CN113369640A - Control method for stirring and balanced oscillation of deep-melting K-TIG welding pool - Google Patents
Control method for stirring and balanced oscillation of deep-melting K-TIG welding pool Download PDFInfo
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- 238000003466 welding Methods 0.000 title claims abstract description 198
- 238000000034 method Methods 0.000 title claims abstract description 49
- 238000003756 stirring Methods 0.000 title claims abstract description 38
- 230000010355 oscillation Effects 0.000 title claims abstract description 35
- 238000002844 melting Methods 0.000 title claims abstract description 27
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 123
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 123
- 239000010937 tungsten Substances 0.000 claims abstract description 123
- 229910001338 liquidmetal Inorganic materials 0.000 claims abstract description 48
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- 239000011261 inert gas Substances 0.000 description 3
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/095—Monitoring or automatic control of welding parameters
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
- B23K9/167—Arc welding or cutting making use of shielding gas and of a non-consumable electrode
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Abstract
本发明涉及一种深熔K‑TIG焊接熔池搅拌与平衡震荡的控制方法，在钨针沿焊接方向运动的同时，控制钨针做轴向运动以调节钨针与焊件之间距离，调整钨针在轴向运动中最低位置与最高位置之间的运动状态，并同步调整焊接电源系统输出的焊接电流，使焊接熔池的受力状态和热传输状态不断发生变化，进而改变焊接熔池中液态金属在径向上和轴向上的运动状态，从而在焊接熔池形成搅拌与震荡效果。本发明方法无需添加外围辅助焊接设备，而是在原有的深熔K‑TIG焊接设备的基础上，通过耦合钨针高度变化和焊接电流变化，使得熔池状态发生改变，实现熔池搅拌震荡的效果，以更低的热输入能量实现单面焊双面成形的焊接过程，熔池的熔透性好，程序移植性好。
The invention relates to a control method for deep-melting K-TIG welding molten pool stirring and balanced oscillation. When the tungsten needle moves along the welding direction, the tungsten needle is controlled to move axially to adjust the distance between the tungsten needle and the weldment. The movement state between the lowest position and the highest position of the tungsten needle in the axial movement, and the welding current output by the welding power supply system is adjusted synchronously, so that the stress state and heat transfer state of the welding pool are constantly changed, and then the welding pool is changed. The movement state of the liquid metal in the radial direction and the axial direction, so as to form a stirring and oscillating effect in the welding pool. The method of the invention does not need to add peripheral auxiliary welding equipment, but on the basis of the original deep-melting K-TIG welding equipment, by coupling the change of the height of the tungsten needle and the change of the welding current, the state of the molten pool is changed, and the stirring and oscillation of the molten pool is realized. As a result, the welding process of single-sided welding and double-sided forming can be realized with lower heat input energy, and the penetration of the molten pool is good, and the program portability is good.
Description
Technical Field
The invention relates to the technical field of welding, in particular to a control method for stirring and balanced oscillation of a deep-melting K-TIG (tungsten inert gas) welding pool.
Background
TIG Welding (Tungsten Inert Gas Welding), also known as non-consumable Inert Gas arc Welding. The welding machine is connected in a way that the workpiece is connected with the positive pole of a power supply, and the tungsten needle in the welding gun is used as the negative pole. In the Keyhole-Turnsten insert Gas (K-TIG) welding process, liquid metal is rapidly generated at a welding joint under the action of large current (more than 500A), so that a welding pool is formed. The uneven heat transfer process of instantaneous heating melting and instantaneous cooling solidification during welding makes the welded joint produce great welding residual stress and strain easily, influences the mechanical properties and the life of welded joint, forms thick and large columnar crystal structure with strong directionality easily in the uneven heat transfer solidification process simultaneously, and these columnar crystal structures not only need to reduce the intensity of welded joint, have still reduced the plasticity and the toughness of welding seam, produce extremely adverse effect to the quality of welded joint.
