WO2002036854A1 - Zinc-based metal plated steel sheet treated with phosphate excellent in formability and method for producing the same - Google Patents

Abstract

A zinc-based metal plated steel sheet excellent in formability having a phosphate film on the surface thereof, characterized in that the phosphate film contains a polyolefin wax or a modified polyolefin wax; a method for producing the galvanized steel sheet, characterized in that it comprises subjecting a surface of a galvanized steel sheet to a phosphate treatment and then applying an aqueous solution containing a polyolefin wax or a modified polyolefin wax, a phosphate ion and a polyvalent metal ion to the resultant steel sheet, followed by drying.

Description

 Description Phosphate-treated zinc-based steel sheet with excellent workability and method for producing the same

 The present invention relates to a phosphate-treated zinc-based steel sheet having excellent workability and used for applications such as automobiles, home appliances, and building materials. Background technology

 Zinc-based steel sheets used for applications such as automobiles, home appliances, and building materials have been conventionally treated with phosphate, chromate, and even organic coatings to improve their added value such as corrosion resistance and workability. Often. In recent years, due to environmental problems, in particular, chromated steel sheets have tended to be disliked because they may contain hexavalent chromium, and there has been an increasing demand for phosphate treatment. From the viewpoint of workability, Zn-Ni alloy-plated steel sheets are widely used because they show good characteristics, but are widely used because of the Ni-containing alloy plating. There is a problem when it becomes expensive. For this reason, attempts have been made to increase the added value by applying phosphate treatment to electric zinc plated steel sheets, molten zinc plated steel sheets, or alloyed molten zinc plated steel sheets, which are inexpensive to manufacture.

However, the conventional phosphate treatment of electric zinc plated steel sheet, molten zinc plated steel sheet, or alloyed molten zinc plated steel sheet is not always sufficient compared to Zn_Ni alloy plated steel sheet. Workability has not been obtained. In particular, in applications where drawing is performed by controlling the inflow of steel sheets using bead retainers, which have been increasing in recent years, the additivity is insufficient. On the other hand, JP-A-7-138764 discloses a zinc phosphate treated zinc-based steel sheet containing at least one of Fe, Co, Ni, Ca, Mg, Mn, etc., and having excellent pressability. However, even in this technique, sufficient performance cannot be obtained in the above-described bead press drawing. Disclosure of the invention

 An object of the present invention is to solve the above-mentioned drawbacks and to provide a phosphate-treated zinc-based steel plate having excellent workability.

 The present inventors have studied the addition of wax to a phosphate-treated film in order to improve the workability of a phosphate-treated zinc-based steel sheet. However, the known phosphating treatment involves spraying an acidic aqueous solution containing phosphate ions and metal cations, or immersing a zinc-based plated steel sheet in the aqueous solution, and treating the phosphating solution on the surface of the plating layer with p. Since crystals are formed by the increase of H, it is difficult to contain the box in the film. Further, when a wax film was further formed on the phosphate film, the wax was not sufficiently fixed to the film, so that there was a problem in workability and, in addition, adhesion of the coating. As a result of intensive studies on these problems, after forming a phosphate film on a zinc-based steel sheet surface by a known method, polyolefin wax or modified polyolefin wax, phosphate ions and polyvalent metal ions were removed. The present inventors have found that a phosphate film containing a polyolefin wax or a modified polyolefin wax can be obtained by applying an aqueous solution containing the solution and drying the solution, and it has been found that extremely good workability can be achieved.

That is, the gist of the present invention is a zinc-based plated steel sheet having a phosphate film on its surface, wherein the phosphate film contains polyolefin wax or modified polyolefin wax. It is a phosphate-treated galvanized steel sheet with excellent workability, and a method for producing such a phosphate-treated galvanized steel sheet includes phosphoric acid on the surface of a zinc-based plated steel sheet. After the salt treatment, an aqueous solution containing polyolefin wax or modified polyolefin wax, phosphate ions and polyvalent metal ions is applied and dried. The zinc-based plating steel sheet used in the present invention is not particularly limited, and any of pure zinc plating and alloy plating can be used, and the good workability improvement effect can be enjoyed. Plating, molten zinc plating, alloyed molten zinc plating Tsuke is preferred.

 There is no particular limitation on the phosphate film formed on the zinc plating, but in general, a zinc phosphate film that forms so-called whipite crystals, or? 6, ^, (0, ¾111, 1 ^, &,

Examples include a zinc phosphate coating modified with an element such as Cu.

 The aqueous solution applied to the upper layer of the phosphate film formed on the zinc plating must contain a polyolefin wax or a modified polyolefin wax, and phosphate ions and polyvalent metal ions. By coating and drying the coexisting aqueous solution, a phosphate film containing wax can be formed.

The polyvalent metal ion is preferably Mg ^{z +} , Mn ^2t , Ca ²⁺ , Zn ²⁺ , Ni ^2t , Co ²⁺ , Al ³⁺ , and may be used alone or in combination of two or more. it can. Of these, Mg ”or Mn ²⁺ is the most preferable in consideration of corrosion resistance.

