Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C18/00—Alloys based on zinc
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C22/00—Alloys based on manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

• Patent Document 1 describes a method for producing a high-strength cold-rolled steel sheet, characterized in that when a high-strength cold-rolled steel sheet is continuously annealed in a continuous annealing furnace or in a cold-rolled steel sheet/hot-dip galvanized steel sheet dual-purpose facility having a continuous annealing furnace, the cooling method in a cooling zone including part or all of the steel sheet temperature range of 600 to 250°C following heating for recrystallization is one or more of gas cooling, diffusion cooling, and cooling pipe cooling, the steel sheet surface is exposed to an atmosphere in which iron oxidizes within the above-mentioned steel sheet temperature range, pickled at the outlet of the annealing furnace, and then iron or Ni plating is applied in an amount of 1 to 50 mg/ m2 .
• Patent Document 1 teaches that while oxidation of a steel sheet is normally prevented by an extremely low concentration of oxygen and/or an inert atmospheric gas with an extremely low dew point around the steel sheet, the steel sheet is instead actively exposed to an oxidizing atmosphere to oxidize not only Si and Mn but also the iron in the steel sheet, and by pickling after the steel sheet leaves the annealing furnace, the oxide films of Si, Mn, etc. are removed together with the oxide film on the iron in the steel sheet, thereby obtaining a high-strength cold-rolled steel sheet that is free from "hollow-out" and has good chemical conversion treatability even if the contents of Si, Mn, etc. are high.
• Patent Document 2 describes an automotive steel sheet containing 0.10% by mass or more and 0.50% by mass or less of copper (Cu), with the number of residual scales on the surface being 160,000 particles/mm2 or less , and the maximum particle size of copper compound particles exposed on the surface being 2 ⁇ m or less.
• Patent Document 2 also teaches that the above configuration makes it possible to provide a steel sheet with excellent chemical conversion treatability, since the particle size of copper compound particles exposed on the steel sheet surface, which serves as the cathode point in chemical conversion treatment, is 2 ⁇ m or less and the residual scale is kept to a predetermined amount or less.
• the inventors conducted research, focusing particularly on the plating layer. As a result, the inventors discovered that coating the surface of a base steel sheet containing Ni, Cu, and Sn with a plating layer of a specified thickness that primarily contains at least one of Zn and Mn can significantly improve paint film adhesion, leading to the completion of the present invention.
• a plated steel sheet comprising a base steel sheet and a plating layer disposed on a surface of the base steel sheet,
• the base steel plate is, in mass%, Ni: 0.010 to 1.000%, A chemical composition including Cu: 0.010 to 1.000% and Sn: 0.003 to 1.000%;
• a plated steel sheet characterized in that the thickness of a plating layer having a total concentration of at least one of Zn and Mn of 60 mass % or more is 0.10 to less than 1.00 ⁇ m.
• the chemical composition is, in mass%, Ni: 0.040-1.000%, Cu: 0.040 to 1.000%, and Sn: 0.004 to 1.000%
• the plated steel sheet according to any one of (1) to (3) above comprising: (5) The plated steel sheet according to any one of (1) to (4) above, characterized in that it has a Vickers hardness of 200 Hv or more. (6) A part comprising the plated steel sheet according to any one of (1) to (5) above.
• a plated steel sheet is a plated steel sheet including a base steel sheet and a plating layer disposed on a surface of the base steel sheet,
• the base steel plate is, in mass%, Ni: 0.010 to 1.000%, A chemical composition including Cu: 0.010 to 1.000% and Sn: 0.003 to 1.000%;
• the plating layer has a total concentration of at least one of Zn and Mn of 60 mass % or more and is characterized in that the thickness is 0.10 to less than 1.00 ⁇ m.
• skid zones areas where the chemical conversion coating is not formed, known as “skid zones,” can appear, which can result in reduced paint adhesion.
• elements such as Ni, Cu, and Sn
• the potential of the steel sheet becomes more noble than when these elements are not present in solid solution, which can reduce the etching ability of Fe during chemical conversion treatment.
• the chemical conversion treatability of the steel sheet declines, resulting in reduced paint adhesion. Therefore, this reduced paint adhesion is particularly problematic when the steel sheet simultaneously contains the three elements Ni, Cu, and Sn.
• the plating layer may consist essentially of at least one of Zn and Mn, consist of at least one of Zn and Mn, or consist of at least one of Zn and Mn.
• the coating weight is not particularly limited and may be appropriately selected within a range that satisfies the requirements for the Zn and Mn concentrations and plating layer thickness, which will be described in detail later.
• the thickness of a plating layer having a concentration of at least one of Zn and Mn totaling 60 mass% or more is controlled to 0.10 to less than 1.00 ⁇ m.
• Zn and Mn function as an anode during chemical conversion treatment and improve the chemical treatability of the steel sheet by dissolving themselves.
• the thickness of a plating layer having a concentration of at least one of Zn and Mn totaling 60 mass% or more to 0.10 to less than 1.00 ⁇ m it becomes possible for the Zn and Mn in the plating layer to effectively function as an anode during chemical conversion treatment.
