JP2000061673A - Fillet welding method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a laser welding method capable of realizing complete penetration into a material to be welded in T-shaped fillet welding. SOLUTION: When performing T-shaped fillet welding by laser welding, the average power density is 125 to 2600 kW /
A laser beam of cm ² is set so that the incident angle is 5 to 30 °, and welding is performed at a welding speed of 0.05 to 0.7 m / min. At that time, the wavelength of the laser light is 0.5-1.5μ.
m, and N ₂ gas is preferably used as the shielding gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a T-shaped fillet welding method using a laser beam, and more specifically, a good welded portion can be obtained even if the incident angle of the laser beam during the T-shaped fillet laser welding is large. Regarding fillet welding method.

[0002]

2. Description of the Related Art Up until now, most of the fillet welding has been arc welding, and this tendency is particularly large in the welding of steel materials having a large plate thickness. On the other hand, laser welding has advantages such as less heat input, less problems such as welding deformation, and generally higher welding speed and better welding work efficiency than arc welding compared to arc welding. It is a welding method. Heretofore, laser welding has been mostly used mainly for butt welding. However, there may be many fillet welds depending on the structure of the welded structure.

A major problem arises when applying laser welding to T-shaped fillet welds. The problem is that the laser welding torch comes into contact with the flat plate and the incident angle cannot be reduced. Therefore, T
When performing fillet welding with a laser, it is necessary to perform welding from both sides. In the case of such laser welding, since the laser light does not penetrate through the steel to be welded, there is a risk that the metal vapor generated at the time of welding will not be able to escape and a defect will be generated in the welded part. It has been considered difficult to apply laser welding to T-shaped fillet welding because there is a problem in welding work efficiency because welding must be performed twice for one joint in order to perform welding. .

[0004]

As described above, a major technical barrier in applying laser welding to a T-shaped fillet weld is that the torch and the flat plate come into contact with each other when the incident angle is reduced. However, in the existing technology, it cannot be said that the characteristics of laser welding are sufficiently utilized.
Therefore, even if the incident angle is large enough that the torch does not hit the flat plate, it is very industrially important to find out the welding condition that the welding bead penetrates to the opposite side by just welding from one side, that is, complete welding is achieved. There are merits.

It is an object of the present invention to provide conditions for laser welding capable of realizing complete penetration into a material to be welded in such T-shaped fillet welding.

[0006]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to find out the welding conditions as described above, and finally,
The present invention has led to the finding of a laser welding condition in which welding is possible even if the incident angle is large, that is, the torch and the flat plate do not contact each other, and the summary thereof is as follows. (1) When performing T-shaped fillet welding by laser welding, laser light having an average power density of 125 to 2600 kW / cm ² was set so that the incident angle was 5 to 30 °, and the welding speed was 0.05. A fillet welding method characterized by welding at ~ 0.7 m / min. (2) The fillet welding method as described in (1) above, wherein a laser beam having a wavelength of 0.5 to 1.5 μm is used. (3) The fillet welding method according to (2), wherein N ₂ gas is used as the shield gas. (4) A CO ₂ laser is used as the laser beam, and O ₂ is contained in a shield gas of any one of He, Ar, and CO ₂ or a mixed gas of two or more kinds thereof in an amount of 5 to 3% by volume.
The fillet welding method according to (1) above, wherein a 0% mixed gas is used and a steel material from which the black skin near the groove is removed is used as the steel material to be welded. (5) A CO ₂ laser is used as the laser light, and O ₂ is contained in a shield gas of He, Ar, or CO ₂ or a mixed gas of two or more of these in an amount of 0 to 2% by volume.
The fillet welding method according to (1) above, wherein a gas mixed with 5% is used and a steel material that does not remove the black skin near the groove is used as the steel material to be welded.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. First, the technical idea of the present invention will be described.
Welding conditions are often evaluated by welding heat input, that is, the heat input per 1 cm of weld bead length. Normal,
When the heat input is high, the depth of penetration is large. But,
Even if the heat input is the same, the melting depth may be different. That is, even if the heat input is the same, the power density is different. For example, when the power density is double and the welding speed is also double, the heat input amount is the same, but the melting shape is usually different. Generally, if the power density is high,
The depth of melting is large, and instead, it tends to be an elongated bead. On the contrary, when the power density is kept low and the welding speed is reduced to obtain the same heat input, the bead width tends to be widened, and the depth of penetration is reduced accordingly. Thus, it can be seen that when the power density is set high, the melting tends to be deep even with the same heat input amount.