 The easiest to manufacture is to use a mixed aqueous solution of polyolefin wax or modified polyolefin wax (hereinafter referred to as wax) and polyphosphate.

 As the biphosphate, Mg biphosphate, AI biphosphate, Mn biphosphate, Ca biphosphate and the like can be used. Among them, Mg biphosphate is most preferable in consideration of corrosion resistance.

 The wax is preferably a cationic or nonionic wax from the viewpoint of stable miscibility with phosphate ion and polyvalent metal ion.

 The amount of the wax added is not particularly limited, but is generally preferably about 10% or less with respect to the total weight of the phosphate film in consideration of the adhesion of the coating.

1 and 2 show SEM photographs (15 Kv, X500) of the wax-containing phosphate film produced by the methods of Examples 1 and 2 described later, and FIG. A SΕ photo (15Κν, X500) of a wax-free phosphate film produced by the method is shown. Fig. 4 shows the FT-IR (PER IN-ELMER, high sensitivity reflection method) chart for each sample. These were observed after ultrasonic cleaning (5 minutes) of the steel sheet in n-hexane solvent. As can be seen from the comparison of FIGS. 1 to 3, the wax-containing phosphate film of the present invention is the same as a normal wax-free phosphate film. Such a uniform and dense crystalline state is exhibited, and the presence or absence of wax cannot be determined from the surface properties. On the other hand, referring to FIG. 4, it can be seen that the wax-containing phosphate film of the present invention has an absorption peak attributable to the C—H bond of the wax at 2800 to 3000 cm ¹ . Can be confirmed.

The OO SOOOcm- ¹ peak in FT-IR is also detected when a thin film is formed by applying only wax on a phosphate coating containing no wax. As the solvent degreasing time increases with the use of xan, etc., the peak intensity decreases significantly, and the peak disappears before long. Therefore, the difference from the wax-containing phosphate film of the present invention can be confirmed (simplified method). In addition, the surface can be rubbed with a solvent to determine whether or not the surface is visible after rubbing. The wax-containing phosphate film of the present invention hardly shows any traces). In addition, a film formed by applying only wax on a phosphate film containing no wax is easily removed by the solvent component in the cleaning oil. ) Does not provide good workability. Also, the adhesion of the coating tends to be inferior, which is not preferable.

If degreasing is inadequate and the surface is protected from oil or stains, the FT-IR may absorb OO SOOOciir ¹ even with a phosphate film that does not contain a box. Therefore, before measurement, degreasing must be performed with a solvent such as n-hexane. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a diagram based on a surface SEM photograph (X500) of the wax-containing phosphate-treated zinc plating steel sheet in Example 1.

 FIG. 2 is a diagram based on a surface SEM photograph (X500) of the wax-containing phosphate-treated galvanized steel sheet in Example 2.

 FIG. 3 is a diagram based on the surface SEM photograph (X500) of the zinc-free phosphate-treated zinc-coated steel sheet in Comparative Example 2.

FIG. 4 is an FT-1R chart of a phosphate-treated zinc plated steel sheet of Example 1, Example 2, and Comparative Example 2. BEST MODE FOR CARRYING OUT THE INVENTION

 Examples of the present invention will be described below, but the present invention is not limited to the following examples.

In each of the examples and comparative examples, an electro-zinc plated steel sheet having a sheet thickness of 0.7 mm, r (rank hood value) = 1.9, and a basis weight of 30 g / m ² (per side) was used as a test material. did.

 (Example 1)

After surface conditioning (Pl-Zn, manufactured by Nippon Paiki Rising Co., Ltd.), the specimen was treated with zinc phosphate (PB-3322, manufactured by Nippon Pariki Rising Co., Ltd.) to obtain an adhesion of 0.7 g / An m ² zinc phosphate treated steel sheet was prepared. Next, an aqueous solution of Mg biphosphate (Yoneyama Chemical Co., Ltd.) and a modified nonionic polyethylene wax emulsion (Semichemical SH5200, Sanyo Kasei Kogyo Co., Ltd.) were mixed at a solid weight ratio of Mg: wax to 1%. The mixture was mixed so that the ratio became 0: 5, and the mixture was applied to the zinc phosphate-treated steel plate with a roll coater overnight, and dried so that the reached plate temperature reached 100 ° C. The weight to be applied was calculated from the weight difference between the steel sheet before application and the steel sheet after application and drying, and the value was set to 0.7 g / m ² .

 (Example 2)

 The adjustment was carried out in the same manner as in Example 1 except that the weight ratio of solid content of Mg: wax phosphate was 100: 1.

 (Example 3)

 The adjustment was carried out in the same manner as in Example 1 except that the weight ratio of solid content of Mg: wax was 100: 10.