Improving the solidification and crystallization structure of weld metal by controlling the dynamic behavior of a weld pool or the heat transfer process is one of the most important methods for improving the quality of a welded joint. Two methods are commonly used in welding production to improve the weld metal crystalline structure: alloying and vibration methods. Alloying is to add certain alloying elements to the weld pool to modify the crystalline state through the metallurgical action of the weld and improve the weld structure, however, in some cases, it is difficult to add elements to the weld or it is not allowable to change the content of the metal component of the weld, and thus the method is limited to a certain extent. The vibration method is that external force is applied to liquid metal melted in a welding molten pool, so that the molten pool is crystallized in a vibration state, growing dendrites are damaged, fine grains are obtained, and the metal structure of a welding seam is improved. The low-frequency mechanical vibration is realized in a mechanical mode, the amplitude is below 2mm, the energy generated by the vibration can break dendritic crystals growing in a molten pool, and simultaneously, the molten pool metal can generate a strong stirring effect, so that the components are uniform, and gas, impurities and the like can quickly float upwards, thereby improving the performance of a welding seam. The high-frequency ultrasonic vibration is to use a professional generator to generate ultrasonic waves with the frequency of thousands of hertz, so that the solidifying metal in a welding pool is subjected to a tensile-compression alternating stress state, grown dendrites are damaged, the crystal form is changed, and grains are refined. The electromagnetic stirring method utilizes an external magnetic field to make liquid metal in a molten pool generate strong stirring motion, the growth direction of dendritic crystals is disturbed, the crystal form is changed, the crystal grains are refined, the residual stress of a joint can be reduced, and the performance of a welding joint is improved. The vibration method is really effective in changing the crystal form, refining the crystal grains, eliminating the defects of air holes, impurities and the like, improving the performance of a welding joint and the like, but the vibration method needs more complex equipment, has higher cost and lower efficiency, and has certain difficulty in wide application in welding production.
In recent years, some researchers have adopted a current waveform control method to generate a welding pool stirring effect, for example, a dual-power structure of MIG welding and pulse TIG welding is adopted, and a dual-arc vibration mode of front-end arc offset vibration and rear-end arc pulse fluctuation is formed by utilizing an electromagnetic repulsion effect between a direct-current reverse-connection arc and a direct-current forward-connection pulse arc. In addition, a welding method of integrating a master power supply and a slave power supply is adopted, a main power supply outputs low-frequency pulse current, a slave power supply outputs direct current, the low-frequency pulse current is chopped and modulated by a high-frequency chopping modulation technology, high-frequency pulse current superposition is completed, the fast-frequency pulse deep-melting lockhole welding is realized, and the balance oscillation of a molten pool is synchronously carried out in the lockhole process. However, the hybrid power supply is easy to generate mutual interference, which affects the stability of the welding process, and increases the complexity of the power supply equipment, and brings great inconvenience to equipment installation, test and debugging in actual welding, especially in the application of large-scale welding workpieces.
In summary, the prior art for controlling the stirring action of the weld pool has the following limitations:
(1) in the prior art, a method of adding auxiliary equipment on the basis of original welding equipment is adopted, and the functions of the auxiliary equipment and the welding equipment are coupled, so that the stirring effect of a welding molten pool is realized.
(2) In the prior art, certain mutual interference exists between main welding equipment and auxiliary equipment, and unreasonable parameters of the auxiliary equipment can bring adverse effects to the normal work of the main welding equipment, but the stability of the welding process is affected, and the welding quality is reduced.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention aims to: the control method for stirring and balanced oscillation of the deep-melting K-TIG welding molten pool is provided, peripheral auxiliary welding equipment is not required to be added, the molten pool state is changed by coupling the height change of a tungsten needle and the change of welding current, the effect of stirring oscillation of the molten pool is realized, and the welding quality is good.
In order to achieve the purpose, the invention adopts the following technical scheme:
a control method for stirring and balanced oscillation of a deep-melting K-TIG welding pool comprises the steps of controlling a tungsten needle to move axially while the tungsten needle moves along a welding direction so as to adjust the distance between the tungsten needle and a weldment, adjusting the motion state of the tungsten needle between the lowest position and the highest position in the axial movement, synchronously adjusting welding current output by a welding power supply system, enabling the stress state and the heat transmission state of the welding pool to be changed continuously, further changing the motion states of liquid metal in the welding pool in the radial direction and the axial direction, and accordingly forming stirring and oscillation effects on the welding pool.
Further, changing the motion state of the liquid metal in the welding pool comprises controlling the liquid metal on the surface of the welding pool to flow from the edge of the welding pool to the center of the welding pool, and controlling the liquid metal in the welding pool to flow from the upper part of the welding pool to the root part of the welding pool and then flow to the inner surface of the welding pool along a liquid/solid interface; alternatively, the liquid metal on the surface of the molten pool is controlled to flow from the center of the molten pool to the edge of the molten pool, and the liquid metal in the molten pool flows from the inner surface of the molten pool to the root of the molten pool along the liquid/solid interface and then flows to the upper part of the molten pool.
Further, controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to jump from a highest position to a lowest position and then from the lowest position to the highest position, and repeating the steps, wherein when the tungsten needle is in a low position area, the welding power supply system outputs low-frequency pulse current, and when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current.
