding using the composite magnetic field waveform of this invention results in excellent sidewall fusion with no obvious incomplete fusion defects.

[0018] This invention employs a tangent function curve as the magnetic field variation law for the transition segment. The tangent curve continuously connects with the constant amplitude segment at the junction point, without any abrupt changes throughout the entire cycle, thus avoiding the arc jitter and spatter problems caused by the steep edges of the square wave magnetic field. The amplitudes of the rising and falling transition segments are equal to the amplitudes of the adjacent constant segments at each junction point, ensuring a smooth rather than abrupt change in the Lorentz force on the arc, resulting in uniform and stable force on the arc during oscillation. In actual welding, the arc oscillates smoothly without any arc breakage, effectively reducing the arc breakage rate and ensuring the continuity and stability of the welding process.

[0019] This invention incorporates a gently descent magnetic field in the transition section, transitioning from a positive constant segment to a negative constant segment. This field allows the welding arc to smoothly swing back from one sidewall to the other, applying an electromagnetic stirring force to the molten pool that gradually weakens and then strengthens. This facilitates the slow escape of gas from the liquid metal within the molten pool, promoting the slag to rise to the surface. Compared to square wave magnetic fields, which suffer from insufficient melting of the lower weld metal and welding wire due to abrupt changes in the magnetic field, this magnetic field waveform effectively applies arc heat, ensuring thorough melting of the welding wire and the previous weld pass, and effective bonding with the sidewall metal.

[0020] This invention allows for flexible adaptation to welding process requirements based on different welding speeds and bevel sizes by adjusting the period parameter T and the tangent scaling factor m. The period parameter T controls the density of waveform repetition, while the tangent scaling factor m controls the steepness of the transition section; both together determine the arc's dwell time and oscillation speed on the sidewalls. When the welding speed increases, the preheating time of the arc on both sidewalls is extended by decreasing the period parameter T; when the bevel opening angle increases, the dwell time of the arc at the weld center is extended by increasing the tangent scaling factor m. This adjustment method makes the invention widely applicable to narrow-gap welding scenarios for titanium alloys and steel with thicknesses ranging from 10mm to 100mm, compatible with various processes such as narrow tungsten inert gas welding and narrow-gap metal arc welding.

[0021] This invention employs the second frequency of the filler soldering stage during the root pass stage. The second frequency was used during the cover welding stage. This allows for a slower arc oscillation speed during the root pass welding stage, preventing overheating and collapse of the root molten pool while ensuring root penetration. During the cover pass welding stage, the arc oscillation speed falls between that of the root pass and the fill pass, ensuring both sidewall fusion quality and minimizing molten pool disturbance to optimize weld surface formation. This differentiated frequency configuration optimizes the process performance at each stage of the welding process. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the I-type bevel and U-type bevel of a narrow gap bevel in one embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the principle of an externally applied alternating magnetic field driving an electric arc to periodically deflect towards the left and right sidewalls of the bevel in one embodiment of the present invention. Figure 3 This is a schematic diagram of a magnetically controlled narrow-gap welding system based on a segmented tangential composite waveform in one embodiment of the present invention; Figure 4 This is a flowchart illustrating the generation and output of a composite magnetic field waveform signal on the welding control equipment side in one embodiment of the present invention; Figure 5 This is a composite magnetic field waveform diagram in a magnetron-controlled narrow gap welding method based on segmented tangential composite waveforms in one embodiment of the present invention; Figure 6 This is a curve showing the variation law of a piecewise tangent composite waveform function in one embodiment of the present invention; Figure 7 This is a waveform comparison diagram in one embodiment of the present invention; Figure 8 It is a cross-sectional view of the weld with a single conventional magnetic field waveform; Figure 8 This is a cross-sectional view of a weld seam based on a segmented tangential composite waveform magnetically controlled narrow gap welding according to an embodiment of the present invention; Figure 10 This is a flowchart of the magnetic induction intensity change curve and excitation steps in one embodiment of the present invention. Detailed Implementation

[0023] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The magnetically controlled narrow-gap welding method based on segmented tangential composite waveforms provided in this invention can be applied to, for example... Figure 3The application environment is shown. Specifically, this magnetron narrow gap welding method is applied in a magnetron narrow gap welding system, which may include, for example... Figure 3 The welding control equipment and excitation coil shown are shown.

