JPH11170075A - Pulse laser welding method of aluminum alloy material - Google Patents

Abstract

(57) [Problem] To provide a pulse laser welding method of an aluminum alloy material capable of welding an aluminum alloy material at a high speed without generating welding defects. SOLUTION: In a method of welding an aluminum alloy material by a pulse laser, a pulse width W of one pulse is 15 ms.
That is all. Further, the output waveform of one pulse includes an initial portion of the pulse width Ws in which the peak value gradually decreases and a subsequent portion in which the subsequent peak value is constant. Initial part width W
s is 20% or more and less than 100% of one pulse width W. Further, it is preferable that the lap ratio of the molten portion of the aluminum alloy material is 50% or more and less than 100% in area ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of welding aluminum or aluminum alloy materials (hereinafter, simply referred to as aluminum alloy material including aluminum) at a high speed and preventing welding defects. The present invention relates to a pulse laser welding method for an aluminum alloy material.

[0002]

2. Description of the Related Art In recent years, lighter structures have been adopted in automobiles, railcars, ship transporting machines, and the like in order to improve fuel efficiency and increase speed. Meanwhile, the phone,
2. Description of the Related Art Personal computers and portable devices such as audio devices have become remarkably widespread, and parts and power source batteries have been reduced in weight due to their weight reduction.

In recent years, aluminum alloys made of aluminum or aluminum alloys have been used instead of steel because of their light weight.

[0004] On the other hand, laser welding can be performed at a high speed with a high energy density power using a condensed beam having a small diameter, so that high-strength welding can be performed by fine processing and low heat effects. Intensive research is being conducted to apply the method to welding of welding members, and practical application is also being pursued.

[0005] The laser welding method can be roughly classified into a method using a continuous wave and a pulse wave. Particularly, in a portion requiring fine processing, a pulse-like output is applied to a material to be welded, and the material is melted by its thermal energy. Laser welding using a pulse wave to be joined by welding (hereinafter, pulse laser welding) is used.

Generally, when the above-mentioned pulse laser welding is applied to an aluminum alloy material, the present welding method involving rapid melting and solidification is liable to cause cracks in a welded portion. In particular, in the case of an aluminum alloy material with a wide solid-liquid phase temperature range, cracking of the weld is remarkable, but this is thought to be because the adhesion of the liquid layer cannot catch up with the tensile strain during solidification. Details have not yet been elucidated.

For this reason, a pulse laser welding method of an aluminum alloy in which pulse irradiation conditions are optimized in order to suppress rapid melting and solidification is known (Japanese Patent Laid-Open No. 9-1229).
No. 58). In addition, a pulse waveform control of a down slope shape in which a peak height is gradually decreased over the entire length of the pulse waveform is generally known, and a pulse laser welding method of an aluminum alloy in which the efficiency is further improved is known. JP-A-6-210472).

[0008]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. 9-1
The technique described in Japanese Patent No. 22958 is a technique in which laser irradiation conditions such as a frequency and a melting lap ratio are optimized.
Since no consideration is given to the pulse waveform, cracks may occur in the aluminum alloy having a wide temperature range between the solid and liquid phases.

On the other hand, in the case of a downslope waveform, it is difficult to suppress cracking defects because there is no slow cooling effect unless the pulse width has a certain pulse width. It is not quantitatively grasped whether this can be suppressed. Further, in order to maintain the melting property, it is necessary to increase the pulse width of the down slope waveform without changing the peak height. In this case, the output per pulse increases. The average output of the laser oscillator device is a value obtained by multiplying the output per pulse by the frequency. When the average output is close to the limit value of the device, an increase in the output per pulse causes a decrease in the frequency. As a result, it is necessary to reduce the welding speed, and the production capacity is reduced.

In the technique described in JP-A-6-210472, although the cracking defect can be suppressed, the pulse waveform itself is extremely complicated, and it is extremely difficult to continuously irradiate this waveform industrially. It is.

The present invention has been made in view of the above problems, and provides a pulse laser welding method of an aluminum alloy material capable of welding an aluminum alloy material at a high speed without generating welding defects. The purpose is to:

[0012]

A pulse laser welding method for an aluminum alloy material according to the present invention is a method for welding an aluminum alloy material with a pulse laser, wherein the pulse width of one pulse is 15 ms or more and the pulse width of one pulse is 15 ms or more. The output waveform is composed of an initial portion in which the peak value gradually decreases and a later portion in which the subsequent peak value is constant. The width of the initial portion is not less than 20% and less than 100% of one pulse width. Features.

