JPH04333377A - Butt welding method for steel and aluminum - Google Patents

Abstract

PURPOSE:To metallurgically perform butt joining on the end faces of a steel plate and am aluminum material. CONSTITUTION:A clad plate 10 of steel and aluminum is sliced in the orthogonal direction to the interface thereof to obtain a joining material 11. A steel material part 11a of the joining material 11 is welded to the steel plate A which is one material to be joined and an aluminum material member 11b is welded to the aluminum material B which is the other material to be joined. As welding, it is desirable to perform laser beam welding where a thermal effect is hardly given to the clad interface 12 of the joining material 11. For the same reason, a thick plate where a long joining material 11. can be obtained is desirable as the clad plate 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallurgical method for butt joining steel and aluminum. In addition, in this specification,
Aluminum includes pure aluminum and aluminum alloys.

0002

BACKGROUND OF THE INVENTION Aluminum has recently been attracting attention as a material in the fields of automobiles, buildings, etc. due to demands for lighter weight, higher corrosion resistance, and higher design. However, aluminum is expensive compared to steel materials and has a problem of low tensile strength. Therefore, for example, in the case of a car body, in addition to deteriorating economic efficiency, the shock absorbing ability in the event of a collision decreases. Therefore, in general, there are many advantages to partially using aluminum materials only in effective areas, rather than using aluminum materials alone.

When aluminum and steel are used in combination, it is necessary to bond the two materials together, and in the case of an automobile body, it is necessary to bond plates of both materials to each other. In addition to automobile bodies, for example, in plate making lines where aluminum plates and steel plates coexist, it is necessary to mutually bond aluminum plates and steel plates in order to perform continuous plate making.

[0004] As for mutually joining aluminum plates and steel plates, butt joining by welding can be considered. However, when welding aluminum and steel, the weld metal
Since the metal structure consists of Al intermetallic compounds and has extremely poor toughness, sufficient bonding strength cannot be obtained. Therefore,
Welding is generally not used to join aluminum plates and steel plates together.

[0005] As a metallurgical joining method that can be applied to mutually joining aluminum materials and steel materials, there is cladding by diffusion bonding. Unlike a welded joint, a cladding joint between steel and aluminum, particularly a cladding joint formed by explosion bonding or cold rolling, has an extremely thin Fe-Al intermetallic compound layer, and no embrittlement is observed at the interface. However, cladding by explosion bonding or cold rolling requires high interfacial cleanliness and large pressing force. Therefore, it is almost impossible to apply this method to joining end surfaces of plates together.

[0006] Under these circumstances, non-metallurgical overlapping bonding using rivets or adhesives is generally used to bond aluminum plates and steel plates to each other.

[0007]

[Problems to be Solved by the Invention] However, in the overlapping joining of aluminum plates and steel plates, a step inevitably occurs at the joint. This step cannot be removed even by post-processing such as grinding, so this joining method
Due to problems in appearance and press molding, it is impossible to use it for automobile bodies. Furthermore, it is difficult to apply the method to interconnecting coils because the stepped portion causes flaws in the rolling rolls.

[0008] An object of the present invention is to provide a method for butt-joining steel and aluminum, which can metallurgically butt-join the end faces of a steel plate and an aluminum plate.

[0009]

[Means for Solving the Problems] The method for butt joining steel and aluminum of the present invention is to collect a joining material with the joint interface as an intermediate part from a steel and aluminum clad material manufactured by explosion bonding or cold rolling. A steel material, which is one of the materials to be butt-jointed, is welded to the steel material portion of the joining material, and an aluminum material, which is the other material to be butt-joined, is welded to the aluminum material portion of the joining material. It becomes as.

0010

[Operation] The method of the present invention is used, for example, to butt join steel plates and aluminum plates. FIG. 1 shows a specific procedure when the method of the present invention is applied to butt-joining a steel plate and an aluminum plate.

[0011] In this joining method, a clad plate 10 of steel and aluminum is used to butt join a steel plate A and an aluminum plate B. The clad plate 10 is manufactured by explosion bonding or cold rolling, and the interface between the steel layer 10a and the aluminum layer 10b has a perfect metal touch.
The Fe-Al intermetallic compound layer is also extremely thin and has excellent adhesive bonding properties.

The width w of the clad plate 10 is set to be the same as or larger than the width wo of the steel plate A and aluminum plate B to be joined. Thickness T is usually several mm to tens of mm
Therefore, the thicker the better. The compositions of the steel layer 10a and the aluminum layer 10b in the cladding plate 10 are preferably the same as those of the steel plate A and the aluminum plate B, and are at least similar to each other to the extent that welding can be performed without any problem.

The clad plate 10 is sliced in a direction perpendicular to its interface. As a result, a thin plate-shaped connecting material 11 is collected from the clad plate 10. Connecting material 11
The thickness (slice width L) is the same as each plate thickness To of the steel plate A and the aluminum plate B.