[0025] In this system, the welding control equipment and the excitation coil communicate via an electrical connection to generate and output a composite magnetic field waveform signal. Specifically, the welding control equipment refers to the control terminal corresponding to the excitation coil, providing the drive signal to the excitation coil. The welding control equipment may include, but is not limited to, arbitrary waveform generators, power amplifiers, programmable constant current sources, and dedicated welding power controllers with integrated waveform generation functions. The welding control equipment generates periodic composite magnetic field waveform signals and outputs them to the excitation coil. The excitation coil generates a composite magnetic field based on the received composite waveform electrical signal and acts on the welding arc, causing the welding arc to oscillate between the two sidewalls of the narrow gap bevel. The excitation coil can be installed on the welding torch, or in front of, behind, or both simultaneously on the welding torch; there are no specific limitations.

[0026] In one application scenario, welding control equipment can currently generate periodic composite magnetic field waveform signals. Each cycle of this waveform signal includes a constant amplitude segment and a tangent function transition segment. The constant amplitude segment is used to preheat the welding arc at a fixed point on the sidewall of the narrow-gap groove, while the tangent function transition segment allows the welding arc to oscillate smoothly between the two sidewalls of the narrow-gap groove without abrupt changes. Specifically, the welding control equipment can set waveform parameters according to the thickness of the workpiece and the opening angle of the narrow-gap groove to adapt to welding conditions with different plate thicknesses and groove sizes.

[0027] For example, the workpiece to be welded may include, but is not limited to, steel structural parts, steel plates for pressure vessels, and thick titanium alloy plates. Corresponding waveform parameters are set by different plate thicknesses and bevel parameters so that the deflection speed of the welding arc and the heat input distribution can be adapted to different welding scenarios.

[0028] like Figure 1As shown, before starting the welding control equipment, the operator pre-treats the workpiece to be welded. A narrow-gap bevel with an opening angle of 2° to 4° is machined; this narrow-gap bevel can be an I-bevel or a U-bevel. Burrs and surface oxide scale are thoroughly removed from the bevel. The base material within a 20mm range on both sides of the bevel and the top two sides is ground. If an I-bevel is used, the backing plate needs to be ground before assembly. Finally, the welding area is cleaned with alcohol to ensure it is free of oil and dust. The workpiece is clamped and fixed using rigid fixtures, and proper grounding is ensured to prevent stray currents from interfering with process stability during welding. The operator also presets key welding parameters such as welding current, welding travel speed, wire feed rate, and shielding gas flow rate based on the material and thickness of the workpiece.

[0029] like Figure 4 As shown, in step S11, the welding control equipment acquires the bevel parameters of the narrow gap bevel. These bevel parameters include at least the plate thickness of the workpiece to be welded and the opening angle of the narrow gap bevel. The welding control equipment determines the period parameter T of the composite magnetic field waveform signal based on the plate thickness and the tangent scaling factor m based on the opening angle. The period parameter T controls the density of repetition of the composite magnetic field waveform signal. The tangent scaling factor m controls the steepness of the transition section of the tangent function curve.

[0030] Optionally, the welding control equipment can acquire bevel parameters by receiving plate thickness and opening angle values ​​input by the operator through a human-machine interface. For example, the welding control equipment can also acquire the bevel parameters corresponding to the current workpiece number by reading a process parameter table pre-stored in local memory. In one embodiment, the welding control equipment can automatically acquire bevel parameters by connecting to an external measuring device, which includes a laser rangefinder or a visual profile scanner.

[0031] Preferably, when the welding control equipment determines the period parameter T and the tangent scaling factor m based on the welding speed, it follows the following rules: the higher the welding speed, the smaller the value of the period parameter T, the higher the frequency f, and the smaller the value of the tangent scaling factor m. The welding control equipment has a pre-stored mapping table of welding speed, period parameter T, frequency f, and tangent scaling factor m. In this mapping table, when the welding speed is 1.0 mm / s, the period parameter T is 0.14-0.17 s, the frequency f is 6-7 Hz, and the tangent scaling factor m is 0-90; when the welding speed is 1.5 mm / s, the period parameter T is 0.09-0.11 s, the frequency is 9-11 Hz, and the tangent scaling factor m is 0-140; when the welding speed is 2.0 mm / s, the period parameter T is 0.07-0.076 s, the frequency is 13-14, and the tangent scaling factor m is 0-180; when the welding speed is 2.5 mm / s, the period parameter T is 0.058-0.063 s, the frequency is 16-17, and the tangent scaling factor m is 0-217.

[0032] Optionally, different welding frequencies can be used at different stages of the welding process. For example, during the root pass welding, a different magnetic field frequency can be used for the fill pass welding. The magnetic field frequencies shown in Table 1 are used during the filler welding stage, and the magnetic field frequencies used during the capping welding stage are those used during the filler welding stage. .

