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EP-4464814-B1 - PLATED STEEL SHEET

EP4464814B1EP 4464814 B1EP4464814 B1EP 4464814B1EP-4464814-B1

Inventors

  • HAYASHIDA, Shota
  • MITSUNOBU, Takuya
  • TAKEBAYASHI, HIROSHI

Dates

Publication Date
20260506
Application Date
20221206

Claims (3)

  1. A plated steel sheet comprising: a base steel sheet; a plated layer formed on a surface of the base steel sheet; and an oxide film formed on a surface of the plated layer, wherein, the plated layer has a chemical composition containing, in mass%, Sc: 0.000010 to 4.0%, Al: 0 to 93.0%, Fe: 0 to 15.0%, Si: 0 to 20.0%, Mg: 0 to 3.0%, Ca: 0 to 3.0%, La: 0 to 0.5%, Ce: 0 to 0.5%, Y: 0 to 0.5%, Cr: 0 to 1.0%, Ti: 0 to 1.0%, Ni: 0 to 1.0%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 1.0%, Cu: 0 to 1.0%, Mn: 0 to 1.0%, Sr: 0 to 0.5%, Sb: 0 to 0.5%, Pb: 0 to 0.5%, B: 0 to 0.5%, Li: 0 to 1.0%, Zr: 0 to 1.0%, Mo: 0 to 1.0%, W: 0 to 0.5%, Ag: 0 to 1.0%, P: 0 to 0.5%, Sn: 0 to 1.0%, Bi: 0 to 1.0%, In: 0 to 1.0%, and a remainder: 7.0% or more of Zn, and impurities, a total amount of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In is 0 to 5.0%, in a cross section of the plated layer in a thickness direction, an area fraction of an intermetallic compound phase containing Sc and having an equivalent circle diameter of 5.0 µm or less is 0.1 to 10.0%, and a thickness of the oxide film is 10 nm or more, wherein the chemical composition of the plated layer, the area fraction of an intermetallic compound phase and the thickness of the oxide film are measured as set out in the description.
  2. The plated steel sheet according to claim 1, wherein the chemical composition of the plated layer contains, in mass%, Al: 19.0 to 93.0%, and Sc: 0.00050 to 0.30%.
  3. The plated steel sheet according to claim 1, wherein the chemical composition of the plated layer contains, in mass%, Al: 19.0 to 93.0%, and Sc: 0.010 to 0.30%, and in the cross section of the plated layer in the thickness direction, the area fraction of the intermetallic compound phase is 1.0 to 10.0%.

Description

[Technical Field of the Invention] The present invention relates to a plated steel sheet. The present application claims priority based on Japanese Patent Application No. 2022-003724 filed in Japan on January 13, 2022. [Related Art] In recent years, suppression of chemical fuel consumption is required for environmental protection and global warming prevention. For example, an automobile as a movement unit indispensable for daily life and activities is no exception to such a request. In response to such a request, for example, improvement of fuel efficiency by vehicle body weight reduction and the like has been studied in automobiles. Most of the structure of an automobile is formed of iron, particularly a steel sheet, and therefore thinning the steel sheet to reduce the weight is highly effective for weight reduction of the vehicle body. However, if the thickness of the steel sheet is simply thinned to reduce the weight of the steel sheet, the strength of the structure is reduced to cause a concern of safety reduction. Therefore, for thinning the thickness of the steel sheet, an increase in the mechanical strength of the steel sheet to be used is required to prevent reduction in the strength of the structure. Therefore, a steel sheet has been studied and developed in which the mechanical strength of the steel sheet is increased and thus the mechanical strength can be maintained or increased even if the steel sheet is thinner than a previously used steel sheet. Such a steel sheet is required not only in the automobile manufacturing industry but also in various manufacturing industries. A material having high mechanical strength generally tends to have low shape fixability in forming such as bending, and in the case of processing into a complicated shape, processing itself becomes difficult. Examples of a method for solving the problem of formability include so-called "hot-pressing methods (a hot stamping method, a high temperature pressing method, or a die quenching method)". In these hot-pressing methods, a material to be formed is once heated to a high temperature, and the material softened by the heating is pressed and formed, and cooled after or simultaneously with the forming. In these hot-pressing methods, a material is once heated to a high temperature and softened, and pressed in a state where the material is softened, so that the material can be easily pressed. Therefore, by the hot pressing, a press-formed article having both good shape fixability and high mechanical strength is obtained. In particular in a case where the material is steel, the mechanical strength of the press-formed article can be increased by the quenching effect due to cooling after the forming. However, in the case of applying such a hot-pressing method to a steel sheet, for example, iron or the like on the surface is oxidized by heating to a high temperature of 800°C or higher, and thus a scale (oxide) is generated. Therefore, a step of removing the scale (descaling step) is required after the hot pressing, so that the productivity deteriorates. Furthermore, in a member or the like that requires corrosion resistance, the member surface after processing is required to be subjected to antirust treatment or metal coating, and therefore a surface cleaning step and a surface treatment step are required, so that the productivity deteriorates. As an example of a method for suppressing such deterioration of productivity, a method in which a steel sheet before hot stamping is subjected to coating such as plating to enhance the corrosion resistance and omit a descaling step is considered. In coating on steel sheets, various materials such as organic materials and inorganic materials are generally used. Among them, zinc plating having a sacrificial protection effect is often applied to steel sheets from the viewpoints of the anticorrosion performance and steel sheet production technology. For example, Patent Document 1 discloses a hot-pressed steel sheet member including a chemical composition containing, in mass%, C: 0.30% or more and less than 0.50%, Si: 0.01% or more and 2.0% or less, Mn: 0.5% or more and 3.5% or less, Sb: 0.001% or more and 0.020% or less, P: 0.05% or less, S: 0.01% or less, Al: 0.01% or more and 1.00% or less, and N: 0.01 % or less, with the remainder being Fe and inevitable impurities; a microstructure in which an average grain size of prior austenite grains is 8 µm or less, a volume percentage of martensite is 90% or more, and a solute C content is 25% or less of a total C content; a tensile strength of 1780 MPa or more; and a surface further having an Al-plated layer or a Zn-plated layer. Patent Document 1 discloses that applying a plated layer to a surface of a steel sheet can prevent oxidation of the sheet surface caused by hot pressing and improve the corrosion resistance of the hot-pressed steel sheet member. Patent Document 2 relates to a hot-dip Zn-Al-Mg-based plated steel comprising a steel; and a plating