CN-116529068-B - Plated steel sheet for precoated steel sheet, and molded article

Abstract

Even when drawing is performed, the occurrence of a coating film floating portion can be more reliably suppressed. The coated steel sheet for a precoated steel sheet of the present invention comprises a steel sheet and a coating layer which is provided on one or both surfaces of the steel sheet and contains 0.5 to 60.0 mass% of aluminum, 0.5 to 15.0 mass% of magnesium, and the balance zinc and impurities, wherein the ratio of the oxide and hydroxide of magnesium to the ratio of the magnesium metal is 2.0 or more or the ratio of the oxide and hydroxide of zinc to the ratio of the zinc metal is 7.0 or more at a depth of 10nm from the surface of the coating layer.

Inventors

• FURUKAWA HIROYASU
• FUJII TAKASHI
• Chai Weishisheng
• NAKAGAWA AKIRA
• UEDA KOHEI

Assignees

• 日本制铁株式会社

Dates

Publication Date

20260505

Application Date

20211005

Priority Date

20201023

Claims (10)

1. 1. A plated steel sheet for a precoated steel sheet, comprising: Steel plate, and A coating layer which is provided on one or both surfaces of the steel sheet and contains 0.5 to 60.0 mass% of aluminum, 0.5 to 15.0 mass% of magnesium, and the balance zinc and impurities, At a depth of 10nm from the surface of the plating layer, the ratio of the oxide and hydroxide of magnesium to the metal magnesium is 2.0 or more, or the ratio of the oxide and hydroxide of zinc to the metal zinc is 7.0 or more, Wherein the ratio of magnesium oxide and hydroxide to magnesium metal is calculated by the ratio of the sum of peak intensities of magnesium oxide and hydroxide in the range of 295-325 cm -1 based on Mg KLL to the peak intensity of magnesium metal at a depth of 10nm from the surface of the plating layer, as observed by X-ray photoelectron spectroscopy; Wherein the ratio of zinc oxide and hydroxide to metallic zinc is calculated by the ratio of the sum of the peak intensities of zinc oxide and hydroxide in the range of 480 to 515cm -1 based on Zn 2p to the peak intensity of metallic zinc at a depth of 10nm from the surface of the plating layer, as observed by X-ray photoelectron spectroscopy.
2. 2. The plated steel sheet for a precoated steel sheet according to claim 1, wherein the ratio of the oxide and hydroxide of magnesium to the ratio of metallic magnesium is 2.0 or more and the ratio of the oxide and hydroxide of zinc to the ratio of metallic zinc is 7.0 or more at a depth of 10nm from the surface of the plated layer.
3. 3. The plated steel sheet for a precoated steel sheet according to claim 1 or 2, wherein the ratio of aluminum oxide and hydroxide to the ratio of metallic aluminum is 1.3 or more at a depth of 10nm from the surface of the plated layer.
4. 4. The plated steel sheet for a precoated steel sheet according to claim 1 or 2, wherein the plating layer is Zn-11% al-3% mg-0.2% si alloy plating.
5. 5. The coated steel sheet for a precoated steel sheet as set forth in claim 3 wherein the coating layer is Zn-11% Al-3% Mg-0.2% Si alloy coating.
6. 6. A pre-coated steel sheet having: a chemical conversion coating film on the coating layer of the plated steel sheet according to any one of claims 1 to 5, and A coating film which is provided on the chemical conversion treatment coating film, At a depth of 10nm from the interface of the chemical conversion treatment coating film and the plating layer toward the inside of the plating layer, the ratio of the oxide and hydroxide of magnesium to the ratio of magnesium to metal is 0.30 or less, or the ratio of the oxide and hydroxide of zinc to the ratio of zinc to metal is 7.0 or more, Wherein the ratio of magnesium oxide and hydroxide to magnesium metal is calculated by the ratio of the sum of peak intensities of magnesium oxide and hydroxide to the peak intensity of magnesium metal in the range of 295-325 cm -1 based on Mg KLL at a depth of 10nm inward of the plating layer from the interface of the chemical conversion treatment film and the plating layer, as observed by X-ray photoelectron spectroscopy; Wherein the ratio of zinc oxide and hydroxide to metallic zinc is calculated by the ratio of the sum of the peak intensities of zinc oxide and hydroxide in the range of 480 to 515cm -1 based on Zn 2p to the peak intensity of metallic zinc at a depth of 10nm inward of the plating layer from the interface of the chemical conversion treatment coating film and the plating layer, as observed by X-ray photoelectron spectroscopy.
7. 7. The pre-coated steel sheet according to claim 6, wherein the ratio of the oxide and hydroxide of magnesium to the ratio of metallic magnesium is 0.30 or less and the ratio of the oxide and hydroxide of zinc to the ratio of metallic zinc is 7.0 or more at a depth of 10nm from the interface of the chemical conversion treatment coating film and the coating layer toward the inside of the coating layer.
8. 8. The precoated steel sheet according to claim 6 or 7, wherein the ratio of the oxide and hydroxide of aluminum to the ratio of metallic aluminum is 0.30 or less at a depth of 10nm from the interface of the chemical conversion treatment coating film and the plating layer toward the inside of the plating layer.
9. 9. A molded article comprising the precoated steel sheet according to any one of claims 6 to 8, In the portion of the formed article where the thickness of the plated steel sheet is increased by 5% or more compared with the non-formed portion, the peel strength measured by cutting the interface between the chemical conversion treatment coating film and the coating film by the saics method is 1.00kN/m or more on average, 20% or less of the cut area is in the interface peel state, and the cut area in the remaining portion is in the cohesive failure state in the coating film.
10. 10. The molded article according to claim 9, wherein the coating layer of the molded article contains 5% to 15% of aluminum and 2% to 4% of magnesium.

