JPH0847788A - Yag laser welding method of aluminum alloy - Google Patents

Abstract

PURPOSE:To provide the welding method of YAG laser not having solidification crack and not generating blow hole. CONSTITUTION:Regions adjacent each other among the aluminum alloy surface region irradiated with YAG laser are to be overlapped while an aluminum alloy surface is irradiated with YAG laser in the prescribed period and pulse, welding of aluminum alloy is executed by mutually traveling position to be irradiated and aluminum alloy at the prescribed speed. In the case that a prescribed welding speed is v (mm/min) and a rate of laser irradiating time per one period for a prescribed cycle is (d)%, YAG laser output is >=4kw and an irradiating heat quantity per one period is <=20J, (v) and (d) are selected to satisfy the relation of v<=4300 further d>=(v/100)+29, thus, the welding is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method for aluminum alloys.

[0002]

2. Description of the Related Art For welding conventional aluminum alloys, a tungsten inert gas (TIG) welding method, a metal inert gas (MIG) welding method or a plasma welding method is generally used. However, with these welding methods,
Since the amount of heat input is large, the number of man-hours required to remove the thermal strain increases. On the other hand, in laser welding, since the light can be focused locally and the energy density can be increased, the width of welding (welding bead) is narrower than the penetration depth, and the thermal strain after welding is also reduced. Therefore, in recent years, it has come to be noticed as a new welding method.

As a light source for laser welding, a carbon dioxide gas laser or a YAG laser is generally used, but a YAG laser is considered to be more advantageous for welding an aluminum alloy. This is because the absorption rate of the aluminum alloy with respect to the wavelength of the YAG laser (1.06 μm) is several times larger than the absorption rate with respect to the wavelength of the carbon dioxide laser (10.6 μm).

[0004]

As described above, the YAG
Laser welding of aluminum alloys has attracted attention, but welding defects at the welded portion by YAG laser, especially solidification cracking during welding and frequent occurrence of blowholes, have become a problem.

An object of the present invention is to provide a method for welding an aluminum alloy by a YAG laser which does not cause solidification cracking or blowholes during welding.

[0006]

According to the laser welding method of the present invention, while irradiating the aluminum alloy surface with YAG laser light in a pulsed manner at a predetermined cycle, the aluminum alloy surface areas irradiated with the YAG laser light are mutually In the laser welding method of welding an aluminum alloy by moving the irradiated position and the aluminum alloy relatively at a predetermined welding speed so that adjacent regions overlap each other, the predetermined welding speed is set to v [mm / Min], and the ratio of the laser light irradiation time per one cycle to the predetermined cycle is d
When set to [%], the peak output of the YAG laser is 4 kW
As described above, the irradiation heat quantity per cycle is set to 20 J or less, and v ≦
4300 and v and d are selected so as to satisfy the relationship of d ≧ (v / 100) +29 and welding is performed.

When the frequency of pulsed YAG laser light irradiation is f [Hz], the peak output of the YAG laser is 4 kW or less, and the irradiation heat quantity per cycle is 20 J.
Below, v ≦ 4300 and f ≧ (v / 50) +5
Welding may be performed by selecting v and f so as to satisfy the relationship of 7.

Further, the predetermined welding speed, frequency and 1
Irradiation heat quantity per cycle, peak output of YAG laser, 1
Welding may be performed under various conditions that allow good welding by changing the ratio of the laser light irradiation time per cycle.

[0009]

By welding the aluminum alloy using the YAG laser under the above-mentioned appropriate conditions, excellent welding without cracks and blow holes can be performed. this is,
It is considered that since the molten pool is cooled at a slower rate, cracking during solidification is less likely to occur. Even if cracks or the like occur, most of the solidified molten pool is remelted, and it is considered that the cracks or the like can be removed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a laser welding apparatus using a YAG laser will be described with reference to FIG.

FIG. 1 shows a perspective view of a YAG laser welding apparatus. A nozzle 11 is arranged above an XY stage 10 on which an object to be processed is placed and which can move in parallel in the X and Y directions. The nozzle 11 is held by an arm 12, and the arm 12 can be moved up and down by a linear motor 13.

The nozzle 11 has an optical fiber 14 for Y
It is connected to the AG laser generator 15. The laser light output from the YAG laser generator propagates to the nozzle 11 through the optical fiber 14 and is irradiated onto the processing object placed on the XY stage 10.

