JPH06190574A - Laser beam welding method for copper structure - Google Patents

Abstract

PURPOSE:To obtain stable penetration and besides, to obtain a weld zone without failure by using a wire having specified content of Si, Mn, Fe and Al at the time of subjecting the copper structure to laser beam welding. CONSTITUTION:When a lap part, etc., of a copper pipe 2 and a copper mesh fin 1 are subjected to laser beam welding, the wire 8 having the content of Si, Mn, Fe, Al and Ni >=0.4% in total and having the composition consisting of each content of Si, Mn, Fe and Al <=15% is supplied. Consequently, base metals melt stably and the weld zone without failure such as blowholes is obtained. When a solution of this wire 8 drops on the welding point surface of the copper base metals 2, since reflectance of the solution is low, laser beam energy is absorbed, this energy is transmitted to the copper base metals, melting and penetration of the base metals are obtained and welding is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a structure made of copper, for example, a bonded structure of a copper pipe and a mesh fin used for a heat exchanger of a home air conditioner or the like.

[0002]

2. Description of the Related Art The heat transfer portion of a heat exchanger that has been widely used in conventional home air conditioners has holes formed in thin aluminum fins stacked at regular intervals, and a copper tube is placed in the holes. The mainstream method is a cross fin method in which a copper tube and an aluminum fin are closely adhered to each other by performing a pipe expanding process to thereby perform efficient heat transfer.

Recently, as a method of further increasing the heat transfer efficiency, a thin plate as shown in FIG. 2 is provided with a large number of cuts, and the cuts are pulled to form a knitted shape, and further, the knitted plate is bent to produce air. A fin of a system aiming to improve the heat transfer efficiency with is developed, and this fin will be referred to as a mesh fin here. Figure 2
In, 1 is a mesh fin. The material of the mesh fin is generally the same as that of the heat transfer tube. In the case of a heat exchanger, a copper tube is arranged in the center and sandwiched by mesh fins from both sides.

FIG. 3 shows an example of the appearance of a joined body of a heat transfer tube and mesh fins. In FIG. 3, 2 is a copper pipe and 3 is a weld bead. This mesh fin 1 is a new method currently under development, and there are not many examples in which it has been put to practical use. However, as a joining method, it is judged from the joining method of the conventional heat exchangers that brazing filler metal or It is conceivable to arrange the solder and heat it in a burner or an atmosphere furnace.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present application have aimed at improving the performance of a heat exchanger and have conducted research and development on copper as a target from among aluminum and copper which are commonly used materials. First, as a method of joining the heat transfer tube and the fin, paste-like and linear solder was placed between the copper tube and the copper mesh fin, and heating in an argon atmosphere furnace and burner heating were tried. As a result, in any heating method, the solder melted and flowed, and the mesh fin and the copper tube were joined. However, the solder excessively flowed and flowed into the mesh fin eyes, and the fins were clogged.

The clogging of the fins increases ventilation resistance and reduces the contact area between the fins and air. As a result, the heat transfer efficiency is lowered and the heat exchanger has a fatal defect.

In addition, joining the copper pipe and the copper mesh fin with a solder or a brazing material having a lower thermal conductivity than copper is inevitable as compared with the case where the copper pipe and the copper mesh fin are directly joined. The thermal conductivity decreases. Therefore, in order to obtain an even better heat transfer coefficient, a method of directly joining the copper pipe and the mesh fin is desirable. As this method, a high energy density welding method, that is, electron beam welding, laser welding and plasma welding is conceivable because the copper base material has a good thermal conductivity and the copper tubes and the copper mesh fins have a small heat capacity.

Among these, electron beam welding requires a vacuum atmosphere, and plasma has a relatively low energy density. Therefore, it is possible to perform welding in the atmosphere and it is appropriate to apply laser welding having a high energy density. I decided it was.

[0009]

In the field of welding and cutting, the laser beam is more advantageous than ordinary arc welding.
Remarkably high energy density, carbon dioxide laser, YA
Since the G laser can obtain a power of more than 1 kW, it is often used for welding and cutting, especially for steel materials, high-speed welding is possible for welding, and a narrow deep-penetration bead can be obtained. It is characterized.

