JP7132830B2 - Lap fillet welding method for aluminum alloy plate - Google Patents

Description

The present invention relates to a lap fillet welding method for aluminum alloy plates.

Conventionally, in joining aluminum alloy plates, lap fillet welding is performed by irradiating laser light. In a lap fillet weld, two plates can be staggered and overlapped and welded between the edge of the top plate and the major surface of the bottom plate. For example, Patent Literature 1 discloses a configuration for performing so-called wobbling irradiation in which a laser beam is irradiated in a circle using a galvanometer scanner in order to widen the bead width of welding. Further, in this configuration, the occurrence of porosity in the welded portion is suppressed by appropriately setting the degree of overlapping of the trajectories of the laser beams.

International publication WO2016/194322

However, when aluminum alloy plates are lapped and fillet welded by laser light irradiation, cracks may occur in the lower plate from the edge of the lower plate toward the weld bead. It was found that such cracks were caused by heat generation due to laser light irradiation. That is, a large tensile stress is generated in the lower plate due to thermal contraction of the weld bead portion immediately after laser welding. Especially in the latter half of welding, the amount of heat input to the object to be welded increases, so the temperature near the weld bead becomes high. If segregation of components, eutectic crystals, or the like occurs at the grain boundaries of the flange portion of the lower plate, the portion is locally melted to form an opening. The crack propagates along the grain boundary of the lower plate and partially reaches the weld bead. Such cracks lead to deterioration of weld quality.

The present invention has been made in view of such a background, and an object thereof is to provide a fillet welding method for aluminum alloy plates that prevents the occurrence of cracks.

One aspect of the present invention is a lap fillet welding method for an aluminum alloy plate,
While moving the irradiation target position of the laser light along the welding line by the galvanometer scanner, the irradiation period for irradiating the laser light and the interruption period for interrupting the irradiation are alternately repeated,
In the irradiation period, a weld bead is formed by scanning a length of 35 mm or less along the welding line,
In the lap fillet welding method for aluminum alloy plates, the irradiation is interrupted for a time corresponding to ⅓ or more of the irradiation period during the interruption period.

In the method for lap fillet welding of aluminum alloy plates, the laser beam is scanned so that the scanning length is 35 mm or less during the irradiation period. As a result, the amount of heat input to the welding target site is moderately suppressed during the irradiation period. Furthermore, during the interruption period, the irradiation is interrupted for a period of time corresponding to ⅓ or more of the irradiation period, so heat dissipation is promoted at the welding target site. Furthermore, during the interruption period, the irradiation is interrupted, but the movement of the irradiation target position of the laser beam by the galvanometer scanner is continued. That is, the movement of the irradiation target position of the laser light by the galvanometer scanner is continued over the entire period in which the irradiation period and the interruption period are alternately repeated. As a result, the welding operation can be completed in the same amount of time as in the case where laser beam irradiation is continuously performed over the entire period without providing an interruption period and scanning is continued. As a result, it is possible to suppress the work time from becoming long.

As described above, according to the lap fillet welding method for aluminum alloy plates, the irradiation period and the interruption period are alternately repeated, so that the laser beam scanning is performed continuously for a short time. Excessive heating of the target part is prevented, and cracks due to thermal contraction are prevented from occurring in the target part and its vicinity, and the target position of laser light irradiation by the galvanometer scanner is moved over the entire period. is continued, it is possible to suppress the work time from becoming long.

As described above, according to the present invention, it is possible to provide a method for lap fillet welding of aluminum alloy plates in which the occurrence of cracks is prevented.

1 is a conceptual diagram showing the configuration of a welding system in Embodiment 1. FIG. 4 is a conceptual diagram showing a welding mode in Example 1. FIG. 4 is a conceptual diagram showing the locus of the focal point of laser light in Example 1. FIG. FIG. 2 is a cross-sectional conceptual diagram showing a welding mode in Example 1; FIG. 4 is a conceptual diagram for explaining aspects of an irradiation period and a discontinuation period in (a) Test Example 1, (b) Test Example 1, and (c) Comparative Example 2; FIG. 10 is a conceptual diagram illustrating aspects of an irradiation period and an interruption period in (a) Test Example 2 and (b) Test Example 3; (a) Comparative Example 1 and (b) A diagram showing an example of a weld bead in Test Example 1. FIG.

It is preferable that the laser beam is scanned at a constant speed during the irradiation period. In this case, since heat is stably input to the welding target portion during the irradiation period, the welding state can be improved.