[0033] Table 1 Relationship between welding speed and custom magnetic field parameters Preferably, the magnitude of the excitation current, which is the peak value of the magnetic field waveform of the present invention, needs to be determined based on the gap and the shrinkage of the sheet metal. The excitation current follows the following rule: the larger the gap, the greater the required magnetic induction intensity, as shown in Table 2. Due to the different manufacturing methods of the excitation device and the electromagnetic core, the magnetic induction intensity produced by the excitation power supply will also be different. Generally speaking, the greater the required magnetic induction intensity, the greater the excitation current.

[0034] Table 2 Relationship between gap and magnetic induction intensity Optionally, given sufficient heat input and deposition amount, the relationship between the magnetic field period T, tangent scaling factor m, peak excitation current, welding speed, narrow gap size, and welding stage described in this invention can be adjusted to suit plates of different thicknesses. Specifically, in this invention, the welding current is 280-340A, the welding voltage is 20.4-23.6V, and the wire feed speed is 16-26mm / s; these welding current, welding voltage, and wire feed speed are fixed parameter windows. This invention adjusts the magnetic field waveform according to different welding speeds and bevel gaps, while ensuring sufficient heat input and deposition amount.

[0035] For example, a pair of 30mm thick titanium alloy plates were welded using a welding current of 330A, a welding voltage of 23V, a wire feed speed of 22mm / s, and a welding speed of 1.5mm / s. The magnetic field frequency f used the tangent scaling factor m of 10Hz and 125 from Table 1, the arc gap between the plates was 10-12mm, and the magnetic induction intensity was 5.5-6.5mT from Table 2. In another example, using the above welding current, voltage, welding speed, and wire feed speed, and guided by the parameters in Tables 1 and 2, a titanium alloy plate with a thickness of 88mm was successfully welded.

[0036] like Figure 4As shown, in step S12, the welding control equipment generates a periodic composite magnetic field waveform signal based on the period parameter T and the tangent scaling factor m. This composite magnetic field waveform signal is used to drive the excitation coil to generate a composite magnetic field acting on the welding arc. In this document, the composite magnetic field waveform signal refers to a periodically changing electrical signal whose amplitude varies with time according to a piecewise function, used to control the magnitude and direction of the magnetic induction intensity generated by the excitation coil.

[0037] The composite magnetic field waveform signal generated by the welding control equipment contains a constant amplitude segment and a tangent function transition segment within a single cycle. The constant amplitude segment is used to preheat the welding arc at a fixed point on the sidewall of the narrow gap groove. The tangent function transition segment is used to allow the welding arc to oscillate smoothly between the two sidewalls of the narrow gap groove without abrupt changes. In this invention, the constant amplitude segment refers to the waveform range where the magnetic induction intensity remains constant, and the tangent function transition segment refers to the waveform range where the magnetic induction intensity changes monotonically and continuously according to the tangent function curve.

[0038] like Figure 5 As shown, within a single period, the constant amplitude segment includes a negative constant segment and a positive constant segment, and the tangent function transition segment includes a rising transition segment and a falling transition segment. The single period consists of: a negative constant segment, a rising transition segment, a positive constant segment, and a falling transition segment. The normalized magnetic induction intensity y, represented by the composite magnetic field waveform signal, changes with time t within a single period according to the following piecewise function: Let a single period be T, t∈[0,T], when When y = -1, this interval is a negative constant segment; when hour, This interval is the rising transition segment. When When y=1, the interval is a positive constant segment; when hour, This interval is the descent transition segment.

[0039] Where m is the tangent scaling factor, used to control the slope of the rising and falling transition segments. k is the amplitude calibration factor. The function values ​​at the junctions of each segment are set to ±1. The magnetic induction intensity variation curves of the rising and falling transition segments are tangent function curves. The amplitudes of the rising and falling transition segments at their respective starting and ending points are continuously connected to the amplitudes of the adjacent constant amplitude segments to ensure that the composite magnetic field waveform signal has no abrupt changes throughout the entire cycle. The negative constant segment is used to bias the welding arc onto the first sidewall. The rising transition segment is used to smoothly oscillate the welding arc from the first sidewall to the second sidewall. The positive constant segment is used to bias the welding arc onto the second sidewall. The falling transition segment is used to smoothly swing the welding arc back from the second sidewall to the first sidewall, and to expel slag from the molten pool during the swing back.