Under the welding conditions in which the heat input is secured by keeping the power density low and the welding speed low, the molten portion is mainly determined by heat conduction from the arc. That is,
Since the heat introduced by the welding arc is conducted not only in the depth direction but also in the bead width direction, it can be considered that the bead width tends to widen accordingly.

When laser welding is applied to fillet welded joints, if the power density is high, as can be understood from the above consideration, the laser beam will be melted in the straight traveling direction, so that the incident angle can be reduced. It can be understood that it is impossible to achieve complete penetration only by welding from one side unless it is done. However, in the T-shaped fillet joint, as shown in FIG. 1, the flat plate 1 generates heat in two directions 1a,
The vertical plate 2 conducts heat in only one direction 2a, while the vertical plate 2 conducts heat in the vertical plate 2 more easily than in the flat plate 1 and therefore melts more easily. If this phenomenon can be effectively utilized, the vertical plate can be effectively melted, and as a result, the weld bead 3 of the fillet weld portion can be penetrated, that is, complete penetration can be realized.

Based on the above analysis, the present inventor has made extensive studies on the weld bead shape of the fillet welded joint when the power density is suppressed as compared with the ordinary laser welding condition and the welding speed is lowered instead, and finally the laser is finally obtained. By limiting the light power density and welding speed to a specific range, we have found that there is a condition under which welding heat is retained in the vertical plate and complete penetration is achieved.

Next, the reason why the average power density of the laser light is limited will be described. With the current technology, the power of laser light has reached a considerably high level. However, as described above, the essence of the present invention is that the heat input amount is secured by suppressing the power of laser light and lowering the welding speed accordingly, and the characteristic of heat conduction in the T-shaped fillet joint is Since it exists in effectively utilizing the property that heat easily stays in the plate portion, it is necessary to set a range for the power density of laser light. Maximum average power density 2600
At kW / cm ² , if the power density exceeds this, melting will occur in the direction in which the laser light travels straight, and in order to achieve complete melting, it is necessary to reduce the incident angle.
Contact between the torch and the flat plate occurs, which is a problem in the conventional technology. Therefore, the upper limit of the average power density of laser light is set to 2600 kW / cm ² . Lower limit 125kW / cm
No. ² shows that the penetration amount is not sufficient at lower power densities, and the welding speed becomes unrealistic when trying to secure the heat input amount to obtain the specified penetration under the conditions of this range. The lower limit was set to this value because the heat input cannot be secured unless the temperature is lowered to.

Next, the reason why the welding speed is limited will be described. If the upper limit of the welding speed, 0.7 m / min, is exceeded, it is necessary to set the average power density of the laser light higher than that of the present invention in order to secure the heat input.
However, as described above, in this case, the fusion occurs in the direction in which the laser light travels straight, so unless the incident angle is made small, fillet welding cannot be realized completely by only welding from one side. On the other hand, if the average power density is suppressed, the welding speed will be high, and the amount of heat input will be insufficient, resulting in insufficient melting, and complete melting will not be realized. The upper limit of the welding speed is set for the above reasons. The lower limit of 0.05 m / min is a speed that can be achieved even with normal arc welding at welding speeds below this,
The benefits of applying laser welding to fillet joints are gone. This is against the intent of the present invention, so the lower limit was set to this value.

Next, the reason why the incident angle is limited will be described. The lower limit of 5 ° uses the conventional technique even if the torch comes into contact with the plate at a smaller angle, and even if the torch and the plate can be prevented from contacting with each other by some technique. It is fillet welding. This is against the intent of the present invention, so the lower limit was set to this value. The upper limit of 30 ° was set because if the incident angle exceeds this, no matter what condition the laser welding is set to, the complete penetration cannot be achieved by fillet welding from only one side.

