CN111604593A - A laser mirror welding method - Google Patents

Abstract

The present invention provides a laser mirror welding method, which has smaller heat input, smaller deformation and residual stress than traditional laser single-side welding. This method is mainly suitable for the docking structure of the plate. The robot linkage system controls the two robots to issue laser output commands at the same time to generate two laser beams with the focal points at the corresponding positions on both sides of the plate, and synchronize the two laser beams at the same speed and direction. Weld, and finally get a through molten pool. The invention reduces the deformation and residual stress in the laser welding process, thereby reducing the tendency of hot cracks; and on the basis that the laser welding has a larger penetration depth, the welding penetration depth is further increased. Therefore, the present invention has many advantages for the welding of thick plates, and the present invention has great application value in actual production.

Description

A laser mirror welding method

technical field

The invention belongs to the technical field of laser welding, and in particular relates to a laser mirror welding method.

Background technique

Laser welding technology has the advantages of high welding efficiency, good weld formability, concentrated welding energy, narrow heat-affected zone, low residual stress after welding, and good air tightness. It is widely used in the aerospace field. However, when the welding thickness is large, a large heat input is required in order to achieve a large penetration depth, and the excessive heat input leads to an increase in the deformation of the weldment and an increase in residual stress. More cracks, resulting in failure of the weldment. At present, the more commonly used double-sided welding are double-sided arc welding, laser-arc double-sided welding, and laser double-sided welding (asynchronous), but due to the wide seam and small penetration of double-sided arc welding; The welding pool is asymmetrical, the shape of the molten pool on the laser side is deep and thin, and the shape of the molten pool on the arc side is shallow and large; , the back of the weld is prone to increase the gap due to welding deformation, which affects the welding quality or even fails to weld.

Therefore, when welding flat plates, the existing welding methods have certain deficiencies in welding deformation, residual stress after welding, and weld penetration depth. A laser welding method that can increase penetration, reduce deformation and reduce residual stress is required.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to propose a laser mirror welding method in order to overcome the defects of insufficient welding quality, large deformation after welding and large residual stress after welding in the laser welding in the prior art.

The present invention solves the above-mentioned technical problems through the following technical solutions:

A laser mirror welding method, characterized in that it mainly comprises the following steps:

Step 1: Locally clean the welding area of the plate to be welded. If there is an oxide layer on the surface of the plate, the oxide layer needs to be treated.

Step 2: Use a flat plate of the same material to conduct a single-side laser welding parameter exploration experiment to obtain the laser power when the penetration depth is one-third of the plate thickness, and determine the appropriate laser incident angle.

Step 3: Pre-fix the plate to be welded by spot welding in a horizontal position to ensure that the gap between the two plates is less than 0.15mm.

Step 4: Clamp the butt test plate pre-fixed by spot welding perpendicular to the horizontal plane.

Step 5: Adjust the position of the welding robot so that the laser welding head is located at a symmetrical position on both sides of the butt test plate, and further adjust the position of the laser welding head so that the focus of the laser beam is at the butt joint of the flat plate.

Step 6: Control the two laser heads to emit light at the same time through the robot linkage system, and start welding synchronously at the same speed and direction.

During welding, in order to ensure that the two laser beams can converge to form a through molten pool, it is necessary to ensure the synchronization of the two laser beams. In order to ensure the safety of the experiment, the incident angle of the laser needs to be deflected to a certain extent. The laser incident angle ranges from 0 to 180° with the test plate. During welding, a shielding gas is blown on the outside of the weld to the welded position, which cools the position and prevents it from being oxidized. In addition, the molten pool is liquid metal and will flow to the lower plate due to gravity. In order to obtain better weld formation, adjust the position of the shielding gas to blow from bottom to top. During the welding process, the two laser beams are always synchronized, but the powers of the two laser beams can be equal or unequal. By changing the welding position in the welding process, four different welding positions are realized, namely horizontal welding, vertical upward welding, vertical downward welding, flat welding + overhead welding.

The laser mirror welding method uses laser welding, including laser wire-filled welding and laser non-wire-filled welding.

The positive progressive effect of the present invention is:

The laser mirror welding method of the present invention can not only effectively solve the problem of reducing the quality of the welding seam caused by increasing the heat input in order to achieve a larger penetration depth, but also can ensure that the deformation after welding is small, and at the same time, the residual stress after welding can be reduced, Helps to improve the yield of weldments and the service life of weldments.

Description of drawings

FIG. 1 is a schematic diagram of the laser mirror welding method of the present invention.

FIG. 2 is a schematic diagram of the change of the welding seam area before and after welding in the present invention.