[0040] like Figure 6 As shown, the piecewise function exhibits a waveform pattern in which a periodically repeating negative constant segment, a positive rising segment, a positive constant segment, and a positive falling segment are sequentially connected. Figure 5 The specific waveform shapes at T=1 and m=11.5 are further illustrated, as shown below. Figure 7 As shown, the value of m has a significant impact on the steepness of the waveform, where, Figure 6 The waveform with amplitude 'a' of T=1 and m=0.5 shows a smooth curve change. Figure 7 The waveform with amplitude b of T=1 and m=12.5 shows a steep curve change. It can be seen that the larger the value of m, the steeper the rising and falling segments, and the smaller the value of m, the gentler the rising and falling segments.

[0041] As one embodiment, the welding control equipment can directly calculate the amplitude corresponding to each time point in real time based on the mathematical expression of the piecewise function, and store the calculated discrete amplitude sequence in the waveform memory. As another embodiment, the welding control equipment can pre-generate and store multiple sets of waveform data tables corresponding to different period parameters T and tangent scaling factors m. After obtaining the bevel parameters, the corresponding waveform data can be directly read by looking up the tables, without the need for real-time calculation.

[0042] Optionally, the specific method for generating the composite magnetic field waveform signal through excitation is as follows: the welding control equipment generates a low-voltage reference electrical signal based on preset waveform data by regulating the arbitrary waveform generator inside the excitation power supply. This preset waveform data is a discrete amplitude sequence conforming to the aforementioned piecewise function expression. The arbitrary waveform generator outputs the generated voltage values ​​point by point, forming an analog low-voltage reference electrical signal.

[0043] like Figure 4 As shown, in step S13, the welding control equipment amplifies the generated composite magnetic field waveform signal to the required excitation current and outputs it to the excitation coil. Specifically, the welding control equipment receives the low-voltage reference signal output by the arbitrary waveform generator through the power amplifier inside the excitation power supply, and amplifies the power of the low-voltage reference signal proportionally. The power amplifier outputs the amplified drive current to the excitation coil. After the drive current is passed through the excitation coil, a composite magnetic field consistent with the change law of the drive current is generated according to the principle of electromagnetic induction. This composite magnetic field acts on the welding arc, causing the welding arc to oscillate within the narrow gap groove according to the law of the composite magnetic field waveform signal.

[0044] Optionally, before outputting the composite magnetic field waveform signal, the welding control equipment also performs the following calibration operation: the welding control equipment calibrates the actual magnetic induction intensity generated by the excitation coil at the center of the molten pool using a gaussmeter. Based on the gaussmeter measurement results, the welding control equipment calibrates the correspondence between the electrical signal amplitude and the actual magnetic induction intensity to determine the peak magnetic induction intensity required for the process. As an example, the welding control equipment adjusts the peak magnetic induction intensity by changing the amplitude of the drive current output to the excitation coil by adjusting the amplification factor of the power amplifier.

[0045] like Figure 4 As shown, in step S14, the welding control equipment adjusts the frequency of the composite magnetic field waveform signal according to the current welding stage. The welding stages include: root pass welding, fill pass welding, and cap pass welding. The root pass welding stage refers to the initial stage of welding the root of the groove. The fill pass welding stage refers to the intermediate stage of filling the groove with multiple layers after the root pass welding is completed. The cap pass welding stage refers to the final stage of shaping the weld surface after the fill pass welding is completed.

[0046] The welding control equipment uses a first frequency to drive the excitation coil during the root pass welding stage. During the fill pass welding stage, it uses a second frequency. During the cover pass welding stage, it uses a third frequency. The first frequency is the same as the second frequency. The third frequency is the second frequency. For example, when the second frequency of the filler welding stage is 12Hz, the welding control equipment sets the first frequency of the root pass welding stage to 6Hz and the third frequency of the cover pass welding stage to 8Hz. Using a lower frequency in the root pass welding stage prevents the molten pool from collapsing and ensures root penetration. Using a frequency between the root pass and filler welds in the cover pass welding stage reduces molten pool disturbance and optimizes weld formation.

[0047] like Figure 4 As shown, in step S15, the welding control equipment synchronously starts the periodic output of the composite magnetic field waveform signal at the instant the welding torch ignites the arc. The welding control equipment achieves synchronization between the welding torch arc ignition signal and the excitation signal output by the excitation power supply through its internal signal control circuit. When the welding control equipment detects that the welding torch arc ignition signal is valid, it simultaneously outputs a trigger pulse to the excitation power supply. In response to the trigger pulse, the excitation power supply outputs the composite magnetic field waveform signal from the waveform start point.

