JPS6249142B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for ultrasonic soldering of metal tubes, such as copper tubes and aluminum tubes.

Conventionally, various methods such as flash welding and butt welding have been used to join copper pipes and aluminum pipes, but it has not always been possible to obtain a robust joint. Therefore, conventionally, a solder coating layer is formed in advance on at least one end of metal tubes that are shaped so that they can fit into each other.
Consideration has been given to a method of joining without using flux by fitting both metal tubes together and applying ultrasonic vibrations to the melted solder.

However, in the conventional ultrasonic soldering method described above, the thickness of the solder coating layer formed in advance on the end of the metal tube is extremely thin, and is only sufficient to fill the gap between the two metal tubes when they are fitted. Therefore, if solder is not used, strict accuracy is required for the clearance of the fitting part of the metal tube, which causes problems in the forming process of metal tubes. It was becoming.

The present invention involves forming a solder coating layer in advance by immersing one end of an outer tube and an inner tube, which are fitted together with one end enlarged in diameter, in a solder bath to which ultrasonic vibrations are applied. In the method of fitting and soldering by applying heat and ultrasonic vibration, the temperature of the solder bath in which the inner tube is immersed is near the melting point of the solder, and the temperature of the solder bath in which the outer tube is immersed is near the melting point of the solder, and the outer tube is immersed in the solder bath at a temperature near the melting point of the solder. The present invention provides an ultrasonic soldering method in which a high-strength joint can be obtained by making the temperature of the solder bath in which the inner tube is immersed higher than the temperature of the solder bath in which the inner tube is immersed.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 1 shows cross sections of a pair of metal tubes to be ultrasonically soldered by the method according to the present invention, 1 being a copper tube and 2 being an aluminum tube. This copper tube 1 is an outer tube, and its end portion is enlarged in diameter so that it can be fitted with an aluminum tube 2 that will become an inner tube.

In order to form a solder coating layer on each of the fitting portions of the pair of metal tubes having fitting portions, the ends of the metal tubes are dipped only once in the solder bath 3 shown in FIG. It is performed by vibrating from a sonic horn 4),
Regarding the formation of the solder coating layer, the inner tube and the outer tube are different as follows. In other words, the solder used is common to both, and zinc
It is a zinc-based alloy with a composition of 95% aluminum and 5% aluminum, and has a melting point of 382°C. For aluminum tubes, this solder is kept in a solder bath 3 at a temperature of 410 to 420 DEG C., which is near the above melting point, and one end of the tube, which has been left at room temperature, is immersed. In this case, the length of one end to be immersed is preferably 1.5 times longer than the fitting length of the copper tube 1 serving as the outer tube, and
After soaking for ~6 seconds and applying ultrasonic vibration, it is pulled up. Through such operations, a solder coating layer 5a is formed as shown in FIG. On the other hand, for copper tube 1, after keeping the solder at 430 to 450℃,
The enlarged end of the tube, which has reached room temperature, is immersed for 4 to 6 seconds to apply ultrasonic vibrations and then pulled up. FIG. 3 shows the cross-sectional shape of the solder coating layer 5 formed in this manner. FIG. 3A shows a solder coating layer formed on the outer tube, and the solder is thinly and uniformly applied to the fitting portion. Figure 3B shows the solder coating layer formed on the inner tube.The solder is uniformly thick near the tip of the fitting part, and gradually increases in thickness as it moves away from the tip. ing. The reason why the solder coating layer 5a of the inner tube is partly thick is because the temperature of the solder bath is low, so the inner tube itself is not sufficiently heated, and the temperature decreases as it goes from the tip of the fitting part. This is because when the inner tube is pulled up from the solder bath, the solder that is in contact with the inner tube solidifies before it flows down, and the solder coating layer 5a having the above-mentioned shape is formed as it is.