Description

Plated steel sheet for precoated steel sheet, and molded article Technical Field The present invention relates to a precoated steel sheet, and a molded article. Background The precoated steel sheet, which is a steel sheet that has been coated in advance, is required to have various properties such as corrosion resistance, formability, coating hardness (flaw resistance), stain resistance, chemical resistance, weather resistance, and the like. The order of these required properties varies depending on the use of the pre-coated steel sheet. For example, in precoated steel sheets used mainly for outdoor use such as air conditioning units and water heaters, the above-mentioned properties, particularly formability and corrosion resistance, are important. As a method for improving the adhesion between a coated steel sheet and a coating film, many techniques have been studied for such a precoated steel sheet. For example, patent document 1 below discloses a precoated metal sheet having excellent press formability without damaging or peeling a coating film of a drawn part during drawing. In patent document 1, in order to obtain a precoated metal sheet excellent in press formability without peeling, it is disclosed that the coating film preferably has a specific viscoelastic curve, the number average molecular weight of the coating film resin is 10000 or more, and the glass transition temperature (Tg) of the coating film resin is 25 ℃ or more. Patent document 2 below discloses a precoated metal sheet having excellent continuous press formability and excellent outdoor corrosion resistance of the end surface portion of the drawn portion. In patent document 2, in order to obtain a precoated metal sheet excellent in continuous press formability, it is disclosed that, as the physical properties of the coating film, it is important that the Tg of the coating film is 40 to 120 ℃, the minimum value of the storage elastic modulus in the rubbery elastic range of the coating film measured by a dynamic viscoelasticity measuring device is 2×10 7 Pa or less, the surface tension of the coating film is 28mN/m or less, and the dynamic friction coefficient of the coating film surface is 0.15 or less. Patent document 3 below discloses a precoated metal sheet having 1 or 2 or more coating layers on one or both surfaces of the metal sheet, wherein the physical properties of the outermost coating film are such that the Tg is 5 to 30 ℃, the hardness at 23 ℃ is 2.5N/mm 2 or more in terms of universal hardness under a load of 5mN, the elongation at break at 23 ℃ is 100% or more, and the specular gloss of the outermost coating film is 60% or more when measured under conditions of an incident angle and a light receiving angle of 60 ℃. Patent document 3 discloses a precoated metal sheet which is less likely to cause a reduction in gloss of a coating film even when deep drawing is performed and a processed portion is formed, and which is excellent in press formability. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2-217500 Patent document 2 Japanese patent laid-open No. 8-253883 Patent document 3 Japanese patent laid-open No. 2007-44922 Disclosure of Invention Problems to be solved by the invention The present inventors have studied to further improve the formability and corrosion resistance of the precoated steel sheet. As a result, it was newly found that when drawing processing such as drawing processing is performed on a top plate of an air conditioner outdoor unit using a precoated steel sheet, a phenomenon called coating film floating (a phenomenon in which a coating film is roughened due to a fine assembly of point-like expansion) occurs in a drawing forming portion. The portion where these phenomena occur will be hereinafter referred to as "coating film floating portion". As is clear from a cross-sectional view of the floating portion of the coating film, the coating film was not allowed to follow the deformation (compression) of the coated steel sheet during the drawing forming of the precoated steel sheet, and was superfluous, and the coating film was peeled off upward at a portion having insufficient adhesion to the coated steel sheet. The technique of patent document 1 is intended to set the physical properties of a coating film and to suppress buckling of the coating film due to compressive strain of a drawn part generated during drawing. However, as a result of the studies by the present inventors, it is presumed that in order to suppress buckling of the coating film, in practice, in addition to the physical properties of the coating film, the hardness of the coating film, the uniformity of the coating film, the physical properties of the coating film by chemical conversion treatment, the shape of the processed film, and the like are also factors that cannot be ignored. Patent document 1 does not describe factors other than the physical properties of the coating film. Accordingly, patent doc