In the picture: 1-12Kw laser, 2-laser welding head, 3-beam splitter, 4-plate, 5-double protection gas pipe, 6-double laser beam, 7-special fixture, 8-work platform, 9-assembly gap, 10- Through the molten pool.

Detailed ways

The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings to illustrate the technical solutions of the present invention in detail, but the present invention is not limited to the scope of the described embodiments.

1 and 2, the laser mirror welding method of the present invention includes a 12Kw laser 1, a laser welding head 2, a beam splitter 3, a flat plate 4, a double protective gas pipe 5, a double laser beam 6, a special fixture 7, a working platform 8, Assembly gap 9 and through molten pool 10 .

The laser light generated by the laser 1 is divided into two laser beams of equal power by the beam splitter 3 and transmitted to the laser head 2 . Laser beams 6 are emitted from the two laser heads, respectively. The incident angles of the two laser beams should be mirror-symmetrical about the weldment. However, it should be understood that in the present invention, as long as the laser incident angles of the two laser beams are mirror-symmetrical about the weldment, it is the scope of mirror welding, and the angle between the laser beam and the weldment can be changed without affecting the implementation of the mirror image welding. Among them, the beam splitter 3 can allocate and adjust the energy ratio of the two laser beams to the total laser power according to the actual welding requirements.

Step 1: Since there is an oxide layer on the surface of most materials, the existence of the oxide layer will affect the welding quality and reduce the performance. Therefore, the welding area of the plate 4 to be welded is partially cleaned, and the cleaning method is determined according to the oxide layer. Mechanical grinding or chemical Wash, re-rub with alcohol and dry.

Step 2: Use the plate 4 of the same material and the same specification to conduct a groping experiment on the parameters of single-sided laser welding, and gradually adjust the laser power. When the penetration depth of the single-sided laser welding reaches one-third of the plate thickness, the parameter is initially determined as mirror welding. parameters; and determine the appropriate laser incident angle according to the actual welding requirements.

Step 3: First, pre-fix the plate to be welded by spot welding under the horizontal clamping, and use continuous laser or pulsed laser with one third of the formal welding power for spot welding. According to actual needs, choose single-sided spot welding or double-sided spot welding to ensure that the gap between the two plates after spot welding is less than 0.15mm.

Step 4: Use the special fixture 7 to clamp the pre-fixed butt-welded butt-welded flat plate 4 perpendicular to the worktable 8 .

Step 5: Adjust the position of the welding robot so that the laser welding head 2 is located at a symmetrical position on both sides of the docking plate 4, and further fine-tune the position of the laser welding head 2 so that the focus of the laser beam is located at the butt joint of the plate butt joint.

Step 6: The laser light generated by the laser 1 is divided into two laser beams with the same power by the beam splitter 3, and transmitted to the laser head 2, and the laser beam 6 with the same power is emitted from the two laser heads at the same time. And through the robot linkage system, the two laser heads are controlled to start welding at the same speed and direction. During welding, in order that the double laser beams 6 can converge to form a through molten pool, high requirements are placed on the synchronization of the double laser beams 6 . In order to ensure the safety of the experiment, a certain deflection of the dual laser beams 6 is required. The laser incident angle ranges from 0 to 180° with the test plate. During the welding process, the double shielding gas pipe 5 blows the shielding gas to the welded position on the outside of the welding seam, which can cool the position and prevent it from being oxidized. In addition, the molten pool is liquid metal and will flow to the lower plate due to gravity. In order to obtain better weld formation, adjust the position of the shielding gas to blow from bottom to top. During the welding process, the two laser beams are always synchronized, but the power of the two laser beams can be selected according to the actual welding requirements. By changing the welding position in the welding process, four different welding positions are realized, namely horizontal welding, vertical upward welding, vertical downward welding, flat welding + overhead welding.

The schematic diagram of the welding process is shown in FIG. 2 . The original assembly gap 9 forms a through molten pool 10 under the action of the two laser beams 6 . When the two laser beams 6 move to the end of the welding seam, the laser head 2 stops emitting light, and the mirror welding is completed. The laser mirror welding method uses laser welding, including laser wire-filled welding and laser non-wire-filled welding.

Example 1

Step 1: Select 2219 aluminum alloy material with a thickness of 6mm for testing. There is a dense oxide layer on the surface of the aluminum alloy material. The existence of the oxide layer will affect the welding quality and reduce the performance. Sanding will remove oxidation, then wipe with alcohol and dry.

Step 2: Use the 2219 plate 4 of the same specification to conduct a groping experiment on the parameters of one-side laser welding. When the laser power is gradually adjusted to 2000W, when the penetration depth of one-side laser welding reaches one-third of the plate thickness, the parameter is initially determined as mirror welding. parameters; and determine the appropriate laser incident angle to be 5°.

