JPH06116737A - Aluminum material excellent in spot resistance weldability, corrosion resistance, and workability - Google Patents

Abstract

PURPOSE:To provide an aluminum material excellent in spot resistance weldability, corrosion resistance, and workability. CONSTITUTION:This material is an aluminum material excellent in spot resistance weldability, corrosion resistance, and workability. This aluminum material has, as a first layer, a layer of aluminum oxide and/or aluminum hydroxide of 0.01-5mum thickness formed by heating the surface of the aluminum material in warm water, warm aqueous solution, or saturated aqueous vapor and further has, as a second layer, a rust preventive oil layer containing 0.05-40wt.%, in total, of 0.05-30wt.% inorganic lubricating grains and/or 0.05-20wt.% organic lubricating grains. It is preferable to use a powder of molybdenum disulfide and/or boron nitride of <=50mum average grain size as the inorganic lubricating grains in the above second layer, and also it is preferable to use, as the organic lubricating grains in the above second layer, a wax having <=50mum average grain size and >=60 deg.C melting point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum material mainly used as a lightweight material for bicycles, and more particularly to an aluminum material (including a wide range of aluminum alloys) having excellent spot weldability, corrosion resistance and workability.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of global environmental problems, in particular, measures against global warming by CO _2, etc., weight reduction of automobile bodies has been actively promoted in order to improve fuel consumption of automobiles. Aluminum alloys have been in the spotlight in terms of material reliability, workability, recycling, etc., and these are now being applied to inner and outer plates of automobile bodies.

[0003]

However, the aluminum material conventionally used for such an automobile body has the following problems. Poor weldability Most of the aluminum alloy sheets are spot welded when assembled into automobile bodies, but aluminum alloy sheets have extremely poor spot weldability, especially electrode life compared to steel sheets, resulting in a significant decrease in vehicle body production efficiency. Is the current situation.

That is, in spot resistance welding of an aluminum alloy plate, a welding phenomenon is likely to occur, and the number of welding spots at which an appropriate nugget can be obtained with the same electrode is extremely short, so that proper nugget cannot be performed before welding occurs. The electrode shape is frequently adjusted before dressing or replaced with a new electrode, which has a great influence on the welding efficiency, and by extension, the production efficiency of the automobile body.

Since aluminum alloys have only recently been put to practical use in mass-produced products with spot resistance weldability such as automobiles, there are very few proposals for appropriate means for solving the above problems. However, for example, JP-A-6
Japanese Unexamined Patent Publication No. 0-187483 provides an improved method by controlling the thickness of the oxide film on the aluminum plate joint surface by anodizing. Further, although it is not intended to be applied to an aluminum alloy plate for automobiles, for example, Japanese Patent Laid-Open No. Sho 5
3-6252, JP-A-53-48954, JP-A-5
In Japanese Patent Publication No. 3-48955, Z is attached to the aluminum joint surface.
An improved method by interposing n, Ti and a stainless steel thin film is disclosed in Japanese Patent Laid-Open No. 57-4389, Cr, N.
An improved method by applying i, Cu, Ag plating is disclosed.

However, the improvement method by controlling only the anodized film is not practical because uniform treatment is difficult and its effect is unstable. Further, the improvement method by interposing Zn, Ti, and stainless steel thin film is difficult to apply for automobiles, and the improvement method by applying Cr, Ni, Cu, Ag plating is the adhesion of these platings to the aluminum alloy. Is extremely bad and not practical.

Poor Workability Further, aluminum has a serious drawback in that it has a small elongation and is soft as compared with a steel sheet, so that the mold is likely to be twisted and the press workability is poor. SPCC as a representative of steel plate
For example, the elongation is 45% and the r value is 1.4.
Reaches 2.15, while aluminum alloy plate has JI
Taking SA5182 as an example, elongation is 30%, r value is 0.7 at L
DR reaches only 1.8. As described above, the formability of the aluminum alloy sheet is remarkably inferior, so that the application of the aluminum alloy sheet to an automobile body is greatly restricted. That is, as an example of application of the aluminum alloy plate to a vehicle body panel, it is limited to a lightly processed member such as a hood, and it is impossible to apply it to a more complicated member accompanied by heavy working.

Poor Corrosion Resistance When an accelerated durability test is performed in a harsh environment after painting, thread-like corrosion (Filiform corrosion) easily occurs,
Not only is it aesthetically unpleasant, but it also causes functional problems as it progresses further.

