JP3207465B2 - Aluminum or aluminum alloy friction welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of frictionally joining aluminum or aluminum alloy used for various strength members to frictionally join aluminum or aluminum alloy to each other.

[0002]

2. Description of the Related Art Recently, due to a demand for lightening of an automobile or the like,
The application of aluminum or an aluminum alloy (hereinafter, referred to as an aluminum material) as the strength member has been expanded. Particularly, an aluminum material has been used as a yoke for a propeller shaft of an automobile and a universal joint. In this case, it is necessary to join the aluminum materials constituting the propeller shaft and the yoke. In the case where a steel material is used as in the related art, the two members are joined by friction welding with little heat influence. However, sufficient joining strength cannot be obtained even if the conditions of friction welding between steel materials are applied to aluminum materials as they are.

[0003] As a joining method of aluminum materials,
In addition to the friction welding method, there are an arc welding method, an electron beam welding method, and a brazing method.

[0004]

However, these conventional joining methods have the following disadvantages.

[0005] First, in the case of the arc welding method, since the heat effect of welding is relatively large, the heat-affected zone of the base material occurs in a wide range. For this reason, the base material near the joint portion is severely softened, and it is difficult to obtain a joint strength equivalent to that of the non-heat-affected zone of the base material. In the case of a high-tensile aluminum alloy, so-called common metal welding cannot be performed from the viewpoint of weldability, so that a joint strength equivalent to that of the base material cannot be obtained.

Further, in the case of the electron beam welding method, although the heat-affected zone due to welding is smaller than that of arc welding, softening of the heat-affected zone of the base material cannot be avoided. You cannot get average strength. Further, since this method is basically a common metal welding, there is a possibility that cracks may occur in the weld metal depending on the type of the alloy.

[0007] The brazing method is a method in which the base material is most easily softened because the entire joint must be heated to the brazing temperature. Therefore, the bonding method is not suitable for a material reinforced by work hardening and heat treatment.

On the other hand, the above-described friction welding method is a method which has the least thermal influence as compared with these methods. For this reason,
Defects such as cracks are unlikely to occur, but when trying to frictionally join aluminum materials reinforced by work hardening or heat treatment,
A softened portion is generated, and a joint strength equal to that of the base material cannot be obtained.

As described above, in the conventional method for joining aluminum materials, an aluminum material reinforced by work hardening or heat treatment is joined with a strength equal to that of the base material, and a joint portion having no decrease in strength with respect to the base material is obtained. It is difficult.

The present invention has been made in view of the above problems, and can join an aluminum material reinforced by work hardening or heat treatment with a joint strength similar to that of a base material. It is an object of the present invention to provide a friction welding method of aluminum or an aluminum alloy that can expand the applicable range.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided a friction welding method for aluminum or an aluminum alloy, in which a first member and a second member made of aluminum or an aluminum alloy are relatively rotated while one member is being rotated by the other. In a frictional joining method of aluminum or an aluminum alloy in which the two members are relatively moved toward and joined to each other by frictional heat at the time of press contact, the preheating step by friction is not required.
After the upset pressure is applied to the first and second members, the relative rotation of the first and second members stops within 0.7 seconds after the first and second members contact each other. It is characterized by doing.

Further, in another friction joining method of aluminum or aluminum alloy according to the present invention, the first member and the second member made of aluminum or aluminum alloy are relatively rotated while one member is joined to the other member. In the aluminum or aluminum alloy friction joining method of moving the members relatively close to each other and joining the two members by frictional heat at the time of press contact, the time when the first and second members come into contact with each other, or Is characterized in that the upset timing is taken at the previous time.

In the present invention, the timing of the upset means that the pressure at the time of joining is applied between the members,
This means issuing a command to stop the motor that drives the members to rotate.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted various experimental studies to develop a method for joining work hardening or heat treatment hardening type aluminum materials, which are recently being used in place of steel as a strength member, while ensuring high joint strength. As a result of repetition of the above, it was found that the softening of the joint part was suppressed and the joint strength could be increased by taking the upset timing at a time before the two members to be frictionally joined to contact each other. . That is, the upset timing is a timing in which the two members are pressed against each other with a predetermined pressure and the pressing force is applied. In this way, by taking the upset timing before the time when the two members come into contact with each other, the both members are set. The overall friction time can be reduced and the heat effect can be reduced.