Next, the reason for limiting the wavelength will be described. In order to obtain a good weld bead shape, in addition to the conditions already described, it is necessary to consider the conditions of the wavelength of the laser beam and the selection of the shielding gas. The present inventors have found that when the wavelength of the laser light is within a certain range, a sufficiently good fillet welded joint can be obtained with a shielding gas used for ordinary laser welding, and the range is set. is there. The upper limit of 1.5 μm was set at a wavelength longer than this, because the object of the present invention cannot be achieved unless the shielding gas is made to have a certain specific component. The lower limit of 0.5 μm was set because it was judged that there was no industrial advantage because there was no practical laser source with a laser beam having a shorter wavelength.

Next, the wavelength of the laser light is 0.5 to 1.5.
The reason why the shielding gas is limited when it is in the range of μm will be described. The shielding gas used in laser welding is generally any one of He, Ar, and CO ₂ or a mixed gas of two or more of these. But N ₂
Gas is a very cheap gas because it exists in the atmosphere,
It goes without saying that if this becomes available, there will be great economic benefits. However, N ₂ gas has not been generally used due to a defective bead shape. But,
The present inventors have found that the wavelength of laser light is 0.5 to 1.5 μm.
Within the range, it was found that a bead shape that can withstand practical use is realized even when N ₂ gas is used as a shield gas, and the present invention has been completed.

Next, the reason why the shield gas is limited when using CO ₂ laser light will be described. First, the case of using a steel material from which the black skin near the groove is removed will be described. The CO ₂ laser has a wavelength of about 10 μm and is not located within the above-mentioned wavelength range.
However, the CO ₂ laser is one of the most used laser sources in the industry. Therefore, if fillet welding can be realized under the condition that the incident angle is increased by using this laser source, there will be a great industrial advantage. From the above viewpoints, the present inventors investigated the effect of the shield gas when using a CO ₂ laser. As a result, He, A
r, CO ₂ or a mixed gas of two or more of these, O
It has been found that fillet welding, which is the object of the present invention, can be realized by using a gas in which ₂ is mixed by 5 to 30% by volume.

It is not clear why the incident angle can be made large by mixing O ₂ .
A possible interpretation is that when O ₂ is mixed, the chemical reaction in the molten portion becomes active, resulting in a large amount of heat generation and a large proportion of melting due to the effect of heat conduction. The reason why the lower limit of the volume% of O ₂ was set to 5% was set because a fillet welded joint, which is the object of the present invention, cannot be obtained by CO ₂ laser welding at a lower content ratio. The upper limit of 30% is set to this value because good weld beads cannot be obtained when the volume ratio exceeds this value.

Next, the case of using a steel material which does not remove the black skin near the groove will be described. The black skin is a film of iron oxide existing on the surface of the steel material. Therefore, welding the steel material with black skin has the same effect as introducing oxygen into the molten portion. Therefore, the present inventors have confirmed that the same effect as in the case of mixing oxygen in the shielding gas can be exhibited in CO ₂ welding. When the steel material with black skin is used, a good fillet weld can be obtained under the condition where the incident angle is set large even when the shield gas mixed with O ₂ gas described above is used. However, since O ₂ is introduced from the black skin, the shielding gas O 2
_{2 It} is necessary to set the content differently from the case without black skin. The inventors diligently studied the relationship between the welding conditions and the bead shape in the presence of a black skin, and when the O ₂ content was 25% or less, the incident angle was set to be large and complete melting was realized. I found that, and set the upper limit to that value. Incidentally, O ₂ may not be contained, but to the bead shape and stable full penetration is preferably is preferably set to 25% content of O ₂ 5%.

[0019]

EXAMPLE FIG. 2 shows a sectional view of a test piece for producing a T-shaped fillet weld joint before laser welding. Thickness as shown in the figure 4.
Using a test piece consisting of a 5 mm flat plate 1 and a vertical plate 2, the incident angle of the laser light (θ in FIG. 2), the average power density, the wavelength of the laser light and the shield gas were variously changed, and the shape of the bead 3 was changed. Was observed. 3 and 4 show sketches of two types of bead shapes. FIG. 3 shows an example in which T-shaped fillet welding with complete penetration can be achieved by only laser welding from one side, and FIG. 4 shows an example in which partial penetration is achieved.
It can be seen that in FIG. 3, which is completely flat, the bead is curved rather than linear as compared to FIG.

