JPS5921715B2 - Electromagnetic solid phase joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of joining copper tubes and aluminum tubes by electromagnetic solid phase joining.

Generally, the weight joint 1 shown in FIG. 1A or B is manufactured by welding, brazing, etc. a pair of pipe materials 2 and 3.

By the way, Japanese Patent Publication No. 47-39825 discloses a method of butt welding a pair of pipe materials by electromagnetic solid phase welding. The electromagnetic solid-phase bonding method disclosed in the publication involves butting a pair of tube materials together, heating the butted portion by passing a high-frequency heating current through a high-frequency induction coil, and then applying a high-frequency heating current to the high-frequency induction coil. This is a method of welding a pair of tubes by applying a forming current consisting of large current pulses and applying pressure to them using the electromagnetic attraction force generated between the pair of tubes, but this method can also be applied to lap welding of a pair of tubes. In this case, the pair of tubes 2 and 3 are affected by the electromagnetic repulsive force in the tube diameter direction that occurs between the high-frequency induction coil and the tube 1 and the electromagnetic attraction force in the tube axis direction that occurs between the tubes 2 and 3. However, when attempting to overlay and join a pair of tube materials 2 and 3 with different melting points using such electromagnetic solid phase joining method, the high melting point material may still have a sufficient temperature due to preheating before joining. It is difficult to increase the joint strength because the low-melting point member melts before the temperature reaches the temperature. Furthermore, in weight joints with the low-melting point member on the outside, there is no The molten part scatters due to electromagnetic repulsive force and electromagnetic attractive force, weakening the pressure bonding strength.Furthermore, as in the case of a weight joint made of copper and aluminum pipes, intermetallic compounds are dispersed by diffusion. In addition to the above-mentioned drawbacks, when joining metals that are susceptible to bonding, a decrease in bonding strength due to the formation of intermetallic compounds at the bonding interface cannot be ignored.
It is already known that the reduction in bonding strength due to the formation of intermetallic compounds can be prevented by providing a plating layer of a high melting point metal such as nickel or chromium at the bonding interface of copper tubes.

However, this prevention method is more effective than when there is no plating layer.
It is necessary to heat with a larger high-frequency power, and good results are not necessarily obtained. The present invention has been made to solve the above-mentioned problems, and when joining a copper pipe and an aluminum pipe with the aluminum pipe on the outside by electromagnetic solid phase joining, at least one end of the aluminum pipe is removed from the outside. A metal coating layer with a higher melting point than aluminum is provided on the side surface to prevent melting and scattering due to electromagnetic force and, in some cases, to prevent the formation of intermetallic compounds between aluminum and copper, resulting in a strong bond. Furthermore, in addition to the above-mentioned coating layer, brazing flux for aluminum is interposed at the joint between the two members, so that a strong joint can be more easily achieved.

Hereinafter, the present invention will be described by way of examples with reference to the drawings.

FIG. 2 shows a weight joint 13 in which one end of an aluminum tube 11 is expanded and overlapped with a copper tube 10, and a metal coating layer 12 made of copper plating is provided on the outer surface of the weight portion of the aluminum tube 11. It is.

In this first embodiment, one end of an aluminum tube 11 is expanded, the outer surface of the one end is plated with copper to a thickness of about 0.3 to 30 μm, and then the one end of the copper tube 10 is overlapped. ,
After that, a high-frequency heating current is passed through the high-frequency induction coil to heat the weight part to the extent that it becomes red-hot, and a forming current consisting of large current pulses is then passed through the coil to create a high-frequency heating current between the high-frequency induction coil and the aluminum tube. This can be achieved by contracting the enlarged portion of the aluminum tube 11 by electromagnetic repulsion in the tube diameter direction, and at the same time by pressing the two members together by the electromagnetic attraction force generated between the two members 10 and 11 in the tube axis direction. .

In this case, if a copper coating layer 12 having a higher melting point than aluminum is provided on the outer surface of the joint part of the aluminum tube 11 serving as the outer tube, it will heat the aluminum tube 11 to activate diffusion.
Even if 1 is melted, its shape is maintained by the metal coating layer 12 made of copper plating on the outer surface, and even during pressure welding, molten aluminum is prevented from scattering due to electromagnetic repulsion and attraction force. , and the molten aluminum is extruded in the tube axis direction, resulting in a strong joint.

FIG. 3 shows a second embodiment in which a metal coating layer 12 made of copper plating is provided on both the inner and outer surfaces of the expanded portion of an aluminum tube 11 serving as the outer tube and joined.