 (Example 4)

 Instead of using an aqueous solution of Mg biphosphate, an adjustment was performed in the same manner as in Example 1 using an aqueous solution of A1 bicarbonate (manufactured by Yoneyama Chemical Industries, Ltd.).

 (Example 5)

 Adjustment was performed in the same manner as in Example 1 using Mn biphosphate (manufactured by Yoneyama Chemical Industry Co., Ltd.) instead of using the aqueous solution of Mg biphosphate.

(Example 6) The adjustment was performed in the same manner as in Example 1 except that Ca biphosphate (manufactured by Yoneyama Chemical Industry Co., Ltd.) was used instead of the aqueous solution of Mg biphosphate.

 (Comparative Example 1)

After surface conditioning (Pl-Zn, manufactured by Nippon Pachiriki Rising Co., Ltd.), the specimen was treated with zinc phosphate (PB-3322, manufactured by Nippon Pachiriki Rising Co., Ltd.) to obtain a phosphorous material with an adhesion amount of 0.7 g / m ² . A zinc-treated steel plate was prepared.

 (Comparative Example 2)

A magnesium phosphate aqueous solution (manufactured by Yoneyama Chemical Industry Co., Ltd.) was applied to the zinc phosphate-treated steel sheet of Comparative Example 1 with a roll coater, and dried so that the reached sheet temperature reached 100 ° C. The weight to be applied was calculated from the weight difference between the steel sheet before application and the steel sheet after application, and the value was set to 0.7 g / m ² .

(Comparative Example 3) '-Nonionic modified polyethylene polyethylene glycol (Semichemical SH5200 manufactured by Sanyo Kasei Kogyo Co., Ltd.) was applied to the zinc phosphate-treated plated steel sheet of Comparative Example 1 with a roll coater, and the reached plate temperature was 100. It was dried to be ° C. The weight to be applied was calculated from the weight difference between the steel sheet before application and the steel sheet after application and drying, and the value was set to O.lg / m ² .

 (Performance evaluation method)

• Wax presence / absence: Ultrasonic degreasing (5 minutes) in each of the samples of Examples 1 to 6 and Comparative Examples 1 to 3 in a solvent (n-hexane), followed by FT_IR measurement, and the peak of OO SOOOciir ¹ Judgment from the presence or absence

• U-bead bending workability: Each sample was coated with oil-proof oil (nox-rust550HN manufactured by Parker Kosan) at about 1.5 g / m ² (per side), left to stand overnight, and then sheared to 30 mm x 300 mm. After immersion in washing oil (Idemitsu Kosan Duff 2-Oil Coat) and squeezing the steel, continuous U-bead bending was performed. The processing conditions were as follows: BHF = l ton, processing height = 40 revs, bead punch R = 5 mm, bead die R = lmm, punch R = 5 thighs, processing speed = 25 spm. The evaluation was "X"; cracking occurred at the first piece, "△"; cracking occurred at the 2nd to 10th piece, "〇": Processing was possible without cracks of 10 or more, but there was slight galling and "◎"; 10 Can be processed without breaking more than one piece, no galling at all. • Coating adhesion: Each sample was degreased with a commercially available alkaline degreasing solution (PH = 10.5, 40 ° C, 1 minute immersion), and then electrodeposition coated (Nippon Paint V20, 20/2, 170 ° 20 minutes) Baking). After standing all day and night, it was immersed in warm water at 50 ° C. After 10 days, it was taken out and cut with limn-spaced cuts, and peeled off with cellophane tape. The evaluations were as follows: "A": 0% peeled area ratio, "〇": Less than 5% peeled area ratio, "△": 5 to 50% peeled area ratio, "X": Over 50% peeled area ratio.

 The evaluation results are shown in Table 1. In Examples of the present invention, good workability was obtained, but in comparison, the workability or paint adhesion was significantly deteriorated in Comparative Examples which were out of the range of the present invention. did. table 1

Industrial applicability

 According to the present invention, it is possible to obtain a phosphate-treated zinc-based steel sheet having unprecedented good workability. The steel sheet of the present invention does not use harmful substances such as hexavalent chromium, has a simple production method, is excellent in cost, and is suitable for various uses such as automatic, home appliances, and building materials.

Claims

The scope of the claims 1. A zinc-based steel sheet having a phosphate coating on its surface, wherein the phosphate coating contains a polyolefin wax or a modified polyolefin wax, and has excellent workability. Treated zinc-based steel sheet.  2. It is characterized by applying a phosphate treatment on the surface of a zinc-based plating steel sheet, then applying and drying an aqueous solution containing a polyolefin resin or a modified polyolefin wax, a phosphate ion and a polyvalent metal ion. 2. The method for producing a phosphate-treated zinc-based steel sheet according to claim 1, wherein: 3. The polyvalent metal ion is one or more of Mg ²⁺ , Mn ²⁺ , Ca ²⁺ , Zn ²⁺ , Ni ²⁺ , Co ²⁺ , and Al ³⁺ , The method for producing a phosphate-treated galvanized steel sheet according to claim 2, wherein '