Table 1 shows the bead shape when T-shaped fillet welding is performed when YAG and iodine lasers are used as the laser source. These have wavelengths of 0.5-
Within the range of 1.5 μm. The steel materials used were No.
Except for 1-16, the black skin near the groove is deleted. The mark * in Table 1 indicates the case where the laser torch was in contact with the test piece and welding could not be performed. Regarding the other ◯ and ×, ◯ means that FIG. 3, that is, the case where complete melting was achieved, and x means FIG. 4, that is, the case where partial and partial melting was achieved.

No. 1 in Table 1 using N ₂ as the shielding gas.
As can be understood by comparing 1-1 to 1-4, it can be understood that complete penetration can be realized under the conditions of the present invention example (1-2, 1-3). No. 1-4
Is an example in which the incident angle is too large and a part of the image is indented. In addition, this is because N using Ar as a shield gas
o. The same applies to 1-5 and 1-6. No. 1
-7 to 1-9 show the influence of the average power density. In addition, under the condition that the average power density is high, the welding speed is set to be high in proportion thereto. From this result, in No. 1-8, which is out of the range of the example of the present invention, the bead was linear and only the part and the indentation occurred. No. 1-10 to 1
No. -15 is a case where an iodine laser is used as a laser source, but the same result as that of the YAG laser was obtained.

The last No. No. 1-16 is a case where the black skin near the groove is not removed, but complete melting is obtained because the conditions are set within the range of the present invention, whereby the wavelength of 0.5 to It has been shown that, in the case of being in the range of 1.5 μm, whether or not the black skin is present, complete penetration is realized within the condition range of the present invention.

Table 2 shows the welding test results with a CO ₂ laser. No. 2-1 and 2-10 are N as a shield gas.
_In the case of using No. 2, many defects occurred in the weld bead, and the bead was not sound (marked with **). In addition, No. Two
-1 to 2-9, when there is no black skin near the groove, No. 2-10 to 2-16 are cases where a black skin exists near the groove. In both cases, it can be understood that complete penetration is achieved when the conditions of the present invention are satisfied.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, according to the present invention, when laser welding is applied to T-shaped fillet welding, even if the incident angle is large, complete penetration can be realized by welding from one side, and therefore laser welding is applied. The range can be greatly expanded. Therefore, it can be said that the industrial value of the present invention is extremely high.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a heat conduction direction when T-shaped fillet welding is performed.

FIG. 2 is a cross-sectional view of a test piece before welding used in a test for examining a bead shape.

FIG. 3 is a diagram illustrating a bead shape when complete penetration is achieved when T-shaped fillet welding is performed from one side.

FIG. 4 is a diagram illustrating a bead shape when partial melting occurs when T-shaped fillet welding is performed from one side.

[Explanation of symbols]

1 flat plate 1a, 1b Heat conduction direction (flat plate) 2 vertical plates 2a Heat conduction direction (vertical plate) 3 welding beads

Claims (5)

[Claims] 1. When performing T-shaped fillet welding by laser welding, a laser beam having an average power density of 125 to 2600 kW / cm ² is set so that the incident angle is 5 to 30 ° and the welding speed is 0. A fillet welding method characterized by welding at 0.05 to 0.7 m / min. 2. The fillet welding method according to claim 1, wherein a laser beam having a wavelength of 0.5 to 1.5 μm is used. 3. The fillet welding method according to claim ₂ , wherein N ₂ gas is used as the shield gas. 4. A CO ₂ laser is used as the laser beam, and O ₂ is contained as a shield gas in a volume ratio of O ₂ , in any one of He, Ar, and CO ₂ or a mixed gas of two or more thereof.
The fillet welding method according to claim 1, wherein the gas mixed with 5 to 30% is used, and the steel material to be welded is a steel material from which the black skin near the groove is removed. 5. A CO ₂ laser is used as the laser light, and O ₂ is contained as a shield gas in a volume ratio of O ₂ , in any one of He, Ar, and CO ₂ or in a mixed gas of two or more thereof.
The fillet welding method according to claim 1, wherein a gas mixed with 25% or less is used, and a steel material that does not remove the black skin near the groove is used as the steel material to be welded.