[0048] Optionally, the welding control equipment detects arc ignition by detecting changes in the current in the welding circuit to determine whether arc ignition is successful. When the welding control equipment detects that the current in the welding circuit exceeds a preset threshold, it determines that the arc ignition is successful and then outputs a trigger pulse. As an example, the welding control equipment can also determine the arc ignition status by detecting the voltage drop between the welding torch electrode and the workpiece; when the voltage drop drops to a preset voltage threshold, it determines that arc ignition is successful.

[0049] The welding control equipment monitors the arc oscillation pattern and magnetic field output stability in real time during welding. It acquires the real-time drive current waveform in the excitation coil via a current sensor and compares this waveform with a preset composite magnetic field waveform signal. When the deviation between the real-time waveform and the preset waveform exceeds a preset threshold, the welding control equipment outputs a warning signal and automatically marks abnormal magnetic induction intensity data. The welding control equipment also acquires images of the welding area via a vision sensor, identifying the arc oscillation amplitude and trajectory from these images. When abnormal arc oscillation occurs, the welding control equipment stops welding output and prompts the operator to check the magnetic field system.

[0050] Optionally, when generating the composite magnetic field waveform signal, the slope of the tangent function transition segment of the welding control equipment is set according to the opening angle of the narrow gap groove. The larger the opening angle, the larger the value of the tangent scaling factor m set by the welding control equipment. The tangent function transition segment changes slowly when approaching 0, allowing sufficient melting at the weld center. As it moves away from the weld center and nears the sidewall, the speed change increases rapidly, providing a stirring effect. The smaller the opening angle, the smaller the value of the tangent scaling factor m set by the welding control equipment. The change in the tangent function transition segment is more gradual, and the oscillation speed of the welding arc tends to be uniform.

[0051] As an example, the welding control equipment also adjusts the peak excitation current based on the values ​​of the bottom and top gaps of the narrow-gap groove. When the gap where the welding arc is located is large, the welding control equipment increases the peak excitation current to ensure that the arc can fully contact the sidewall and ensure that the sidewall receives sufficient heat input.

[0052] In another embodiment, the welding control equipment employs different waveform parameters for different weld layers during the filler welding stage. For the initial layer of the filler weld, a larger tangent scaling factor *m* is used to allow the arc to quickly sweep across the sidewalls, eliminating any potential incomplete fusion defects at the root. For the middle layer of the filler weld, a moderate tangent scaling factor *m* and period parameter *T* are used to maintain stable molten pool stirring. For the final layer of the filler weld, a smaller tangent scaling factor *m* is used to reduce the arc oscillation amplitude and prevent excessive erosion of the formed weld bead.

[0053] After welding is completed, the welding control equipment sends a welding completion notification to the operator. The operator then applies heat preservation or stress-relieving annealing treatment to the weld, depending on the base material, to effectively eliminate residual welding stress. Subsequently, non-destructive testing is used to inspect the weld for defects such as incomplete fusion, porosity, and cracks on the surface and interior. Simultaneously, weld samples are taken for metallographic and mechanical property testing to verify the effectiveness of the composite magnetic field in refining grains and improving sidewall fusion. Finally, based on the weld inspection quality, the operator iteratively optimizes waveform parameters such as the magnetic field period parameter T, tangent scaling factor m, and peak amplitude to continuously improve the welding process.

[0054] It is important to note that the welding control equipment includes an arbitrary waveform generator, a power amplifier, and a programmable constant current source. The arbitrary waveform generator generates a low-voltage reference electrical signal based on preset waveform data. The power amplifier, electrically connected to the arbitrary waveform generator, amplifies the power of the low-voltage reference electrical signal to the required excitation current. The programmable constant current source, also electrically connected to the power amplifier, provides a stable drive current to the excitation coil. The welding control equipment also includes a timing control circuit, which is electrically connected to both the welding torch power supply and the arbitrary waveform generator. This circuit outputs a trigger pulse to the arbitrary waveform generator at the moment the welding torch ignites, achieving timing matching between the welding process and the magnetic field.

[0055] The welding control equipment is connected to the excitation coil via an electrical connection cable. The welding control equipment transmits the amplified composite magnetic field waveform signal to the excitation coil through this cable. The excitation coil is installed in front of the welding torch. When a driving current is applied to the excitation coil, a periodically changing composite magnetic field is generated in the space surrounding the molten pool. The direction and intensity of this composite magnetic field change with the driving current. Under the influence of this composite magnetic field, the welding arc is driven by a Lorentz force and deflects towards the bevel sidewall.