When the connecting material 11 is collected, a steel surface 13a parallel to the interface 12 is formed with the cladding interface 12 in the middle.
and the end face of the steel plate A are butt welded, and the aluminum surface 13b parallel to the interface 12 and the end face of the aluminum plate B are butt welded. In this way, the steel plate A and the aluminum plate B are metallurgically butt-joined via the connecting material 11.

In this joining method, the distance from the center of the steel welded part a to the cladding interface 12 of the connecting material 11 is determined by the length of the steel portion 11a of the connecting material 11, and It becomes equal to the layer thickness Ta. Also, from the center of the aluminum welding part b to the joint edge 11
The distance to the cladding interface 12 is determined by the length of the aluminum material portion 11b of the connecting material 11, and is equal to the layer thickness Tb of the aluminum material layer 10b in the cladding plate 10. In both cases, the thickness T of the clad plate 10 is several mm.
Since it is only ~10-odd mm, it cannot be made that large.

Therefore, in butt welding between the steel portion 11a and the steel plate A and between the aluminum portion 11b and the aluminum plate B, welding such as T1G in which the weld bead is wide causes the welding heat to cause the cladding interface 12 to This is not preferable because it causes a problem of embrittlement. Preferred welding is laser welding, which has a small bead width and is less affected by heat. Further, even when laser welding is used, consideration is desired so that the relationship between the bead width and the layer thickness of the clad plate 10 satisfies Equation 1.

[0017]

[Formula 1] Ta≧2.5Wa Tb≧2.5Wb Ta: Layer thickness Tb of steel layer 10a in clad plate 10
: Layer thickness Wa of aluminum material layer 10b in clad plate 10: Bead width Wb by butt welding between steel material portion 11a of connecting material 11 and steel plate A: Bead width Wb due to butt welding between aluminum material portion 11b of joining material 11 and aluminum plate B Bead width

[0018]
If the relationship of Equation 1 is not satisfied, the maximum temperature reached at the cladding interface 12 of the connecting material 11 will exceed approximately 550°C, and the interface 12
This promotes the growth of intermetallic compounds and reduces bond strength.

In order to satisfy the relationship of formula 1, test welding using a laser is performed in advance, and the bead widths Wa and Wb when laser welding is performed under appropriate conditions are determined.
A clad plate 10 having a thickness commensurate with the bead widths Wa and Wb is used. The bead widths Wa and Wb increase as the thickness T0 of the steel plate A and the aluminum plate B, which are the materials to be joined, increase, and a thicker clad plate 10 is required.

[0020]

[Examples] Examples of the present invention will be described below. A cold-rolled steel plate of JIS standard SPCD and an aluminum plate of JIS standard A1100 were used as the materials to be joined, and butt joints were performed by welding using a thin plate taken from the clad plate of the same combination as a connecting material. The results are shown in Table 1. Bonding performance was evaluated by repeatedly bending with a bending radius of 60 mmR, and those that did not break after 20 bends were evaluated as good (○), and those that broke after less than 20 times were evaluated as poor (x).

[0021]

[Table 1]

[0022] When welding is TIG, the bead width is too large and the cladding interface of the connecting material becomes brittle (No. 2, 9).
. When welding is done by laser, the thickness of the material to be joined is 0.5mm,
As the thickness increases to 1.0 mm and 3.0 mm, the bead width increases to 0.5 mm, 0.8 mm, and 1.8 mm, but the thickness of each of the steel layer and aluminum layer in the clad plate is 2 mm, 3 mm, A good butt joint can be achieved by gradually increasing the length to 5mm and extending the lengths of the steel and aluminum parts of the connecting material (
No. 1, 6, 8, 10).

[0023]

As is clear from the above description, the method for butt joining steel and aluminum of the present invention enables metallurgical butt joining of plates, which was previously considered impossible, to be performed without any problem. Therefore, a step-free plate joint is provided,
The use of aluminum in parts of automobile bodies and the production of steel plates and aluminum plates on the same line will be promoted.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the method of the present invention.

[Explanation of symbols]

A Steel plate which is a material to be joined B Aluminum plate 10 which is a material to be joined Clad plate 10a Steel material layer 10b in the clad plate Aluminum material layer 11 in the clad plate
Connecting material 11a taken from the clad plate Steel portion 11b of the connecting material Aluminum material portion 12 of the connecting material
Cladding interface in tie material

Claims (1)

[Claims] Claim 1: From a steel and aluminum cladding material manufactured by explosion bonding or cold rolling, a connecting material with the bonding interface as the intermediate part is taken, and one of the joining materials to be butt-jointed is attached to the steel part of the connecting material. A method for butt joining steel and aluminum, comprising welding a steel material, and then welding an aluminum material, the other material to be butt joined, to the aluminum material portion of the connecting material.