阅读说明：本技术 一种随焊超声与激冷复合的激光焊接方法 (Laser welding method combining welding-following ultrasound and chilling ) 是由 马广义 刘俊 吴东江 刘德华 牛方勇 于 2019-12-12 设计创作，主要内容包括：本发明属于焊接领域,涉及一种随焊超声与激冷复合的激光焊接方法。该方法在焊接过程中在熔池后方一定距离的焊缝背面施加冷却水并在正面施加超声振动；冷却水的温度和流量根据所用焊接方式确定；超声施加的位置、功率和力根据样件材料力学性能进行调整。本发明可以有效减小焊接残余应力,减少气孔和裂纹,从而提高焊缝的疲劳性能,同时减小焊接横向和纵向变形。随焊激冷可以有效减小纵向残余应力和变形。超声冲击可以抵消激冷和焊接所造成的横向应力,同时进一步抑制纵向应力,这样可以有效减小变形；超声的声流效应和空化效应可以细化晶粒并减少气孔和裂纹,从而提高焊缝的疲劳性能。(The invention belongs to the field of welding, and relates to a welding-following ultrasonic and chilling combined laser welding method. In the method, cooling water is applied to the back side of a welding seam at a certain distance behind a molten pool in the welding process, and ultrasonic vibration is applied to the front side; the temperature and the flow rate of the cooling water are determined according to the welding mode; the position, power and force of ultrasonic application are adjusted according to the mechanical property of the sample piece material. The invention can effectively reduce the welding residual stress and reduce air holes and cracks, thereby improving the fatigue property of the welding line and simultaneously reducing the transverse and longitudinal deformation of welding. The longitudinal residual stress and deformation can be effectively reduced by the welding chilling. The ultrasonic impact can offset the transverse stress caused by chilling and welding, and further inhibit the longitudinal stress, so that the deformation can be effectively reduced; the ultrasonic acoustic flow effect and the cavitation effect can refine grains and reduce air holes and cracks, thereby improving the fatigue property of the welding seam.)

1. A laser welding method combining welding ultrasound and chilling is characterized by comprising the following steps:

firstly, a clamp (1) is placed on a workbench, a workpiece (8) is placed on the clamp (1), copper clamping blocks are used for clamping the workpiece (8), and the distance between the clamping blocks is 4-8 mm; the coaxial protection of the workpiece (8) is realized by the protective gas through the coaxial protection device (7), and the axis of the protective gas nozzle is superposed with the axis of the laser;

when wire filling welding is carried out, a wire feeding mechanism (2) is arranged above a workpiece (8), a wire feeding head of the wire feeding mechanism (2) forms a angle of 20-40 degrees with the surface of the workpiece (8), the wire is fed out for 1-3 mm, the front end of the wire is aligned with the edge of a welding position, and then the wire is pressed down for 1-1.5 mm;

secondly, setting the position and ultrasonic parameters of the ultrasonic head (5)

Adjusting the ultrasonic head (5) to be 8-16mm behind the molten pool, setting the position of the ultrasonic head (5), and enabling the top end of the ultrasonic head (5) to be 0.1-0.2 mm away from the surface of the workpiece (8); after the angle and the position of the ultrasonic head (5) are determined, the ultrasonic head (5) and a machine tool cantilever are fixed, and the relative positions of the ultrasonic head and the machine tool cantilever are ensured;

thirdly, setting chilling parameters

Adjusting the position of a cooling water nozzle (9) to be behind a molten pool, wherein the distance d between the cooling water nozzle and the molten pool is 4-8 mm, the temperature T of the cooling water is-4-2 ℃, the flow Q of the cooling water is 30-90 ml/min, Q & gt 162 & gt η & gt is used for preventing the ultrasonic atomization effect from influencing the application of the cooling water, η is the efficiency of the ultrasonic action on the cooling water, and the distance H (unit: mm) between the cooling water nozzle (9) and a workpiece (8) in the vertical direction meets the following requirements:

fourthly, setting parameters of a heat source (6), wherein the laser single pulse energy is more than or equal to 2J and less than or equal to 2300 plus 1000P)/400 so as to ensure that effective welding can be realized and no thermal crack is generated, wherein the unit of E is J, and the unit of P is kW; the pulse width is set to be 2-8 ms;

fifthly, after the setting is finished, sequentially starting a cooling water nozzle (9), an ultrasonic power supply and a coaxial protective gas valve, wherein the protective gas is argon with the purity of 99.9 percent, the flow of the upper protective gas is 15l/min, and the flow of the lower protective gas is 3-15 l/min; starting a heat source (6) for welding after waiting for 5-10 s;

and sixthly, after welding, closing the heat source (6), the shielding gas and the cooling water in sequence.

2. A combined ultrasonic and shock welding laser welding method as set forth in claim 1 wherein said heat source (6) is a pulsed laser and the heat source (6) is perpendicular to the work surface of the workpiece (8).

3. The welding process of claim 1 or 2, wherein the ultrasonic power P of the ultrasonic head (5) is 0.4-1.5 kW.

4. The welding-following ultrasonic and chilling composite laser welding method according to claim 1 or 2, wherein the diameter of the cooling water nozzle (9) is 2-4 mm.

5. A welding-following ultrasonic and chilling composite laser welding method according to claim 3, wherein the diameter of the cooling water nozzle (9) is 2-4 mm.

6. The laser welding method combining ultrasonic welding and chilling according to claim 1, 2 or 5, wherein in the second step, the angle of the ultrasonic head (5) is set, and the adjustment range of the ultrasonic vibration incidence angle is 20-60 °.

7. A laser welding method combining ultrasonic welding and chilling according to claim 3, wherein in the second step, the angle of the ultrasonic head (5) is set, and the adjustment range of the ultrasonic vibration incidence angle is 20-60 °.

8. The welding-following ultrasonic and chilling combined laser welding method according to claim 4, wherein in the second step, the angle of the ultrasonic head (5) is set, and the adjustment range of the ultrasonic vibration incidence angle is 20-60 °.

9. The device adopted by any one of the welding-following ultrasonic and chilling composite laser welding method according to claims 1-8 is characterized by comprising a clamp (1), a wire feeding mechanism (2), a lower shielding gas inlet (3), a cooling water pump (4), an ultrasonic head (5), a heat source (6), a coaxial protection device (7), a cooling water nozzle (9) and a cooling water tank (10);

the clamp (1) is arranged on the upper surface of the workbench, a copper clamping block is used for clamping a workpiece (8), an ultrasonic head (5), a heat source (6) and a protective gas nozzle are arranged above the workpiece (8), and a cooling water nozzle (9) and a cooling water outlet are arranged below the workpiece (8); the heat source (6) is vertical to the processing surface of the workpiece (8), the protective gas nozzle realizes coaxial protection through the coaxial protection device (7), and the axis of the protective gas nozzle is superposed with the axis of the laser; the ultrasonic head (5) is connected with the amplitude transformer and the ultrasonic transducer, and then an ultrasonic power supply is connected into a circuit of the ultrasonic transducer; the cooling water nozzle (9) is connected with the cooling water pump (4) and the cooling water tank (10); a clapboard with small holes is arranged between the cooling water outlet and the cooling water nozzle (9) to ensure that the cooling water flows out; the wire feeding mechanism (2) is arranged above the workpiece (8), and the wire feeding mechanism (2) is adjusted to perform wire alignment during machining.

Technical Field

The invention belongs to the field of welding, and relates to a welding-following ultrasonic and chilling combined laser welding method.

Background

Welding is a heating and cooling process with localized heating and cooling. When heating, the metal around the welding seam expands and generates compression plastic deformation under the constraint action of the clamp. When cooled, the metal shrinks to produce tensile plastic deformation, elastic deformation and tensile stress, and the stress still existing after cooling to room temperature is residual stress. After the welding is finished and the clamp is loosened, the residual stress is redistributed, and the workpiece deforms under the action of the stress. It can be seen that the main cause of welding deformation is welding residual stress.