[0056] like Figure 8 As shown, Figure 8 The image shows a cross-sectional view of the weld after narrow-gap welding of a thick titanium alloy plate using a single conventional magnetic field waveform. There are obvious sidewall fusion defects in the weld. Figure 9 A photograph of the weld cross-section after narrow-gap welding of a thick titanium alloy plate using the composite magnetic field waveform of an embodiment of the present invention is shown. The sidewall fusion is good and no obvious non-fusion defects are observed.

[0057] The above comparison results show that the segmented tangential composite magnetic field waveform of the present invention can effectively eliminate the problem of sidewall incomplete fusion in narrow gap welding. At the same time, the arc oscillates smoothly during the welding process without shaking or spattering. The welding arc can be stably biased to the sidewall for preheating in the constant magnetic field segment, and can smoothly oscillate to the opposite sidewall in the tangential transition segment, thus achieving full fusion of the left and right sidewalls.

[0058] like Figure 10As shown, in step S16, the excitation coil receives the composite magnetic field waveform signal output by the welding control equipment. The excitation coil is electrically connected to the welding control equipment via an electrical connection cable. The welding control equipment outputs the amplified composite magnetic field waveform signal as a drive current to the electrical connection cable. The excitation coil obtains this drive current from the electrical connection cable. In this document, the composite magnetic field waveform signal refers to the periodically changing electrical signal generated by the welding control equipment. The amplitude of this electrical signal changes with time according to a piecewise function, and is used to control the magnitude and direction of the magnetic field strength generated by the excitation coil.

[0059] Optionally, the excitation coil can receive the composite magnetic field waveform signal by receiving a differential current signal from the electrical connection cable through its terminals. As an example, the excitation coil receives a modulated wireless drive signal sent by the welding control equipment via a wireless receiving module. This wireless drive signal carries composite magnetic field waveform information, and the demodulation circuit inside the excitation coil converts the wireless drive signal into a drive current.

[0060] like Figure 10 As shown, in step S17, the excitation coil generates a composite magnetic field based on the composite magnetic field waveform signal. After a driving current is passed through the excitation coil, a magnetic field consistent with the changing pattern of the driving current is generated in the space around the molten pool according to the principle of electromagnetic induction. This composite magnetic field acts on the welding arc, causing the welding arc to oscillate within the narrow gap groove according to the changing pattern of the magnetic field.

[0061] In this invention, the composite magnetic field refers to a magnetic field generated by an excitation coil whose direction and intensity change periodically with time. The variation law of the magnetic induction intensity of this composite magnetic field within a single cycle includes a constant magnetic induction intensity range and a tangent function transition magnetic induction intensity range. The constant magnetic induction intensity range, as used herein, refers to the period during which the magnetic field intensity remains constant. The tangent function transition magnetic induction intensity range, as used herein, refers to the period during which the magnetic field intensity changes monotonically and continuously according to the tangent function curve.

[0062] like Figure 10 As shown, within a single cycle, the constant magnetic flux density range includes a negative constant range and a positive constant range, and the tangent function transition magnetic flux density range includes a rising transition range and a falling transition range. This single cycle consists of: a negative constant range, a rising transition range, a positive constant range, and a falling transition range. The normalized magnetic flux density generated by the excitation coil varies with time t within a single cycle according to the following piecewise functional relationship: Let the single period be T, t∈[0,T]. When When y = -1, this interval is a negative constant segment; when hour, This interval is the rising transition segment. When When y=1, the interval is a positive constant segment; when hour, This interval is the descent transition segment.

[0063] Where m is the tangent scaling factor, used to control the slope of the rising and falling transition segments. k is the amplitude calibration factor. This is used to ensure that the magnetic induction intensity value at the connection point of each segment is equal to ±1, so that the magnetic field change is not abruptly changed throughout the entire cycle.

[0064] Within the negative constant range, the excitation coil generates a constant magnetic field directed towards the first sidewall. This constant magnetic field continuously biases the welding arc against the first sidewall of the narrow-gap bevel, providing targeted preheating of the first sidewall. Within the rising transition range, the magnetic induction intensity generated by the excitation coil monotonically and smoothly transitions from a negative peak to a positive peak along the tangent function curve. This changing magnetic field causes the welding arc to smoothly oscillate from the first sidewall to the second sidewall. Within the positive constant range, the excitation coil generates a constant magnetic field directed towards the second sidewall. This constant magnetic field continuously biases the welding arc against the second sidewall of the narrow-gap bevel, providing targeted preheating of the second sidewall. Within the falling transition range, the magnetic induction intensity generated by the excitation coil monotonically and smoothly transitions from a positive peak to a negative peak along the tangent function curve. This changing magnetic field causes the welding arc to smoothly swing back from the second sidewall to the first sidewall, and during this swing-back process, it facilitates the removal of air and slag from the molten pool.