FIG. 1 is a graph showing the total friction time, and FIG. 2 is a timing chart showing the friction joining process. FIG.
As shown in the above, when frictionally joining metals including steel, conventionally, one member is driven to rotate at a high speed by a motor, and after the number of rotations becomes constant, the other member is rotated. It is moved closer to the one member (in the figure, indicated by the approach margin), applying a friction pressure P ₁ of the relatively low pressure therebetween. As a result, both members frictionally slide with each other, and are heated by the frictional force, so that both members are preheated. This friction time T
When _one has passed, it starts a so-called upset, the pressure between the two members to upset pressure P ₂ with increased stepwise to stop the rotation of the motor. Thereby, the joining surface of both members reaches a predetermined joining temperature and is joined. Conventionally, in the case of friction joining of an iron-based material, a friction time, that is, a time for preheating a member to be joined was set to about 10 seconds.

The condition factors affecting the friction welding include:
In addition to the number of rotations of the member, there are the friction pressure and the friction time in the friction process, and the upset pressure and the upset time (retention time after upset) in the upset process. These conditions differ depending on the material and shape of the materials to be joined. Steel materials have high friction pressure and upset pressure, and the friction time is long,
Aluminum material has low friction pressure and upset pressure,
Even if the friction time is shorter than that of steel, sufficient bonding can be achieved. The present invention takes this idea one step further and eliminates the time required for the friction step, which was conventionally considered an essential step, thereby preventing the heat-affected zone from spreading widely into the base material and reducing the heat-affected zone at the joint. The joint strength is increased by limiting the joint strength only. Therefore, in the present invention, the other member is moved closer to the rotating one member, and the upset is performed at the same time as or before the contact. By this upset timing, the rotation drive of the motor is stopped and the brake is applied to the motor, but by the time the motor is completely stopped, for example,
An extremely short time of about 0.3 seconds is required.

FIG. 1 shows the distance from the start of the upset to the contact in the case where the left half of the horizontal axis takes the upset timing before the contact of the members, with a negative number. The right half of the horizontal axis represents the time interval (friction time) from contact to the upset timing, as in the prior art, and the vertical axis represents the total friction time. As is apparent from FIG. 1, even when the upset timing is set at the same time as the contact, that is, even when the friction step is eliminated, there is a friction contact time of about 0.7 seconds. This is after taking upset timing by contact members, until upset pressure P ₁ rises, as an example, it takes about 0.3 seconds, after the rise of the upset pressure, about the and the start of the motor brake 0 .15
Seconds are required, and it takes about 0.17 to 0.2 seconds after the brake starts to be applied until the motor completely stops.

As a result of an experimental study by the present inventors, in the case of aluminum material, the preheating step based on friction time was eliminated, and the upset pressure was applied from the beginning to increase the 0.7 mm.
Even if friction welding is performed with an extremely short upset time of less than seconds,
It has been found that a temperature at which sufficient bonding can be achieved is reached.

The invention of the present application has been completed as a result of such experimental research, and is completely different from the conventional idea. The upset is started at the time when the members to be joined come into contact with each other or at an earlier time. I do. This eliminates the friction step and stops the rotation of the members within at least 0.7 seconds after the two members come into contact, ending the friction joining before excessive heat is generated and affects the base material.

When the friction welding is performed by such a method, the heat-affected zone is drastically reduced as compared with the conventional friction welding method, and a joint having the same strength as the base material can be obtained. On the other hand, in the case of the conventional method, for example, the friction time is set to 0.1.
Even if it is shortened to seconds, since the above-mentioned motor braking time is actually added to the time lag of pressure detection, relay and hydraulic system,
The true friction time amounts to about 0.75 seconds. For this reason, softening of the joint becomes a problem.

[0021]

Next, an embodiment of the present invention will be described. Example 1 Friction welding test of aluminum alloy pipes A6061 pipes (outer diameter: 40 mm, thickness: 3 mm, length: 100 mm), which are heat-treated aluminum alloys, were subjected to a friction welding test. This friction welding test used a brake type. The friction welding conditions are shown in Table 1 below. Example methods of the present invention, pressure pressure P ₂ is 9 kgf / mm ² or 7 kgf / mm ^2, in the case of conventional methods friction pressure P ₁ 4kgf / mm ² or 2 kgf /
mm ² , and the pressing pressure is the same as in the example. The upset timing in the present embodiment indicates a position before the end faces contact each other with a negative number.For example, -3 mm means that the upset is set 3 mm before the end faces contact each other, and the pressing pressure is set. those when multiplied by the motor brake at the same time applying a P _2. The friction time in the conventional method is the time of the friction step after the end faces of the members come into contact. After the pressure welding, the joint is centered, and FIG.
The tensile test pieces shown in Table 1 were sampled and their joint strength was tested.

