RU2704874C1 - Hybrid ultrasonic welding method and device for its implementation - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to welding production and can be used in hybrid laser welding with ultrasonic effect on welding bath. Method involves synchronous movement of the ultrasonic exposure instrument together with the laser radiation source and the welding arc burner throughout the welding process. At the same time prior to the beginning of the welding process, the ultrasonic action instrument is installed in a position providing its direct contact with the surface of one of the welded workpieces at a distance before the welding bath equal to or a multiple half-length of the ultrasonic radiation wave, and pressing tool to workpiece in point of contact with specified force, and during entire welding process in automatic mode provides continuous contact of said tool with surface of workpiece with given constant pressing force.EFFECT: use of the invention improves the quality of welded joints.4 cl, 4 dwg

Description

FIELD OF TECHNOLOGY

The invention relates to the field of welding, namely hybrid laser welding and can be used to improve the structure of the welded joint and reduce the defectiveness of the weld in the process of industrial hybrid laser welding of large-sized products from various metal materials.

BACKGROUND OF THE INVENTION

Known technical solutions in which the improvement of the quality of the welded joint is achieved by either affecting the joint zone by ultrasound during the welding process (non-contact), or by applying ultrasonic vibrations to the welded workpiece (mechanical contact).

For example, China's application [CN105710537 (A) - 2016-06-29] discloses a laser assisted ultrasonic assisted laser arc welding of aluminum alloys. Based on the combination of TIG electric arc welding and laser welding, ultrasonic vibration pressure is introduced into the weld, where the developed vibration head is in direct contact with the weld. Due to this, most of the gas in the weld is removed, so that defects in the welds are reduced or eliminated; due to the effect of cavitation and the acoustic effect caused by the fact that ultrasonic waves are transmitted to the liquid; and the welding residual stress is effectively eliminated or reduced, and the strength and corrosion resistance of the joint are increased. Ultrasound is applied through mechanical contact directly on the hardened weld metal behind the welding head.

The disadvantages include the fact that the movement of the ultrasound tool is not implemented simultaneously with the weld pool, therefore, along the entire length of the welded joint, an uneven structure of the weld can be obtained. Also, in this TIG welding method, welding with filler wire is not provided with the laser, which limits the possibility of welding thicker plates. The method is intended for laser electric arc welding only for aluminum alloys.

China's known application [CN105880852 (A) - 2016-08-24] for an invention disclosing a method for hybrid laser and electric arc welding of MIG ultrasonic assisted aluminum alloys only, in which the head of an ultrasonic vibrating tool has the ability to move relative to aluminum alloy plates to be welding. The head of the ultrasonic instrument performs reciprocating movements: in the direction of welding, the distance between the ultrasonic vibrating head and the welding area, which is 20-50 mm, is maintained. Contact pressure between the head of the ultrasonic vibrating tool and the aluminum alloy plate to be welded is also maintained between 0.2-0.6 MPa.

The disadvantages include the practical impracticability of the method for the production of large-sized products. The design solution of the installation involves a movable welding table (or workpiece).

Known Chinese patent CN104785926 (B) for the invention, which discloses the technology of laser welding MIG also only aluminum alloys with ultrasonic action. It proposes three types of ultrasonic exposure modes:

- ultrasonic vibration is applied to the workpiece or base plate, and ultrasound is transmitted to the weld pool by mechanical vibration of the workpiece or base plate;

- an ultrasonic pulse through a pulsed power source with an ultrasonic frequency is superimposed on the MIG power source, causing ultrasonic pulsation of the arc (hybrid laser-arc welding of steels with pulse modulation of the arc of the melting electrode);

- a pulsed laser is used, adapted to radiate an ultrasound beam into the weld pool (pulsed modulation of laser radiation), while the laser beam oscillates across the seam.

Those. the invention simultaneously proposes both the use of mechanical contact to realize ultrasonic vibration, and pulsations by the arc current or by a laser beam.

When using pulsed modulation of the arc or laser radiation, the effect occurs directly on the melt pool, but this is not enough to reduce the residual stresses that arise after crystallization of the metal during its cooling.

