JPH0747477A - Method for joining al member and steel member - Google Patents

Abstract

PURPOSE:To provide a joining method which can obtain high strength of a joined joint at the time of joining an Al member and a steel member. CONSTITUTION:At the time of joining an Al member 11 and a steel member 12, resistance spot welding is executed by using a clad material 13 of Al 13a and steel 13f, arranging an alloy or a mixture 14 of Al and Si on the surface of the Al 13a side of the clad material 13, and interposing the clad material 13 in the direction in which each Al and each steel come into contact with each other between the Al member 11 and the steel member 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al member and a steel member used for firmly joining an Al member made of aluminum or an aluminum alloy and a steel member made of carbon steel or a low alloy steel. The present invention relates to the joining method.

[0002]

2. Description of the Related Art Among the social needs for automobiles,
In recent years, in order to reduce CO ₂ which is a main cause for global warming, increase in vehicle weight by adding safety equipment, and of course, from the viewpoint of energy situation, improvement of fuel consumption has been strongly desired.

In order to improve the fuel efficiency of automobiles, improvement of the engine,
Besides reducing friction loss, reducing vehicle weight is the most effective.

The weight of the vehicle can be reduced to some extent by reviewing the distribution of the wall thickness of each member or integrating a plurality of members. However, material replacement, that is, conventional steel members are replaced with aluminum, titanium, magnesium, plastics. It is effective to replace it with a lightweight material such as.

Among them, the balance between various properties and cost,
In terms of recyclability, aluminum-based materials are the easiest to use and are already used in some passenger cars.

It is expected that aluminum-based materials will be used more and more in automobile bodies in the future, but in many cases, they will be hybrid vehicle bodies in which Al members and steel members are combined, rather than aluminum vehicle bodies entirely. Expected to be.

In that case, joining of the Al member and the steel member becomes indispensable. Further, even when the entire body is made of aluminum, since the reinforcing member and the metal fittings are often made of steel, it is still necessary to join the Al member and the steel member.

Thus, in order to reduce the weight of the vehicle body, if an aluminum-based material is used, the Al member and the steel member must be joined.

Generally, when an Al member and a steel member are directly melt-bonded to each other, a brittle Al-Fe compound is formed at the bonded portion, and it is difficult to obtain a satisfactory joint. It is necessary to add.

A technique often used in this case is mechanical fastening such as bolt tightening, rivet, caulking,
Although they may be joined by an adhesive, these are not fusion-joined.

Then, in order to perform the fusion bonding, the surface of the joint portion of the steel member is subjected to some treatment (for example, Japanese Patent Laid-Open No. 58-93583, "Materials and Processes" Vo.
l. 4 No. 2 1991 Japan Iron and Steel Institute), in the case of joining a thick Al member and a steel member such as a ship or a rail car, a clad material (laminated plate material) produced by explosive pressure welding of Al and steel is used as an insert material. Insert members in the direction in which Al and steel contact each other between the Al member and the steel member, and perform melt welding by arc welding or spot welding (for example, "light metal welding").
Vol. 27 No. 10, 1989, "Light Metal Welding" V
ol. 18 No. 3, 1980).

On the other hand, when joining a thin Al member such as an automobile body and a steel member, it is desirable to adopt a joining method by resistance spot welding in view of productivity and welding distortion. Rolling thin Al and steel clad materials that can be used in the method are also being developed.

Then, using such a thin clad material of Al and steel, resistance spot welding is performed by interposing the clad material between the Al member and the steel member in a direction in which Al and steel contact each other. By this, it is possible to join in a state where two nuggets composed of an Al-side nugget and a steel-side nugget are formed, and thereby, a joining strength approximately the same as that in the case of Al can be obtained (for example, "Welding Society"). National Convention Lecture Summary "Vol. 51 (1992) 3
02, "Welding Technology", Vol. 41 No. 3 (199
3) Pages 83-87).

[0014]

However, in the method of resistance spot welding by interposing the clad material of Al and steel in a direction in which Al and steel contact each other between the Al member and the steel member, the resistance spot welding is performed as shown in FIG. As shown in FIG. 3, the clad material 23 of Al 23a and steel 23f is interposed between the Al member 21 and the steel member 22, and resistance welding is performed in a state where Als and steels are in contact with each other. Nugget 2
5 and the steel-side nugget 26 are joined together, but the molten Al-side nugget 25 formed at the interface between the Al member 21 and the Al 23 a of the clad material 23 is the clad material 2.
No. 3 was formed so as to be in contact with the interface between the Al 23a and the steel 23f (this is because the thermal conductivity of Fe is smaller than the thermal conductivity of Al), and the cladding material 23.
Since the molten Al-side nugget 25 reaches the interface between the Al 23a and the steel 23f, a fragile compound of Al and Fe (Al-Fe compound 24) is formed,
There is a problem that the joint strength at this portion becomes unstable. Therefore, the clad material of Al and steel is inserted between the Al member and the steel member in a direction in which Al and steel contact each other. Then, it was a problem to prevent the Al-side nugget at the interface between Als formed in the case of resistance welding and joining, from being biased to the interface between Al of the clad material and steel.

