JPS59104279A - Resistance welding method of composite metallic material having resin film - Google Patents

Abstract

PURPOSE:To perform welding by interposing conductive metallic pieces between respective welding electrodes and a composite metallic material, short circuiting these materials and passing shunt current thereby breaking resin films right under the electrodes and short circuiting the metallic plates in the required positions right under the electrodes. CONSTITUTION:A conductive metallic piece 3 is interposed between one electrode 1 and the resin film 12 of a metallic plate 10 facing said electrode; a conductive metallic piece 4 is similarly interposed between the other electrode 2 and the resin film 22 of a metallic plate 20 facing said electrode. The pieces 3, 4 are short circuited with a conductive material, thereby forming a shunt circuit 5. When shunt current is passed while the composite material is pressed by the electrodes 1, 2, Joule heat is generated in the pieces 3, 4 and at the boundary between the respective metallic pieces and the electrodes and since the resin films are kept pressed by the welding electrodes, the films are broken right under the electrodes, then the plates 11 and 21 touch the pieces 3 and 4 respectively, by which the metallic plates are short circuited to each other and a nugget is formed. The metallic plates are thus welded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of resistance welding a metal composite material having a resin coating.

Metal composite materials with a resin coating, such as painted steel plates with paint applied and baked on the surface of the steel plate, and steel plates with a resin film adhered to the surface of the steel plate, have excellent rust prevention and aesthetics, and also have a moderate elasticity between the steel plates. A laminated steel plate provided with a resin coating having a laminate is lightweight and has excellent vibration distribution performance and soundproofing performance.

Therefore, a metal composite material with such a resin coating,
For example, it is suitable as a material for automobile bodies that strongly require lightness, rust prevention, vibration damping, soundproofing, etc.

However, such metal composite materials have a resin coating on the surface or between the metal plates, and this resin coating is generally insulating, and when these are stacked, the metal plates are insulated, so it is not common Cannot be welded by resistance welding method. That is, even though it has the above-mentioned favorable properties, it has difficulties in welding, which limits its use in the above-mentioned applications. For this reason, for example, Japanese Patent Publication No. 53-37821 describes a method in which composite metal materials having insulating resin coatings on both surfaces are overlapped and resistance welded by sandwiching them between a pair of welding electrodes. Before applying current, a superimposed current that simultaneously applies high-frequency current and low-frequency current is passed between the welding electrodes to generate arc heat and Joule heat. After destroying and removing the resin coating with this heat, the general resistance Similar to welding, a method has been proposed in which welding is performed by passing a welding current between electrodes to form a nugget in the metal material between the electrodes. However, according to this method, as the thickness of the resin coating increases, the applied voltage for flowing high-frequency current also becomes extremely high. Since it requires voltage, it is difficult to put into practical use. In particular, when the thickness is several hundred microns or more, it is impractical due to equipment costs and the danger of using high voltage.

In addition, when the above method is applied to resistance welding of metal composite materials that have a resin coating between the metal plates, the metal plates in contact with the electrode are all at the same potential inside, so the high voltage current is applied to the metal plates. The current from the electrodes passes through the lowest resistance part of the resin film sandwiched between the electrodes, that is, the part where defects such as pinholes exist, and flows to the other metal plate. It does not necessarily flow through the coating to the opposing electrode, and therefore, welding may not be possible at the intended metal plate location.

In addition, in the case of resistance welding of composite materials that have a resin coating between the metal plates, even if the metal plates in contact with each electrode are short-circuited and a shunt current is passed, the metal plates are usually thin, so -□- Not only is the Joule heat generated by the electrode small, but the heat loss to the electrode is large, so it is difficult to obtain enough heat to destroy the resin coating. In addition, even if the current is applied for a long time, the metal plate will generate abnormal heat in the area near the electrode that is not cooled by the electrode, and the metal in this area will melt and scatter, making it impossible to apply current, making welding similarly difficult. It is.

The present invention has been made to solve the various problems described above, and an object of the present invention is to provide a method for simply and accurately resistance welding a metal composite material having a resin coating at a predetermined location.

The resistance welding method for metal composite materials having resin coatings according to the present invention includes stacking metal composite materials having resin coatings,
In the method of resistance welding by sandwiching it between a pair of welding electrodes,
A conductive metal piece is interposed between each electrode and the metal composite material, and a shunt current is passed between these conductive metal pieces to destroy the resin coating, and then a welding current is passed between the electrodes. It is characterized by resistance welding.