Welding can be performed by moving the object to be processed on the XY stage 10 and irradiating the object to be processed with a pulsed YAG laser from the nozzle 11. Although FIG. 1 shows the case where the nozzle is fixed and the object to be processed is moved, the object to be processed may be fixed and the nozzle may be moved.

When welding an aluminum alloy, there is a problem that defects are more likely to occur during welding, as compared with general steel materials. The thermal conductivity of aluminum alloy is about 4 times that of general steel materials, and the thermal contraction rate is about 1.5 times. When local melting is performed with a heat source having a high energy density such as a laser beam, a molten pool formed by melting the aluminum alloy is formed at the position irradiated with the laser beam. When the laser beam irradiation is stopped or the laser beam irradiation position is moved, this molten pool is rapidly cooled and solidified. In particular, since the oscillation form of the YAG laser is pulse oscillation,
The molten pool is cooled rapidly during the period when the laser beam irradiation is stopped.

Further, the heat shrinkage ratio of the aluminum alloy is
Since it is about 1.5 times that of general steel materials, cracks are likely to occur inside the solidified portion during solidification. Further, due to a large difference in hydrogen solubility between the solid phase and the liquid phase, holes (blowholes) are likely to occur. In order to prevent cracks during solidification and the formation of blowholes, it is considered that the solidification rate of the molten pool should be slowed down.

FIG. 2 shows a surface region irradiated with a YAG laser when welding an aluminum alloy. The beam spot of the circular YAG laser moves on the aluminum alloy surface. Since the YAG laser is intermittently irradiated in a pulsed manner, the area irradiated during one pulse irradiation is an elliptical area in which the circular area is translated and scanned.

The oval region C1 in FIG. 2 shows the region irradiated by the first pulse irradiation. Points P _1s and P _1e respectively represent the center points of the beam spots at the start and end of pulse irradiation.

Since the workpiece (eg, aluminum alloy) is moving even during the period when the YAG laser is not irradiated,
The second pulse irradiation start position is a position moved by a predetermined distance from the final irradiation position of the oval region C1 irradiated by the first pulse irradiation. The elliptical region C2 in FIG. 2 indicates the region irradiated by the second pulse irradiation, and the point P _2s ,
P _2e represents the center point of the beam spot at the start and end of the second pulse irradiation, respectively.

By welding the elliptical regions similar to the elliptical regions C1 and C2 irradiated by the first and second pulse irradiation in one direction with a predetermined overlap, the workpiece is linearly welded. can do. The degree of overlap of the oval areas is called a wrap rate, and is defined as w = (bv / (60 * f)) / b * 100 (1). Here, the lapping rate is w [%], the laser beam spot diameter is b [mm], and the relative speed between the workpiece and the beam spot (hereinafter referred to as welding speed) is v [mm / mi].
n], and the frequency of pulse irradiation is represented by f [Hz].

V / (60 * f) represents the distance traveled by the beam spot in one cycle, that is, the length of the line segment P _1s P _2s in FIG. From this, it can be said that the lap rate w corresponds to the degree of overlap between the circular regions that are first irradiated in the first and second pulse irradiations. Therefore, to be precise, it differs from the degree of overlap of the elliptical regions C1 and C2. However, since the distance moved in one pulse irradiation time is relatively shorter than the beam spot diameter, the lap rate w
Can be considered to approximately correspond to the degree of overlap between the oval regions C1 and C2.

It is considered that the lapping rate should be increased in order to prevent cracks and blowholes from occurring in laser welding. If the lapping rate is increased, cracks and blowholes generated by the first pulse irradiation can be remelted and removed by the second pulse irradiation.

In order to gradually cool the molten pool, the time from the first pulse irradiation to the second pulse irradiation may be shortened. That is, the ratio (duty ratio) of the pulse irradiation time per cycle may be increased as much as possible and the frequency may be increased. When the pulse irradiation time (on-time) per cycle is a [s], the duty ratio d [%]
Is expressed as d = a * f * 100 (2).

Furthermore, the peak output P [W], 1 of the YAG laser is set as a parameter that affects the presence or absence of welding defects.
The amount of heat C [J] per cycle can be considered. The peak output P [W] and the amount of heat C [J] per cycle have a relationship of C = a * P (3).

