JPH07164158A - Method for joining dissimilar metal - Google Patents

Abstract

PURPOSE:To prevent the thermal deformation of a metallic member on the lower melting point side by interposing an intermediate member which has the higher electric resistance than that of the metallic member on the lower melting point side for the current during the energization, and can be melted by Joule's heat earlier than the metallic member on the lower melting point side between the surfaces to be joined of both metallic members and executing the energizing. CONSTITUTION:An intermediate member 16 is interposed in a butted manner between surfaces 12a, 14a to be joined of axial members 12, 14, and when the energizing is started between electrodes B1, B2 in the condition where the both axial members 12, 14 are pressed against each other in the butt direction by the electrodes B1, B2, the axial member 12 made of iron with high specific resistance and the part of small sectional area with high current density of the intermediate member 16 are rapidly heated to high temperature. The heat in the axial member 12 made of iron moves into the intermediate member 16, but the heat is difficult to move into the axial member 14 made of aluminum because a part of small sectional area is present in the intermediate member 16. Thus, the part with small sectional area of the intermediate member 16 is remarkably heated, and the intermediate member 16 is melted before the axial member 14 is deformed by high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining dissimilar metals, and more particularly to a method for joining two metal members having different melting points by pressurizing and heating.

[0002]

2. Description of the Related Art Upset butt welding has been conventionally known as a method for joining metal members of the same type. This upset butt welding is a kind of butt resistance welding,
As shown in FIG. 7A, the end faces of the two metal members (for example, aluminum) A1 and A2 are butted against each other, and the electrodes B1 and
Both members A1 and A2 are pressed by B2 in the abutting direction, and current is applied between the electrodes B1 and B2, so that both members A
Generates heat due to contact resistance between the joining surfaces of 1 and A2,
This is a joining method of welding both members A1 and A2.

In Japanese Unexamined Patent Publication No. 63-295077, two metal members having different melting points are subjected to high-frequency induction heating while the end faces to be joined are separated from each other, and then the end faces of both members are butted to each other and joined. Butt resistance welding of the type described is disclosed.

[0004]

If the upset butt welding is directly adopted as a method of joining two kinds of metal members having different melting points, the following problems will occur.

That is, for example, when joining the aluminum member A and the iron member Fe, the specific resistance of aluminum is about 1/4 of that of iron, and the temperature rise of the joint surface is almost the same as the movement of heat from the iron member Fe side. Caused by.

However, since the thermal conductivity of aluminum is 3 times higher than that of iron, most of the heat of the joint surface is conducted into the aluminum member A, and when the joint surface is melted, the iron member Fe and the aluminum member A are melted. Becomes a fairly high temperature. Therefore, the member A (aluminum) having a lower melting point is softened entirely by Joule heat,
As a result, distortion occurs due to the pressing force in the butt direction, and as shown in FIG. 7B, there arises a problem that parts other than the parts that should be melt-deformed due to welding are deformed.

The present invention has been made in view of the above circumstances, and when one metal member has a lower melting point and a smaller specific resistance than the other metal member, both metal members are butt welded. It is an object of the present invention to provide a method for joining dissimilar metals, which can minimize unnecessary deformation of the metal member on the low melting point side when joining by means of.

[0008]

The method for joining dissimilar metals according to the present invention has a higher electric resistance between the joining surfaces of both metal members than the metal member on the low melting point side with respect to the current when energized. And energizing the intermediate member, which can be melted earlier than the metal member on the low melting point side due to the jule heat, in such a manner as to cover almost the entire joint surface of at least the first metal member. It is characterized by.

According to the first aspect of the present invention, the intermediate member is formed of the same material as the metal member on the low melting point side. The intermediate member is characterized in that the low melting point side metal member side portion has a smaller diameter than the high melting point side metal member side portion.

According to a second aspect of the present invention, the intermediate member is made of a green compact containing a powder of the same material as the metal member on the low melting point side as a main component.

In this case, the green compact may contain a powder having a higher oxidizing property than the powder which is the main component of the green compact.

[0012]

According to the present invention, the electric resistance between the joining surfaces of both metal members is higher than that of the metal member on the low melting point side (for example, an aluminum member) with respect to the current during energization, The intermediate member, which can be melted earlier than the metal member on the low melting point side by the heat of the Joule, is energized so that the metal member on the low melting point side can be prevented from being thermally deformed.

According to the present invention, the intermediate member is
Since at least almost the entire bonding surface of the metal member (for example, iron member) on the high melting point side is covered, oxidation of the bonding surface of the metal member on the high melting point side at high temperature can be prevented.

Further, because of the presence of the intermediate member, the oxide film on the joint surface of the metal member on the low melting point side is taken into the molten portion at the same time as the melting of the intermediate member and is removed to the outside by the pressurization. A good bonding interface can be obtained.