The stationary supply and fixing of the ultrasonic tool to the workpiece does not provide uniform power when transmitting vibrations along the entire length of the welded joint, and the application of vibrations to the base plate is an ineffective supply of ultrasonic vibrations.

In the technical solution, disclosed in the application of Japan [JP2008049351 A –2008-03-06] it is proposed to carry out an ultrasonic effect of a non-contact type. The main material being welded is melted by heating, and the molten part is irradiated by ultrasonic waves non-contact (there is a gap between the ultrasonic emitter and the workpiece, through which vibrations are transmitted to the weld pool) and hardens with stirring. The solution provides means for synchronizing the movement of the melting means with the movement of a non-contact ultrasonic waveguide. In a preferred embodiment, a tungsten electrode inert gas arc welding apparatus is used as the melting means. The device can be supplemented with a laser.

The disadvantages of this solution include the fact that with the non-contact transmission of ultrasonic vibrations through the air gap, there is a weakening of the impact on the welding samples. This design involves excessive energy consumption to achieve the goal, otherwise it will not be effective to use an ultrasonic tool in the welding process with this design.

Also, with prolonged uninterrupted use, which production processes need, excessive heating of the sonotrode (waveguide) occurs due to the absorption of ultrasonic vibrations, and then up to its destruction. This remark is valid with excessive power of ultrasonic vibrations necessary for transmitting vibrations through the air gap.

Thus, there is a need to develop a method of hybrid laser welding with ultrasonic exposure, which allows us to solve the problem of manufacturing large-sized products from various materials in their industrial production, due to the production of high-quality welded joints along the entire length of the weld.

SUMMARY OF THE INVENTION

The problem to which this invention is directed is to provide an ultrasonic contact method with constant parameters on the weld pool along the entire length of the weld in the process of obtaining a welded joint by hybrid laser welding of large-sized products (up to 10 m) of various thicknesses made of various metals and alloys.

The technical result is an improvement in the operational characteristics of the welded joint, ensuring the required reliability of the welded structures and reducing the cost of eliminating defects in production by improving the structure of the welded joint and reducing the defectiveness throughout the entire weld.

Another technical result is the universality of the method or the ability to perform welded joints of products from various metals and alloys with improved performance characteristics.

The task is achieved by the fact that as in the known in the proposed method of hybrid laser welding with ultrasonic action throughout the welded joint carry out synchronous movement of the ultrasonic tool with the main energy sources (laser source and welding torch), while the tool for ultrasonic treatment (ultrasound - tool) is installed in front of them in the direction of welding.

New is that the ultrasonic action is carried out by the contact method using ultrasonic tools, while at the initial stage, before the start of the welding process, the ultrasonic tools are installed in the selected horizontal and vertical position in manual mode relative to the weld pool: in front of it at a distance l equal to or a multiple half-length of the wave of ultrasonic radiation (point of application) and pressed with the selected force to ensure continuous ultrasonic action on the weld pool, and then automatically During the entire welding process, a continuous operation ensures a constant clamping force of the indenter of the ultrasonic tool.

It is advisable that for synchronous movement of the ultrasound tool with a laser source and a welding torch, it is fixed on the same carriage with them.

In addition, an ultrasound tool with a tip in the form of a spherical carbide indenter is used.

At the same time, for tracking and adaptive adjustment of the continuous and constant clamping force of the ultrasound instrument to the surface of the workpiece, registration of deviations of its position in the horizontal direction with a piezoceramic sensor, which is installed on the body of the ultrasound instrument, is used.

The choice of the distance l equal to or a multiple of the half-wavelength of the ultrasonic radiation is due to the difference in the wavelengths of different materials, the sound propagating in them.

To implement the method proposed in the present invention, a device was developed (Fig. 1).

Ultrasound - a tool for setting it to a predetermined position relative to the weld pool and the surface of the workpiece to be welded and the possibility of its deviation from the preset position during welding, movably connected to a slider, which in turn is connected to the carriage, while the device contains means for manually adjusting the ultrasound tool to the specified position, as well as the control unit for the implementation of the adaptive control algorithm for clamping the ultrasound tool to the surface of the workpiece during the entire welding process, and the piezoceramic sensor is installed embedded on the body of the ultrasonic tool to track its position and connected to the mentioned control unit.