[0015]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems.
In the case where resistance welding is performed by interposing Al in a direction in which Al and steel are in contact with each other between the 1-member and the Fe-member, an Al-side nugget formed particularly at the interface between Als among the nuggets formed at the joint portion. To prevent the Al-side nugget formed at the interface between Als from reaching the steel of the clad material. Al
It is an object of the present invention to provide a method for joining an Al member and a steel member, which is capable of improving the joining strength by preventing the formation of (-Fe compound).

[0016]

According to the present invention, when joining an Al member and a steel member, a clad material of Al and steel is used, and an alloy or mixture of Al and Si is disposed on the Al side surface of the clad material. Between the Al member and the steel member.
It is characterized in that resistance welding is performed by interposing a clad material in a direction in which the steel and steel are in contact with each other. In the embodiment, the alloy or mixture of Al and Si is S
The i content or blending amount may be 10 to 25% by weight, and in the same embodiment, among the electrodes used for resistance welding, the cooling capacity of the Al member side electrode is the steel member side. It is possible to make it smaller than the cooling capacity of the electrode.

In the method for joining an Al member and a steel member according to the present invention, when using a clad material of Al and steel, an alloy or a mixture of Al and Si is arranged on the Al-side surface of the clad material, and the Al member and the steel are joined. When resistance welding is performed by interposing a clad material in a direction in which Als and steels are in contact with the member, it may be an alloy or a mixture.
When 1 contains Si, the electric resistance value, which is a dominant factor for the formation of a nugget in resistance welding, increases, and heat generation and melting are promoted. For example, in the well-known A5182 alloy as a practical alloy, the conductivity IACS
Is 30%, whereas the A390 alloy containing about 17 wt% Si reduces the conductivity IACS to 25-27%.

In the case of an alloy, the Al--Si alloy is a eutectic type alloy, has a low melting start temperature, and contains Mg and N.
By including a trace amount of alloying elements such as i and Cu, the melting start temperature is further lowered, and melting is facilitated. For example, A5
In the 182 alloy, the melting start temperature is about 580 ° C., whereas in the A390 alloy containing about 17 wt% of Si,
The melting start temperature is about 510 ° C.

That is, since the Al--Si alloy or the mixture is present between the Al member and the Al of the clad material, the heat generation during the energization of the spot welding is caused by the above A.
It becomes larger than when there is no 1-Si alloy or mixture, and the Al-side nugget is at the position A of the cladding material.
It grows flat in a shorter time than it grows at the interface between 1 and steel. Therefore, Al formed at the interface between Al
The energization may be stopped during the time when the side nugget grows flat and at the time when the Al-side nugget does not reach the interface between the Al of the clad material and the steel, whereby the interface between the Al of the clad material and the steel is fragile. By preventing the formation of the compound (Al-Fe compound), it becomes possible to obtain a joint having stable bonding strength.

In an alloy or mixture of Al and Si,
If the Si content or the blending amount is too small, the increase in electric resistance is small and the function of promoting melting cannot be sufficiently obtained. Therefore, it is preferably 10% by weight or more.

Further, if the Si content or blending amount is too large, the electric resistance becomes too large and the current flow becomes unstable, and the current locally concentrates and flows.
In some cases, the nugget is not formed because it is scattered or, in a marked case, it is not energized. Further, in the case of a mixture of Al and Si, the melting point of Si alone is considerably higher than that of Al, and even in the case of an alloy, the melting end temperature rises as the Si content increases, and the nugget formation becomes unstable. .
Therefore, it is desirable that the Si content or blending amount be 25% by weight or less.

As the method of arranging the alloy or mixture of Al and Si on the Al side of the clad material, thermal spraying using a powder or wire, coating the powder with a binder, or bonding a foil or a thin plate is performed. It is possible to adopt a means for doing so. However, if a large amount of binder, adhesive, etc. remains, it causes welding defects, so it is necessary to dry in advance. Also, on the Al side of the clad material of Al and steel, Al-
If thin plates of Si alloy are further stacked and formed as a clad material consisting of three layers in advance, the efficiency can be increased because it can be directly inserted between the Al member and the steel member. On the other hand, there is no particular limitation on the thickness of the Al-Si alloy or the mixture, but if it is too thin, the resistance will be insufficient, so it is desirable to set it to about 0.1 mm or more. However, if it is too thick, not only becomes uneconomical, but also causes scattering.