The workpiece may generate residual stress after welding, the generation of the residual stress may cause welding deformation, and fatigue property of the weld may be reduced. Therefore, it is important to reduce or eliminate residual stress in the welded structure. While many approaches have been explored for reducing or eliminating residual stresses, they are typically performed separately after welding, which is inefficient and difficult to handle for large welds; the newly developed method, although performed during the welding process, has difficulty in effectively eliminating the residual stress. Although the traditional ultrasonic technology along with welding can eliminate residual stress, some welding methods and materials have small high-temperature plastic areas and are close to a molten pool, so that the ultrasonic is difficult to apply to the high-temperature plastic areas.

Chinese patent CN 104726687B discloses a method and device for reducing or eliminating welding deformation and residual stress with welding ultrasonic impact, which designs a device for reducing deformation and residual stress by applying ultrasonic impact on the back of the welding seam. But ultrasonic impact is applied to the back of the workpiece, and the process system is complex.

Chinese patent CN1029669C discloses a low stress non-deformation welding method and device for dynamically controlling thin plate members, which designs a device for restraining longitudinal bending deformation of welding by using welding chilling. This method, however, can adversely affect the transverse deformation of the weld.

In a study on the influence of the front welding-following ultrasonic impact on welding residual stress and deformation in a university of Shandong Lidong on the academic paper, the deformation is improved by adopting a welding-following ultrasonic impact method, and experiments show that the deformation improving effect is best when the impact application position is 45mm away from a heat source. However, this method has a large distance between the heat source and the impact position, and is difficult to apply to small-sized parts.

In the study on laser welding deformation prediction and regulation and control of thin plates for nuclear main pump shielding sleeves of university of continental regulations, a method of chilling along with welding is adopted to improve deformation, and experiments show that when the distance between chilling and a heat source is 6mm, and the chilling strength is 15000W/(m)²K), the effect of improving the weld longitudinal deflection is best. The adverse effects of this approach on transverse shrinkage distortion are not completely eliminated by clamp restraint.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a laser welding method combining welding with ultrasonic and chilling, which reduces the residual stress generated in the welding process, improves the fatigue property of a welding line and reduces the welding deformation. The method is follow-up, the distance between the tool head and the heat source is small, and the method can be suitable for welding workpieces with most sizes.

In order to achieve the purpose, the invention adopts the technical scheme that:

a laser welding method combining welding ultrasound and chilling is characterized in that the back of a welding seam which is applied to a certain distance behind a molten pool in the welding process is applied with the chilling of welding and the front is applied with ultrasonic vibration for reducing residual deformation and improving fatigue performance, and the method comprises the following specific steps:

the method comprises the following steps that firstly, a clamp is placed on a workbench, a workpiece is placed on the clamp, the workbench and the workpiece are fixed, copper clamping blocks are used for clamping the workpiece, and the distance between the clamping blocks is 4-8 mm. An ultrasonic head, a heat source and a protective gas nozzle are arranged above the workpiece, and a cooling water nozzle and a cooling water outlet are arranged below the workpiece. The heat source is a pulse laser and is vertical to the processing surface of the workpiece. The shielding gas is coaxial protection, and the axis of a nozzle of the shielding gas is coincided with the axis of the laser. And after the ultrasonic head is connected with the amplitude transformer and the ultrasonic transducer, the ultrasonic power supply is connected into a circuit of the ultrasonic transducer. And the cooling water nozzle is connected with a cooling water pump and a cooling water tank. A clapboard with small holes is arranged between the cooling water outlet and the cooling water nozzle to ensure the cooling water to flow out.

When wire filling welding is needed, a wire feeding mechanism is needed to be arranged above the workpiece, and the wire feeding mechanism is adjusted to align wires during machining. The wire feeding head of the wire feeding mechanism is 20-40 degrees to the surface of the workpiece, the wire is fed out for 1-3 mm, the front end of the wire is aligned with the edge of a welding position, and then the wire is pressed for 1-1.5 mm.