Further, controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to gradually move from a lowest position to a highest position and then jump from the highest position to the lowest position, and repeating the steps, wherein when the tungsten needle is in a low position area, the welding power supply system outputs low-frequency pulse current, and when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current.
Further, controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to gradually move from a lowest position to a highest position, then gradually move from the highest position to the lowest position, and repeating the steps, wherein when the tungsten needle is in a low position area, the welding power supply system outputs low-frequency pulse current; when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current.
Further, the low-frequency pulse current and the high-frequency pulse current adopt the same peak current IpSum base current IbThe duty ratio of the low-frequency pulse current and the high-frequency pulse current is D-80%.
Further, the frequency f of the high-frequency pulse currentH5 x low frequency pulse current frequency fLPeak current Ip＝1.1ImBase value current Ib＝0.6ImAnd satisfies the following relationships:
DIp+(1-D)Ib＝Im；
in the formula ImThe average current of the low-frequency pulse current and the high-frequency pulse current is equal to the direct current I during the critical penetration of the molten poolmNamely, the input energy during the critical penetration of the molten pool is adopted to realize the complete penetration of the molten pool.
Further, in a molten pool oscillation period, the low-frequency pulse current time TLPAnd a high frequency pulse current time THPThe following relation is satisfied:
wherein f is the bath oscillation frequency HmaxHeight of highest position of tungsten needle, HminHeight of the lowest position of the tungsten needle HDThe height of the tungsten needle is adjusted by current. When the highest position H of the tungsten needlemaxAnd the lowest position H of the tungsten needleminAfter determination, the parameter H is adjustedDThe low frequency pulse current time and the high frequency pulse current time can be adjusted.
Further, the motion trail of the tungsten needle is controlled by a robot control system, the robot control system and the welding power supply system are cooperatively controlled, the robot control system sends a current adjusting signal to the welding power supply system according to the position of the tungsten needle, and the welding power supply system correspondingly outputs welding current according to the characteristics of the current adjusting signal, so that the welding current is converted between low-frequency pulse current and high-frequency pulse current.
Further, the robot control system determines the position of the tungsten needle according to the low-frequency pulse current time and the high-frequency pulse current time timed by the timer, the characteristics of the current adjusting signal comprise a low-frequency pulse current mark and a high-frequency pulse current mark, the output welding current is adjusted from the low-frequency pulse current to the high-frequency pulse current or from the high-frequency pulse current to the low-frequency pulse current, when the welding power supply outputs the low-frequency pulse current, if the low-frequency pulse current mark is received, the welding power supply outputs the unchanged, and if the high-frequency pulse current mark is received, the welding power supply outputs the high-frequency pulse current; when the welding power supply outputs high-frequency pulse current, if the high-frequency pulse current mark is received, the welding power supply output is unchanged, and if the low-frequency pulse current mark is received, the welding power supply outputs low-frequency pulse current.
In summary, the present invention has the following advantages:
(1) according to the method, peripheral auxiliary welding equipment is not required to be added, and on the basis of the original deep-melting K-TIG welding equipment, the state of the molten pool is changed by coupling the height change of the tungsten needle and the change of the welding current, so that the effect of stirring and oscillating of the molten pool is realized, the cost is low, and the practicability is good.
(2) The method realizes the welding process of single-side welding and double-side forming with lower heat input energy, and has good fusion permeability of a molten pool and high welding efficiency.
(3) Through program cooperative control, the state and the welding current of the welding gun tungsten needle are changed, and the method is convenient and quick, good in debugging performance and good in program portability.
Drawings
FIG. 1(a) is a schematic view showing the flow of liquid metal from the edge of the molten bath to the center of the molten bath at the surface of the molten bath;
FIG. 1(b) is a schematic view showing the flow of liquid metal from the center of the molten bath to the edge of the molten bath on the surface of the molten bath;
FIG. 2 is a schematic view showing the coupling effect of the motion state of the tungsten needle and the welding current in the first embodiment;
FIG. 3 is a schematic view showing the coupling effect of the motion state of the tungsten needle and the welding current in the second embodiment;
FIG. 4 is a schematic view showing the coupling effect of the motion state of the tungsten needle and the welding current in the third embodiment;
FIG. 5 is a graph of peak current, base current, and duty cycle for a constant input energy;
FIG. 6 is a graph of the relationship between low pulse current time and high pulse current time in the second embodiment;
FIG. 7 is a graph of the relationship between low pulse current time and high pulse current time in the third embodiment.
Detailed Description
The present invention will be described in further detail below.