Based on the above consideration, welding speed v, frequency f,
The duty ratio d, the lap rate w, the on-time a, the peak output P, and the heat amount C per cycle were variously changed, the aluminum alloy was welded, and the occurrence of cracks and blowholes in the welded portion was examined. The beam spot diameter b is 1
It was fixed to mm. However, since the above parameters have the relationships of the expressions (1) to (3), only five of the eight parameters can be independently selected.

FIG. 3 shows the occurrence of welding defects when the welding conditions are changed. The horizontal axis of FIG. 3A represents the welding speed in the unit of mm / min, and the vertical axis represents the duty ratio in the unit of%.
It is represented by. The symbols Δ, −, ×, and □ in the figure show the cases where the lap rates are 90%, 70%, 50%, and 30%, respectively.
The amount of heat per pulse irradiation was 20 J and the peak output was 4 kW. Since the heat quantity is 20 J and the peak output is 4 kW, the irradiation time is 5 ms from the relationship of the equation (3).

FIG. 4 shows a sketch of a cross-sectional photograph of a typical welded portion when pulse irradiation is performed twice under the above various conditions. FIG. 4 (A) shows a case where there is no welding defect, and FIG.
Indicates the case where welding defects remain.

As shown in FIG. 4A, a molten pool mark 22 formed by the second pulse irradiation is formed so as to partially overlap the molten pool mark 21 formed by the first pulse irradiation. No weld defect is found in the weld pool trace 21. Figure 4 (B)
In the case of No. 3, a welding defect 25 is generated in the trace 23 of the molten pool.

In FIG. 3 (A), the welding conditions in which no welding defect has occurred are surrounded by white circles. Good welding can be performed under the conditions above the polygonal line L1.
The polygonal line L1 is a straight line rising to the right when the welding speed is 4300 mm / min or less, and indicates that the duty ratio must be increased when the welding speed is increased.

That is, regardless of the lapping rate, when the welding speed is 4300 mm / min or less, good welding can be performed when the condition of d ≧ (v / 100) +29 (4) is satisfied. .

The welding speed is 4300 to 6000 mm.
/ Min, the polygonal line L1 becomes substantially horizontal, and good welding can be performed under the condition of d ≧ 70 (5) regardless of the welding speed.

FIG. 3B shows the state of occurrence of welding defects when the frequency is changed instead of the duty ratio of FIG. In FIG. 3A, the on-time a per time
^Was fixed at 5 × 10 ^-3 s and welding was performed, so the formula (2)
From this, the relationship of f = 2 * d is derived. Using this relationship,
3B is obtained by converting the duty ratio on the vertical axis of FIG. 3A into a frequency. Good welding can be performed in a region above the polygonal line L2 in the figure.

From FIG. 3B, excellent welding can be performed when the welding speed is 4300 mm / min or less regardless of the lapping rate and when the condition of f ≧ v / 50 + 57 (6) is satisfied.

The welding speed is 4300 to 6000 mm.
/ Min, good welding can be performed when the condition of f ≧ 140 (7) is satisfied.

In equations (4) to (7), the lap rate w is 30%.
Applies in the range of up to 90%. In the experiment shown in FIG. 3, the beam spot diameter was fixed at 1 mm, but if the lap ratio is within this range even if the beam spot diameter is changed, the formula (4)
It is considered that good welding can be performed under the conditions (7) to (7).

Next, the heat quantity per pulse irradiation is set to 2
The result of performing the same experiment while changing the peak output while keeping the value constant at 0J will be described. FIG. 5 (A) shows appropriate conditions for welding speed and duty ratio, and FIG. 5 (B).
Indicates appropriate conditions for welding speed and frequency. The polygonal lines indicated by symbols ●, ■, and ▲ in the figure indicate boundaries of appropriate conditions when the peak outputs are set to 4 kW, 5 kW, and 7 kW, respectively. Good welding can be performed without welding defects in the regions above the broken lines.

The amount of heat per pulse irradiation is 2
Since it is 0J constant, the peak output is 4kW, 5kW, 7
On time at kW is 5ms, 4ms,
It will be 2.9 ms. When the peak output is 4kW,
The polygonal lines L1 and L2 shown in (A) and (B) are reprinted.