However, when the base material is copper, the reflectance of the laser is extremely high, and 90% or more of the incident beam is reflected. As described above, a copper tube of 9 mmφ × 0.3 mmt is When the copper mesh fins shown in 2 were stacked and irradiated with a 5 kW carbon dioxide laser, melting did not occur at all in the copper tube and the mesh fins.

Therefore, in order to increase the absorption rate of the laser, a black paint is applied to the mesh fin surface at the welding start position,
When welding under the same conditions, copper melted and a deep penetration was obtained at the welding start position, but as the welding progressed,
The penetration became shallow. This is because the black paint absorbed the laser and melted at the start of welding, but when the welding progressed, it became the absorption rate of the molten copper and the penetration became shallow.

Therefore, next, black paint was applied and welded to the entire length of the welded portion of the mesh fin. As a result, stable penetration was obtained over the entire welding line length. However,
When an X-ray transmission test was carried out, blow holes (defects) which were not observed in the case where the black paint was not applied were found in the case where the black paint was applied.

In the heat exchanger, defects such as pits and blow holes formed in the copper pipe lead to the leakage of CFC gas, which is a problem that must be eliminated. As described above, in the conventional laser welding method, penetration hardly occurs,
Further, there is a problem that a defect is likely to occur even when the penetration is obtained. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a welding method that can obtain stable penetration with a simple configuration and that can obtain a weld portion without a defect.

[0014]

The above object can be achieved by the joining method described in the claims.
That is, when laser welding a structure made of copper, the total content of Si, Mn, Fe, Al, and Ni is 0.4% or more, and the content of each of Si, Mn, Fe, and Al is 15% or more. %, There is a purpose in welding while supplying a wire of not more than%. Hereinafter, the operation and the like of the present invention will be described based on Examples.

[0015]

EXAMPLES It is well known that the addition of a trace amount of additive element to pure copper causes a rapid change in its physical properties. For example, FIG. 4 shows the effect of the amount of impurities in oxygen-free copper on the electrical conductivity, but the electrical conductivity is extremely reduced only by adding about 0.01 to 0.1% of Fe, Si, or the like. . At the same time, it is estimated that the thermal conductivity, which shows the same tendency as the electrical conductivity, also decreases.

The inventors of the present application have thought that these trace amounts of additional elements may greatly affect the reflectivity, which is a problem in laser welding of copper, and as described above,
A wire in which Si, Mn, Fe, Al, and Ni were added to copper was prototyped. These elements take into consideration the deoxidizing effect for preventing problems such as blowholes during welding, and that the characteristics of the copper alloy base material are also utilized in the welded portion,
It is a choice.

Laser welding of the copper pipe and the copper mesh fin shown above was carried out while feeding trial wires of various addition amounts, and the total amount of added elements was 0.4%.
By the above, the base material was stably melted, and a welded portion free from defects such as blowholes was obtained.

The above welding process will be described in more detail. First, the welding wire to which the alloying element has been added is supplied to the welding point surface irradiated with the laser beam from the direction of about 30 ° above the front side of the welding line to the welding point. The laser beam applied to the welding point heats the copper base material and the wire, but the copper base material has a high reflectance, almost no laser energy is absorbed, and the base material does not melt. However, since the wire supplied to the welding point contains the above-mentioned additional elements, the reflectance of the laser decreases, the thermal conductivity also decreases, and the wire diameter is as small as about 1 mmφ, so the wire melts. Will be done.

When the melt of this wire falls on the welding point surface of the copper base material, the energy of the laser is absorbed due to the low reflectivity of the melt, and this energy is transmitted to the copper base material to melt the base material. It is considered that penetration is obtained and welding is achieved.

When the amount of the additive to the wire is small, the decrease in the reflectance and the decrease in the thermal conductivity of the wire are insufficient, so that the initial melting of the wire does not occur during laser irradiation,
It is considered that melting of the copper base material does not occur.