In addition, the means for manual adjustment of the ultrasound instrument include a helical gear for adjusting the position of the ultrasound instrument in the horizontal direction, mounted on one side of the carriage, and a helical gear for adjusting its position in the vertical direction, mounted on the other side of the carriage.

To realize the possibility of deviation from the set position, the fastening - the bracket of the ultrasonic tool in the lower part is connected to the slider through the axis of rotation.

In addition, the electronic control unit processes the signals from the piezoceramic sensor, and transmits a command to the actuator, providing a change in the force of pressing of the ultrasound instrument to the workpiece.

In this case, the actuator includes a stepper motor whose shaft is aligned with the end of the adjusting screw, which compresses the spring stop, on which the upper part of the fastening - bracket of the ultrasonic tool rests.

The ultrasound instrument contains a stepwise sonotrode (waveguide) and a tip attached to the end of the sonotrode (waveguide), while the tip is an indenter made of carbide material, the working end of which has a spherical shape.

The indenter is in contact with the surface of one of the workpieces being welded and ensures the transmission of ultrasonic action to the weld pool over the entire length of the welded joint.

The proposed method is designed to provide ultrasonic effects with constant parameters on the weld pool in the process of obtaining a welded joint over its entire length (up to 10 m).

A prerequisite for supplying ultrasound is the ability to control the position of the ultrasound tool in the horizontal and vertical direction relative to the weld pool. This is due to the fact that billets of various materials, which also have different thicknesses, are subject to hybrid laser welding. Vertical movement of the ultrasonic tool provides contact with the surface of the welded workpieces of various thicknesses. The horizontal movement of the ultrasonic tool provides a predetermined distance from the point of application of ultrasonic vibrations to the weld pool. This is due to the need to maintain the ultrasonic effect of a given intensity on the weld pool and is associated with the following factors. Firstly, the nature of the material being welded, as well as its thickness, determines the attenuation of the ultrasonic vibrations propagating in it. Secondly, the excessive intensity of ultrasonic vibrations leads to defects in the welded joint such as discontinuities and excessive penetration. Given these factors, a prerequisite for obtaining high-quality welded joints is the ability to control the position of the place of application of ultrasonic vibrations relative to the weld pool.

For the most effective impact on the weld pool, it is necessary to provide a distance from the contact of the carbide indenter with the surface of the welded workpieces to the weld pool equal to or a multiple of the half-wavelength of the emitted radiation . This is due to the properties of sound waves, which are periodically alternating compressions and discharges, the maximum peak of which is at multiples of the half-length of the radiation wave. The propagation velocity of sound waves, as well as the wavelength, for each material will be different. Given these factors, one of the necessary conditions for obtaining high-quality welded joints is the ability to adjust the position of the initial application of ultrasonic vibrations relative to the weld pool for a particular material of the welded workpieces.

A necessary condition is continuous contact with a constant clamping force of the tip of the ultrasound tool with the surface of the material being welded, which can be characterized by differences in thickness (within the tolerance of sheet metal), waviness, or a combination of these factors.

Initially, the clamping force is set in manual mode, and then during the welding process it is controlled using an adaptive mechanism for adjusting the parameters of ultrasonic action, based on continuous recording of deviations of the position of the ultrasonic instrument in the horizontal direction by a piezoceramic sensor and transmitting signals to the control unit, in which, using the developed software, , the signal is processed and sends the appropriate command to the actuator provided for in the fastening design of the ultrasonic tool ment to the carriage.

The solution described above minimizes the influence of possible surface roughness of the workpiece on the contact of the indenter with the material associated with uneven rolling of the sheet, and also provides uniform and necessary force, pressing the indenter of the ultrasonic tool.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 shows a side view of a device for attaching ultrasound tools to hybrid laser welding equipment.

In FIG. Figure 2 shows a front view and a rear view of a device for attaching an ultrasound instrument to hybrid laser welding equipment.

In FIG. 3 shows macro images of welded joints of steel 09Г2С (ASTM 516) after hybrid laser welding of FIG. 3a; hybrid laser welding with ultrasonic treatment, FIG. 3 b, hybrid laser welding with ultrasonic treatment at 630 W and adaptive adjustment, FIG. 3 c.