Next, as shown in FIG. 4, the copper tube 1 and the aluminum tube 2 are fitted and heated, and ultrasonic vibrations are applied by the ultrasonic horn 6 that is in contact with the upper end of the aluminum tube 2. First, a pair of metal tubes on which the solder coating layer 5a has been formed are pushed in the direction of the arrow as shown in FIG. 5A, and then they are fitted together. Solder coating layer 5
a and 5b are heated and melted with a gas burner 7. On the surface of the metal tube that is in contact with this molten solder, the oxide film adhering to the surface is destroyed by the cavitation phenomenon of the molten solder caused by ultrasonic vibration, exposing the active metal surface, which indicates that flux was used. In a similar manner, the molten solder blends with the metal tube, and furthermore, it effectively penetrates into the space between the fitting parts due to the thermal expansion of the aluminum tube and capillary action. As shown in FIG. 3B, the surface layer of the solder coating layer 5a formed thickly on the aluminum tube 2 flows down due to heating and fills the space between the fitting parts.

After a certain period of time has elapsed, heating and ultrasonic vibration are stopped and cooling is performed. However, if the gas burner 7 is immediately stopped, the solder filled between the mating parts will be removed from the parts that are in contact with the outer tube and the upper part. Start solidifying from the exposed surface. However, as the molten solder solidifies, it contracts and its volume decreases. Therefore, when the solder finally solidifies, various defects such as solidification shrinkage holes and blowholes occur inside the solder. To prevent the above defects, the upper exposed surface must be the last to solidify. Therefore, in the method according to the present invention, after heating the area around the fitting part, the inner tube is heated with a gas burner 7 as shown in FIG.
Make sure that the upper exposed surface of the solder to be filled remains as molten solder until the end.

In the above method, the solder coating layer 5a formed on the fitting portion of the inner tube of a pair of metal tubes, one of which has a fitting portion with an enlarged diameter as described above, has a melting point of solder that is lower than the normal solder bath temperature. It is thicker than the solder coating layer formed on the fitting portion of the outer tube by immersing it in a solder bath maintained at a nearby temperature, and the thickness gradually increases as it moves away from the tip. By doing this, the solder coating layer 5a that has been deposited on the inner tube in a large amount will melt and fall due to heating, and will supply solder between the fitting parts, which will be sufficient to compensate for the shrinkage holes caused by solidification and shrinkage. It is possible to supply a large amount of solder. Therefore, there is no need to tighten the dimensional accuracy of the clearance of the fitting portion of the pair of metal tubes, and the metal tubes can be easily formed. By delaying the cooling of the exposed surface of the solder and compensating for the shrinkage of the solder due to solidification, it is possible to suppress the occurrence of defects such as solidification shrinkage holes and blowholes, and to obtain a bond with high reliability and high bonding strength. Ta.

In the embodiments of the present invention, copper and aluminum were used as materials for the pair of metal tubes, but the materials are not limited to these, and similar metals such as copper and copper or aluminum and aluminum may be used. Other metals such as stainless steel and titanium alloys may also be used.

Further, it goes without saying that the present invention can be modified in various ways without departing from the gist thereof.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of a pair of metal tubes that are used for ultrasonic soldering, Figure 2 is a sectional view of a device that forms a solder coating layer on the fitting part of the metal tubes, and Figure 3 is a sectional view of a pair of metal tubes. 4 is an explanatory diagram of a method of joining a pair of metal tubes, and FIG. 5 is a diagram illustrating the joining method of FIG. 4 in more detail. It is. 1: Copper tube, 2: Aluminum tube, 3: Solder bath, 5: Solder coating layer, 6: Ultrasonic horn, 7:
gas burner.

Claims (1)

[Claims] 1. A step of forming a solder coating layer by immersing one end of the outer tube whose diameter has been expanded and one end of the inner tube fitted into this one end in a solder bath to which ultrasonic vibrations are applied, and the above coating layer. In the ultrasonic soldering method, the inner tube is immersed in an ultrasonic soldering method comprising a step of fitting the two formed ends together and a step of applying heat and ultrasonic vibration to the fitted portion and soldering. An ultrasonic soldering method characterized in that the temperature of the solder bath in which the outer tube is immersed is set to be near the melting point of the solder, and the temperature of the solder bath in which the outer tube is immersed is higher than the temperature of the solder bath in which the inner tube is immersed.