It is preferable to scan along the welding line while wobbling the laser beam during the irradiation period. In this case, the width of the weld bead can be increased without increasing the spot diameter of the laser beam. As a result, the welding state can be further improved.

Moreover, it is preferable that the welding target portion is melted up to the back surface on the side opposite to the surface to be irradiated with the laser beam during the irradiation period. In this case, it is possible to effectively suppress the occurrence of cracks that tend to occur at the weld-side end of the lower plate. In this case, the parts to be welded are reliably melted, and the welding state can be further improved.

(Example 1)
An embodiment of the lap fillet welding method for aluminum alloy plates will be described with reference to FIGS. 1 to 6. FIG.
In the lap fillet welding method for aluminum alloy plates of the present embodiment, while moving the irradiation target position Qf of the laser beam Q along the welding line G by the galvanometer scanner 20 shown in FIG. As shown in (b), an irradiation period S1 during which the laser beam Q is irradiated and an interruption period S2 during which the irradiation is interrupted are alternately repeated.
In the irradiation period S1, a welding bead is formed by scanning along the welding line G for a length of 35 mm or less.
In the interruption period S2, the irradiation of the laser beam Q is interrupted for a time corresponding to ⅓ or more of the irradiation period S1.

In the lap fillet welding method of this example, a welding system 100 shown in FIG. 1 was used. The welding system 100 includes a laser oscillator 60 , a galvanometer scanner 20 , an output control section 30 , a scanning control section 40 and a mounting table 50 . The laser oscillator 60 is configured to output laser light Q. As shown in FIG. The output of the laser oscillator 60 is adjusted by the output controller 30 . The galvanometer scanner 20 includes motors 21 and 22, a mirror 23 and a condenser lens 24.

The galvanometer scanner 20 transmits the laser light Q through the condenser lens 24 and reflects it on the mirror 23 to change its trajectory and direct it toward the welding target site A of the aluminum alloy plate 10 mounted on the mounting table 50. Irradiate. The mirror 23 is connected to motors 21 and 22 so as to be rotatable, and is driven and controlled to a desired state by a scanning control section 40 . The condenser lens 24 is configured to align an irradiation target position Qf, which is the focal point of the laser beam Q, with the welding target site A. As shown in FIG. Thereby, as shown in FIG. 3, the galvanometer scanner 20 can move the irradiation target position Qf of the laser beam Q in a predetermined manner. In this embodiment, as the laser oscillator 60, TruDisk 6002 manufactured by Trumpf was used. As the galvanometer scanner 20, model number 8MC39A-3C4C8A manufactured by YE Data was used.

A desired composition can be used as the aluminum alloy plate 10 to be welded. For example, as the aluminum alloy plate 10, a plate material made of a 1000 series to 6000 series aluminum alloy can be used. Note that the aluminum alloy plate 10 includes a plate material made of pure aluminum. The thickness and shape of the aluminum alloy plate 10 to be used are not particularly limited.

As a preparatory step before the irradiation period S1, as shown in FIGS. The welding side end portion 111, which is one end portion, is shifted from each other so as to be positioned above the plate surface of the lower plate 12, which is the other aluminum alloy plate. Thereby, the lower plate 12 has the flange portion 121 exposed without overlapping with the upper plate 11 . As shown in FIGS. 2 and 3, the width F of the flange portion 121 can range from 2.0 mm to 5.0 mm, and is 3.0 mm in this embodiment.

In the two aluminum alloy plates 10 superimposed as described above, the top plate 11 has a light beam extending from the welding side end 111 of the top plate 11 toward the irradiated surface 114, which is one plate surface of the top plate 11. A welding line G is set at a position separated by a predetermined distance. In this example, as shown in FIG. 2 , the welding line G is a straight line that is 1.5 mm away from the welding-side end 111 and parallel to the welding-side end 111 . The movement of the laser beam irradiation target position Qf by the galvanometer scanner 20 is performed along the welding line G in the welding direction X1.

As shown in FIG. 3, the movement of the irradiation target position Qf of the laser beam Q by the galvanometer scanner 20 is performed throughout the irradiation period S1 and the interruption period S2. That is, as indicated by the dashed line in FIG. 3, in the irradiation period S1, the irradiation target position Qf moves and the laser beam Q is irradiated along the trajectory of the irradiation target position Qf indicated by the solid line Qfa. Although the movement of the irradiation target position Qf by the galvanometer scanner 20 continues, the laser beam Q is not irradiated.