In FIG. 4 shows macro images of welded joints of steel 12X18H10T after hybrid laser welding of FIG. 4a; hybrid laser welding with ultrasonic treatment, power 600 W, with adaptive adjustment FIG. 4b.

DETAILED DESCRIPTION OF THE INVENTION

To implement the method proposed in the present invention, a device was developed (Fig. 1) containing a laser radiation source 1, a welding arc torch 2, and an ultrasonic instrument (ultrasonic tool) 3. For synchronous movement, an ultrasonic tool 3 with a laser radiation source 1 and a welding torch 2 is mounted on the carriage 4. The ultrasonic tool 3 with the mounting bracket 5 is movably connected through the axis of rotation 6 to the slider 7. The slider 7 is mounted on the carriage 4 with the possibility of horizontal and vertical movement together with the US tool relative to the carriage 4. To move the slider 7 relative to the carriage in the horizontal direction, it is equipped with a helical gear transmission 8 and holders 9, 10. The slider 7 is mounted on the holders 9 and 10. When the transmission screw 8 is rotated, the holders 9, 10 make translational motion, which is converted in the horizontal movement of the ultrasound - tool. The upper part of the bracket 5 is supported by a spring mechanism (stop) 11. To move the ultrasonic tool 3 in an upright position, the slider 7 is equipped with a helical gear 12 with a holder 13 (Fig. 2a). When the transmission screw is rotated, the translational movement of the slider 7 is provided, which is converted into the vertical movement of the ultrasound tool. To adjust the position of the ultrasonic tool in automatic mode, the device contains a spring mechanism (emphasis) 11, which is preloaded by the adjusting screw 14 installed in the support plate 15, mounted on the slider 7. The end of the adjusting screw 14 is aligned with the shaft of the stepper motor 16, also installed on the slider 7 through the support plate 17. The piezoceramic sensor 18 is placed on the body 19 of the ultrasound instrument.

The device operates as follows.

The initial horizontal position of the ultrasonic tool 3 is set by means of a helical gear transmission 8 with holders 9, 10 fixed on a slider 7, i.e. distance is set l  (figure 1) from the point of application of ultrasonic vibrations to the weld pool. When the transmission screw 8 is rotated, its holders 9, 10 perform translational motion in the horizontal direction together with the slider 7 and the ultrasonic tool 3.

The vertical movement of the ultrasonic tool 3, using a helical gear transmission 12, provides the initial clamping force of the carbide indenter 20, mounted on the sonotrode 21, with the surface of the welded workpieces. When the transmission screw 12 is rotated, the translational movement of the slider 7 is provided, which is converted into vertical movement of the ultrasonic tool 3.

The adaptive clamping mechanism of the ultrasonic tool 3 in the welding process is based on the registration of deviations of its position in the horizontal direction relative to the carriage 4 (around the axis of rotation 6) with a piezoceramic sensor 18.

Further, after registering the deviation from the optimal position of the ultrasonic tool 3 and processing the signal in the electronic control unit 22, it sends a corresponding command to the stepper motor 16, which rotates the screw 14. The screw 14 translates in the direction of the stop 11, as a result of which through the spring of the stop pressure is applied to the mount (upper part of the bracket) of the ultrasonic tool. The force provides rotation of the ultrasound tool relative to the axis of rotation so that when the tip of the ultrasound tool contacts the workpiece surface, the required pressure force on the material arises, providing continuous contact and adjustment of the clamp of the ultrasound tool in real time.

After fixing the blanks for the welding process, the initial position of the ultrasonic tool 3 was made in the following order:

- According to the known data on the propagation velocity of ultrasonic waves in the workpiece material, by adjusting screw 8, the distance l from the point of contact of the carbide indenter with the surface of the workpiece to the proposed weld pool is set equal to or a multiple of the ultrasound wave half-length.

- After setting the required value of l, we started to adjust the position of the ultrasound instrument in the vertical position with the screw 12.

