JP3126827B2 - Resistance welding method of aluminum material and insert member - 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 for resistance welding aluminum-based materials such as aluminum and aluminum alloys (hereinafter referred to as aluminum-based materials) and an insert member used for the resistance welding.

[0002]

2. Description of the Related Art As one of conventional joining methods of aluminum plate materials (aluminum-containing alloy plate materials), there is a method disclosed in Japanese Patent Application Laid-Open No. 58-47576. In this method, an anodic oxide film or a chemical oxide film is formed in advance on the overlapped portion of the aluminum plate and welded. For example, after the work is coated with a margin, the work is immersed in a sulfuric acid bath to form an anodic oxide film. Then, the part is welded.

However, this method has a disadvantage that not only the number of steps up to welding is large but also a processing bath is required, so that the cost is increased.

[0004] In general, when resistance welding is performed on an aluminum plate, there is a tendency that the pressing force and welding current must be increased because the aluminum has high electrical conductivity. In addition, an oxide film is formed on the surface of the aluminum plate material, which serves as a resistor. Since the oxide film is sandwiched between the electrode chip and the work contact surface, heat is generated also in this portion, and as a result, dust and welding are generated. There were defects such as deterioration of appearance quality. Note that the occurrence of dust, welding, and the like also affects the life of the electrode chip, and has the disadvantage of shortening the life.

Further, another prior art is disclosed in
Japanese Patent Application Publication No. 278679 and Japanese Patent Application Laid-Open No. 55-100882 are known.

[0006] In the above-mentioned Japanese Patent Application Laid-Open No. 63-278679, there is a drawback that the insert material (plate material) is provided in advance at the welding portion, so that waste is increased and the cost is increased. On the other hand, in Japanese Patent Laid-Open No. 55-100882, since the insert material is a plate-like solid such as a disk or a plate, it is necessary to set the insert at each welding point. Therefore, it is good when the work is a single work (one with one hit point and the welding is completed), but there is a drawback that when the work is welded continuously, the work becomes difficult. In addition, the use of a plate-like solid material as the insert material has a disadvantage that the cost is increased.

Further, Japanese Patent Application Laid-Open Nos. 64-62284 and 63-1 disclose techniques for interposing a substance for increasing the resistance between the plates between the plates to be welded.
Japanese Patent Application Laid-Open No. 1998-88 and Japanese Patent Application Laid-Open No. 1-254388. Each of these sheet materials is a galvanized steel sheet, and the inclusions are Al ₂ O ₃ (particle diameter: 50 to 500 μm), mending tape (thickness: 0.1 mm), salt particles (particle diameter: 25 mm).
0 μm) and MnSi ₂ (particle size 100 μm).

[0008] These methods increase the resistance of the site by inserting inclusions, thereby reducing the current and shortening the energization time, reducing the amount of zinc lost from the two, and improving the corrosion resistance. It is intended to improve the lifetime of the electrode. Also, by forming a nugget between the plates to be welded, the strength is improved.

However, if the above-mentioned inclusions are used for the aluminum-based material to be welded according to the present invention, the welding characteristics are rather deteriorated, and such inclusions cannot be applied to the present invention. The reason is as follows.

The surface of an aluminum plate is easily oxidized and is usually covered with an oxide film of Al ₂ O ₃ .
The affinity between aluminum and oxygen is about 100 times greater than the affinity between Zn and O ₂ . Therefore, the film thickness of Al ₂ O _{3 on} the surface of the aluminum plate material is much larger than the oxide film on the surface of the galvanized steel plate. Moreover, further the use of for Al ₂ O ₃ inclusions from the resistivity of the Al ₂ O ₃ [rho large as ^{1 × 10 16 Ω · cm (} 14 ℃), becomes too large the resistance between the welding electrodes, The welding can no longer be performed. In this case, Japanese Patent Application Laid-Open No. Sho 64-62284
As described in Japanese Patent Application Laid-Open No. H10-209, if a particle having a large particle size of 50 μm to 500 μm is used, the resistance is further increased, and welding becomes more and more impossible.