The present inventors conducted the following experiments in order to confirm the effects of the present invention described in detail above. First, as shown in FIG. 1, a 9 mmφ × 0.3 mmt copper tube 2
2 and the copper mesh fin 1 shown in FIG.
Carbon dioxide welding was carried out while supplying the 0.8 mmφ wire 8 produced by trial with various components. In FIG. 1, 5 is a laser nozzle, 6 is a laser beam, and 7 is a wire nozzle. The results of the experiment are shown in Tables 1 and 2 (Table 2 is a continuation of Table 1).

[0022]

[Table 1]

[0023]

[Table 2]

The welding conditions were determined as optimum conditions by performing a preliminary test. A parabolic mirror having a laser power of 4.5 kW, a welding speed of 5 m / min and a focal length of 10 inches was used.
The focus position was adjusted to the surface of the work piece. Shield gas is Ar
And supplied 20 liters / minute. The diameter of the wire is
It was 0.8 mmφ and was supplied at a constant speed of 5 m / min.

In Tables 1 and 2, No. 1, 4, 7,
Nos. 10, 13, 16, 17, 18, and 25 are comparative materials in which the total amount of additives is less than 0.4%, and even if welding is performed under the above conditions, neither the wire, the mesh fins, nor the copper pipe melts, I couldn't weld.

On the other hand, Si, Mn, Fe, Al, N
With respect to those having a total addition amount of i of 0.4% or more, as shown in FIG. 5, a welded portion having a good appearance and no defect in the X-ray transmission test was obtained.

In the composition of the wire, Si, Mn, F
When the content of each of e and Al exceeds 15%, the content of each of the above components is set to 15%. However, even within this range, as the content increases, the characteristics of the copper base material and the welded portion (thermal conductivity, electrical conductivity,
Corrosion resistance, etc.) becomes large, so it is necessary to select the addition amount of the components in consideration of the ease of welding or the performance of the welded joint.

Further, as a comparative example, welding results when no wire is supplied are shown. Under the above-mentioned welding conditions, laser power was 5 kW and welding speed was 10 m / min. As a result, the reflectance of the base material was high, and neither the mesh fin nor the copper tube was melted at all. Therefore, when the black magic ink was applied to the surface of the mesh fin over the entire length of the welding line and welding was performed, the base material melted and welding was performed, but pits were scattered on the surface and blown even in the X-ray transmission test. Hole defects were observed.

[0029]

As described above, according to the present invention, as described in detail in the above embodiment, a structure made of copper, for example, a joint structure of a copper pipe and a mesh fin used for a heat exchanger or the like is provided. In laser welding, it is possible to obtain a stable penetration and to obtain a welded portion having no defects.

[Brief description of drawings]

FIG. 1 is a perspective view of an experimental device carried out to confirm the effect of the welding method of the present invention.

FIG. 2 is a perspective view of a copper mesh fin.

FIG. 3 is a perspective view showing an example of a joined body of a heat transfer tube and a mesh fin.

FIG. 4 is a diagram showing the influence of the amount of impurities in oxygen-free copper on the electrical conductivity.

FIG. 5 is a diagram showing an example of the appearance of a copper structure welded by the method according to the present invention.

[Explanation of sign]

 1 mesh fin 2 copper pipe 3 welding bead 4 holding jig 5 laser nozzle 6 laser beam 7 wire nozzle 8 wire

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[Procedure amendment]

[Submission date] February 4, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

The inventors of the present application have aimed to improve the performance of the heat exchanger by selecting from the commonly used materials aluminum and copper.
We selected copper as the target and worked on research and development. First, as a method of joining the heat transfer tube and the fin, paste-like and linear solder was placed between the copper tube and the copper mesh fin, and heating in an argon atmosphere furnace and burner heating were tried. As a result, in any heating method, the solder melted and flowed, and the mesh fin and the copper tube were joined. However, the solder excessively flowed and flowed into the mesh fin eyes, and the fins were clogged.

Front Page Continuation (72) Inventor Masataka Noguchi 65 Hirasawa, Hadano City, Kanagawa Prefecture Kobe Steel Works Hadano Plant

Claims (1)

[Claims] 1. When laser welding a structure made of copper, the total content of Si, Mn, Fe, Al and Ni is 0.4% or more, and the content of each of Si, Mn, Fe and Al is contained. A laser welding method for a copper structure, which comprises welding while supplying a wire having an amount of 15% or less.