• the anodic dissolution (etching) of Zn and/or Mn in the plating layer is promoted during chemical conversion treatment, allowing a chemical conversion treatment film to be formed uniformly over the entire steel sheet, resulting in significantly improved paint adhesion.
• the P ratio represents the ratio of hopite ( Zn3 ( PO4 ) 2.4H2O ) to phosphophyllite ( Zn2Fe ( PO4 ) 2.4H2O ) in the coating obtained by phosphating. More specifically, it is a value expressed as IP /(IP+ IH ) x 100(%), where IP is the X-ray diffraction intensity of the (100) plane of phosphophyllite and IH is the X-ray diffraction intensity of the (020) plane of hopite, as measured using an X- ray diffractometer .
• the base steel sheet has a chemical composition containing, in mass %, Ni: 0.010 to 1.000%, Cu: 0.010 to 1.000%, and Sn: 0.003 to 1.000%.
• an object of the present invention is to provide a plated steel sheet containing Ni, Cu, and Sn that can exhibit improved paint adhesion, and this object is achieved by controlling the thickness of a plating layer having a concentration of at least one of Zn and Mn in total of 60 mass % to 0.10 to less than 1.00 ⁇ m when a cross section of the plated steel sheet is measured by EPMA.
• the base steel plate contains, in mass%, C: 0.001 to 0.500%, Si: 0-3.00%, Mn: 0.10-3.00%, Al: 0.001-2.000%, Ni: 0.010 to 1.000%, Cu: 0.010-1.000%, Sn: 0.003-1.000%, P: 0.100% or less, S: 0.100% or less, N: 0.0100% or less, Ti: 0 to 0.150%, Nb: 0 to 0.150%, B: 0 to 0.0100%, Mo: 0-1.000%, Cr: 0-1.000%, V: 0 to 0.150%, W: 0-1.000%, Hf: 0 to 0.050%, Mg: 0 to 0.050%, Zr: 0 to 0.050%, Ca: 0-0.010%, REM: 0-0.010%, As: 0 to 0.010%, It is preferable that the chemical composition be Ir: 0 to 1.000%, and the balance: Fe and impurities.
• the chemical composition be Ir: 0
• P is an element that segregates at grain boundaries and promotes embrittlement of steel. Since a lower P content is preferable, ideally it is 0%. However, excessive reduction in the P content may result in a significant increase in costs. Therefore, the P content may be 0.0001% or more, 0.001% or more, or 0.005% or more. On the other hand, excessive P content may result in embrittlement of steel due to grain boundary segregation, as described above. Therefore, the P content is preferably 0.100% or less. The P content may be 0.050% or less, 0.030% or less, 0.020% or less, or 0.010% or less.
• [B: 0 to 0.0100%] B segregates at grain boundaries to increase grain boundary strength, thereby improving low-temperature toughness.
• the B content may be 0%, but to obtain this effect, the B content is preferably 0.0001% or more.
• the B content may be 0.0002% or more, 0.0005% or more, or 0.0010% or more.
• the B content is preferably 0.0100% or less.
• the B content may be 0.0050% or less, 0.0030% or less, 0.0020% or less, or 0.0015% or less.
• Hf, Mg, Zr, Ca, and REM are elements that can control the morphology of non-metallic inclusions.
• the Hf, Mg, Zr, Ca, and REM contents may be 0%, but to obtain these effects, the contents of these elements are preferably 0.0001% or more, and may be 0.0005% or more, or 0.001% or more. However, even if these elements are contained in excess, the effects are saturated, and adding more than necessary to the steel sheet increases production costs.
• the water rinse after the secondary pickling is also extremely important.
• the electrical conductivity of the water rinse used in the water rinse is relatively high, more specifically, if it is higher than 40 mS/m, iron oxides may form on the surface of the cold-rolled steel sheet during the water rinse after the secondary pickling.
• the obtained base steel sheet was electroplated using a bath containing metal species such as Zn and Mn at predetermined concentrations under conditions of a current density of 10 A/ dm2 and an energization time of 5.0 seconds, thereby obtaining a plated steel sheet in which a plating layer containing the metal species shown in Table 2 was attached to both sides of the base steel sheet.
• the "thickness of the plating layer" in Table 2 indicates the thickness of the plating layer in which the concentration of at least one of Zn and Mn in total was 60 mass% or more, when the cross section of the plated steel sheet was measured by EPMA.
• the low coiling temperature resulted in insufficient formation of an internal oxide layer, making it impossible to form an Mn-Si depleted layer with a thickness of 0.3 ⁇ m or more.
• the thickness of the plating layer in which the concentration of at least one of Zn and Mn was 60 mass% in total, was less than 0.10 ⁇ m, and coating adhesion was reduced.
• the coating thickness was controlled to 0.10 to less than 1.00 ⁇ m, and the total concentration of at least one of Zn and Mn was 60 mass% or more. This significantly improved the coating adhesion of the plated steel sheets.
• the coating adhesion was evaluated as AA, demonstrating further improvement.
• the coating adhesion was evaluated as AAA, demonstrating further improvement in coating adhesion.

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• Chemical & Material Sciences (AREA)
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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)

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Citations (4)

• 2025
  • 2025-01-27 JP JP2025536343A patent/JP7836021B2/ja active Active
  • 2025-01-27 WO PCT/JP2025/002440 patent/WO2025169775A1/ja active Pending

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