The present invention overcomes the drawbacks of the above-mentioned aluminum materials, significantly improves the electrode life during spot resistance welding, that is, continuous spotting property, corrosion resistance, and press formability, and is industrially easy. The purpose is to provide an aluminum material that can be manufactured economically.

[0010]

First, the improvement of spot weldability is based on the following knowledge. That is,
When spot resistance welding is repeatedly performed on an aluminum alloy plate using the same copper-based electrode, the current-carrying diameter at the electrode tip expands with the dot, and the nugget diameter also decreases due to the decrease in the current density in the plate. Finally, although the life of the electrode is extended, the aluminum alloy plate is characterized in that the expansion speed of the electrode tip diameter is significantly higher than that of the steel plate. Therefore, paying attention to such a phenomenon,
As a result of diligent examination of the cause, in the case of continuous spot welding of an aluminum alloy plate, molten aluminum adheres to the current-carrying part of the electrode tip, and its oxide deposits together with the spot.
This forms an insulating layer, and finally sparks occur between the electrode and this insulating layer, at which time the electrode is damaged like a worm and the insulating oxide film on the surface of the aluminum alloy plate at the joint surface It has been found that it inhibits rapid welding. It was found that such a peculiar phenomenon of the aluminum alloy plate promotes the enlargement of the electrode tip diameter and the electrode life is extremely deteriorated.

Further, the occurrence of such a spark on the electrode surface side,
It was found that the poor welding on the joining surface side is promoted by the nonuniformity of the oxide film layer on the surface of the as-rolled aluminum material.

Therefore, it is important to control the film thickness of the aluminum oxide and / or hydroxide layer on the surface of the aluminum material, and in the present invention, it is defined as 0.01 to 5 μm. It is possible to secure better weldability by adjusting the thickness of the electrode contact surface side to be ⅔ or less of the spot welding joint surface side.

Regarding the corrosion resistance after coating, the thread rust that usually occurs in the coating material of an aluminum body originates from a defective portion of the coating film such as a scratch on the surface, and in a corrosive environment where chlorine is present. At this time, corrosive substances reached the aluminum base,
The main cause is corrosion of the aluminum substrate. Therefore, it is important to form a film capable of obtaining a strong anticorrosion effect on the aluminum base material. From this point as well, in the present invention, the film thickness of the aluminum oxide and / or hydroxide is 0.01 to 5 μm. Sufficient corrosion resistance was able to be obtained by controlling to.

On the other hand, regarding press formability, it is essentially important to improve the elongation of aluminum.
We have found that even the same material can improve the formability by improving the lubricity of the surface, and as a measure to improve this lubricity, it is necessary to coat it with a rust preventive oil containing a powdered lubricant. It turned out to be very effective.

That is, according to the present invention, in order to achieve the above object, the surface of the aluminum material as the first layer is formed by heating the surface of the aluminum material in hot water, a hot aqueous solution or saturated steam and has a thickness of 0.01 μm to 5 μm. Having a layer of aluminum oxide and / or aluminum hydroxide,
A second layer is a rust preventive oil layer containing 0.05 to 30% by weight of inorganic lubricating particles and / or 0.05 to 20% by weight of organic lubricating particles in total as a second layer. An aluminum material having excellent spot resistance weldability, corrosion resistance and workability is provided.

The inorganic lubricating particles have an average particle size of 50 μm.
It is preferably molybdenum disulfide and / or boron nitride powder having an average particle size of 5 or less.
The wax is preferably 0 μm or less and has a melting point of 60 ° C. or more. It is preferable to apply these lubricating powders by uniformly dispersing them in rust preventive oil. Further, in the first layer, the film thickness on the electrode contact surface side is 2/3 of the film thickness on the spot welding joint surface side.
The following is preferable.

[0017]

The present invention will be described in more detail below. The aluminum material in the present invention broadly includes aluminum materials such as aluminum and aluminum alloys, and its form is arbitrary such as plate material, bar material and can material.

In the present invention, the geometric structure of the oxide film formed by heating the above-mentioned aluminum material in hot water, hot aqueous solution or saturated steam depends on the processing conditions and is not particularly limited.

The aluminum oxide and / or aluminum hydroxide is usually Al ₂ O ₃ , AlOOH, Al (OH) ₃
A film is formed in a state where crystal water is attached to etc., but the presence or absence of crystal water does not pose any particular problem in this film. Further, the pretreatment of the film forming treatment does not have to be particularly carried out and may be directly subjected to the film forming treatment after rolling, but usually, for the purpose of removing the heterogeneous film formed during the aluminum production step, an acid,
It is desirable to appropriately select etching in an alkali and smut (insoluble residue) removal in an acid solution. The alkali etching treatment and the pickling treatment may be the methods generally used as a treatment method for an aluminum material, and a commercially available treatment liquid may be used.