[0065] The magnetic flux density variation curves within both the rising and falling transition intervals are tangent function curves. The magnetic flux density values ​​at the start and end points of each of the rising and falling transition intervals are continuously connected to the magnetic flux density values ​​of the adjacent constant intervals, ensuring that the composite magnetic field generated by the excitation coil has no abrupt changes throughout the entire cycle.

[0066] Optionally, when the excitation coil generates a composite magnetic field according to the driving current, the correspondence between the driving current and the magnetic induction intensity depends on the number of turns and the magnetic circuit structure of the excitation coil. The welding control equipment pre-calibrates the actual magnetic induction intensity generated by the excitation coil at the center of the molten pool using a gaussmeter, and stores the calibration coefficients in the welding control equipment. The welding control equipment adjusts the amplitude of the driving signal according to these calibration coefficients so that the magnetic induction intensity output by the excitation coil precisely matches the preset piecewise function.

[0067] The excitation coil receives composite magnetic field waveform signals of different frequencies at different welding stages and generates a composite magnetic field of corresponding frequencies accordingly. During the root pass welding stage, the excitation coil receives a drive signal of a first frequency and generates a composite magnetic field of the first frequency, which is the second frequency for the fill pass welding stage. During the filler soldering stage, the excitation coil receives a drive signal at a second frequency and generates a composite magnetic field at the second frequency. During the cap soldering stage, the excitation coil receives a drive signal at a third frequency and generates a composite magnetic field at a third frequency, which is a fraction of the second frequency. .

[0068] For example, when the drive signal frequency during the filler welding stage is 12Hz, the excitation coil receives a drive signal frequency of 6Hz during the root pass welding stage and generates a 6Hz composite magnetic field. During the cap pass welding stage, it receives a drive signal frequency of 8Hz and generates an 8Hz composite magnetic field. Using a lower frequency composite magnetic field during the root pass welding stage prevents molten pool collapse and ensures root penetration. Using a composite magnetic field with a frequency between that of the root pass and filler welds during the cap pass welding stage reduces molten pool disturbance and optimizes weld formation.

[0069] Optionally, the excitation coil can be an air-core coil or a coil with a magnetic core. As one embodiment, the excitation coil is made of solid copper wire wound with a layer of insulating tape and an additional U-shaped copper tube containing cooling water. This cooling water carries away the heat generated by the coil during operation, preventing overheating. As another embodiment, the excitation coil uses a coil with a high-saturation silicon steel laminated magnetic core. This core is used to conduct the magnetic field lines generated by the coil, allowing the welding arc to achieve a more stable deflection amplitude under the same driving current.

[0070] Optionally, the excitation coils can be installed on one side of the welding torch, either before or after it, or symmetrically before and after it. As one embodiment, a single excitation coil is installed in front of the welding torch, generating a composite magnetic field that acts on the welding arc, causing the arc to oscillate left and right within the narrow gap bevel. As another embodiment, two excitation coils are symmetrically installed in front of and behind the welding torch, respectively. The welding control equipment outputs drive signals in the same direction to the two excitation coils, and the two excitation coils work together to generate a composite magnetic field that acts on the welding arc.

[0071] Preferably, when the excitation coil generates a composite magnetic field, the peak value of its magnetic induction intensity is set according to the size of the gap between the arc and the coil. A larger gap results in a larger peak value of magnetic induction intensity generated by the excitation coil and a greater oscillation amplitude of the welding arc. A smaller gap results in a smaller peak value of magnetic induction intensity generated by the excitation coil and a smaller oscillation amplitude of the welding arc. The excitation power supply controls the peak value of the magnetic induction intensity by adjusting the amplitude of the drive current output to the excitation coil.

[0072] It is important to note that the excitation coil is installed in front of and behind the welding torch. The excitation coil includes a coil frame and conductive windings wound on the coil frame. The coil frame is made of insulating material and is used to fix the shape and position of the conductive windings. Terminals are connected to both ends of the conductive windings, which are electrically connected to the output of the power amplifier of the welding control equipment via electrical connection cables. The excitation coil also includes cooling pipes, which are embedded inside the coil frame or attached to the surface of the conductive windings, for introducing a cooling medium to dissipate the Joule heat generated during the operation of the excitation coil. The excitation coil receives the drive current output from the welding control equipment via electrical connection cables. When the drive current flows through the conductive windings, a composite magnetic field is generated around the conductive windings, exhibiting a pattern consistent with the change of the drive current. The direction of this composite magnetic field is determined by the direction of the drive current, and its strength is determined by the amplitude of the drive current and the number of turns of the conductive windings. The welding arc is located within the range of this composite magnetic field, and the charged particles in the arc are driven by the Lorentz force, deflecting towards the bevel sidewall.