The mode of movement of the irradiation target position Qf of the laser beam Q by the galvanometer scanner 20 is not limited, but may be a movement mode of wobbling the laser beam Q during the irradiation period S1. can be helical, wavy, or the like. In this example, as shown in FIG. 3, the irradiation target position Qf of the laser beam Q is moved in a circular motion and parallel to the welding line G, so that the irradiation target position Qf of the laser beam Q is I'm trying to draw a spiral. The radius of the circle when moving the locus of the focal point of the laser beam Q can be set as appropriate. In this example, as shown in FIG. The distance S is set to 1.5 mm. As a result, the wobbling width R is set to 3.0 mm. The frequency of circular movement in wobbling can be set as appropriate, and the speed of movement in the direction parallel to the welding direction can also be set as appropriate. In this example, the frequency of circular movement in wobbling is set to 50 Hz, and the movement speed in the direction parallel to the welding direction X1 is set to 33.3 mm/s.

As shown in FIG. 3, in the irradiation period S1, the scan length L is 35 mm or less, preferably 1 to 30 mm, more preferably 2 to 20 mm. 5 mm or 1.0 mm. In the repeated irradiation period S1, all scanning lengths L may be the same, or scanning lengths L may vary within a range of 35 mm or less. The scanning length L is the length of the region irradiated with the laser beam Q in the welding direction X1, as shown in FIG.

In the irradiation period S1, as shown in FIG. 4B, the laser beam Q is irradiated to the welding target portion A, and the welding target portion A reaches the back surface 124 opposite to the irradiated surface 114 irradiated with the laser beam Q. to melt. Thereby, a weld bead 70 is formed. In this example, the irradiation of the laser beam Q melts the welding target portion A up to the back surface 124 on the opposite side, and the back bead 82 is exposed on the back surface 124 on the opposite side.

As shown in FIGS. 3 and 5A, the interruption period S2 comes after the irradiation period S1 ends. In the interruption period S2, the irradiation of the laser light Q is stopped. As described above, the duration of the interruption period S2 is a time corresponding to 1/3 or more of the irradiation time of the laser light Q in the irradiation period S1, and 40% or more of the irradiation time of the laser light Q in the irradiation period S1. It is good also as 50% or more and 60% or more. As described above, in the interruption period S2, the movement of the irradiation target position Qf of the laser beam Q by the galvanometer scanner 20 is continued while the irradiation of the laser beam Q is stopped. That is, during the interruption period S2, the laser beam Q is not irradiated, but the motor 22 in the galvanometer scanner 20 is driven in the same manner as during the irradiation period S1, and the mirror 23 is displaced.

(Evaluation test)
Next, in the lap fillet welding method of the aluminum alloy plate of Example 1, an evaluation test was conducted regarding the presence or absence of cracking.
One cycle was defined as one irradiation period S1 and one discontinuation period S2. The duration of the irradiation period S1 in one cycle is the irradiation time (ms/cycle), the duration of the interruption period S2 in one cycle is the irradiation interruption time (ms/cycle), and the irradiation in one cycle shown in FIG. Table 1 shows the test conditions including the scanning length L (mm/cycle) in the period S1.

As shown in Table 1, in all test examples and comparative examples, the laser output was 3 kW, the welding speed (moving speed of the irradiation target position Qf in the welding direction X1) was 33.3 mm/s, and The length of the entire weld bead was 50 mm. Incidentally, as shown in FIG. 4B, the spot diameter T of the laser beam Q on the irradiated surface 114 of the upper plate 11 was set to 0.6 mm.

In Comparative Example 1, as shown in Table 1 and FIG. 5B, the entire weld bead of 50 mm was formed at once with the irradiation interruption time of 0 ms and no interruption period S2. The irradiation time was 1500 ms.

Then, in Test Example 1, as shown in Table 1 and FIG. After 7 cycles of 50 ms, irradiation was performed until the total scanning length was 50 mm as the final irradiation period, and the entire welding operation was completed. As a result, as shown in Table 1, the irradiation interruption time per cycle in Test Example 1 was 33.3% of the irradiation time of the laser light Q in the irradiation period S1.

On the other hand, in Comparative Example 2, as shown in Table 1 and FIG. As a result, the irradiation interruption time per cycle in Comparative Example 2 was 16.7% of the irradiation time of the laser light Q in the irradiation period S1.

