CN-119136977-B - Coated steel sheet and method for producing same

Abstract

The present invention provides a coated steel sheet having excellent press formability. The coated steel sheet comprises a base steel sheet and a coating film provided on at least one surface of the base steel sheet, wherein the organic resin is at least one selected from the group consisting of an acrylic resin, an epoxy resin, a urethane resin, a phenolic resin, a vinyl acetate resin and a polyester resin, the wax is a polyolefin wax having a melting point of 100-145 ℃ and an average particle diameter of 3.0 [ mu ] m or less, the proportion of the wax in the coating film is 5-70% by mass, the deviation sigma' of the coating film adhesion amount is 0.300 or less, and the coating film adhesion amount [ mu ] W is 0.3g/m 2 or more.

Inventors

• LI YUANJUN
• Qingshan Penghong
• FURUTANI SHINICHI
• MATSUDA TAKESHI
• KONO TAKASHI

Assignees

• 杰富意钢铁株式会社

Dates

Publication Date

20260512

Application Date

20230515

Priority Date

20220607

Claims (13)

1. 1. A coated steel sheet comprising a base steel sheet and a coating film provided on at least one surface of the base steel sheet, the coating film comprising an organic resin and a wax, The organic resin is at least one selected from the group consisting of acrylic resins, epoxy resins, polyurethane resins, phenolic resins, vinyl acetate resins and polyester resins, The wax is a polyolefin wax having a melting point of 100-145 ℃ and an average particle diameter of 3.0 μm or less, The wax in the coating is in a proportion of 5 to 70 mass%, The deviation sigma' of the film adhesion amount defined by the following formula (1) is 0.300 or less, The film has an adhesion amount mu W of 0.3g/m 2 or more, Wherein, the W i the amount of the coating film attached at the point i was measured in g/m 2 , H i measuring the height of the base steel plate at point i, Mu W the adhesion amount of the coating, Mu H average value of the heights of the base steel plates, A, the slope of a regression line in a scatter diagram obtained by plotting the adhesion amount of the coating film relative to the height of the base steel plate, And b, intercept of the regression line.
2. 2. The coated steel sheet according to claim 1, wherein the proportion of the organic resin in the coating film is 30 to 95% by mass, The proportion of the wax in the coating is 5-50% by mass.
3. 3. The coated steel sheet according to claim 1 or 2, wherein the arithmetic average roughness Ra of the surface of the base steel sheet is 0.4 μm to 2.5 μm.
4. 4. The coated steel sheet according to any one of claims 1 to 3, wherein the coating film has an adhesion amount μ W of 2.5g/m 2 or less.
5. 5. The coated steel sheet according to any one of claims 1 to 4, wherein the organic resin is an alkali-soluble resin.
6. 6. The coated steel sheet according to any one of claims 1 to 5, wherein the coating film further contains an anti-rust agent.
7. 7. The coated steel sheet according to claim 6, wherein the rust inhibitor is at least one selected from the group consisting of aluminum salts, zinc salts, and zinc oxides of phosphoric acids.
8. 8. The coated steel sheet according to any one of claims 1 to 7, wherein the coating further contains a dispersant.
9. 9. The coated steel sheet according to claim 8, wherein the dispersant is at least one selected from the group consisting of sodium polycarboxylic acid, sodium polyacrylate, carboxylic acid copolymer and sulfonic acid copolymer.
10. 10. The coated steel sheet according to any one of claims 1 to 9, wherein the coating further contains silica.
11. 11. A method for producing a coated steel sheet according to any one of claims 1 to 10, wherein a coating material comprising an organic resin and a wax is applied to at least one surface of a base steel sheet and dried, The organic resin is at least one selected from the group consisting of acrylic resins, epoxy resins, polyurethane resins, phenolic resins, vinyl acetate resins and polyester resins, The wax is a polyolefin wax having a melting point of 100-145 ℃ and an average particle diameter of 3.0 [ mu ] m or less.
12. 12. The method for producing a coated steel sheet according to claim 11, wherein the maximum reaching temperature of the base steel sheet at the time of drying is 60 ℃ or higher and the melting point of the wax is lower.
13. 13. The method for producing a coated steel sheet according to claim 11 or 12, wherein the proportion of the total solid content in the paint is 1 to 30 mass%.