[0011] In addition, with regard to the welding strength after welding, the use of inclusions can only be expected to improve the strength due to the reduced thermal effect on the base material. That is, when using Al ₂ O ₃ as inclusions, since the Al ₂ O ₃ is inclusion weld members not be alloyed or combined by welding, welding by the complexing or alloying This is because the strength cannot be improved.
Rather, when the plate material to be welded is an aluminum plate material, if Al ₂ O ₃ particles having a particle size of 50 to 500 μm are interposed, the strength is rather deteriorated, and further, under stress, the Al ₂ O ₃ particles become a source of fracture. Also, when the mending tape is used as the inclusion, the mending tape itself is too thick, so that electricity cannot be applied between the plate materials to be welded as in the case of using Al ₂ O _3. Cannot be performed.

Further, when salt grains are used as the inclusions, the welding strength between the aluminum plates is reduced.

Further, the plate material to be welded is made of aluminum.
Material, MnSi as an inclusion _TwoWhen using
Therefore, Mn and Si cause a needle-like phenomenon,
The welding strength decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. The present invention aims at increasing the efficiency of resistance welding by interposing a metal insert member between aluminum plates to be welded, and at the same time, the occurrence of electrolytic corrosion and the like. It is an object of the present invention to provide a resistance welding method and an insert member for an aluminum-based material, which can effectively prevent the formation of a welded product and obtain a stable welded product.

[0015]

According to the present invention, in a resistance welding method for an aluminum-based material in which an insert member is interposed when an aluminum-based material is resistance-welded, the insert member is made of Fe, Ni and Co. At least one substance selected from the group consisting of Ti, Cr and Mo
Powder containing a mixture of at least one substance selected from the group consisting of: an insert member interposed between the joining surfaces; removing an oxide film on the surface of the aluminum-based material during energization; and complexing or alloying after energization. Thus, a resistance welding method for an aluminum-based material is obtained.

According to the present invention, there is provided an insert member to be interposed in a joint surface when resistance welding of an aluminum-based material, wherein the insert member is 62% by weight ≦ Fe + N
4% by weight ≦ Cr + Ti + Mo + W + Nb + Al ≦ 38% by weight in at least one material selected from Fe, Ni and Co having a composition range of i + Co ≦ 96% by weight
Is obtained by mixing at least one substance selected from the group consisting of Cr, Ti, Mo, W, Nb and Al having the following composition range.

The aluminum material has a high electrical conductivity, and has a large current and a large current when performing resistance welding, compared to SP steel sheets and galvanized steel sheets.
Requires high pressure. Therefore, in order to maintain sufficient heat generation and enable welding, increase the current-carrying area by enlarging the current-carrying area (increase the electrode tip diameter) or increase the resistance of the weld between aluminum materials. Need to be done.

Now, as shown in FIG.
Insert member 1 that increases resistance between workpieces between 12
When 5 is inserted, a preferential heat generation site is provided in that portion, so that the Joule heat generation efficiency can be increased and the generation site can be limited. At this time, if conditions such as the amount, type, particle size, and particle size of the insert member 15 are appropriately determined, it is expected that a great effect can be obtained by a simple method of interposing a substance between works.

If the insert member 15 interposed between the workpieces is made of powder, a flash should occur for a very short time in the initial stage of energization. This is because the powder has a small contact particle area and a large current is concentrated here.

On the other hand, the surface of the aluminum material is generally covered with Al ₂ O ₃ which is an oxide film. Therefore, at the time of resistance welding, an oxide film having a high electric resistance is sandwiched between the aluminum-based material and the aluminum-based material. Therefore, it is considered that this portion is initially melted by energization. However, it is well known that the aluminum material has high thermal conductivity and the nugget moves to above or below the oxide film. In particular, in the case of direct current, this phenomenon is remarkable, and the nugget is biased to the + side. This is a phenomenon that is often seen in TIG welding, but eliminates the effect of such an oxide film.
It is thought that bringing the nugget to the center leads to improvement in weldability. In order to eliminate the influence of the oxide film, it is preferable to break the oxide film. In this case, too, a powder having a high resistance is interposed between the oxide films, and at least a powder having a higher resistance than an aluminum-based material as a base material. It would be appropriate to let them.