In the pulse laser welding method for an aluminum alloy material, it is preferable that a lap ratio of a molten portion of the aluminum alloy material is 50% or more and less than 100% in area ratio.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be specifically described with reference to the accompanying drawings. 1A and 1B are pulse waveform diagrams showing a method according to an embodiment of the present invention, wherein FIG. 1A shows a monitor waveform, and FIG. 1B shows a control waveform. The pulse width of one pulse is W, the pulse width of the downslope waveform portion in the pulse initial part where the peak value gradually decreases is Ws, the initial peak height is h1, and the late peak height is h2. In the control waveform, the height of the segment S gradually decreases in the initial portion of the pulse.

In this one pulse, the pulse width W is 15
ms, and the width Ws of the initial portion where the peak value gradually decreases is not less than 20% and less than 100% of one pulse width W.

In the present invention, when the aluminum alloy material is welded by the pulse laser, the pulse width of one pulse is set to 15 ms or more. This is because when the pulse waveform is a down-slope waveform, when the pulse width is approximately 15 ms or more, the portion where the material is melted is held as molten metal for a certain period of time, which has the effect of suppressing rapid solidification. This suppresses weld cracking defects.

On the other hand, the purpose of using the down-slope waveform is to cause the initial portion of the pulse to have a higher peak than the other portions in addition to the slow cooling effect, so that a molten portion is first formed in the aluminum alloy material. That's why. Thus, a high peak is required during the initial period of the pulse because solid aluminum alloy has low light absorption, good thermal conductivity, and high specific heat. This is because it is necessary to melt. Once melted, the aluminum alloy material has a higher light absorptivity than the solid, so that the molten state can be maintained with a lower calorie than the calorie given at the time of fusion. Therefore, in the latter part of the pulse,
As shown in FIG. 2, by gradually decreasing the amount of heat, the molten metal holding time can be lengthened and rapid solidification can be suppressed.

However, when the peak value is gradually reduced in the latter part of the pulse, the pulse width becomes longer, so that the output per pulse becomes higher, and the welding speed is reduced. Therefore, instead of having a smooth down slope as shown in FIG. 2, as shown in FIG. In the subsequent latter period, an output waveform having a constant peak height is used. Thereby, the pulse output of the surplus portion 7 shown by hatching in FIG. 4 can be reduced without substantially changing the size and the fusion depth of the fusion zone.

The width Ws of the initial portion of one pulse shown in FIG.
However, when the pulse width W is less than 20%, the size and depth of the fusion portion are significantly reduced as compared with the fusion portion using a down slope waveform having the same initial peak power (FIG. 2). In addition, since the molten portion at the initial stage of the pulse is small and the amount of heat cannot be maintained, the solidified portion may be rapidly solidified to cause a crack defect. Further, when the portion of Ws becomes 100% of one pulse, that is, W, the output pulse waveform becomes as shown in FIG. 2, and as shown in FIG. 4, the effect of the pulse output labor saving of the present invention can be obtained. Absent.

Further, even when welding is performed using a pulse wave having a waveform shown in FIG. 1, it is not always possible to completely suppress cracking defects depending on a material having high cracking susceptibility. In such a case, in the center of the spot melting portion, which is the final solidified portion, a strain may remain to cause a crack defect. Then, by re-melting that portion with the thermal energy of the next pulse and relaxing the strain, it is possible to completely suppress cracking defects. The lap ratio of the fusion zone for obtaining such an effect is 5
It is necessary to be 0% or more and less than 100%, and the highest effect can be obtained in this wrap ratio range.

The welding conditions for laser welding applied to the welding of aluminum materials are not particularly limited. For example, the welding conditions such as laser output and welding speed may be selected according to the type of laser to be used, the thickness and shape of the workpiece, and the like.

As the welding method, an appropriate welding method such as a butt welding and a lap welding may be selected according to a joining portion, and the present invention can be applied to any joint.

The flow rate of the shielding gas varies depending on the welding conditions. However, to get a good weld,
Preferably, the flow rate of the shielding gas is about 5 to 30 liters per minute.

[0024]

Next, examples of the present invention will be described in comparison with comparative examples which are out of the scope of the present invention. The welding conditions are
Test material: JIS A5052P-O, A5182P-
O, plate thickness: 1 mm, type of shielding gas: Ar gas, flow rate of shielding gas: 15 liters per minute, welding method: bead-on-plate welding.

First Example The first example was performed under pulse irradiation conditions of a welding speed of 200 mm / min and a frequency of 20 Hz, using the pulse waveforms shown in FIGS. FIG. 3 shows a pulse waveform having a constant peak value h3. In the pulse output shown in FIGS. 1 to 3, the peak height h1 is 1600 w and h2 is 1200.
W and h3 were set to 1400W. Further, in the waveform of FIG. 1, the pulse width Ws of the initial portion is set to 50% of one pulse width W. Moreover, the crack length measured the total crack length in the welding bead of welding length 50mm. The result is shown in FIG. In FIG. 5, 8 is a molten spot 8, and 9 is a weld crack. As shown in FIG. 5, in the rectangular wave (Comparative Example 2) shown in FIG. 3, cracks occurred, and no crack suppressing effect was recognized even when the pulse width was widened. In contrast, in FIG. 1 (Example) and FIG. 2 (Comparative Example 1), no crack defect occurred when the pulse width was 15 ms or more. As described above, in the pulse waveforms of FIGS. 1 and 2, when the pulse width is 15 ms or more, crack defects can be suppressed.