Second, setting the ultrasonic head position and ultrasonic parameters

Adjusting the ultrasonic head to be 8-16mm right behind the molten pool to ensure that the ultrasonic generates cavitation, acoustic flow and other effects in the molten pool; setting an ultrasonic head angle, wherein the adjustment range of the ultrasonic vibration incidence angle is 20-60 degrees, so that the ultrasonic can be effectively conducted in the workpiece; setting the position of an ultrasonic head, wherein the distance between the top end of the ultrasonic head and the surface of the workpiece is 0.1-0.2 mm; after the angle and the position of the ultrasonic head are determined, the ultrasonic head and a machine tool cantilever are fixed, and the relative position of the ultrasonic head and the machine tool cantilever is ensured not to change in the welding process. And (3) connecting the ultrasonic head with an ultrasonic power supply, wherein the ultrasonic power P is 0.4-1.5 kW.

Thirdly, setting chilling parameters

The diameter of the cooling water nozzle is 2-4 mm, the cooling water nozzle can directly influence a molten pool if the diameter of the cooling water nozzle is too large, the cooling water nozzle can directly influence the molten pool if the diameter of the cooling water nozzle is too small, the cooling water outflow can be influenced if the diameter of the cooling water nozzle is too small, the position of the cooling water nozzle is adjusted to be right behind the molten pool, the distance d between the cooling water nozzle and the molten pool is 4-8 mm, the temperature T of the cooling water is adjusted to be-4-2 ℃, the flow Q of the cooling water is adjusted to be 30-90 ml/min, Q & gt 162X η X P is used for preventing the atomization effect of ultrasonic from influencing the application of the cooling water, η is the efficiency of the ultrasonic action on the:

to ensure that atomized cooling water droplets do not directly interfere with the molten pool, v is the lower protective gas flow rate (in mm/s), and μ is the lower protective gas dynamic viscosity (in mm/s)Bit: n.s/mm²) And t is a cooling water surface tension coefficient (unit: n/m), ρ₁Is the density (unit: g/mm) of cooling water³)，ρ₂For protecting the air density (unit: g/mm)³) And f is the ultrasonic frequency (unit: hz), g is the acceleration of gravity; the cooling water temperature T (unit:. degree. C.), the cooling water flow Q (unit: ml/min) and the temperature T0 (unit:. degree. C.) of the cooling water nozzle position when not chilled are satisfied: 4000 (T0-T) xQ is less than or equal to 7000, and the chilling effect is ensured while the chilling influence on the temperature of the molten pool is prevented. And after the adjustment is finished, fixing the relative position of the cooling water nozzle and the cantilever of the machine tool, and ensuring that the relative heat source and the shielding gas position are unchanged in the welding process.

Fourthly, setting laser parameters, wherein the single pulse energy of the laser is more than or equal to 2J and less than or equal to (2300 plus 1000P)/400 so as to ensure that effective welding can be realized and no thermal crack is generated, wherein the unit of E is J, and the unit of P is kW; the pulse width is set to 2-8 ms.

Fifthly, after the setting is finished, a cooling water nozzle, an ultrasonic power supply and a coaxial protection gas valve are sequentially started, wherein the protection gas is argon with the purity of 99.9 percent, the flow of the upper protection gas is 15l/min, and the flow of the lower protection gas is 3-15 l/min, so that the protection effect can be ensured, and the cooling water can be prevented from being interfered to flow out; and starting the pulse laser for welding after waiting for 5-10 s.

And sixthly, after welding is finished, closing the pulse laser, the shielding gas, the cooling water and the ultrasonic power supply in sequence.

The invention has the beneficial effects that:

(1) the welding chilling can reduce the longitudinal residual stress of the welding by generating tensile stress to be offset with the longitudinal tensile stress generated by the welding.

(2) The follow-up ultrasonic vibration can further reduce the residual tensile stress near the welding seam, and can even introduce the residual compressive stress, thereby simultaneously reducing the transverse and longitudinal deformation and improving the fatigue property of the welding seam; the vibration can close the generated defects such as cracks, air holes and the like under the action of pressure, so that the stress concentration is reduced, and the fatigue performance of the welding seam is improved; the ultrasonic vibration can cause the surface of the welding line to generate plastic deformation for many times, and the microhardness of the surface of the material is improved.