When the powder is interposed between the aluminum plates to be welded as described above, the aluminum plates 21 and 25 face each other via the powder 23 as shown in FIG. Is limited, so that the arc can be easily estimated. This is in a plasma state, and has sufficient energy to destroy the oxide films 22 and 24. When the current value is several KA (direct current) or several hundreds A, the energy obtained by this flash can be expressed by the following equation:
It has the ability to destroy oxide films 22 and 24 having a thickness of μm. Therefore, the oxide films 22 and 24 are removed by the flash, and a clean metal surface appears, which is welded.

Electrode 1 after energization and flashing
Considering the resistance between 3 and 14, as shown in FIG. 1, the internal resistance 31 of the electrode 13, the contact resistance 32 between the electrode 13 and the work 11, the resistance 33 in the work 11, the work 11-insert member (powder). (Contact) resistance 3 between 15 and work 12
4, a series resistance of the resistance 35 in the work 12, the contact resistance 36 between the work 12 and the electrode 14, and the internal resistance 37 in the electrode 14. Of these, in resistance welding, as is well known, when the resistance 34 is overwhelmingly larger than other resistances, welding with high efficiency and high welding strength can be performed. An insert member (powder) 15 sandwiched between the clean metal surfaces created by the flash is arranged to raise and control this resistance 34.

For this reason, after flashing, a temperature rise of the metal on the clean metal surface, that is, a so-called Joule heat is selectively generated here. If the temperature rises, the electric resistance further rises exponentially, so that this part eventually melts and becomes composite or alloyed with the interposed insert member (powder) 15.

In the latter stage of welding, the power supply is stopped, and the heat of the molten portion is diffused to the base material and the electrode by heat conduction. At this time, the used insert member (powder) 15 is contained in the nugget and solidified together with the melting of the contact portion. Since the thermal conductivity of the insert member (powder) 15 is usually about 1/1000 compared to the base material aluminum, the cooling rate is reduced.

In conventional resistance welding of aluminum materials, the cooling rate at this time is extremely rapid and rapid cooling.
Cracks are likely to occur at the interface between the surrounding structure and the weld, and even if a post-heating current is applied, the heat conduction is too good and a great effect cannot be expected.However, according to this method, the soundness is so high that the post-heating current is unnecessary. Tissue was obtained.

FIG. 3 shows these welding models. Due to the flash area, it is easy to think that there will be a time delay, but after the flash, a clean metal surface will be welded, so the subsequent current rises sharply, and in fact it is faster than the delay It is.

The interposed insert member (powder) 15 must be selected so as to be compounded or alloyed with the material of the work, and not to deteriorate the strength of the material. Preferably, it is desirable to select so as to increase the strength or rigidity of the (material) welded portion by compounding or alloying.

As described above, in the case of an aluminum-based material, Al ₂ O _{3 as} an oxide film is formed on the surface thereof (see FIG. 2). Therefore, the aluminum plates 21 and 2
In addition to the particle size of the powder 23, the distance between
And 24 are added. The specific resistance of Al ₂ O ₃ as oxide films 22 and 24 is about 1 × 1.
Since 0 ¹⁶ Ω · cm and high aluminum sheet material 21, 25
In order to flow a large current that enables welding therebetween, it is necessary that the specific resistance of the interposed powder 23 is not too large.

For example, when a powder made of Al ₂ O ₃ is used as the powder 23, the specific resistance of Al ₂ O ₃ is large. Must be reduced. On the other hand, since the surface of the aluminum plates 21 and 25 originally has irregularities, the particle size of the powder 23 becomes small, and if the degree of the irregularities becomes the same or less, the oxide films 22 and 24 come into contact with each other. As a result, the significance of interposing the powder 23 is lost. Therefore, it is required that the material of the powder 23 to be interposed has a low specific resistance to some extent. Metals can be considered as a material satisfying this requirement.

Further, when the aluminum material is welded, the aluminum material is melted.
Thus, the powder 23 is taken into the inside by being compounded or alloyed with the material No. 3. Aluminum materials are generally brittle, and it is necessary to prevent impact fracture when objects hit. Therefore, the substance used for the powder 23 is preferably a substance that strengthens the aluminum material when incorporated into the aluminum material. Such materials include Ni, C among metals.
o and Fe are preferred. Note that these materials can be used alone or a plurality of materials can be used simultaneously.