Second Embodiment Welding was carried out under pulse irradiation conditions of a welding speed of 300 mm / min and a frequency of 25 Hz, using the waveforms shown in FIGS. The peak values h1 and h2 are the same as in the first embodiment, and Ws shown in FIG. 1 is 5 to 100% of one pulse width.
And The length of the crack 9 was evaluated in the same manner as in the first example. The width of the weld was the diameter of the welding spot 8. FIG. 6 shows the result. FIG. 6 is a graph showing the effect of Ws / W, with Ws / W plotted on the horizontal axis and one pulse output (a), melting width (b), and crack length (c) plotted on the vertical axis.

From the results shown in FIG. 6, Ws / W is 20
% Or more, it was possible to save the power of the pulse output only in the surplus portion indicated by hatching, and to have a sufficiently large melting width. Ws / W is 20%
No cracks occurred in the above cases. On the other hand, when Ws / W is less than 20%, the melting width is drastically reduced and crack defects are generated.

The welding speed is the width Ws of the initial part of one pulse.
Although determined by the peak values h1 and h2, when the ratio of the initial waveform was 50%, the welding speed could be improved by about 20% compared to the case of the waveform shown in FIG. Therefore, FIG.
As shown in FIG. 1, in the case of the waveform shown in FIG. 1 of the present invention, the welding speed can be improved as compared with the conventional down slope waveform.

Third Embodiment This embodiment shows the effect of the lap ratio of the molten spot. Welding was performed using the waveform shown in FIG. 1 under pulse irradiation conditions with a welding speed of 200 to 600 mm / min and a frequency of 20 to 30 Hz. The welding conditions are as follows:
This is the same as the embodiment and the second embodiment, and the method for measuring the crack length is also the same. Ws / W was 50%. FIG. 7 shows the result. FIG. 7 is a graph showing the relationship between the melting spot wrap ratio on the horizontal axis and the crack length on the vertical axis. FIG. 7 is for the 5052 alloy. As shown in FIG. 7, cracks occurred when the lap ratio was less than 50%, whereas no cracks occurred when the lap ratio was 50% or more. Therefore, crack defects can be prevented when the molten portion lap ratio is 50% or more in area ratio. However, with the 5182 alloy, no change in the crack length due to the lap ratio was observed. Therefore, in the case of a type affected by the lap rate, it is necessary to adopt the pulse waveform shown in FIG.

[0030]

As described in detail above, according to the present invention, it is possible to prevent the occurrence of welding defects during laser welding and to stably perform pulse laser welding of aluminum alloy materials with high productivity. As a result, a high-quality welding member can be manufactured.

Thus, by applying laser welding to a structure using an aluminum alloy material, mechanical performance such as strength and ductility of the entire structure can be improved, and the applicable range of the aluminum alloy material can be expanded. It is possible to take advantage of the weight reduction by the aluminum alloy material in various fields. Therefore, the value of the present invention is extremely high.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a pulse waveform according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a pulse waveform according to Comparative Example 1.

FIG. 3 is a waveform diagram showing a pulse waveform according to Comparative Example 2.

FIG. 4 is a diagram for explaining an effect of the present invention by comparing an example and a comparative example 1;

FIG. 5 is a graph showing a relationship between one pulse width W and a crack length.

FIG. 6 is a graph showing the relationship between Ws / W and one pulse output, melting width and crack length.

FIG. 7 is a graph showing a relationship between a molten spot wrap ratio and a crack length.

[Explanation of symbols]

 h1; initial peak value h2; late peak value h3: rectangular wave peak height Ws; pulse width of the down slope waveform portion in the initial portion W; 1 pulse width S; segment 7; surplus portion of pulse output 8; Weld crack

Claims (2)

[Claims] 1. A method for welding an aluminum alloy material with a pulse laser, wherein a pulse width of one pulse is 15 ms or more and an output waveform of one pulse has an initial portion where a peak value gradually decreases and a peak value subsequent thereto. Wherein the width of the initial portion is at least 20% and less than 100% of one pulse width. 2. The pulse laser welding method for an aluminum alloy material according to claim 1, wherein the lap ratio of the molten portion of the aluminum alloy material is 50% or more and less than 100% in area ratio.