In this case as well, the same effect as in the above embodiment can be obtained, but in addition, the formation of such a metal coating layer 12 further ensures that the shape of the aluminum tube 11 is maintained during preheating, and
Since the metal coating layer 12 is made of the same material as the inner tube, it does not require particularly high-output joining energy, and has the advantage that similar metal tubes can be joined with the same level of power as the electromagnetic solid-phase joining method. FIG. 4 shows that a coating layer 12 made of copper plating is formed with a thickness of 0.3 to 30 μm on the outer surface of the expanded part of an aluminum tube 11 that will become the outer tube, and one end of the copper tube 10 that will become the inner tube is A coating layer 14 made of nickel plating is also applied to one side of the box by 0.5.
A third example is shown in which the film is formed to a thickness of 10 μMf) and bonded. In this case as well, the same effect as in the above embodiment is achieved, but
In addition, in the method of this embodiment, since the coating layer 14 of another metal with a high melting point is interposed at the bonding interface between the aluminum tube 11 and the copper tube 10, the generation of intermetallic compounds due to diffusion of both components is suppressed. effective. In addition to nickel, other high melting point metals such as chromium and cobalt can be used for the coating layer 14 of the copper tube 10.

FIG. 5 shows a metal coating layer 1 formed by cutting the inner surface of one end of an aluminum tube 11, which becomes the outer tube, and coating the inner and outer surfaces other than the cut portion with a metal coating having a higher melting point than aluminum, for example, copper plating.
At the same time, the outer surface of one end of the copper tube 10 that will become the inner tube is cut and overlapped, and a low melting point brazing flak for aluminum (Japan Anoremitsu DM-
055) 16 is shown in the fourth embodiment.

In this case, although the type of the joint is different from those in the above embodiments, the presence of the metal coating layer 12 provides the same effect as in the above embodiments, and the presence of the brazing flux 16 allows for low temperature bonding. is now possible, and this breathing flux 1
A strong bond could be obtained extremely easily by the sum of the bonding force of No. 6 and the pressure bonding force of electromagnetic solid-phase bonding. In each of the above embodiments, the metal coating layer 12 provided on the aluminum tube 11 may be made of other metals such as nickel and chromium in addition to copper.

Table 1 below shows the bonding strength when a copper tube 16 and an aluminum tube 11 having an outer diameter of 6 wm and a wall thickness of 1 TWI are used in comparison with a case where no metal coating layer 12 is formed.

Numbers (1) to (4) in the table refer to the first to fourth numbers, respectively.
This corresponds to the embodiment. As can be seen from this table, when aluminum pipes are plated with copper, it is possible to obtain a bond with greater strength than with the normal electromagnetic solid phase bonding method in which copper plating is not applied.

The present invention has been described above with reference to several embodiments, but in short, the present invention provides a method for joining copper tubes and aluminum tubes with different melting points when overlapping and bonding them by electromagnetic solid phase bonding. A metal coating layer with a higher melting point than aluminum is provided on the aluminum part to increase the bonding strength and a good bond can be obtained.Furthermore, the above coating layer and brazing flux for aluminum are used together to increase the bonding strength. This makes it easy to achieve good bonding.

[Brief explanation of the drawing]

Figures 1A and 1B are diagrams of weight joints joined by a conventional electromagnetic solid phase joining method, and Figures 2 to 5 are diagrams of weight joints joined by the method of the present invention, respectively. . 10: Copper tube, 11: Aluminum tube, 12, 14: Metal coating layer, 16: Blazing flux for aluminum.

Claims (1)

[Scope of Claims] 1. A method of forming a metal coating layer having a higher melting point than aluminum on at least the outer surface of one end of an aluminum tube that is overlapped and joined to the outer surface of one end of the copper tube, and A method of heating one end of the tube and one end of the aluminum tube on which the coating layer is formed by passing a high-frequency heating current through a high-frequency induction coil, and subsequently applying a large current pulse larger than the high-frequency heating current to the high-frequency induction coil. An electromagnetic solid phase bonding method comprising: applying a forming current to press one end of the aluminum tube to the outer surface of the one end of the copper tube. 2. A method of forming a metal coating layer having a higher melting point than aluminum on at least the outer surface of one end of an aluminum tube to be overlapped and joined to the outer surface of one end of the copper tube, and A method of overlapping one end of an aluminum tube on which a coating layer is formed, interposing a brazing flux for aluminum in the weight part, and heating the weight part by flowing a high-frequency heating current through a high-frequency induction coil; The method is characterized by comprising a method of press-contacting one end of the aluminum tube to the outer surface of one end of the copper tube by subsequently passing a forming current consisting of a large current pulse larger than the high-frequency heating current through a high-frequency induction coil. Electromagnetic solid phase joining method.