In the present invention, the metal composite material having a resin coating is
Includes metal materials with a resin coating on one or both sides of a metal plate and laminated materials with a resin coating between the metal plates, where the resin coating is a paint coating applied and baked on the metal plate surface or adhered to the metal plate surface. It includes an integrated resin sheet or film, and a resin film or sheet held between metal plates with or without adhesive. In addition, the resin coating may contain various additives, fillers, etc.
Furthermore, the resin coating is generally insulative, but may contain conductive powder such as metal powder to have conductivity.

The present invention will be described below based on drawings showing examples.

FIG. 1 shows a metal composite material 10 having insulating resin coatings 12 and 13 on both sides of a metal plate 11 according to the method of the present invention.
, and a metal composite material 20 having insulating resin coatings 22 and 23 on both sides of a metal plate 21 are similarly overlapped and sandwiched between a pair of welding electrodes 1 and 2 to perform resistance welding,
One electrode 1 and the resin coating 12 on the metal plate 10 facing it
Similarly, a conductive metal piece 4 is interposed between the other electrode 2 and the resin coating 22 of the metal plate 20 facing it, and these conductive metal pieces A shunt circuit 5 is formed by short-circuiting with a conductive material. Therefore, when a shunt current is passed while pressurizing the composite material with a welding electrode, Joule heat is generated inside the conductive metal piece and at the interface between each metal piece and the electrode, and the resin coating is pressurized by the welding electrode. Therefore, the metal plates 11 and 21 are brought into contact with the conductive metal pieces 3 and 4, respectively, and the metal plates are short-circuited to each other to form a nugget and are joined together.

The conductive metal piece described above forms a contact interface with the metal composite material that is the material to be welded, and functions as a heat generating material that increases heat generation, thereby enabling the required resistance welding.
The compatibility is not particularly limited, but it is preferable to use a material that has high electrical resistance and does not damage the welding electrode, such as a mild steel plate.

Moreover, the dimensions of the conductive metal piece preferably have an area of about 70 to 100% of the diameter of the tip of the electrode. In this case, the conductive metal piece is crushed by the pressure applied by the electrode and has a good appearance. The area of the conductive metal piece is
If it is too small than the tip diameter of the welding electrode, the diameter of the nugget formed will be small and there is a risk that the specified welding strength will not be obtained.On the other hand, if it is too large, the specified function of the welded composite material may be impaired. This is not desirable because it not only damages the need but also makes the appearance worse. Furthermore, if the conductive metal piece is too thin, the heat loss to the electrode will be large relative to the amount of heat generated, reducing its effectiveness as a heat generating material, while if it is too thick, a high current will be required. and the appearance after welding is bad (so it is preferable to
In the case of welding a composite material that has an insulating resin coating on the surface of a metal plate, the range is 0.6 to 3.5 fins, and in the case of a composite material that has a resin coating between the metal plates described later, it is 0.3 to 3. ．．
The range is between 5 and 5.

In the present invention, the conductive metal piece does not need to be made of a single member, and a plurality of conductive metal pieces can be stacked and used. Layering a plurality of conductive metal pieces is also an advantageous method because the contact resistance increases and the amount of heat generated increases.

FIG. 2 shows an insulating resin coating 3 between metal plates 31 and 32.
3 and metal composite material 30 having metal plates 41 and 4 as well.
2 and insulating resin fI! , and a metal composite material 40 having a membrane 43 are overlapped and resistance welded, and as in the case of FIG. Similarly, a conductive metal piece 4 is interposed between the other electrode 2 and a metal plate 41 of a metal composite material facing the other electrode 2 to form a shunt circuit 5. Therefore, in this case as well, when a shunt current is passed, Joule heat is generated at the interface between each conductive metal piece and the metal plate in contact with it, and at the same time, the resin coating is pressurized by the electrode, so it is heated directly under the electrode. destroyed, thus causing all adjacent metal plates to short circuit each other,
By subsequently applying a welding current, a nugget is formed and the metal composites are welded together.

It should be noted that the short circuit may be formed directly between the metal plates 31 and 41, and the metal piece may have a diameter equal to or smaller than the electrode diameter.

