JPH06116670A - Solid lubricant applied aluminum alloy sheet excellent in weldability and its production - Google Patents

Abstract

PURPOSE:To provide an aluminum alloy sheet free from problems of the deterioration in joining strength caused by the application of a solid lubricant for increasing formability, the consumption of a welding electrode material or the deterioration in productivity caused by the frequent exchange of the welding electrode or the like and excellent in weldability. CONSTITUTION:This sheet is an aluminum alloy sheet excellent in weldability in which the thickness of the surface oxidized film is regulated to <=50Angstrom and its surface is coated with a solid lubricant and liquid lubricating oil. It is produced by dissolving away the oxidized film of the aluminum alloy sheet by alkali and/or acid to regulate its thickness into <=50Angstrom , thereafter coating it with the solid lubricant and furthermore coating it with liquid lubricating oil. Preferably, the coating weight of the solid lubricant is regulated to 0.1 to 2g/m<2>, the viscosity of the liquid lubricating oil is regulated to <=10cst/40 deg.C and its coating weight is regulated to 0.5 to 5g/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of aluminum alloy sheets having excellent weldability, and is particularly suitable for aluminum alloy sheet material for press forming of automobile parts, which is used by resistance spot welding after press forming. There is.

[0002]

2. Description of the Related Art Aluminum alloys are excellent in corrosion resistance and formability in addition to their light weight, and are therefore used as general-purpose metal materials next to steel materials in automobiles and various industrial fields. Is often used in.

Recently, in order to reduce the weight of automobiles, the use of aluminum alloy sheets is gradually increasing. However, aluminum alloy sheets are inferior in formability to steel sheets, so that cracks are generated during forming and design Sometimes the shape is limited, which is a big problem.

Further, since it is used also as a conventional press line for steel, lubricating oil and the like are not always suitable for aluminum materials, which is disadvantageous in formability.

Therefore, it has been attempted to apply a solid lubricant to the surface of an aluminum plate in advance to improve the formability at the time of pressing. Without degreasing process,
Spot welding is performed with the solid lubricant applied. However, if welding is performed with the lubricant film on the surface of the material, there are problems that the electrode material is significantly consumed and dust is generated during the bonding to lower the bonding strength. For these problems, at present, it is necessary to frequently replace the electrode material, which significantly deteriorates the productivity.

Under such circumstances, the present invention is intended to reduce the joint strength caused by applying a solid lubricant in order to improve the formability, wear the welding electrode material, or frequently replace the welding electrode. It is an object of the present invention to provide an aluminum alloy sheet excellent in weldability without causing problems such as poor productivity due to the above, and to provide a manufacturing method thereof.

[0007]

Means for Solving the Problems The present inventor has completed the present invention as a result of intensive studies to solve the above problems.

That is, the present invention is characterized in that the surface oxide film of the aluminum alloy plate is adjusted to have a thickness of 50 Å or less, and a solid lubricant and a liquid lubricant are further applied thereon. The main point is an aluminum alloy plate with excellent weldability.

Further, the manufacturing method is such that the oxide film of the aluminum alloy plate is dissolved and removed with an alkali and / or an acid to adjust the thickness to 50 Å or less, then a solid lubricant is applied, and further a liquid lubricating oil is applied. It is characterized by doing.

The present invention will be described in more detail below.

[0011]

[Action]

The reasons for limiting the conditions in the present invention are as follows.

Aluminum alloys have the property of forming a strong oxide film on the surface by combining with oxygen in the air.
This makes the energization state of the welding current unstable and causes scattering. Therefore, in the present invention, the surface oxide film, alkali cleaning (sodium phosphate, sodium carbonate, caustic soda, etc.) and acids are dissolved and removed by acid (nitric acid, sulfuric acid, etc.),
Weldability can be improved by adjusting the film thickness, which used to be around 70Å, to 50Å or less.

After adjusting the thickness of the surface oxide film, a solid lubricant is applied. Thereby, the moldability can be improved.

The coating amount of the solid lubricant is not particularly limited, but is preferably in the range of 0.1 to 2.0 g / m ² . If the coating amount exceeds 2.0 g / m ² , the solid lubricant film is too thick,
The energization state of the welding current becomes unstable, and the characteristics due to the adjusting effect of the surface oxide film cannot be exhibited. On the other hand, if the coating amount is less than 0.1 g / m ² , peeling of the coating film will occur during processing, which will cause galling and cracking during molding.

Further, liquid lubricating oil is applied on the solid lubricant. The applied lubricating oil is carbonized and vaporized during spot welding, and it adheres to the welding electrode to protect the electrode and has the function of improving the life.

The properties and coating amount of the liquid lubricating oil are not particularly limited, but the viscosity is 10 cst / 40 ° C. or less,
It is preferable to adjust the coating amount to 0.5 to 5.0 g / m ² .
If the amount of liquid lubricating oil applied deviates from the range of 0.5 to 5.0 g / mm ^{2 and} the amount of cleaning oil is too large or too small, carbonization and evaporation will be less likely to occur and the electrodes will not be protected. Further, when the viscosity of the lubricating oil is 10 cst / 40 ° C. or higher, a strong lubricating oil film is formed, and likewise, carbonization and evaporation are less likely to occur.