The particle size of Ni, Co and Fe is 2
It is preferably in the range of 00 μm or less, more preferably in the range of 5 to 100 μm. If the particle size is larger than this,
The resistance value of the powder 23 becomes too large, and it becomes difficult for a current necessary for welding to flow.

When the particle size and the particle size are small, the powder coating layer may be composed of multiple particles. That is, when a particle size smaller than this is used, the powder is superimposed on the powder, and it is possible to make the thickness of the superposed layer fall within the specified range.

As a material of the powder 23, Fe, Ni, Co
When a powder is used, a large current flows intensively in a portion where the powder 23 is in contact with the oxide films 22 and 24, so that a flash occurs at the beginning of energization. The oxide films 22 and 24 are removed by the flash, and the clean metal surfaces of the aluminum plate 21 and the aluminum plate 25 are exposed and welded from this portion. As a result, since these metals have a lower thermal conductivity compared to Al, this metal part is preferentially heated, and if heated, the electrical resistance will be higher, and this metal part will be heated more and more Melts.

When these metals are incorporated into an aluminum material, they function to increase the welding strength, but may cause electrolytic corrosion. For this reason, the above metals
By mixing at least one selected from Ti, Cr, Mo and the like, corrosion resistance including weather resistance can be improved, and a stable molten product can be obtained.

The present invention can be applied not only to aluminum plate materials but also to aluminum-based materials such as aluminum alloys.

The powder 23 is interposed on the joint surface by applying a solution in which the powder 23 is mixed. This solution is preferably a binder such as vinyl acetate, nitrocellulose, polystyrene, polyacrylic resin, melamine resin, acetone, alcohol, thinner,
It is prepared using a solvent such as triene or hexane, a developing agent such as (ethyl) cellosolve, ethyl phthalate or butyl phthalate, and a drying controlling agent such as butyric acid. Note that these combinations can be freely set as appropriate.

Further, a tape member can be used in place of the above solution in order to interpose the powder 23 on the joint surface. That is, a metal tape in which the powder 23 is deposited on a thin tape member of about 5 μm is prepared, and this metal tape is attached to the joint surface.

Further, the powder 23 is temporarily attached to the tape member, and the tape member is once adhered to the joining surface.
By detaching the tape member, the powder 23 can be left on this joint surface.

Further, instead of the powder used as the powder 23, the powder is melted in a vacuum and then a foil plate having a size of about several tens μ is formed, and the foil plate is attached to one of the joining surfaces. It is also possible to interpose an insert member on the joint surface.

[0040]

EXAMPLE 1 The member to be welded was a plate equivalent to JIS A5052P with a thickness of 2.
It was an aluminum material of 0 mm, and two aluminum materials were overlapped and welded. Welding is performed using a DC resistance welding machine. The welding conditions are that the welding current is about 8 KA.
４０40 KA, and the energization time was 15 cycles. The electrode used was chromium copper φ16 × 190 mm (water cooled). As the powder interposed between the aluminum materials, the average particle size is 1
4 to 8 (No. 3, No. 4, No. 1).
6, no. 29 and no. 34). This powder was added to a mixture of melamine, acetone, alcohol, ethyl cellosolve, and butyl phthalate at 10 g / 100 m
1 was dispersed and interposed at the joint surface by drying after dipping.

Therefore, the welding current value at which a nugget diameter corresponding to the Class B guaranteed value of 5√t (t is the plate thickness) was obtained and the tensile shear strength at this time were measured, and the powder was sandwiched between the members to be welded. An experiment was performed to detect how the welding current changed. The nugget diameter generated by spot welding is about 1.15 times the Class B guaranteed value of 5 値 t in the conventional method, that is, the welding method in which no insert member is interposed on the joint surface. The continuous point test was performed by multiplying the current value at which each class B guaranteed value of 5√t was obtained by 1.15 times. In FIGS. 4 to 8, the column of continuous hitting points, the left side shows the number of hitting points satisfying the tensile shear strength, and the parentheses in the right side of this column, the same values at the level determined as 15 hitting points in the conventional method. This is a comparison and shows the number of continuous hits having a quality that can be distributed as a product in appearance.