A control method for stirring and balanced oscillation of a deep-melting K-TIG welding pool comprises the steps of changing the position height of a tungsten needle and changing the welding current output by a deep-melting K-TIG welding power supply system through a robot control system, and changing the stress state and the heat transmission process of the welding pool through cooperatively controlling the change of the position height of the coupled tungsten needle and the change of the welding current, so that the motion states of liquid metal in the welding pool in the radial direction and the axial direction are changed, and the stirring and oscillation effects of the welding pool are generated.
In the welding process, the liquid metal in the molten pool is subjected to the comprehensive action of electric arc force, electromagnetic force, surface tension and other forces, and violently moves according to a certain rule, so that the transmission process of energy, momentum and mass in the welding molten pool is carried out. Under the action of electromagnetic force, the liquid metal on the surface of the welding molten pool flows from the edge of the molten pool to the center of the molten pool, and the liquid metal in the welding molten pool flows from the upper part of the molten pool along the central line to the root part and then flows along the liquid/solid interface to the inner surface of the molten pool. The surface tension causes convection of the liquid metal in the weld pool, causing it to flow in the direction of increasing surface tension. The welding arc generates positive pressure and radial shearing force on the surface of the molten pool, so that the surface of the welding molten pool is deformed, and the liquid metal of the molten pool is pushed to flow outwards in the radial direction by the shearing force.
As shown in FIG. 1(a), the molten metal movement state of the molten bath includes a state in which the liquid metal on the surface of the molten bath flows from the edge of the molten bath toward the center of the molten bath, and the liquid metal in the molten bath flows from the upper portion of the molten bath toward the root along the center line and further flows toward the inner surface of the molten bath along the liquid/solid interface. As shown in FIG. 1(b), the liquid metal on the surface of the molten bath flows from the center of the molten bath toward the edge of the molten bath, and the liquid metal in the molten bath flows from the inner surface of the molten bath toward the root along the liquid/solid interface and further toward the upper part of the molten bath along the center line.
The welding current includes a low frequency pulse current and a high frequency pulse current. Under the action of pulse current, the liquid metal on the surface of the molten pool flows from the center of the molten pool to the periphery, and two outward eddy currents flowing from the center of the molten pool to the edge are arranged on the symmetrical plane. On the cross section of the welding seam, the flow fields are symmetrically distributed, the center of a vortex in a molten pool is close to a mushy zone at the edge of the molten pool, the molten metal flowing outwards turns at the front edge of the solid-liquid interface of the molten pool, flows into the interior of the molten pool at the edge of the molten pool, and sends high-temperature molten metal on the surface into the molten pool, heat is transferred to workpiece metal at the bottom of the molten pool, the melting of the zone is accelerated, the molten low-temperature metal and the cooled high-temperature molten metal are brought to the central zone of the molten pool together by the moving fluid, the flow direction changes again near the central line, the fluids at two sides of the symmetrical axis meet, flow to the high-temperature surface from the bottom of the molten pool, and heat of the electric arc is obtained again on the surface, and the circulation is continuous, so that a relatively wide and shallow welding seam is formed. Due to the backward dragging of the molten pool, the maximum penetration depth of the molten pool and the maximum capacity width of the molten pool do not exist on one section synchronously, the maximum penetration depth lags behind the maximum capacity width, and the penetration capacity width is increased along with the increase of welding current.
The change of the position height of the tungsten needle comprises three modes, namely jumping from a lowest position to a highest position and then jumping from the highest position to the lowest position, gradually moving from the lowest position to the highest position and then jumping from the highest position to the lowest position, and gradually moving from the lowest position to the highest position and then gradually moving from the highest position to the lowest position. Assuming that the height of the tungsten needle is H, the height of the highest position of the tungsten needle is HmaxThe height of the lowest position of the tungsten needle is HminSetting the height of the tungsten needle to be H during current adjustmentDWhen the tungsten needle is at the lowest position height HminAnd the position height HDWithin a region, i.e., H ∈ [ H ]min,HD]Called low position region, when the tungsten needle is at the position height HDAnd the highest position height HmaxWithin a region, i.e., H ∈ [ H ]D,Hmax]Referred to as high position area.
The invention discloses a control method for stirring and balanced oscillation of a deep melting K-TIG welding pool, which comprises the following three control methods:
example one
As shown in fig. 2, when the tungsten needle jumps from the highest position to the lowest position, the tungsten needle is in the low position area, and the welding power supply system outputs low-frequency pulse current; when the tungsten needle jumps from the lowest position to the highest position, the tungsten needle is in a high position area, and the welding power supply system outputs high-frequency pulse current.