As shown in FIG. 5A, the welding speed is 430.
In the region of 0 mm / min or less, there is little difference between the proper conditions regarding the duty ratio. Welding speed is 4300 mm / mi
In the region of n or more, the lower limit of the proper duty ratio becomes smaller as the peak output becomes larger. Peak output is 5
At kW, the lower limit of the duty ratio is about 67%, and when the peak output is 7 kW, the lower limit of the duty ratio is about 59%. In this way, as the peak output is increased,
The lower limit of the proper duty ratio becomes smaller.

As shown in FIG. 5B, the peak output is 5
At kW, good welding can be performed when the welding speed is within a range of 5000 mm / min or less and f ≧ (3/100) * v + 57 (8) is satisfied, and the welding speed is 5000 In the range of up to 7,000 mm / min, good welding can be performed when the condition of f ≧ 170 (9) is satisfied.

When the peak output is 7 kW, good welding is performed when the welding speed is within the range of 3600 mm / min and the condition of f ≧ (3.3 / 100) * v + 90 (10) is satisfied. When the welding speed is in the range of 3600 to 6000 mm / min, good welding can be performed when the condition of f ≧ 210 (11) is satisfied.

Thus, when the peak output is reduced,
The lower limit of the proper frequency is low. FIG. 6 shows an appropriate condition similar to FIG. 5 when the amount of heat per pulse irradiation is 30 J.

As shown in FIGS. 6 (A) and 6 (B),
When the peak output is 4 kW and 5 kW, the lower limits of the appropriate conditions for the duty ratio and the frequency show almost the same tendency.
That is, in the range where the welding speed is 2000 mm / min or less, the condition of d ≧ (2.2 / 100) * v + 35 (12) f ≧ (2.5 / 100) * v + 50 (13) Good welding can be performed when the above conditions are satisfied, and when the welding speed is in the range of 2000 to 5000 mm / min, it is good when the conditions of d ≧ 79 (14) f ≧ 120 (15) are satisfied. Welding can be done.

When the peak output is 7 kW, the duty ratio is 7 when the welding speed is 2000 mm / min or more.
Good welding could not be performed in the range of 0% or less or the frequency of 160 Hz or less. Welding speed is 100
At 0 mm / min or less, it is considered that good welding can be performed when d ≧ 40 (16) f ≧ 100 (17).

As shown in the above experimental results, when welding an aluminum alloy using a YAG laser, it is necessary to select an appropriate welding speed, duty ratio or frequency, heat quantity of pulse irradiation per time, and peak output. Due to
Good welding can be performed without cracks and blow holes.

Further, in FIGS. 5 and 6, the heat quantity of one pulse irradiation was set to 20 J and 30 J, respectively. Comparing FIG. 5 and FIG. 6, it can be seen that if the amount of heat of one pulse irradiation is increased, it is necessary to increase the duty ratio or the frequency. From this, it is considered that good welding can be performed under appropriate conditions shown in FIG. 5 when the amount of heat of one pulse irradiation is 20 J or less. Further, when the heat quantity of one pulse irradiation is 30 J or less, it is considered that good welding can be performed under the appropriate conditions shown in FIG.

From the viewpoint of productivity, a higher welding speed is preferable. More specifically, the welding speed is 1000 mm / min
It is preferable that it is above. Although the present invention has been described above with reference to the embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0046]

As described above, according to the present invention,
A YAG laser can be used to successfully weld aluminum alloys without cracks and blowholes.

[Brief description of drawings]

FIG. 1 is a perspective view of a laser welding device.

FIG. 2 is a plan view of a laser irradiation area when welding is performed using a YAG laser.

FIG. 3 is a graph showing a state of occurrence of welding defects with respect to welding conditions of welding using a YAG laser.

FIG. 4 is a sketch of a photograph showing a cross section of a weld.

FIG. 5 is a graph showing appropriate welding conditions when the heat quantity of one pulse irradiation is 20J.

FIG. 6 is a graph showing appropriate welding conditions when the heat quantity of one pulse irradiation is 30 J.