(3) The follow-up ultrasonic wave is applied to the front surface of the workpiece and the follow-up welding chilling is applied to the back surface of the workpiece, so that the interference between the follow-up ultrasonic wave and the welding chilling is avoided, and the implementation and the control are convenient.

(4) The method is follow-up, the ultrasonic application distance is short, and the applicable welding size range is wide. The tool head applies 20kHz force, and welding seam uniformity can be guaranteed.

(5) The ultrasonic cavitation effect and the ultrasonic sound flow effect can not generate turbulence in the molten pool, so that the flow of the molten pool is accelerated, the crystal grains are refined, and the fatigue property and the tensile strength of the welding line are improved.

Drawings

FIG. 1 is a schematic view of the apparatus of the present invention.

Fig. 2 is a cross-sectional view of the device.

In the figure: 1 is a clamp; 2, a wire feeding mechanism; 3 is a lower protective gas inlet; 4, a cooling water pump (capable of adjusting water temperature and flow speed); 5 is an ultrasonic head; 6 is a heat source (a laser head in fig. 1, a laser beam in fig. 2); 7 is a coaxial protection device; 8 is a workpiece; 9 is a cooling water nozzle (the front section is rigid, and the rear section is flexible); and 10 is a cooling water tank.

Detailed Description

The invention is described in detail below with reference to the drawings and the implementation process.

A laser welding method combining welding-following ultrasound and an electric field is realized based on the following devices: first, the jig 1 is placed on a table, the workpiece 8 is placed on the jig 1, the jig 1 and the table are fixed, and the workpiece 8 is clamped by a copper clamp block. And a heat source 6, an ultrasonic head 5 and a coaxial protection device 7 are arranged above the workpiece 8, and a cooling water nozzle 9 is arranged below the workpiece. The heat source 6 is a pulse laser and is vertical to the processing surface of the workpiece 8. The shielding gas is coaxial protection, and the axis of a nozzle of the shielding gas is coincided with the axis of the laser. And after the ultrasonic head 5 is connected with the amplitude transformer and the ultrasonic transducer, an ultrasonic power supply is connected into a circuit of the ultrasonic transducer. The cooling water nozzle 9 is connected with the cooling water pump 4 and the cooling water tank 10. A clapboard with small holes is arranged between the cooling water outlet 3 and the cooling water nozzle 9 to ensure the cooling water to flow out.

Specific embodiment of self-welding:

A. a hastelloy C-276 plate with a thickness of 0.5mm was placed on the jig 1 and clamped using copper clamping blocks with a 6mm spacing. The fixture 1 is placed on a workbench, and the relative position of the fixture 1 and the workbench is fixed.

B. And adjusting ultrasonic parameters. The ultrasonic head 5 is adjusted to be positioned at the position which is 10mm right behind the molten pool, so that the ultrasonic can be transmitted into the molten pool. The angle of the ultrasonic head 5 is adjusted to ensure that the axis of the ultrasonic head 4 forms an angle of 30 degrees with the horizontal plane. Adjusting the position of the ultrasonic head 5 to enable the top end of the ultrasonic head to be 0.1mm lower than the surface of the workpiece; after the ultrasonic head 5 is positioned, the ultrasonic head and a machine tool cantilever are fixed, and the relative position of the ultrasonic head and the machine tool cantilever is ensured not to be changed in the welding process. The ultrasonic vibrator is connected with the ultrasonic generator, the power supply of the ultrasonic generator is started, and the ultrasonic power is set to be 1 kW.

C. And setting chilling parameters. The cooling water nozzle 9 is connected to the cooling water pump 4 and the cooling water tank 10. The cooling water nozzles 9 have a diameter of 3 mm. And adjusting the position of a cooling water nozzle 9 to be 4mm right behind the molten pool and 3mm below the workpiece, adjusting the temperature of cooling water to be-2 ℃, and adjusting the flow of cooling water to be 68 ml/min. After the adjustment is finished, the relative position of the cooling water nozzle 9 and the cantilever of the machine tool is fixed, and the relative heat source and the shielding gas position are ensured to be unchanged in the welding process.