Further, it is also effective to consider the balance of the cooling ability of the electrode used for resistance welding as a means for correcting the unevenness of the Al-side nugget formed between the Al-side of the clad material and the Al member.

That is, the heat flow generated when the nugget is generated is partially generated in the peripheral direction of the nugget of the material to be welded, but most of it is generated on the electrodes on both sides, strictly speaking, the cooling water flowing inside the electrode. Therefore, by making the cooling capacity of the electrode on the Al member side smaller than that of the electrode on the steel member side, the heat in the surface direction on the Al member side tends to be retained during the formation of the Al side nugget, and the Al side nugget is made of steel. It is possible to suppress the biased generation on the member side.

As a method of making the cooling capacity of the electrode on the Al member side smaller than the cooling capacity of the electrode on the steel member side,
(1) The diameter of the electrode on the Al member side is made smaller than the diameter of the electrode on the steel member side, and the cross-sectional area of the portion where the heat from the Al side nugget is transferred to the cooling water in the Al member side electrode is reduced to reduce the heat. The amount of heat is reduced by decreasing the amount of conduction. This method is the most convenient, but other than this,
(2) The flow rate of the cooling water of the electrode on the Al member side is made smaller than the flow rate of the cooling water of the electrode on the steel member side to reduce the amount of heat conduction in the electrode on the Al member side.

(3) The material of the electrode on the Al member side has a lower thermal conductivity than the material of the electrode on the steel member side. For example, as an electrode on the Al member side, beryllium-cobalt-
A copper alloy and a tungsten-copper sintered alloy are used, and a cadmium-copper alloy and a chromium-copper alloy are used as electrodes on the steel member side.

By making the cooling capacity of the electrode on the Al member side smaller than the cooling capacity of the electrode on the steel member side in this way, the heat generated during resistance welding is likely to accumulate in the Al member side, and the cladding It becomes possible to suppress the Al-side nugget formed between the Al side of the clad material and the Al member from being biased toward the interface side between the clad material Al and the steel, and at the interface between the clad material Al and the steel. It is preferable to prevent the formation of a brittle compound so that the joint has a stable joint strength.

[0028]

In the method of joining an Al member and a steel member according to the present invention, since the above-mentioned constitution is adopted, the clad material A
Since an alloy or a mixture of Al and Si is arranged between 1 and the Al member, the heat generated during the resistance welding is A
It becomes larger than the case where an alloy or mixture of 1 and Si is not provided, and at this position, the Al-side nugget is A of the cladding material.
In the time period during which the Al-side nugget grows flat at the interface between Als and does not reach the interface between Al and steel in the clad material, the flat growth occurs in a shorter time than the growth at the interface between 1 and steel. By stopping the energization, Al of the clad material
A brittle compound (Al-Fe compound) is not formed at the interface between the steel and steel, and a joint having stable joint strength can be obtained.

[0029]

Example 1 As shown in FIG. 1, an aluminum alloy plate (JIS H
4000 mm, A5052) Al with a plate thickness of 1.0 mm
Member 11 and cold rolled steel plate (JIS G 3141, S
When joining a steel member 12 made of PCC) having a plate thickness of 0.8 mm, a clad material 13 of Al 13a and steel 13f
Resistance spot welding was performed by using the clad material 13 between the Al member 11 and the steel member 12 in a direction in which Al and steel contact each other. In this case, clad material 1
No. 3 was produced by a rolling method, and was made of Al 13
A pure aluminum having a thickness of 0.5 mm was used as a, a SPCC equivalent material having a thickness of 0.5 mm was used as the steel 13f, and a clad thickness of 1.0 mm was used.

Prior to interposing the clad material 13 between the Al member 11 and the steel member 12, the surface of the clad material 13 on the Al 13a side is sprayed with Al--S.
i coating layer (Al or Si alloy or mixture 1
After forming 4), resistance spot welding is performed by interposing the coated clad material 13 between the Al member 11 and the steel member 12, and as shown in FIG. A joint formed with the steel-side nugget 16 was obtained.

Table 1 shows the specifications of the coating layer (Al or Si alloy or mixture 14), Table 2 shows the resistance spot welding conditions, and Table 3 shows the joint strength measurement results of the spot welds.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

As is clear from the results shown in Tables 1 to 3, the No. 2 alloys containing Al-Si alloys having Si contents of 12% by weight, 17% by weight and 22% by weight were arranged on the Al side of the clad material. In the case of 1 to 4, fragile Al at the interface of the clad material
The -Fe compound was not formed, and the strength of the joint showed a good value.