An Fronius TPS 600i arc source was used as a welding arc torch 2, and an LS-15 ytterbium fiber laser with a wavelength of 1.6 μm was used as a laser source. As an ultrasonic instrument 3, a magnetostrictive transducer with an operating frequency of 21–23 kHz was used. The power of ultrasonic exposure ranged from 500 to 1200 W, with the possibility of regulation.

Example 1

Welded sheets of 09G2S structural steel - experimental samples, 300x240 mm in size, 5 mm thick.

Welding modes: laser power: 3.8 kW; arc current: 100 A; arc voltage: 35 V; welding speed: 2.5 m / min; filler wire feed speed: 1.6 m / min; filler wire diameter: 0.8 mm.

For comparison, the samples were welded without ultrasonic exposure and using ultrasonic exposure at two power values: 1200 W and 630 W. At a power of 1200 W without adaptive process control, and at a power of 630 W with adaptive control, according to the invention.

The contact point of the ultrasound instrument with the surface of the sample (the point of application) was determined 155 mm from the weld pool, which corresponds to an entire wavelength . The data on the propagation of sound waves for this material are taken from the reference book [N.I. Koshkin, M.G. Shirkevich (1972) Handbook of elementary physics. Moscow, 106 pp.].

The required constant indenter clamping force of 0.45 MPa ± 5% was determined experimentally.

Comparative research results are shown in FIG. 3. As can be seen from the images, the sample obtained without the use of ultrasonic vibrations and the adaptive mechanism, FIG. 4a has pores observed throughout the weld. When ultrasonic action is included in the hybrid laser welding process, FIG. 3b, an uneven structure arises with a defect in the form of interdendritic shrinkage. In FIG. 3c, an adaptive adjustment of the clamping force of an ultrasound tool was included in the welding process with ultrasonic action, as a result of which a uniform structure without defects was obtained throughout the entire weld.

Example 2

Welded sheets of stainless steel 12X18H10T - experimental samples, 2.5 mm thick, 300x240 mm in size.

Welding modes: laser power: 2.5 kW, arc current: 85 A, arc voltage: 25 V, welding speed: 2.2 m / min, filler wire feed speed: 5.3 m / min, filler wire diameter: 0 , 8 mm.

The contact point of the ultrasound tool with the surface of the sample was 75 mm from the weld pool, which corresponds to the half-length of the wavelength.

Hybrid laser welding without ultrasonic treatment was performed. FIG. 4a and with the use of ultrasonic action with a power of 600 W with adaptive adjustment FIG. 4b, according to the described product. The required constant indenter clamping force of 0.45 MPa ± 5% was determined experimentally.

Due to the fact that in this welding mode, defect-free welds were obtained, emphasis was placed on differences in the boundary between the weld metal and the metal not subject to melting (fusion boundary). As seen in FIG. 4b, the fusion boundary has a complex form of adhesion and, as a result, better tensile strength between them.

Claims (4)

1. A method of hybrid laser welding with ultrasonic action on the weld pool, comprising synchronously moving the ultrasonic tool together with a laser source and a welding arc torch throughout the welding process, characterized in that before the start of the welding process, the ultrasonic tool is set to, providing direct contact with the surface of one of the welded workpieces at a distance in front of the weld pool is m or a multiple half-length of the wave of ultrasonic radiation, and they press the tool to the workpiece at the point of contact with the force selected from the condition for providing pre-set parameters of ultrasonic action, and then during the entire welding process automatically provide continuous contact of the said tool with the surface of the workpiece with constant force clip. 2. The method according to p. 1, characterized in that the ultrasonic tool is mounted on the same carriage with a laser source and a welding arc torch. 3. The method according to p. 1, characterized in that they use an ultrasonic tool with a tip in the form of a spherical carbide indenter. 4. The method according to one of paragraphs. 1-3, characterized in that the continuous contact of the ultrasonic tool with the surface of the workpiece with a given constant clamping force during the entire welding process in automatic mode is carried out by means of an adaptive adjustment mechanism that continuously records deviations of the position of the said tool in the horizontal direction using a piezoceramic sensor installed on the tool body, the transmission of appropriate signals to the control unit for their rabotki for a given program, and the direction corresponding to the command from the control unit to the actuating mechanism mounted in the support structure of the ultrasonic impact tool.

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