In the present invention, the thickness of the first layer is 0.01
When the thickness is less than 0.01 μm, the desired electric resistance cannot be obtained, the weldability is deteriorated, and the anticorrosion effect on the aluminum base becomes insufficient, resulting in poor corrosion resistance. If it exceeds 5 μm, the electric resistance becomes too large and welding becomes impossible. Also, by adjusting the film thickness on the electrode contact surface side to be 2/3 or less of the thickness on the spot welding joint surface side, the prevention of sparks on the electrode surface side and the prevention of aluminum welding on the electrode surface Has a great effect on.

On the other hand, the rust preventive oil layer formed as the second layer is a base oil containing inorganic lubricating particles and / or organic lubricating particles. As the inorganic lubricating particles, for example, molybdenum disulfide, boron nitride powder, or a mixture of two or more thereof is used. If the amount of these mixtures is too small, the lubricating effect will be small, and if they are excessive, the viscosity of the oil will be increased and the coating operation will be inconvenient.
Further, particles having an average particle size of more than 50 μm have poor dispersibility, resulting in poor uniformity after oiling.
The following is recommended.

As the organic lubricating particles, either synthetic wax or natural wax may be used. However, if the melting point is less than 60 ° C., the viscosity under extreme pressure becomes too small and the lubricating effect is not sufficient, so the melting point is 60 ° C. or more. It is better to use the one. Further, the addition amount and the average particle diameter are preferably 0.05 to 20% by weight and the average particle diameter is 50 μm or less for the same reason as the inorganic lubricating particles.

When the inorganic lubricating particles and the organic lubricating particles are used in combination, the limit of the amount added increases to 40% by weight.
If it is more than that, 0.05 occurs because it causes inconvenience in coating work.
Limited to ~ 40% by weight.

[0024]

EXAMPLES The present invention will be specifically described below based on examples.

(Example) JI having a thickness of 1 mm which is a typical aluminum alloy used as a material for automobiles
S A5182 (Al-0.3% Mn-4.5% Mg)
Using an alloy plate, first the aluminum alloy plate surface 1,1,
After steam degreasing with 1 trichloroethane, etching with a commercially available alkaline detergent, washing with water, smut removal by washing with nitric acid, and washing with water were performed, and oxidation treatment was performed by the method shown in Table 1.

Next, a commercially available rust preventive oil, Preton R303P manufactured by Sugimura Chemical Co., Ltd. and T7F16 manufactured by Showa Shell Sekiyu Co., Ltd., were used as base oils, and inorganic lubricating powder and / or organic lubricating powder were added and mixed, and blended in the proportions shown in Table 2. The oil was applied to the surface of the alloy plate by the dipping method. The coating amount was measured from the difference between the weight of the plate after coating and the weight of the plate after degreasing and washing. The pulverization, stirring, and mixing of the lubricating powder was performed by stirring with a base oil in a ball mill. The particle size was measured by a method of directly observing the oil after mixing with an optical microscope and a light dispersion method.

The following waxes were used in Table 2. Wax 1 San Nopco SN Wax 22-SF Wax 2 San Nopco SL 506 Wax 3 Yasuhara Yushi Kogyo Arrow Wax Wax 4 Same as above Wax stirring and grinding time shortened Wax 5 Nippon Oil Co., Ltd. Paranock 203 For pretreatment Drug Alsoft 108, Desmut N-2
0 is a commercially available pretreatment liquid for aluminum plates, which is manufactured by Okuno Chemical Industries.

(Test of Workability and Evaluation Method) The workability of the aluminum alloy plate after the surface treatment was such that each sample punched to 70 mmφ was subjected to high-speed cylindrical drawing with a diameter of 30 mmφ (processing speed 500 mm / sec) The cracked ones were judged as bad (marked with X), the ones that had galling but could be machined were evaluated as normal (Δ), and those that could be machined with almost no galling were judged as good (◯).

(Welding Test and Evaluation Method) The electrode life of the aluminum alloy plate after the coating treatment was evaluated using an inverter DC welding machine under the following electrodes and welding conditions. The number of dots until welding or the nugget diameter was 4√t (t:
The effect was judged by the smaller number of RBIs, which is the number of RBIs below the plate thickness). The evaluation standard is 500 points
Less than points is bad (x), 500 to 1000 points is normal (△), 1000 to 1500 points is good (◯), 1500
Exceeding the point was rated as excellent (◎).