Step 3: First, pre-fix the plate to be welded by spot welding under the horizontal clamping, and use 770W continuous laser spot welding. According to actual needs, double-sided spot welding is selected, and the gap between the two boards is measured to be 0.1mm after welding.

Step 4: Use the special fixture 7 to clamp the pre-fixed 2219 docking plate 4 perpendicular to the workbench 8.

Step 5: Adjust the position of the welding robot so that the laser welding head 2 is located at a symmetrical position on both sides of the docking plate 4, and further fine-tune the position of the laser welding head 2 so that the focus of the laser beam is located at the butt joint of the plate butt joint.

Step 6: The laser light generated by the laser 1 is divided into two laser beams with a power of 2000W by the beam splitter 3, and transmitted to the laser head 2, and the laser beam 6 is emitted from the two laser heads at the same time. And through the robot linkage system, the two laser heads are controlled to start welding at a speed of 1.8m/min and in the same direction. During welding, in order that the double laser beams 6 can converge to form a through molten pool, high requirements are placed on the synchronization of the double laser beams 6 . In order to ensure the safety of the experiment, a certain deflection of the dual laser beams 6 is required. The incident angle of the laser is 5° with the test plate. During the welding process, the double shielding gas pipe 5 blows the shielding gas to the welded position on the outside of the weld, which can cool the position and prevent it from being oxidized, and the flow rate of the protection zone is 15L/min. In addition, the molten pool is liquid metal and will flow to the lower plate due to gravity. In order to obtain better weld formation, adjust the position of the shielding gas to blow from bottom to top. By changing the welding position in the welding process, four different welding positions are realized, namely horizontal welding, vertical upward welding, vertical downward welding, flat welding + overhead welding, and the welding position selected in this embodiment is horizontal welding. The welds obtained after welding are well formed, have a penetrating molten pool, less residual stress and less welding deformation.

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the embodiments of the present invention. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (8)

1. a laser mirror welding method, is characterized in that, mainly comprises the following steps: Step 1: Locally clean the welding area of the plate to be welded. If there is an oxide layer on the surface of the plate, the oxide layer needs to be treated. Step 2: Use a flat plate of the same material to conduct a single-side laser welding parameter exploration experiment to obtain the laser power when the penetration depth is one-third of the plate thickness, and determine the appropriate laser incident angle. Step 3: Pre-fix the plate to be welded by spot welding in a horizontal position to ensure that the equipment gap between the two plates is less than 0.15mm. Step 4: Clamp the butt test plate pre-fixed by spot welding perpendicular to the horizontal plane. Step 5: Adjust the position of the welding robot so that the laser welding head is located at a symmetrical position on both sides of the butt test plate, and further adjust the position of the laser welding head so that the focus of the laser beam is at the butt joint of the flat plate. Step 6: Control the two laser heads to emit light at the same time through the robot linkage system, and start welding synchronously at the same speed and direction. 2 . The laser mirror welding method according to claim 1 , wherein there are two laser beams in the welding process, which are located on both sides of the workpiece, and the positions of the two laser beams form a mirror image distribution with the welding plate as the central axis. 3 . 3. The laser mirror welding method according to claim 1 is characterized in that in order to ensure that the two laser beams can converge to form a through molten pool, the focus of the two laser beams is located on both sides of the same position of the flat plate, and it is necessary to ensure that two beams of laser light are in the welding process. The laser beam moves synchronously. 4. The laser mirror welding method according to claim 1, characterized in that in order to ensure the safety of the experiment, the incident angle of the laser needs to be deflected to a certain extent. The laser incident angle ranges from 0 to 180° with the test plate. 5 . The laser mirror welding method according to claim 1 , wherein during the welding process, the welded position is blown with a protective gas which can cool the position and prevent it from being oxidized. 6 . In addition, the molten pool is liquid metal and will flow to the lower plate due to gravity. In order to obtain better weld formation, adjust the position of the shielding gas to blow from bottom to top. 6 . The laser mirror welding method according to claim 1 , wherein the two laser beams are kept synchronized at all times during the welding process, but the power ratio of the two laser beams can be adjusted according to actual needs. 7 . 7. The laser mirror welding method according to claim 1 is characterized in that the welding position can be changed to realize welding under four different positions, which are respectively horizontal welding, upward vertical welding, downward vertical welding, flat welding+overhead welding . 8 . The laser mirror welding method according to claim 1 , wherein the welding adopts laser welding, including laser wire-filled welding and laser non-wire-filled welding. 9 .

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