The method of the present invention is particularly effective when the thickness of the metal plates sandwiching the insulating resin coating is 1 mm or less, preferably 0.8 part m or less. When the metal plate is thin, not only little Joule heat is generated internally, but also the heat loss to the electrode is large, making it difficult to obtain enough heat to destroy the insulating film. However, according to the present invention, by interposing a conductive metal piece between the metal plate and the electrode, a large amount of Joule heat is generated and the resin coating can be easily destroyed. However, in the method of the present invention, the thickness is
This does not in any way prevent its application to composite materials containing metal plates of aIa or higher, and even in such cases, resistance welding can be performed while ensuring welding stability.

As described above, according to the method of the present invention, a conductive metal piece is interposed between each welding electrode and the metal composite material, and these are short-circuited to flow a shunt current. Joule heat sufficient to destroy the resin film is generated at the contact interface of short-circuited and welded.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 As shown in FIG. 1, both surfaces have a thickness of 3. o, l m
Mild steel plates with a hinyl chloride resin coating of 0.6 mm thick, 100 mm long, and 30 mm wide were stacked together and held together with 2 wedges of 30 parts, each having a length of 20 ml and a width of 6 mm. A mild steel plate having the thickness shown in Table 1 in 0 mm was interposed as a conductive metal piece between each welding target and the electrode, and the tip diameter was 6.0 parts, 4. Sandwiched between the dome-shaped welding electrodes of the OR with a pressure of 250 kg f,
Single spot welding was carried out at the center of the above-mentioned overlap for a welding time of 50 cycles.

In this way, 20 sets of test specimens were resistance welded, and the welding current range was from the welding current that provided a predetermined welding strength to the maximum welding current that did not cause spatter, that is, the appropriate welding current range, and welding! ?
The shear tensile strength of 1; was investigated. The results are shown in Table 1. When the conductive metal piece is thin, the prescribed welding cannot be performed, but these cases are also shown.

Table 1 (Note) The * mark is three 0.2 inch thick metal pieces stacked one on top of the other.

Example 2 As shown in Figure 2, thickness 0.4 m+i, length 100
mm, thickness 0.4 n+m between mild steel plates of width 30+nm
Two sheets of metal material sandwiching a polypropylene resin sheet were stacked with an overlap distance of 30 m + 111, and an annealed copper plate with a diameter of 5 mm and a thickness shown in Table 2 was interposed as a conductive metal piece between each welded material and the electrode, Single spot welding was carried out at the center of the overlap under the same conditions as in Example 1.

Table 2 shows the appropriate welding current range and shear strength of the welded part, which were evaluated in the same manner as in Example 1.

Table 2 (Note) *marked is o, tsmm thick metal pieces stacked together.

[Brief explanation of drawings]

1 and 2 are conceptual diagrams illustrating the method according to the invention. 1.2... Welding electrode, 3.4... Conductive metal piece, 5
...Shunt circuit, 11.21.31.32.41.42
...Metal plate, 12.13.22.23.33.43.
・Resin coating. Patent Applicant Kobe Steel Co., Ltd. Agent Patent Attorney Ittsu Makino Voluntary amendment to Figure 1 procedure) February 2, 1980 - Mr. Commissioner of the Japan Patent Office ■, Petition No. 213727 of 1988, Minor Case Indication 2. Name of the invention Resistance welding method for metal composite materials having a resin coating 3. Relationship to the amended case Patent applicant address 1-3-18 Wakihama-cho, Chuo-ku, Kobe Name
Kobe Steel, Ltd. 4, Agent Address: 1-8-3-5 Shinmachi, Nishi-ku, Osaka, Date of Amendment Order: Showa, Month, Day (Shipping Date: Showa)
6. Number of inventions increased by amendment 7. Subject of amendment Detailed explanation of the invention in the specification Φ fence and -
(1) Add the following sentence between lines 8 and 9 on page 10 of the specification. ``Adhesives may be used to attach the conductive metal piece to the planned welding position of the metal composite material, but if the metal plate constituting the metal composite material and the conductive metal piece are magnetic, A method that uses magnetic force is effective.'' (2) Figure 2 of the drawing is corrected as shown in the attached sheet.

Claims (1)

[Claims] (1) In a method of resistance welding by stacking metal composite materials having resin coatings and sandwiching them between a pair of welding electrodes, a conductive metal piece is interposed between each electrode and the metal composite material, and these conductive metal pieces are interposed between each electrode and the metal composite material. 1. A method for resistance welding a metal composite material having a resin coating, the method comprising: passing a shunt current between the metal pieces to destroy the resin coating, and then passing a welding current between the electrodes to perform resistance welding.