Example two
As shown in fig. 3, when the tungsten needle moves gradually from the lowest position to the highest position, the tungsten needle enters the high position region from the low position region, and when the tungsten needle is in the low position region, the welding power supply system outputs a low-frequency pulse current; when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current; when the tungsten needle jumps from the highest position to the lowest position, the tungsten needle enters the low position area from the high position area, and the welding power supply system outputs low-frequency pulse current.
EXAMPLE III
As shown in fig. 4, when the tungsten needle moves gradually from the lowest position to the highest position, the tungsten needle enters the high position region from the low position region, and when the tungsten needle is in the low position region, the welding power supply system outputs a low-frequency pulse current; when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current; when the tungsten needle position gradually moves from the highest position to the lowest position, the tungsten needle enters the position area from the high-low position area, and when the tungsten needle is in the high position area, the welding power supply system outputs high-frequency pulse current; when the tungsten needle is in the low position area, the welding power supply system outputs low-frequency pulse current.
In the first, second and third embodiments, when the welding power supply system outputs the low-frequency pulse current, the distance between the welding gun tungsten needle and the molten pool is small, the current density on the surface of the molten pool is large in the peak current stage, the electric arc force applied to the molten pool is large, and the contact surface of the electric arc force to the molten pool is large; on the other hand, because of the difference of heat dissipation environments in the lock hole of the molten pool, the liquid metal of the molten pool has a temperature gradient, namely the temperature from the middle part to the edge part of the molten pool is decreased, the temperature from the front end to the rear end of the molten pool is also decreased, the surface tension of the liquid metal is a function of the temperature, and the surface tension is increased along with the decrease of the temperature, so that the surface tension gradient also exists on the wall of the molten pool, namely the surface tension of the edge part of the molten pool is greater than that of the middle part of the molten pool, and the surface tension of the front end of the molten pool is less than that of the rear end of the molten pool. The liquid metal on the wall of the molten hole flows backwards and downwards, and when the welding process is stable, the molten hole moves along with the change of the position of the welding gun. In the stage of base current, welding current is reduced, heat input energy is reduced, electric arc force is reduced, surface tension changes direction due to the change of the direction of temperature gradient, larger surface tension gradient exists, liquid metal on the surface of a molten pool changes the momentum direction of the molten pool under the action of gravity due to the reduction of the electric arc force, larger momentum gradient exists, the liquid metal on the surface of the molten pool flows back or tends to flow back from the edge of the molten pool to the center of the molten pool under the action of the tension gradient and the momentum gradient, the liquid metal at the bottom of the molten pool begins to solidify, the front end of the molten pool is always acted by the electric arc force, and the liquid metal flows to the rear end of the.
When a welding power supply system outputs high-frequency pulse current, the distance between a welding gun tungsten needle and a molten pool is larger, the electromagnetic force of an electric arc per se is increased along with the increase of the frequency of the pulse current in a peak current stage, a stronger magnetic compression effect is caused by the electromagnetic force of the electric arc and the airflow around the electric arc, the diameter of the electric arc is reduced, the contact surface of the electric arc force and the molten pool is reduced, the acting force of the electromagnetic force of the electric arc on the molten pool is larger than the acting force of the electric arc force and the surface tension on the molten pool, liquid metal on the surface of the molten pool flows to the center of the molten pool from the edge of the molten pool and the rear end of the molten pool under the action of the electromagnetic force of the electric arc, the liquid metal in the center of the molten pool flows to the bottom of the molten pool from the bottom along a liquid/solid interface, in a base current stage, the acting forces of the electromagnetic force, the electric arc force and the surface tension on the molten pool are reduced, and the liquid metal in the center of the molten pool is blocked from flowing to the bottom, thereby further hindering the liquid metal on the surface of the molten pool from flowing from the edge of the molten pool and the rear end of the molten pool to the center of the molten pool, and the liquid metal on the surface of the molten pool flows from the center of the molten pool to the edge of the molten pool under the action of the tension gradient and the momentum gradient due to the momentum gradient existing in the change of the fluidity of the liquid metal.