(Electrode) -Shape: Cone frusto-conical (CF) type-Tip diameter: 5.0 mmφ-Material: Cr-Cu (welding condition) -Pressure: 150 kgf-Initial pressurization time: 20/50 seconds-Electrification time : 6/50 seconds ・ Holding time: 5/50 seconds ・ Welding current: 15kA

(Corrosion resistance after coating) From the coil after treatment to 70
A test piece of × 150 mm is cut out, degreased at 43 ° C for 2 minutes using a weak alkaline degreasing agent, washed with water, and then surface-adjusted at room temperature for 30 seconds with a colloidal titanium-based solution, and then, as it is. In this state, chemical conversion treatment was carried out with a commercially available zinc phosphate treatment liquid at 43 ° C. for 2 minutes. Then, after washing with water and drying, an undercoat by cationic electrodeposition coating, an intermediate coating by spraying, and an overcoat coating were carried out to prepare a sample. The total coating film thickness at this time was 100 μm.

A cross-cut reaching the aluminum substrate was put on the surface of this sample, salt water spray according to JIS Z2371 was carried out for 24 hours, and after that, it was left for 2000 hours in a humid atmosphere of 50 ° C. × 95% RH, and then it was generated from the cross-cut portion. The maximum length of thread rust was measured. Judgment was made such that the thread rust length of 4 mm or more was poor (x), 2 to 4 mm was normal (◯), and 2 mm or less was good (⊚).

Table 3 shows the evaluation results of the examples of the present invention and the comparative examples. As is clear from Table 3, the present invention is extremely effective in improving spot weldability, corrosion resistance and workability of aluminum alloy sheets.

On the other hand, in Comparative Example 1, the aluminum oxide and / or hydroxide layer was too thin, and the weldability and corrosion resistance were poor. In Comparative Examples 2 to 4, the amount of lubricating powder added was small and sufficient processing was performed. I can not get sex. In Comparative Examples 5 to 8, the amount of lubricating powder added was too large to cause non-uniformity, resulting in poor workability and poor weldability. In Comparative Example 9, the oxide or / and hydroxide layer is too thick and the weldability is poor.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[0038]

As described above, according to the present invention,
Spot resistance welding by forming an aluminum oxide and / or hydroxide layer on the surface of an aluminum plate or an aluminum alloy plate to improve corrosion resistance and forming an anticorrosion oil layer containing powdered lubricating particles on the surface. And press workability are significantly improved. by this,
It can be expected that the productivity of welded structures such as those for automobile parts processed by press forming and spot weldability will be remarkably improved and the stability of quality will be improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Totsuka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Headquarters (72) Inventor Koji Uesugi Chuo-ku, Chiba-shi, Chiba Kawasaki-cho No. 1 Kawasaki Steel Co., Ltd., Technical Research Division (72) Inventor Naoki Nishiyama No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Toshio Tani Tokyo 2-6-1, Marunouchi, Chiyoda-ku, Furukawa Aluminum Co., Ltd. (72) Inventor, Motohiro Namba 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd.

Claims (4)

[Claims] 1. A layer of an aluminum oxide and / or aluminum hydroxide having a thickness of 0.01 μm to 5 μm, which is formed by heating the surface of an aluminum material in warm water, a warm aqueous solution or saturated steam as the first layer. Have,
A second layer is a rust preventive oil layer containing 0.05 to 30% by weight of inorganic lubricating particles and / or 0.05 to 20% by weight of organic lubricating particles in total as a second layer. An aluminum material with excellent spot resistance weldability, corrosion resistance and workability. 2. The spot resistance weldability according to claim 1, wherein the inorganic lubricating particles in the second layer are molybdenum disulfide and / or boron nitride powder having an average particle diameter of 50 μm or less.
Aluminum material with excellent corrosion resistance and workability. 3. The organic lubricating particles in the second layer have an average particle size of 5
The aluminum material having excellent spot resistance weldability, corrosion resistance, and workability according to claim 1, which is a wax having a melting point of 0 ° C. or less and a melting point of 60 ° C. or more. 4. The film thickness of the first layer on the electrode contact surface side is ⅔ or less of the film thickness on the spot welding joint surface side.
An aluminum material excellent in spot resistance weldability, corrosion resistance and workability according to any one of 1.