Next, in Test Example 2, as shown in Table 1 and FIG. 6A, the scanning length per cycle was 2.5 mm, the irradiation time per cycle was 75 ms, and the irradiation 15 cycles were performed with an interruption time of 25 ms. As a result, as shown in Table 1, the irradiation interruption time per cycle in Test Example 2 was 33.3% of the irradiation time of the laser light Q in the irradiation period S1.

In Test Example 3, as shown in Table 1 and FIG. 6B, the scanning length per cycle was 1.0 mm, the irradiation time per cycle was 30 ms, and the irradiation interruption per cycle After performing 37 cycles with a time of 10 ms, irradiation was performed until the total scanning length reached 50 mm as the final irradiation period, and the entire welding operation was completed. As a result, as shown in Table 1, the irradiation interruption time per cycle in Test Example 3 was 33.3% of the irradiation time of the laser light Q in the irradiation period S1.

The evaluation results in each test example and each comparative example are as follows.
First, in Comparative Example 1, as shown in FIG. 7A, a weld bead 70 having a length of 50 mm in the welding direction X1 was formed by the above method. A crack 113 was generated in the lower plate 12 from the welding side end 111 of the lower plate 12 toward the weld bead 70 at a position 40 mm from the welding start point 71 in the welding direction X1. Although not shown, there was also a crack reaching the inside of the weld bead 70 .

Further, in Comparative Example 2, the irradiation of the laser beam Q is interrupted during the interruption period S2, but the weld bead pieces formed during the irradiation period S1 before and after the interruption period S1 are extended and connected to each other, so that the weld bead pieces are connected to each other as a whole. A weld bead was formed. Also in Comparative Example 2, cracks 113 occurred in the lower plate 12 in the same manner as in Comparative Example 1, although not shown.

On the other hand, in Test Example 1, as shown in FIG. 7B, a weld bead having a length of 50 mm in the welding direction X1 was formed by the above method. In the interruption period S2, the irradiation of the laser beam Q is interrupted, but the weld bead pieces formed in the irradiation period S1 before and after the interruption period S2 are extended and connected to each other, so that the weld bead 80 is connected as a whole. rice field. Also in Test Examples 2 and 3, although not shown, a continuous weld bead with a length of 50 mm in the welding direction X1 was formed in the same manner as in Test Example 1. In Test Examples 1 to 3, cracks did not occur in the lower plate 12 during the formation of the weld bead 80 in any case.

As described above, as shown by the results of Test Examples 1 to 3, cracks occurred in the lower plate 12 during the formation of the weld bead 80 when the irradiation interruption time per cycle was 33.3% of the irradiation time. It has been confirmed that this does not occur.

In Comparative Example 1, when the weld-side end portion 122 of the lower plate 12 was observed, many granular fracture surfaces were observed, which were thought to be caused by fusion cracks (weld cracks). On the other hand, the fracture surface in the region closer to the center of the flange portion 121 than the welded end portion 122 was brittle, and cracks were confirmed to propagate along grain boundaries. Based on these, the cause of cracking in the flange portion due to laser welding is presumed as follows. That is, a large tensile stress is generated in the lower plate due to thermal contraction of the weld bead portion immediately after laser welding. In Comparative Example 1, since no irradiation interruption period is provided, the amount of heat input increases in the latter half of welding, and the temperature of the flange portion 121 becomes high. In this case, if segregation of ingredients, eutectic, etc. occurs in the crystal grain boundary in the flange portion 121, it will be locally dissolved and opened, and this will be the starting point and crack will occur from the welding side end portion 122 of the lower plate. , the crack propagates along the grain boundary and partially reaches the weld bead 70 .

On the other hand, in Test Examples 1 to 3, since sufficient time is ensured to interrupt the irradiation of the laser beam Q in the interruption period S2, the heat of the flange portion 121 is released and the flange portion 121 is prevented from becoming high temperature. be. As a result, the welding-side end portion 122 of the lower plate 12 is maintained at a low temperature, so local melting of the welding-side end portion 122 is suppressed, and cracking in the lower plate 12 is suppressed.

However, in Comparative Example 2, cracks 113 occurred in the lower plate 12 as in the case of Comparative Example 1, although the interruption period S2 was provided. This is because in Comparative Example 2, the irradiation interruption time per cycle is 16.7% of the irradiation time, and the irradiation interruption time is relatively short. It is presumed that the above crack 113 occurred as a result of the 121 being maintained at a high temperature.