On the other hand, the Si content in the Al--Si alloy is 5
No. as small as wt% In the case of No. 5, since the increase in electric resistance is small and it is difficult to promote the melting, a small amount of Al—Fe compound is formed at the interface of the clad material. Some of them had lower strength than the joints of 1-4.

In addition, the Si content in the Al--Si mixture was as high as 27% by weight, and the No. In the case of No. 6, although the Al—Fe compound was not formed at the interface of the clad material, the electric resistance increased and the amount of Si having a high melting point increased, so that the formation of the Al-side nugget became unstable and No. 1-4
Some of the joints had lower strength than the other joints.

Further, in No. 3 in which no coating layer is provided on the Al side of the clad material. In the case of No. 7, a brittle Al-Fe compound was formed at the interface of the clad material, and No. 7 was used. 1 to
There were some whose strength was considerably lower than that of No. 4.

Example 2 Similar to the case shown in FIG. 1, an aluminum alloy plate (JIS
H 4000, A5052) and an Al member 11 having a plate thickness of 1.0 mm, and a cold rolled steel plate (JIS G3141,
When joining a steel member 12 made of SPCC) and having a plate thickness of 0.8 mm, a clad material 1 of Al 13a and steel 13f
Resistance spot welding was performed by using No. 3 with the clad material 13 interposed between the Al member 11 and the steel member 12 in the direction in which Al and steel contact each other.

In this case, the clad material 13 was produced by a rolling method, and had a thickness of 0.1% as Al 13a.
5mm of pure Al, 0.5mm thick as steel 13f
The SPCC equivalent material having a clad thickness of 1.0 mm was used.

Prior to interposing the clad material 13 between the Al member 11 and the steel member 12, the surface of the clad material 13 on the Al 13a side was sprayed with Al--S.
i coating layer (Al or Si alloy or mixture 1
After forming 4), resistance spot welding is performed by interposing the clad material 13 between the Al member 11 and the steel member 12, and as shown in FIG.
A joint in which the steel-side nugget 16 was formed was obtained.

The electrodes used in the resistance spot welding had different diameters on the Al member 11 side and the steel member 12 side.

Table 4 shows the specifications of the coating layer (Al or Si alloy or mixture 14) and the electrode diameter, Table 5 shows the resistance spot welding conditions, and Table 6 shows the joint strength measurement results of the spot welds. .

[0044]

[Table 4]

[0045]

[Table 5]

[0046]

[Table 6]

As is clear from the results shown in Tables 4 to 6, No. 3 which does not make a difference in the cooling ability of the electrodes. In comparison with No. 11, the diameter of the electrode on the side of the Al member was made smaller than the diameter of the electrode on the side of the steel member to reduce the cooling capacity. The joint strength of 12.13 was higher and stable.

[0048]

As described above, according to the present invention, when joining an Al member and a steel member, a clad material of Al and steel is used, and an Al-side surface of the clad material is coated with Al.
And an alloy or a mixture of Si are arranged, and a clad material is interposed between the Al member and the steel member so that Al and steel contact each other, and resistance welding is performed. It is possible to prevent the Al-side nugget formed at the interface between Als from among the nuggets from being biased toward the interface between the Al and the steel of the clad material, and the Al-side nugget formed at the interface between Als is the clad material. It is possible to avoid reaching the steel of
It is possible to prevent the formation of a fragile compound with Al (Al-Fe compound), and it is possible to obtain a joint joint between an Al member and a steel member having high joint strength, which is a remarkably excellent effect. Be brought.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of a joint obtained by a method for joining an Al member and a steel member according to the present invention.

FIG. 2 is a sectional explanatory view showing an example of a joint obtained by a conventional method for joining an Al member and a steel member.

[Explanation of symbols]

 11 Al member 12 Steel member 13 Al and steel clad material 13a Clad material Al 13f Clad material steel 14 Al and Si alloy or mixture 15 Al side nugget 16 Steel side nugget

Claims (3)

[Claims] 1. When joining an Al member and a steel member,
Using a clad material of Al and steel, and arranging an alloy or mixture of Al and Si on the Al side surface of the clad material,
A method for joining an Al member and a steel member, characterized by interposing a clad material in a direction in which Al and steel contact each other between the member and the steel member and performing resistance welding. 2. The alloy or mixture of Al and Si is Si
The content or blending amount is 10 to 25% by weight.
A method for joining an Al member and a steel member according to 1. 3. The joining of an Al member and a steel member according to claim 1, wherein among the electrodes used for resistance welding, the cooling capacity of the Al member side electrode is smaller than the cooling capacity of the steel member side electrode. Method.