The result was judged to be a nugget satisfying the guaranteed value of class B of 5√t and having a tensile shear strength of class A of 7
The test was performed on the basis of satisfying 50 kgf and having no deformation in appearance, surface irregularities and dust. As a result,
Compared with the conventional method, the current value at which the nugget diameter of the class B guaranteed value of 5√t was obtained was reduced to about 以下 or less in FIGS. In addition, the numerical value in parentheses of the number of continuous hits is the same comparison at the level determined as 15 hits in the conventional method, whereby in this embodiment, the continuous hitting performance possible as a product is remarkably improved, and the electrode life is improved. The effect of improving all at once was obtained.

Furthermore, in the conventional method, when a member to be welded having a plate thickness of 2.0 mm is welded, a blow hole having a maximum of about 1.5 mm and an average of about 1.0 mm was confirmed in the generated nugget. In this embodiment, almost no blow holes of this kind are generated. This is because the blow holes are generated by the H ₂ gas contained in the aluminum material, and as in this embodiment, when the powder is interposed between the members to be welded, the powder has a lower thermal conductivity than the aluminum material. Low,
Local concentration of blowholes due to solidification delay can be suppressed as compared with the conventional method, and surface oxygen and adsorbed oxygen existing on the surface of the powder and organic carbon used as a bridge effectively act. It is thought that there is. That is, hydrogen which causes blowholes in the aluminum material is consumed by a reaction as shown in FIG. Since the generated H ₂ O and CH ₄ molecules are larger than H ₂ and are removed to the outside during melting before forming the nugget, the generation of not only blowholes but also grain boundary cracks is prevented as much as possible. be able to.

Next, a corrosion promotion test of a welded article welded using various powders having the composition ratios shown in FIGS. 4 to 8 was conducted. That is, as shown in FIG. 10, only the nugget portions of the works A and B are brought into contact with each other, and a potential difference is applied from outside to promote the corrosion, and the work is immersed in the ion-exchanged water C. Then, after a certain period of time, break it,
The strength and corrosion status were confirmed. As a result, a result was obtained that was superior in breaking strength and less corroded than the conventional method. In particular, in the conventional method, the tensile shear strength was reduced by 10 to 15%, which is considered to be because cracks generated in the welded portion grew during the corrosion test.

In this case, in this embodiment, at least one of the materials selected from Fi, Ni and Co is Ti, C
By interposing a powder mixed with at least one substance selected from r and Mo on the joint surface, the current value for obtaining a desired nugget diameter can be reduced to about ２ compared with a powder not using this kind of powder. In addition to the reduction below, it is possible to obtain the effect of improving the welding quality and the corrosion resistance. At that time, No. 4 in FIG. As shown in FIG. 3, when Cr + Ti + Mo + Nb + W is 2% by weight,
The tensile shear strength does not satisfy Class A (750 kgf), and the continuous hitting property is not significantly improved. On the other hand, in FIG.
o. 34, Cr + Ti + Mo + W + Nb +
When Al is 38.5% by weight, the same problem occurs. Therefore, 4% by weight ≦ Cr + Ti + Mo + W +
By setting the composition range of Nb + Al ≦ 38% by weight, it is possible to easily improve the continuous hitting point.

Further, by mixing at least one kind of material selected from Cu, Zn, Mg and Si in the powder, it is possible to stabilize the member itself at the welded portion of the work and to prevent electric corrosion and aging. (See FIG. 7).

Note that FIG. 29 ☆ (See Fig. 7)
The relationship between the welding current and the nugget diameter in the case of using the powder No. 3 is shown. A desired nugget diameter, which could not be obtained with a welding current of not less than 30 KA in the conventional welding method, is obtained at around 11.5 KA in this embodiment, and the welding current is reduced at a stroke. Example 2 No. 2 shown in FIG. A composition of 16 * is selected, the composition is melted in a vacuum, cut into thin pieces, and further pressed to form a foil plate having a size of several tens of microns.
Then, similarly to the first embodiment, A505 is used as the member to be welded.
Using a 2P equivalent product, a plate thickness of 2.0 mm, a two-ply stack, a current supply time of 15 cycles with a foil plate adhered to one of the members to be welded, water-cooled chrome copper φ16 × 190 mm as an electrode, A welding test was performed with a welding current of 8 KA to 40 KA.