According to the analysis process, the motion states of the liquid metal on the surface of the molten pool are different in the pulse current peak value stage and the pulse current base value stage, so that a certain stirring oscillation effect is generated. The duty ratio of the low-frequency pulse current and the high-frequency pulse current is 80 percent, the influence of the pulse current on the motion state of the liquid metal on the surface of the molten pool is mainly reflected in the peak value stage, because the acting time of the base value current is short, the motion state of the liquid metal of the molten pool is not changed, the peak value current is switched, the state of motion of the liquid metal on the surface of the molten pool appears to flow from the center of the molten pool to the edge of the molten pool and the rear end of the molten pool when the low-frequency pulse current is output, when high-frequency pulse current is output, the motion state of liquid metal on the surface of the molten pool is shown to flow from the edge of the molten pool and the rear end of the molten pool to the center of the molten pool, the motion state of the liquid metal on the surface of the molten pool is different when the low-frequency pulse current is output and the high-frequency pulse current is output, the secondary stirring and shaking effect on the molten pool is more obvious than the primary stirring and shaking effect generated in the pulse current peak value stage and the pulse current basic value stage. In the first embodiment, the tungsten needle enters the high position region from the low position region or enters the low position region from the high position region in a jumping manner, and when the low-frequency pulse current and the high-frequency pulse current are switched, a relatively violent stirring and vibrating effect is generated on the molten pool. In the second embodiment, the tungsten needle enters the high position area from the low position area in a gradual change mode, the height of the tungsten needle is gradually increased, when the low-frequency pulse current and the high-frequency pulse current are switched, the situation that acting force on a molten pool is also suddenly changed due to sudden change of pulse frequency is improved, the stirring oscillation effect on the molten pool is mild, and the tungsten needle enters the low position area from the high position area in a jumping mode, so that the violent stirring oscillation effect on the molten pool is generated. In the third implementation, the tungsten needle enters the high position area from the low position area or enters the low position area from the high position area in a gradual change mode, and when the low-frequency pulse current and the high-frequency pulse current are switched, the stirring and shaking effect on the molten pool is mild.
As shown in fig. 2-4, when the tungsten needle is in the low position area, the welding power supply system outputs low-frequency pulse current, the arc force and the surface tension are large, the contact surface with the molten pool is large, the current density is large, the arc stiffness is large, the molten metal is more, the fusion width and the fusion depth are large, and the fusion permeability of the molten pool is good; when the tungsten needle is in the high position area, the electric arc force and the surface tension are reduced, the contact surface with a molten pool is reduced, the fusion width and the fusion depth are reduced, the molten pool permeability is poor, when a welding power supply system outputs high-frequency pulse current, the electromagnetic force of the electric arc is increased, the stiffness of the electric arc is increased, the fusion depth of the molten pool is good, and the fusion permeability of the molten pool is ensured when the tungsten needle is in the low position area and the high position area, so that the effect of balancing the molten pool oscillation is achieved.
In the first, second and third embodiments, the peak current I is the same as the peak current I for the low frequency pulse current and the high frequency pulse currentpSum base current IbIs provided with Ip＝kpIm，Ib＝kbImThe duty ratio is D, the peak current ispBase current IbAnd duty cycle D satisfies the following relationship:
DIp+(1-D)Ib＝Im；
Dkp+(1-D)kb＝1；
in the formula ImIs the direct current k at critical penetration of the molten poolpIs the peak current IpAnd a direct current ImRatio of (a) to (b), kbIs a base value current IbAnd a direct current ImThe average current of the low-frequency pulse current and the high-frequency pulse current is equal to the direct current I when the melting pool is in critical penetrationmNamely, the input energy during the critical penetration of the molten pool is adopted to realize the complete penetration of the molten pool.
According to the actual welding parameter setting, the ratio kp>1, and the ratio kb<1 and>0, their relationship satisfies the series relation:
when the ratio k ispWhen the ratio is 1.1, 1.2, 1.3, 1.4 and 1.5, the ratio k isbThe relationship with the duty ratio D is shown in FIG. 5 when the ratio k ispA timing, ratio kbDecreases as the duty cycle D increases; while following the ratio kpIncreasing the value of the duty ratio D, and when the ratio k is increasedpWhen the duty ratio is 1.1, the duty ratio D is less than or equal to 0.9; when the ratio k ispWhen the duty ratio is 1.2, the duty ratio D is less than or equal to 0.83; when the ratio k ispWhen the duty ratio is 1.3, the duty ratio D is less than or equal to 0.76; when the ratio k ispWhen 1.4, it is accounted forThe space ratio D is less than or equal to 0.71; when the ratio k ispWhen the duty ratio is 1.5, the duty ratio D is less than or equal to 0.66.