Description

Coated steel sheet and method for producing same Technical Field The present invention relates to a coated steel sheet, and more particularly, to a coated steel sheet excellent in press formability (press formability). The present invention also relates to a method for producing the coated steel sheet. Background Steel sheets such as cold-rolled steel sheets and hot-rolled steel sheets are widely used in various fields, and for example, in applications such as automobile bodies, steel sheets are generally used by press forming. Therefore, the steel sheet is required to have excellent press formability. In particular, in recent years, press molding tends to be performed into a more complex shape in order to improve the design of the product. In addition, in order to simplify the manufacturing process, the pushing member is integrated, and in this sense, the pushing member tends to be press-molded into a more complicated shape. However, when a steel sheet is press-formed into a complicated shape, the steel sheet may not withstand the forming and may break, or die wear may occur during continuous press forming (diegalling). As a result, the productivity of products such as automobiles is adversely affected. Therefore, further improvement in press formability is required. As a method for improving the press formability, for example, a method of performing surface treatment on a die used for press forming is mentioned. Although this is a widely used method, there is a problem in that once the surface treatment is performed, the adjustment of the mold cannot be performed thereafter. In addition, there is a problem of high cost. As a method for improving the press formability without subjecting the die to surface treatment, there is a method using a high-viscosity lubricating oil. However, since the press-molded part obtained by this method is in a state of adhering high-viscosity lubricating oil, there is a case where degreasing failure occurs after press molding, and if degreasing failure occurs, the coatability is deteriorated. Therefore, instead of the surface treatment of the mold and the high-viscosity lubricating oil, improvement of the press formability of the steel sheet itself is demanded. As a technique for improving the press formability of a steel sheet itself, it has been proposed to perform a surface treatment to form a lubricating film on the surface of the steel sheet. For example, patent document 1 proposes a coated steel sheet in which an acrylic resin coating film is formed on the surface of a galvanized steel sheet. Patent document 2 proposes that a solid lubricant protrude from the surface of a resin coating film by 0.01 to 1.5 μm in a coated metal plate in which the resin coating film is formed on the surface of the metal plate. Patent document 3 proposes a coating film comprising a polyurethane resin and a lubricant, wherein the coating film is formed by coating the surface of a metal product with a thickness of 0.5 to 5 μm. Patent document 4 proposes a coated steel sheet having an alkali-soluble organic coating film in which a lubricant is added to an epoxy resin. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 09-170059 Patent document 2 Japanese patent laid-open No. 10-052881 Patent document 3 Japanese patent laid-open No. 2000-309747 Patent document 4 Japanese patent laid-open No. 2000-167981 Disclosure of Invention However, in the techniques proposed in patent documents 1 to 4, although some improvement in lubricity is observed due to the effect of the lubricant contained in the coating film, moldability in complicated press molding is not sufficient. Specifically, there is a problem in that cracks are generated at a crack risk portion at the time of press molding or die wear is generated at a portion where the face pressure becomes high. The present invention has been made in view of the above circumstances, and an object thereof is to provide a coated steel sheet having excellent press formability. The present inventors have focused on a coated steel sheet having a coating film containing an organic resin and a wax, and have made intensive studies to solve the above problems, and as a result, have obtained the following findings. (1) If a steel sheet having a coating film formed thereon, the coating film being composed of an organic resin and a wax is press-formed, the coating film is scraped off by the mold when the surface of the coating film and the surface of the mold slide, and the sliding surface of the steel sheet is covered with a lubricant coating film formed by mixing the organic resin and the wax in the coating film. Therefore, in order to improve press formability, it is necessary to improve the sliding properties of the lubricant film covering the die surface and the sliding surface of the steel sheet, that is, to reduce the coefficient of friction. (2) By using a specific organic resin and wax, the variation in the amount of partia