Needless to say, the aluminum alloy of the present invention is not limited as long as it has a component system and a component composition that can be processed.

Next, examples of the present invention will be described.

[0020]

【Example】

An Al-4.5% Mg alloy plate (tempering: T4, thickness: 1 mm) was used as a test material, and after adjusting the amount of oxide film of this aluminum plate, a solid lubricant was adhered to the surface thereof. ,
Lubricant was applied and the formability and resistance spot weldability were evaluated. The results are shown in Table 1. The method of adjusting the amount of oxide film, the method of applying the solid lubricant, and the method of applying the lubricating oil were performed as follows.

Method of adjusting the amount of oxide film: The amount of film was adjusted by the method of cleaning the surface of the material as described below. The coating amount was measured by the electrostatic dissolution method. Amount of coating: 70 Å: Cleaning with organic solvent (triethane) 45 Å: Alkali cleaning with 3% Rydrin N8 solution (standard) 35 Å: Cleaning with 15% nitric acid 25 Å: Nitric acid cleaning after alkali cleaning

Solid lubricant adhesion method: After applying a wax-type solid lubricant, it was dried (80 ° C. × 5 minutes in a constant temperature bath). The coating amount was adjusted with a bar coder and the standard was 0.5 g / m ² .

Lubricant application method: mineral oil type cleaning oil
(4 cst / 40 ° C., 2 g / m ² as a standard) was used, and the coating amount was adjusted by measuring with an electronic balance after brush coating.

Formability evaluation method: A drawing test was carried out under the following conditions, and the drawing height at which cracking occurred was evaluated. Test piece shape: 1.0 x 100 x 100 (mm) Punch diameter: □ 40 mm (Punch R: 4.5 mm, die R:
Punch speed: ~ 20mm / min Wrinkle holding force: 39200N

Resistance spot weldability evaluation method: Continuous spotting properties were investigated under the following welding conditions, and evaluation was made by the number of spots until the joint strength started to fall below 1.5 kN. Pressurizing force: One-step constant pressure 300kgf Electrode: Chromium-copper alloy, DR type with tip radius 40mm Welding current: 20-30kA (Adjusted to nugget diameter 5mm) Welder: Single layer low frequency resistance spot welder

As is clear from Table 1, in all the examples of the present invention, even if the moldability was improved by the adhesion of the solid lubricant,
Good weldability is obtained.

Regarding the influence of the amount of oxide film, the weldability deteriorates if it is large as in Comparative Example No. 9, whereas it is reduced as in the range of the present invention (50 Å or less) (Inventive Example No. 9). 2, No. 6, 7), the weldability can be improved. Regarding the effect of the coating amount of the solid lubricant, no moldability was obtained with no coating or a small amount of coating (Comparative Examples No. 10 and 11), and a proper amount of coating (Inventive Examples No. 1 to 3) was used for molding. However, if it is too much (Comparative Example No. 1
2) On the contrary, the weldability deteriorates. Regarding the influence of the viscosity and coating amount of the liquid lubricating oil, an appropriate viscosity and coating amount are desirable in order to prevent the deterioration of processability due to the coating of the solid lubricant (Invention Examples No. 2, 4, 5). Is too high or the coating amount is too large (Comparative Examples No. 13, 14).

[0029]

[Table 1]

[0030]

As described in detail above, according to the present invention,
By applying a solid lubricant, the press formability of the aluminum alloy is improved, and spot welding becomes possible, so it is possible to easily form and assemble even complicated shapes. By improving the formability and weldability, aluminum The alloy plate can be processed in a steel plate line. As a result, the range of application of the aluminum alloy plate is widened, the weight of the automobile can be reduced by using aluminum, and it is effective in saving energy and reducing exhaust gas.

Claims (4)

[Claims] 1. An excellent weldability, characterized in that the surface oxide film of an aluminum alloy plate is adjusted to have a thickness of 50 Å or less, and a solid lubricant and liquid lubricant are further applied thereon. Aluminum alloy plate. 2. The coating amount of the solid lubricant is 0.1 to ² g / m ² , the viscosity of the liquid lubricating oil is 10 cst / 40 ° C. or less, and the coating amount is 0.5 to 5 g / m ² . The aluminum alloy plate according to claim 1. 3. A thickness of 50 Å by dissolving and removing an oxide film of an aluminum alloy plate with an alkali and / or an acid.
A method for producing an aluminum alloy sheet having excellent weldability, which comprises applying a solid lubricant and then applying a liquid lubricating oil after adjusting the following. 4. The coating amount of the solid lubricant is 0.1 to ² g / m ² , the viscosity of the liquid lubricating oil is 10 cst / 40 ° C. or less, and the coating amount is 0.5 to 5 g / m ² . The method according to claim 3.