In the embodiment of the present invention, it is preferable that the duty ratio D of the low frequency pulse current to the high frequency pulse current is 80%, and the ratio k isp1.1, ratio kb0.6, peak current Ip＝1.1ImBase value current Ib＝0.6ImThe frequency of the high-frequency pulse current being 5 times the frequency of the low-frequency pulse current, i.e. fH＝5fL。
In the above embodiment, the low-frequency pulse current time T is within one molten pool oscillation periodLPAnd a high frequency pulse current time THPDetermined by the following relationship:
wherein f is the bath oscillation frequency HmaxHeight of highest position of tungsten needle, HminHeight of the lowest position of the tungsten needle HDThe height of the tungsten needle is adjusted by current, and when the height of the tungsten needle is the highestmaxAnd the lowest position height H of the tungsten needleminAfter determination, the parameter H is adjustedDThe low frequency pulse current time and the high frequency pulse current time can be adjusted.
As shown in fig. 6, which is a graph of the relationship between the low pulse current time and the high pulse current time in the second embodiment, the tungsten needle is located in the low position region when gradually moving from the lowest position to the position a, the welding power source outputs the low frequency pulse current, the welding power source enters the high position region after passing through the position a, the welding power source outputs the high frequency pulse current, the tungsten needle jumps to the lowest position after reaching the highest position, the welding power source outputs the low frequency pulse current, and the low frequency pulse current flowsStreaming time TLPAnd a high frequency pulse current time THPThe following relation is satisfied:
as shown in fig. 7, which is a graph of a relationship between low pulse current time and high pulse current time in the third embodiment, when the tungsten needle moves gradually from the lowest position to the position a, the tungsten needle is located in the low position region, the welding power source outputs a low frequency pulse current, the tungsten needle passes through the position a and enters the high position region, when the tungsten needle reaches the highest position, the tungsten needle moves gradually to the position a ', the tungsten needle moves from the position a to the position a ', the tungsten needle is located in the high position region, the welding power source outputs a high frequency pulse current, the tungsten needle passes through the position a ' and enters the high position region, the welding power source outputs a low frequency pulse current, and the low frequency pulse current time T is obtained by the welding power sourceLPAnd a high frequency pulse current time THPThe following relation is satisfied:
TLP1+TLP2＝TLP；
THP1+THP2＝THP；
in the formula, TLP1The low-frequency pulse current time T when the tungsten needle moves gradually from the lowest position to the highest positionHP1The high frequency pulse is generated when the tungsten needle moves from the lowest position to the highest position graduallyTime of rush current, TLP2The low-frequency pulse current time T when the tungsten needle moves gradually from the highest position to the lowest positionHP2The high-frequency pulse current time when the tungsten needle moves gradually from the highest position to the lowest position.
When the tungsten needle moves gradually from the lowest position to the highest position, the following relation is satisfied:
when the tungsten needle moves gradually from the highest position to the lowest position, the following relation is satisfied:
low frequency pulse current in one oscillation period of the molten poolTime TLPAnd a high frequency pulse current time THPThe following relation is satisfied:
by combining the above analysis processes, the low-frequency pulse current time T in the first, second and third embodimentsLPAnd a high frequency pulse current time THPThe relation of (A) is consistent when the highest position H of the tungsten needle ismaxAnd the lowest position H of the tungsten needleminAfter determination, the low frequency pulse current time TLPTime T of high frequency pulse currentHPAnd adjusting the parameter HDIs in one-to-one correspondence, by setting the parameter HDThe low frequency pulse current time and the high frequency pulse current time can be set. During the welding process, the parameter H is measuredDThe low-frequency pulse current time T can be timed by a timerLPAnd a high frequency pulse current time THPTo set a parameter HD。
In the welding process, the robot control system controls the movement of the welding gun tungsten needle in the welding direction and also needs to control the welding gun tungsten needle to reciprocate in the axial direction, the robot control system and the deep-melting K-TIG welding power supply system realize cooperative control through CAN bus communication, and the robot control system times T according to a timerLPAnd THPTo determine the position of the tungsten needle and to generate a current regulation signal, the welding power supply system adjusting the output welding current from a low frequency pulse current to a high frequency pulse current or from a high frequency pulse current to a low frequency pulse current based on characteristics of the current regulation signal, the characteristics including a low frequency pulse current signature and a high frequency pulse current signature, when the welding power supply outputsDuring low-frequency pulse current, if a low-frequency pulse current mark is received, the output of the welding power supply is unchanged, and if a high-frequency pulse current mark is received, the welding power supply outputs high-frequency pulse current; when the welding power supply outputs high-frequency pulse current, if the high-frequency pulse current mark is received, the welding power supply output is unchanged, and if the low-frequency pulse current mark is received, the welding power supply outputs low-frequency pulse current.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A control method for stirring and balanced oscillation of a deep-melting K-TIG welding pool is characterized by comprising the following steps: when the tungsten needle moves along the welding direction, the tungsten needle is controlled to do axial movement to adjust the distance between the tungsten needle and a weldment, the movement state of the tungsten needle between the lowest position and the highest position in the axial movement is adjusted, and the welding current output by a welding power supply system is synchronously adjusted, so that the stress state and the heat transmission state of a welding molten pool are continuously changed, the movement states of liquid metal in the welding molten pool in the radial direction and the axial direction are further changed, and the stirring and oscillation effects are formed in the welding molten pool.
2. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 1, characterized by comprising the following steps: changing the motion state of the liquid metal in the welding molten pool comprises controlling the liquid metal on the surface of the welding molten pool to flow from the edge of the molten pool to the center of the molten pool, and controlling the liquid metal in the molten pool to flow from the upper part of the molten pool to the root part of the molten pool and then flow to the inner surface of the molten pool along a liquid/solid interface; alternatively, the liquid metal on the surface of the molten pool is controlled to flow from the center of the molten pool to the edge of the molten pool, and the liquid metal in the molten pool flows from the inner surface of the molten pool to the root of the molten pool along the liquid/solid interface and then flows to the upper part of the molten pool.
3. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 1, characterized by comprising the following steps: controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to jump from the highest position to the lowest position and then from the lowest position to the highest position, and repeating the steps, wherein when the tungsten needle is in the low position area, the welding power supply system outputs low-frequency pulse current, and when the tungsten needle is in the high position area, the welding power supply system outputs high-frequency pulse current.
4. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 1, characterized by comprising the following steps: controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to gradually move from a lowest position to a highest position and then jump from the highest position to the lowest position, and repeating the steps, wherein when the tungsten needle is in a low position area, the welding power supply system outputs low-frequency pulse current, and when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current.
5. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 1, characterized by comprising the following steps: controlling the motion state of the tungsten needle and adjusting the welding current comprises controlling the tungsten needle to gradually move from the lowest position to the highest position, then gradually moving from the highest position to the lowest position, and repeating the steps, wherein when the tungsten needle is in a low position area, the welding power supply system outputs low-frequency pulse current; when the tungsten needle is in a high position area, the welding power supply system outputs high-frequency pulse current.
6. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to any one of claims 3 to 5, characterized by comprising the following steps of: the low-frequency pulse current and the high-frequency pulse current adopt the same peak current IpSum base current IbThe duty ratio of the low-frequency pulse current and the high-frequency pulse current is D-80%.
7. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 6, characterized by comprising the following steps: frequency f of high-frequency pulse currentH5 x low frequency pulse current frequency fLPeak current Ip＝1.1ImBase value current Ib＝0.6ImAnd satisfies the following relationships:
DIp+(1-D)Ib＝Im；
in the formula ImIs the direct current when the melting pool is in critical penetration.
8. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 7, characterized in that: within a molten pool oscillation period, the low-frequency pulse current time TLPAnd a high frequency pulse current time THPThe following relation is satisfied:
wherein f is the bath oscillation frequency HmaxHeight of highest position of tungsten needle, HminHeight of the lowest position of the tungsten needle HDThe height of the tungsten needle is adjusted by current.
9. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 1, characterized by comprising the following steps: the motion trail of the tungsten needle is controlled by a robot control system, the robot control system and a welding power supply system are cooperatively controlled, the robot control system sends a current adjusting signal to the welding power supply system according to the position of the tungsten needle, and the welding power supply system correspondingly outputs welding current according to the characteristics of the current adjusting signal, so that the welding current is converted between low-frequency pulse current and high-frequency pulse current.
10. The method for controlling stirring and balanced oscillation of the deep-melting K-TIG welding pool according to claim 9, characterized in that: the robot control system determines the position of a tungsten needle according to the timing of low-frequency pulse current time and high-frequency pulse current time by a timer, the characteristics of a current adjusting signal comprise a low-frequency pulse current mark and a high-frequency pulse current mark, the output welding current is adjusted from the low-frequency pulse current to the high-frequency pulse current or from the high-frequency pulse current to the low-frequency pulse current, when the welding power supply outputs the low-frequency pulse current, if the low-frequency pulse current mark is received, the welding power supply outputs unchanged, and if the high-frequency pulse current mark is received, the welding power supply outputs the high-frequency pulse current; when the welding power supply outputs high-frequency pulse current, if the high-frequency pulse current mark is received, the welding power supply output is unchanged, and if the low-frequency pulse current mark is received, the welding power supply outputs low-frequency pulse current.
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