JPH11106886A - Hot dip zinc-aluminum plated steel sheet excellent in lubricity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot dip zinc-aluminum plated steel sheet in which the lubricity and degreasing properties of the steel sheet are good. SOLUTION: This steel sheet has the following coating composition and characteristics: (1) the composition of hot dip plating coating on the surface of the base steel sheet is composed of, by weight, 50 to 60% Al, <=2% Si, and the balance Zn with inevitable impurities, and water dispersible wax is adhered to the plating surface by 0.01 to 1.0 /gm<2> and (2) as for the adhering state of the water dispersible wax, not coating but particles are discretely adhered to the surface, and the size of the particles is regulated to <=5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip galvanized aluminum steel sheet used for building materials and the like, which has good lubricity particularly in press forming, bending, roll forming and the like. And a member that also requires degreasing.

[0002]

2. Description of the Related Art A hot-dip galvanized steel sheet has excellent bare corrosion resistance and is therefore often used mainly for construction materials. However, the hot-dip galvanized steel sheet does not have sufficient lubricity between the plating surface and the mold surface during the forming process, and the plating surface suffers surface flaws called galling by the mold and causes problems such as press cracking. Or Therefore,
Various countermeasures have conventionally been proposed for such a problem. For example, Japanese Patent Publication No. 2-305950 proposes a method of applying a water-soluble wax to improve the degreasing property. In the case of a water-soluble wax, once the film is dried to form a film on the surface, the degreasing is performed. This causes a problem of deterioration in performance.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems in the surface treatment of a conventional hot-dip galvanized steel sheet. It is intended to provide a good hot-dip galvanized aluminum-plated steel sheet.

[0004]

In order to solve these problems, the present invention provides a galvanized steel sheet having the following film structure and characteristics. (1) The composition of the hot-dip coating on the surface of the base steel sheet is Al: 5
0 to 60 wt%, Si: 2 wt% or less, the balance consisting of Zn and unavoidable impurities, and 0.01 to 1.0 g / m ² of a water-dispersible wax adhered to the plating surface; Hot-dip zinc-aluminized steel sheet with excellent degreasing properties. (2) The state of adhesion of the water-dispersible wax is not a film but discretely adheres to the surface as particles, and the particle size is 5 μm.
m or less, and is a hot-dip galvanized steel sheet having excellent lubricity and degreasing property according to the above (1).

[0005] The hot-dip galvanized steel sheet in the present invention is a steel sheet produced by a method of immersion plating in a hot-dip aluminum plating bath in a continuous hot-dip galvanizing facility. In the coating film composition of the hot-dip zinc-aluminized steel sheet, Al is set to 50 to 60 wt%. Al improves the bare corrosion resistance of the plating film. If it is less than 50 wt%, the corrosion resistance is insufficient, and if it exceeds 60 wt%, the workability of the plating layer decreases,
Not economic. Si is set to 2 wt% or less. Si suppresses the growth of the Fe-Al-based alloy phase growing at the interface between the plating layer and the base steel sheet. If it exceeds 2 wt%, the effect is not only saturated, but also the appearance becomes poor.

[0006] A water-dispersed wax is attached to the surface of a hot-dip galvanized aluminum steel sheet. The method of attaching the water-dispersed wax to the surface of the steel sheet is performed by a roll coater method, a ringer roll method after spraying or dipping, an air knife method, a method of spraying the water-dispersed wax, or the like. . Drying after application may be performed by natural drying, hot-air drying, or the like. Drying conditions are not particularly limited, but may be performed at a temperature equal to or lower than the softening point of the wax.

The water-dispersed wax enters between the steel plate and the mold surface during press forming to improve lubricity. Adhesion amount is 0.01 ~
1.0 g / m ² . The reason is 0.01 g / m ²
If less, the effect of improving lubrication performance is not exhibited, and 1.0 g
If the ratio exceeds / m ² , the surface of the steel sheet turns white, resulting in poor appearance. The adhesion state of the water-dispersed wax to the surface of the hot-dip galvanized steel sheet is not a film but a discrete adhesion. When compared with a continuous film by discrete adhesion, it is possible to improve the removability of the water-dispersed wax in the degreasing treatment step and prevent a decrease in the degreasing property.