[0073] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnetron-controlled narrow-gap welding method based on segmented tangent composite waveforms, characterized in that, Applications in welding control equipment, including: Generate a periodic composite magnetic field waveform signal; The composite magnetic field waveform signal is output to the excitation coil to generate a composite magnetic field that acts on the welding arc. The composite magnetic field waveform signal contains a constant amplitude segment and a tangent function transition segment within a single cycle. The constant amplitude segment is used to bias the welding arc to the sidewall of the narrow gap bevel for fixed-point preheating. The tangent function transition segment is used to make the welding arc oscillate smoothly between the two sidewalls of the narrow gap bevel without abrupt changes.

2. The magnetron-controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 1, characterized in that, Within a single cycle, the constant amplitude segment includes a negative constant segment and a positive constant segment, and the tangent function transition segment includes an ascending transition segment and a descending transition segment; The individual cycles are, in sequence: the negative constant segment, the rising transition segment, the positive constant segment, and the falling transition segment; The negative constant segment is used to bias the welding arc onto the first sidewall, the rising transition segment is used to make the welding arc swing smoothly from the first sidewall to the second sidewall, the positive constant segment is used to bias the welding arc onto the second sidewall, and the falling transition segment is used to make the welding arc swing smoothly back from the second sidewall to the first sidewall.

3. The magnetically controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 2, characterized in that, The magnetic flux density variation curves of the rising transition segment and the falling transition segment are tangent function curves; the amplitudes of the rising transition segment and the falling transition segment at their respective starting and ending points are continuously connected with the amplitudes of the adjacent constant amplitude segments, so that the composite magnetic field waveform signal has no abrupt changes throughout the entire cycle.

4. The magnetically controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 2, characterized in that, The descending and ascending sections allow the molten pool to release air and slag during the oscillation process, ensuring that the welding wire is fully melted and effectively bonded to the sidewall.

5. The magnetron-controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 1, characterized in that, The slope of the transition segment of the tangent function is set according to the opening angle of the narrow gap bevel.

6. The magnetron-controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 2, characterized in that, The normalized magnetic induction intensity y represented by the composite magnetic field waveform signal changes with time t within a single period, satisfying the following piecewise function: Let the single period be T, t∈[0,T]; when When y=-1; when hour, ; when When y=1; when hour, ; Where m is the tangent scaling factor, used to control the slope of the rising transition segment and the falling transition segment; k is the amplitude calibration factor. This is used to ensure that the function values ​​of each segment at the connection point are equal to ±1.

7. The magnetron narrow-gap welding method based on segmented tangential composite waveform according to claim 6, characterized in that, The period T and the tangent scaling factor m are determined according to the welding process. The greater the welding travel speed, the smaller the period T and the larger the tangent scaling factor m.

8. The magnetically controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 2, characterized in that, It also includes adjusting the frequency of the composite magnetic field waveform signal according to the welding stage: The first frequency is used during the root pass soldering stage, the second frequency is used during the fill pass soldering stage, and the third frequency is used during the cover pass soldering stage; the first frequency is the same as the second frequency. The third frequency is the second frequency. .

9. The magnetically controlled narrow-gap welding method based on segmented tangential composite waveform according to claim 1, characterized in that, The generation of the periodic composite magnetic field waveform signal includes: A low-voltage reference electrical signal is generated by an arbitrary waveform generator based on preset waveform data; The low-voltage reference electrical signal is amplified to the required excitation current and then output to the excitation coil.

10. A magnetically controlled narrow-gap welding method based on a segmented tangent composite waveform, applied to excitation coils, characterized in that... include: Receives the composite magnetic field waveform signal output by the welding control equipment; A composite magnetic field is generated based on the composite magnetic field waveform signal, and the composite magnetic field acts on the welding arc; The variation law of magnetic induction intensity of the composite magnetic field in a single cycle includes: a constant magnetic induction intensity range and a tangent function transition magnetic induction intensity range; Within the range of constant magnetic induction intensity, the composite magnetic field causes the welding arc to be continuously biased to one side wall of the narrow gap bevel. Within the range of the transition magnetic induction intensity of the tangent function, the composite magnetic field causes the welding arc to oscillate smoothly between the two sidewalls of the narrow gap bevel.

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