The resulting relationship between the welding current and the nugget diameter and the relationship between the welding current and the tensile shear strength are shown in FIG.
2 and FIG. As a result, the welding current is slightly increased compared to the one using powder,
The strength is sufficiently stable. In addition, almost no cracks due to blowholes, rapid heating, and rapid cooling occurred, and good welded products were obtained.

[0049]

As described above, according to the present invention, by using the insert member, it is possible to easily reduce the welding current and shorten the energizing time. Further, a powder based on at least one substance selected from Fe, Ni and Co is used as the insert member, and Ti,
At least one substance selected from Cr and Mo is mixed. Therefore, corrosion resistance including electric corrosion resistance is improved, and stable welding quality can be ensured. In addition, Cr, Ti, Mo, W,
By selectively mixing Nb and Al, the continuous hitting property is further improved, and it is possible to effectively prevent a decrease in the electrode life and the like.

[Brief description of the drawings]

FIG. 1 is a view for explaining a resistance welding method of an aluminum-based material in which an insert member is interposed on a joining surface.

FIG. 2 is a view for explaining a method of resistance welding by interposing powder between aluminum plate materials.

FIG. 3 is a diagram for explaining a welding model according to the present invention and a conventional method.

FIG. 4 is an explanatory diagram of a composition ratio of powder and a determination result.

FIG. 5 is an explanatory diagram of a powder composition ratio and a determination result.

FIG. 6 is an explanatory diagram of a composition ratio of a powder and a determination result.

FIG. 7 is an explanatory diagram of a composition ratio of a powder and a determination result.

FIG. 8 is an explanatory diagram of a composition ratio of powder and a determination result.

FIG. 9 is an explanatory diagram showing a reaction of H ₂ in Al.

FIG. 10 is a schematic explanatory view of a corrosion acceleration test.

FIG. 11 is a relationship diagram between a welding current and a nugget diameter in the second embodiment.

FIG. 12 is a diagram showing a relationship between a welding current and a nugget diameter when powder and a plate-like foil are used.

FIG. 13 is a diagram showing the relationship between welding current and tensile shear strength when using powder and a foil plate.

[Explanation of symbols]

 11, 12: Workpiece to be welded 15: Insert member 21, 25: Aluminum plate material 22, 24: Oxide film 23: Powder

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 11/18 B23K 11/11 B23K 103: 10

Claims (4)

(57) [Claims] 1. A resistance welding method for an aluminum-based material in which an insert member is interposed when an aluminum-based material is resistance-welded, wherein the insert member includes Fe, Ni, and C.
a powder in which at least one substance selected from Ti, Cr and Mo is mixed with at least one substance selected from o, the insert member is interposed in the joining surface, and the surface of the aluminum-based material is electrically energized. A resistance welding method for an aluminum-based material, wherein an oxide film of the aluminum-based material is removed and composited or alloyed after energization. 2. The method according to claim 1, wherein a solution in which the powder as the insert member is mixed is applied to the joining surface of the aluminum-based material, and an oxide film on the surface of the aluminum-based material is removed at the time of energization. A resistance welding method for an aluminum-based material, wherein the method is compounding or alloying. 3. An insert member interposed between joining surfaces when aluminum material is resistance-welded, wherein the insert member is made of Fe, Ni and Co having a composition range of 62% by weight ≦ Fe + Ni + Co ≦ 96% by weight. 4% by weight ≦ Cr + Ti + Mo for at least one selected material
C having a composition range of + W + Nb + Al ≦ 38% by weight
An insert member comprising a mixture of at least one substance selected from r, Ti, Mo, W, Nb and Al. 4. The insert member according to claim 3 , wherein
An insert member comprising at least one substance selected from Cu, Zn, Mg and Si having 0.2% by weight ≦ Cu + Zn + Mg + Si ≦ 10.0% by weight.