The longer the interruption period S2, the more advantageous the heat dissipation of the flange portion 121. Therefore, when the irradiation interruption time per cycle is 1/3 or more of the irradiation time of the laser beam Q in the irradiation period S1, the lower plate 12 It was presumed that the occurrence of cracks in was suppressed.

The effects of the lap fillet welding method for aluminum alloy plates in this embodiment will be described in detail below.
In the lap fillet welding method for aluminum alloy plates of this example, the laser beam is scanned so that the scanning length is 35 mm or less during the irradiation period S1. As a result, the amount of heat input to the welding target site A is moderately suppressed during the irradiation period S1. Furthermore, in the interruption period S2, the irradiation of the laser beam Q is interrupted for a period of time corresponding to ⅓ or more of the irradiation period S1, so heat dissipation at the welding target site A is promoted. Furthermore, during the interruption period S2, the irradiation is interrupted, but the movement of the irradiation target position Qf of the laser beam Q by the galvanometer scanner 20 is continued. That is, the movement of the irradiation target position Qf of the laser beam Q by the galvanometer scanner 20 is continued over the entire period in which the irradiation period S1 and the interruption period S2 are alternately repeated. As a result, the welding operation can be completed in the same amount of time as in the case where the irradiation of the laser beam Q is continuously performed over the entire period without providing the interruption period S2. As a result, it is possible to suppress the work time from becoming long.

As described above, according to the lap fillet welding method for aluminum alloy plates of the present example, the irradiation period S1 and the interruption period S2 are alternately repeated, so that the scanning of the laser beam Q that is continuously performed is short. Therefore, the welding target site A is prevented from being excessively heated, and the occurrence of cracks due to thermal contraction in the welding target site A and its vicinity is prevented, and the galvano scanner 20 over the entire period Since the irradiation target position Qf of the laser beam Q continues to move, it is possible to prevent the working time from becoming longer.

Furthermore, in this example, the laser beam Q is scanned at a constant speed during the irradiation period S1, so that the formed weld bead 80 can have a size within a predetermined range, improving reliability and improving the appearance. Get better.

Further, in this example, in the irradiation period S1, the laser beam Q is scanned along the welding line G while wobbling. As a result, the width of the formed weld bead 80 can be increased without increasing the spot diameter T of the irradiated laser beam Q, thereby improving the welding state.

In this example, in the irradiation period S1, the welding target site A is irradiated with the laser beam Q, and the welding target site A is melted up to the back surface 124 opposite to the irradiated surface 114 irradiated with the laser light Q. As a result, the portion A to be welded is reliably melted, and the joint state between the upper plate 11 and the lower plate 12 can be improved.

In this example, in the irradiation period S1, the welding target site A is irradiated with the laser beam Q, and the welding target site A is melted up to the back surface 124 opposite to the irradiated surface 114 irradiated with the laser light Q. As a result, it is possible to effectively suppress the occurrence of cracks that are likely to occur in the weld-side end portion 122 of the lower plate 12 . As a result, the parts to be welded are reliably melted, and the welding state can be further improved.

As described above, according to this example, it is possible to provide a fillet welding method for an aluminum alloy plate that prevents the occurrence of cracks.

10 Aluminum alloy plate 11 Upper plate 111 Welding side end 114 Irradiated surface 12 Lower plate 121 Flange 122 Welding side end 124 Back surface 20 Galvano scanner 60 Laser oscillator 80 Weld bead 82 Back bead 100 Welding system

Claims (3)

A method for lap fillet welding of an aluminum alloy plate,
While moving the irradiation target position of the laser light along the welding line by the galvanometer scanner, the irradiation period for irradiating the laser light and the interruption period for interrupting the irradiation are alternately repeated,
In the irradiation period, a weld bead is formed by scanning a length of 35 mm or less along the welding line,
A method for lap fillet welding of aluminum alloy plates, wherein the irradiation is interrupted for a time corresponding to ⅓ or more of the irradiation period in the interruption period. 2. The method of lap fillet welding of aluminum alloy plates according to claim 1, wherein during said irradiation period, said laser beam is scanned along said welding line while wobbling it. The lap fillet welding method for aluminum alloy plates according to claim 1 or 2, wherein during the irradiation period, the welding target portion is melted up to the back surface opposite to the surface to be irradiated with the laser beam.

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