According to the first aspect of the present invention, the intermediate member is formed of the same material (for example, aluminum) as the metal member on the low melting point side, and the metal member on the low melting point side of the intermediate member. Since the portion on the side has a smaller diameter than the portion on the metal member side on the high melting point side, the current density of the portion with the smaller diameter becomes higher, and the portion with the smaller diameter has a higher temperature first. Therefore, the small diameter portion melts earlier than the metal member on the low melting point side, and thermal deformation of the metal member on the low melting point side can be prevented.

Further, according to the second aspect of the present invention, the intermediate member is formed of a powder compact whose main component is powder of the same material (for example, aluminum) as the metal member on the low melting point side. Therefore, the specific resistance of the intermediate member is higher than the specific resistance of the metal member on the low melting point side. Therefore,
The intermediate member melts earlier than the metal member on the low melting point side, and thermal deformation of the metal member on the low melting point side can be prevented.

In this case, the intermediate member made of the green compact is made to contain a powder (eg, magnesium powder) having a higher oxidizing property than the powder (eg, aluminum powder) which is the main component of the green compact. The effect of preventing oxidation at the bonding interface is obtained.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side view showing a first embodiment of a method for joining dissimilar metals according to the present invention, and FIGS. 2 (a) and 2 (b).
Is a plan view and a side view of the intermediate member used here,
FIG. 3 is a side view for explaining the first embodiment of the method for joining dissimilar metals according to the present invention in the order of (a), (b) and (c).

This method of joining dissimilar metals has a lower melting point than the iron shaft member (first metal member) 12 used in the propeller shaft 10 of an automobile and the iron shaft member 12.
A method of joining an aluminum shaft member (second metal member) 14 having a small specific resistance, wherein the joining surfaces 12a and 14b of the two types of members 12 and 14 having substantially the same diameter are used. (A) and (b) are abutted by interposing an intermediate member 16 having a shape as shown in FIG. 2 and both members 12, 14 are energized in the abutting direction while pressing the members 12, 14 in the abutting direction. , 14 are to be welded.

The intermediate member 16 is a frustoconical body made of the same material as the aluminum shaft member 14 which is the member on the low melting point side, and has a large diameter which contacts the joint surface 12a of the iron shaft member 12. The side surface 16a covers almost the entire joint surface 12a of the iron shaft member 12, so that the iron shaft member 12 is
Is formed to have a diameter substantially the same as that of the joining surface 12a of the aluminum shaft member 14, and a surface 16b of the aluminum shaft member 14 that is in contact with the joining surface 14a and has a smaller diameter than the joining surface 14a of the aluminum shaft member 14, that is, a cross-sectional area is smaller. ing. Therefore, the portion of the intermediate member 16 having a small cross-sectional area, which is in contact with the joining surface 14a of the aluminum shaft member 14, has a higher electric resistance than the other portions, that is, the aluminum shaft member 14 (specific resistance). Are the same).

Thus, the joint surface 1 of the shaft members 12 and 14
As shown in FIG. 3 (a), the intermediate members 16 are abutted against each other between 2a and 14a, and the shafts 12 and 14 are pressed in the abutting direction by the electrodes B1 and B2.
When energization is started between the electrodes B1 and B2, the iron shaft member 12 having a high specific resistance and the portion of the intermediate member 16 having a high current density and a small cross-sectional area are rapidly heated to a high temperature. Further, the heat in the iron shaft member 12 moves into the intermediate member 16 as shown in FIG. 3B, but since the intermediate member 16 has a portion having a small cross-sectional area, the heat is generated in the aluminum member. It is difficult to move into the shaft member 14.

Due to these two factors, the portion of the intermediate member 16 having a small cross section is remarkably heated, and the intermediate member 1
No. 6 melts before the aluminum shaft member 14 deforms at high temperature. At this time, since both shaft members 12 and 14 are pressed in the butt direction, the melted intermediate member 16 spreads over the entire joint surface 14a, and the oxide film on the joint surface 14a of the aluminum shaft member 14 is a molten portion. As shown in FIG. 3C, the oxide film is taken in, and the oxide film is pushed out of the bonding surface.

At the same time when the intermediate member 16 is melted, the electrode B is
The energization between B1 and B2 is stopped. At that time, the iron shaft member 12 and the aluminum shaft member 14 are joined to each other at the joint surface 12
Since the a and 14a are in contact with each other over the entire surface, the heat of the iron shaft member 12 and the joint surfaces 12a and 14a quickly moves into the aluminum shaft member 14. Therefore, the joint surface temperature is lowered, and the formation of the intermetallic compound of iron and aluminum is suppressed.

Further, the intermediate member 16 is the iron shaft member 12
Since it covers almost the entire joint surface 12a, it is possible to prevent the joint surface 12a of the iron shaft member 12 from being blackened and oxidized at a high temperature.

Even when the intermediate member 16 is formed integrally with the aluminum shaft member 14 as shown in FIG. 4, the same effect can be expected.

Next, FIG. 5 is a side view showing a second embodiment of the method for joining dissimilar metals according to the present invention.