D. And setting parameters of the pulse laser. The laser single pulse energy was 2.5J and the pulse width was set to 6 ms.

E. And (5) opening protective gas. The shielding gas was argon (purity 99.9%), and the flow rate was: the upper protective gas is 15l/min, and the lower protective gas is 5 l/min.

F. And after the output of the ultrasonic power supply and the alternating current power supply is stable, waiting for 10s, and starting the pulse laser for laser welding.

G. And after the welding is finished, closing the pulse laser, the shielding gas, the ultrasonic power supply and the cooling water in sequence.

Specific embodiments of the wire-filling welding:

A. a hastelloy C-276 plate with a thickness of 0.5mm was placed on the jig 1 and clamped using copper clamping blocks with a 6mm spacing. The fixture 1 is placed on a workbench, and the relative position of the fixture 1 and the workbench is fixed. 8 tops of work piece still need set up wire feeder 2, wire feeder including sending the silk head, sending a silk pipe, silk dish and sending a silk wheel four bibliographic categories and divide, what show in the picture is a sending silk head part, adds the adjustment wire feeder 2 and carries out the alignment silk during processing: the wire feeding head is 30 degrees to the surface of the workpiece, the front end of the wire is aligned with the edge of the welding position after the wire is fed out for 2mm, and then the wire is pressed down for 1 mm. The wire feeding pipe is connected with the wire feeding head through threads, and wires are conveyed from the inside of the wire feeding pipe; the wire disc is a position for placing wires, and the wires need to be checked to ensure the sufficiency of the wires before the experiment is carried out; the wire feeding wheel is driven by a gear to ensure the speed stability.

B. And adjusting ultrasonic parameters. The ultrasonic head 5 is adjusted to be positioned at the position which is 10mm right behind the molten pool, so that the ultrasonic can be transmitted into the molten pool. The angle of the ultrasonic head 5 is adjusted to ensure that the axis of the ultrasonic head 4 forms an angle of 30 degrees with the horizontal plane. Adjusting the position of the ultrasonic head 5 to enable the top end of the ultrasonic head to be 0.08mm higher than the surface of the workpiece; after the ultrasonic head 5 is positioned, the ultrasonic head and a machine tool cantilever are fixed, and the relative position of the ultrasonic head and the machine tool cantilever is ensured not to be changed in the welding process. The ultrasonic vibrator is connected with the ultrasonic generator, the power supply of the ultrasonic generator is started, and the ultrasonic power is set to be 1 kW.

C. And setting chilling parameters. The cooling water nozzle 9 is connected to the cooling water pump 4 and the cooling water tank 10. The cooling water nozzles 9 have a diameter of 3 mm. And adjusting the position of a cooling water nozzle 9 to be 4mm right behind the molten pool and 3mm below the workpiece, adjusting the temperature of cooling water to be-2 ℃, and adjusting the flow of cooling water to be 68 ml/min. After the adjustment is finished, the relative position of the cooling water nozzle 9 and the cantilever of the machine tool is fixed, and the relative heat source and the shielding gas position are ensured to be unchanged in the welding process.

D. And setting parameters of the pulse laser. The laser single pulse energy was 2.5J and the pulse width was set to 6 ms.

E. And (5) opening protective gas. The shielding gas was argon (purity 99.9%), and the flow rate was: the upper protective gas is 15l/min, and the lower protective gas is 5 l/min.

F. And after the output of the ultrasonic power supply and the alternating current power supply is stable, waiting for 10s, and starting the pulse laser for laser welding.

G. And after the welding is finished, closing the pulse laser, the shielding gas, the ultrasonic power supply and the cooling water in sequence.

The above examples are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical scope of the present invention, the technical solutions according to the present invention and the inventive concept thereof, with equivalent substitutions or changes.