The size of the individual particles of the water-dispersed wax is 5
μm or less. The reason for this is that if it exceeds 5 μm, it becomes difficult for water-dispersible wax to enter between the surface of the hot-dip aluminum-plated steel sheet and the surface of the mold during press forming, and the effect of improving lubrication performance is reduced. The shape of the water-dispersed wax is not particularly limited, but is preferably spherical.
Compared to the case of a plate shape, it is difficult to form a continuous film on the plating surface, which causes a decrease in degreasing property. The water-dispersed wax is prepared by using a polyolefin resin, an ethylenically unsaturated carboxylic acid, or a modified polyolefin, a surfactant or the like as a raw material, and dispersing a low-molecular-weight polyolefin in water without using an emulsifier.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hot-dip galvanized steel sheet manufactured by a continuous hot-dip galvanized steel sheet manufacturing line was used.
As an example of the present invention, a water-dispersible wax (trade name: Chemipal W) manufactured by Mitsui Petrochemical Co., Ltd. was sprayed on the surface of the steel sheet, and then applied by a ringer roll drawing method and dried at 60 ° C. As a comparative example, a steel sheet in which an oil-soluble wax and a water-soluble wax were applied to a hot-dip galvanized steel sheet was manufactured. The manufactured steel plate is made of Idemitsu's rust-preventive oil (trade name: Z3)
After lubrication, lubricity and degreasing property were evaluated. Each evaluation condition is as follows.

As for lubricity, the coefficient of kinetic friction was evaluated by a flat plate sliding test shown in FIG. That is, FIG. 1 is a schematic diagram showing a flat plate sliding test.
0 mmR) using a chip die 2 having a drawing speed of 150 mm / sec and a pressure of 5 kgf, n = 4.
The average was arranged. A hot-dip galvanized steel sheet coated with only rust-preventive oil exhibits a coefficient of dynamic friction of about 0.15. The acceptance criteria for lubricity is 0.13 or less.

The degreasing property is as follows. A degreasing agent (trade name: PB4460) manufactured by Nippon Parker Co., Ltd. is mixed and stirred in a 1 liter beaker, and a 150 mm × 70 mm steel plate is immersed at 40 ° C. for 2 minutes and washed with water. Thirty seconds later, the area ratio of water wetting at the time of ten seconds of vertical standing was evaluated. The hot-dip galvanized steel sheet coated with only rust-preventive oil shows a water wet area ratio of 90 to 100%.
The acceptance criteria for the degreasing property is a water wet area ratio of 90% or more. Table 1 shows the results. While the steel sheet of the present invention shows good results in all performances, the steel sheet of the comparative example has a problem in lubricity or degreasing.

[0012]

[Table 1]

[0013]

As described above, according to the present invention, a hot-dip galvanized steel sheet can have a significantly improved lubricity while having a degreasing property. As a result, the problem of molding failure of the steel sheet for building materials can be solved, and this has a great industrial effect.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a flat plate sliding test.

[Explanation of symbols]

 1 Test material 2 Chip dice

Claims (2)

[Claims] The composition of a hot-dip coating film on the surface of a base steel sheet is
Al: 50 to 60 wt%, Si: 2 wt% or less, balance Z
A hot-dip galvanized steel sheet having excellent lubricity and degreasing property, comprising n and unavoidable impurities, and having a water-dispersible wax attached to the plating surface in an amount of 0.01 to 1.0 g / m ² . 2. The lubricating and degreasing method according to claim 1, wherein the adhesion state of the water-dispersible wax is discretely adhered to the surface as particles, not as a film, and the size of the particles is 5 μm or less. Hot-dip zinc-aluminized steel sheet with excellent properties.