Also in this embodiment, an iron shaft member (first metal member) 12 and an aluminum shaft member (second metal member) 14 having a lower melting point and a smaller specific resistance than the iron shaft member 12 are provided. In this embodiment, the intermediate member 16 made of a truncated cone in the first embodiment is joined.
In place of the above, the intermediate member 18 made of a green compact made by pressurizing aluminum powder is replaced by the above-mentioned two types of shaft members 12, 14
It is interposed between the joint surfaces 12a and 14b.
The green compact is formed in a disk shape having substantially the same diameter as the shaft members 12 and 14 so as to cover the joint surfaces 12a and 14a of the iron shaft member 12 and the aluminum shaft member 14, and the specific resistance of aluminum itself. It has a higher specific resistance.

An intermediate member 18 made of such a green compact
6 are interposed between the joint surfaces 12a and 14a of the shaft members 12 and 14 and abutted, and the shafts 12 and 14 are pressed by the electrodes B1 and B2 in the abutting direction.
As shown in FIG. 6A, when energization is started between the electrodes B1 and B2, as shown in FIG. 6B, the iron shaft member 12 having a high specific resistance is heated first, and the heat is transferred to the intermediate member 18. Move in. Moreover, since the specific resistance of the green compact is high, the intermediate member 1
8 is also heated rapidly. Due to these two factors, the intermediate member 18 melts before the aluminum shaft member 14 undergoes high temperature deformation. After the melting, the oxide film of the aluminum powder and the impurities are pushed out of the joint surface by the pressure applied to the shaft members 12 and 14, as shown in FIG. 6C.

After the energization is stopped, the iron shaft member 12 and the aluminum shaft member 14 are in contact with each other over the entire joint surfaces 12a, 14a.
The heat of 2a and 14a quickly moves into the aluminum shaft member 14 and is cooled.

By the way, oxygen is mixed in the green compact forming the intermediate member 18. Therefore, in order to eliminate this adverse effect of oxygen, it is preferable to add a few percent of magnesium powder, which has a stronger oxidizing property than aluminum, to the green compact. The magnesium oxide produced by the combination of this magnesium and oxygen in the green compact is removed outside the joint surface after the intermediate member 18 is melted.

As is clear from the above description, according to the first and second embodiments, the aluminum shaft member is provided between the joint surfaces 12a, 14a of both shaft members 12, 14 with respect to the current during energization. Since the intermediate member 16 or 18 having a higher electric resistance than that of the aluminum shaft member 14 and having a higher electric resistance than the aluminum shaft member 14 which can be melted earlier than the aluminum shaft member 14 is energized, the aluminum shaft member 14 is used. It is possible to prevent thermal deformation of the.

Further, according to the above embodiment, the intermediate member 16
Or 18 is at least the joint surface 12 of the iron shaft member 12.
Since almost all the surface of a is covered, it is possible to prevent the joint surface 12a from being oxidized at a high temperature.

Further, due to the presence of the intermediate member 16 or 18, the oxide film on the joining surface 14a of the aluminum shaft member 14 is taken into the molten portion at the same time as the melting of the intermediate member 16 or 18, and is pressurized to the outside. Therefore, a good bonding interface can be obtained.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of a method for joining dissimilar metals according to the present invention.

FIG. 2 is an enlarged plan view and side view of an intermediate member used in the first embodiment of the method for joining dissimilar metals according to the present invention.

FIG. 3 is a side view illustrating a first embodiment of a method for joining dissimilar metals according to the present invention in the order of (a), (b) and (c).

FIG. 4 is a side view showing another embodiment of the intermediate member used in the first embodiment of the method for joining dissimilar metals according to the present invention.

FIG. 5 is a side view showing a second embodiment of the method for joining dissimilar metals according to the present invention.

FIG. 6 is a side view illustrating a first embodiment of a method for joining dissimilar metals according to the present invention in the order of (a), (b) and (c).

FIG. 7 is a side view showing a conventional joining method.

[Explanation of symbols]

 10 Propeller shaft 12 Iron shaft member 14 Aluminum shaft member 16, 18 Intermediate member

Claims (4)

[Claims] 1. A first metal member and a second metal member having a melting point lower than that of the first metal member and a specific resistance lower than that of the first metal member are abutted with each other at their end faces, and both members are provided in the butting direction. In a method of joining dissimilar metals, which is joined by energizing between both members while applying pressure, between the joining surfaces of the first and second metal members, a current at energization is higher than that of the second metal member. An intermediate member having a high electric resistance and capable of being melted earlier than the second metal member by a Jule heat is interposed so as to cover at least almost the entire joint surface of the first metal member. A method for joining dissimilar metals, characterized by energizing electricity. 2. The intermediate member is formed of the same material as the second metal member, and the second member of the intermediate member is formed.
2. The method for joining dissimilar metals according to claim 1, wherein the portion on the metal member side has a smaller diameter than the portion on the first metal member side. 3. The method for joining dissimilar metals according to claim 1, wherein the intermediate member is a green compact having a powder of the same material as the second metal member as a main component. 4. The method for joining dissimilar metals according to claim 3, wherein the green compact contains a powder having a higher oxidative property than a powder which is a main component of the green compact.