[0022]

[Table 1] Table 1 (Part 1) Table 1 (Part 2)

FIG. 4 is a graph showing the values obtained from the tensile test.
It is a graph which shows the relationship between 2% proof stress and pressure welding conditions (upset timing). As shown in this figure, in the case of the conventional method, the longer the friction time, the lower the proof stress of the joint.
It is kgf / mm ² or 21kgf / mm ^2. According to the present embodiment, on the other hand, 22 kgf / mm ² or more yield strength is obtained, 28 kgf / mm ²
In some cases, the proof stress was obtained. This is equivalent to the yield strength of the base material.

FIG. 5 is a graph showing the relationship between the tensile strength and the pressure welding condition obtained in the same tensile test.
As is clear from this figure, in the case of the method of the present embodiment, a significantly higher strength than that of the conventional method is obtained also in the tensile strength.

FIG. 6 shows the hardness distribution of the joints frictionally joined under the No. 10 condition of this embodiment in Table 1. Also,
FIG. 7 shows the hardness distribution of the joint portion frictionally joined under the No. 14 condition of the conventional example in Table 1. In the case of the conventional method, the softening in the joint portion occurs in a wide range, whereas in the case of the present embodiment, although the softening is slightly performed in an extremely narrow region, the degree of this softening is also small, which is extremely excellent. It has a characteristic hardness distribution. Example 2: Friction welding of thin large diameter aluminum alloy pipe
In order to develop a test aluminum alloy drive shaft, A606
The pipe No. 1 (outer diameter 80 mm, thickness 2.5 mm, length 400 mm) and a yoke-equivalent member processed to have a diameter of 80 mm and a thickness of 2.5 mm only in the press-contact portion were friction-welded. FIG. 8 shows the shape of the test material. Table 2 shows the friction welding conditions. Then, after the pressure welding test, after removing the burrs at the joint, a tensile test was performed.
Table 3 below shows the results of the tensile test. In the table,
The results of a tensile test of a joining material by MIG welding using a 5183 filler material are also shown.

[0026]

[Table 2]

[0027]

[Table 3]

As is clear from Table 3, a joint having higher strength is obtained by the conventional friction welding method than by MIG welding, but the strength of the base material (about 30) is obtained.
kgf / mm ² ). In contrast,
In the case of the present embodiment, a joint having a strength of about 30 kgf / mm ² and almost the same strength as the base material is obtained.

[0029]

As described above, according to the present invention,
The region softened by heat at the time of friction welding is extremely narrow, and the degree of softening is extremely small, so that a high-strength joint can be obtained, and the same joining strength as that of the base material can be obtained. For this reason, the applications of work hardening or heat treatment hardening type aluminum alloys are expanded, and it is possible to apply various strength members by taking advantage of their light weight, and the present invention is extremely useful in industry.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an upset timing and a total friction time.

FIG. 2 is a timing chart of friction welding.

FIG. 3 is a plan view showing a tensile test piece.

FIG. 4 is a graph showing the relationship between upset timing and 0.2% proof stress.

FIG. 5 is a graph showing the relationship between upset timing and tensile strength.

FIG. 6 is a graph showing a hardness distribution according to the present embodiment.

FIG. 7 is a graph showing a hardness distribution in the case of a conventional friction welding method.

FIG. 8 is a schematic view showing a pressure welding test material.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-22651 (JP, A) JP-A-54-26945 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 20/12

Claims (2)

(57) [Claims] 1. While relatively rotating first and second members made of aluminum or an aluminum alloy, one member is moved relatively close to the other member, and both members are moved by frictional heat at the time of pressure contact. a friction bonding method of an aluminum or aluminum alloy joining member, pre frictional
The first and second members are applied without heat treatment.
Wherein the relative rotation of the first and second members stops within 0.7 seconds after the first and second members come into contact with each other by applying a cut pressure. Or a friction joining method of an aluminum alloy. 2. While relatively rotating first and second members made of aluminum or an aluminum alloy, one member is moved relatively close to the other member, and both members are moved by frictional heat at the time of pressure contact. An aluminum or aluminum alloy friction joining method for joining members, wherein the upset timing is set at a time when the first and second members come into contact with each other or before the contact time. Or a friction joining method of an aluminum alloy.