[Explanation of symbols]

 10 XY stage 11 Nozzle 12 Arm 13 Linear motor 14 Optical fiber 15 YAG laser generator 21-24 Mark of molten pool 25 Welding defect

Claims (11)

[Claims] 1. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. In a laser welding method for welding an aluminum alloy by moving a position and an aluminum alloy relatively at a predetermined welding speed, the predetermined welding speed is v [mm / min] The ratio of laser light irradiation time is d
[%], The peak output of the YAG laser is 4 kW or more and the irradiation heat amount per cycle is 20 J or less, and v and 4 are satisfied so that the relationship of v ≦ 4300 and d ≧ (v / 100) +29 is satisfied. A laser welding method in which welding is performed by selecting d. 2. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. In a laser welding method for welding an aluminum alloy by moving a position and an aluminum alloy relatively at a predetermined welding speed, the predetermined welding speed is v [mm / min] The ratio of laser light irradiation time is d
[%], The peak output of the YAG laser is 4 kW or more, the irradiation heat amount per cycle is 20 J or less, and v and d are selected so as to satisfy the relationship of v ≦ 6000 and d ≧ 70. Laser welding method for welding. 3. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. In a laser welding method for welding an aluminum alloy by moving a position and an aluminum alloy relatively at a predetermined welding speed, the predetermined welding speed is v [mm / min] The ratio of laser light irradiation time is d
When [%] is set, the peak output of the YAG laser is 4 to 7 kW or more, the irradiation heat amount per cycle is 20 J or less, and v and d are selected so as to satisfy the relationship of v ≦ 6000 and d ≧ 59. Welding method for welding by welding. 4. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency to be set is f [Hz], the peak output of the YAG laser is 4 kW or less, the irradiation heat amount per cycle is 20 J or less, and v ≦ 4300 and f ≧ (v / 50) +57 are satisfied. Welding method in which welding is performed by selecting v and f as described above. 5. Irradiation is performed in such a manner that the YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency to be set is f [Hz], the peak output of the YAG laser is 4 kW or less, the irradiation heat amount per cycle is 20 J or less, and v and f are set so as to satisfy the relationship of v ≦ 6000 and f ≧ 140. A laser welding method for selecting and welding. 6. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency to be set is f [Hz], the peak output of the YAG laser is 4 to 7 kW or less, the irradiation heat amount per cycle is 20 J or less, and v ≦ 3600, and f ≧ (3.3 / 100) * v + 9
A laser welding method in which v and f are selected so as to satisfy the relationship of 0 and welding is performed. 7. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency to be set is f [Hz], the peak output of the YAG laser is 4 to 7 kW or less, the irradiation heat amount per cycle is 20 J or less, and v ≤ 6000 and v ≥ 210 And f are selected for welding. 8. Irradiation is performed such that YAG laser light is pulsedly irradiated on the aluminum alloy surface at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated by the YAG laser light overlap each other. In a laser welding method for welding an aluminum alloy by moving a position and an aluminum alloy relatively at a predetermined welding speed, the predetermined welding speed is v [mm / min] The ratio of laser light irradiation time is d
[%], The peak output of the YAG laser is 4 to 5 kW, the irradiation heat amount per cycle is 30 J or less, v ≦ 2000, and d ≧ (2.2 / 100) * v + 3
A laser welding method in which v and d are selected so as to satisfy the relationship of 5, and welding is performed. 9. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. In a laser welding method for welding an aluminum alloy by moving a position and an aluminum alloy relatively at a predetermined welding speed, the predetermined welding speed is v [mm / min] The ratio of laser light irradiation time is d
[%], The peak output of the YAG laser is 4 to 5 kW or less, the irradiation heat amount per cycle is 30 J or less, and v and d are selected so as to satisfy the relationship of v ≦ 5000 and d ≧ 79. Welding method for welding by welding. 10. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency to be set is f [Hz], the peak output of the YAG laser is 4 to 5 kW or less, the irradiation heat amount per cycle is 30 J or less, v ≦ 2000, and f ≧ (2.5 / 100) * v + 5
A laser welding method in which v and f are selected so as to satisfy the relationship of 0 and welding is performed. 11. Irradiation is performed such that YAG laser light is applied to the aluminum alloy surface in a pulsed manner at a predetermined cycle, and areas adjacent to each other among the aluminum alloy surface areas irradiated with the YAG laser light overlap each other. A laser welding method in which a position and an aluminum alloy are relatively moved at a predetermined welding speed to perform welding of an aluminum alloy, wherein the predetermined welding speed is v [mm / min] and pulsed YAG laser light is applied. When the frequency is set to f [Hz], the peak output of the YAG laser is 4 to 5 kW or less, the irradiation heat amount per cycle is 30 J or less, and v ≦ 5000 and f ≧ 120 are satisfied. And f are selected for welding.