CN-122003516-A - Steel sheet and component comprising same

Abstract

The present invention provides a steel sheet containing Ni, cu and Sn, which has excellent chemical conversion treatability even when a certain time has elapsed after degreasing, and a member comprising the steel sheet. The steel sheet and the member containing the steel sheet are characterized in that the steel sheet has a chemical composition comprising, in mass%, 1.20-3.00% of Mn, 0.010-1.000% of Ni, 0.010-1.000% of Cu, 0.003-1.000% of Sn and 0.01-less than 0.75% of Si, and satisfies Mn/(Si+Mn) >0.80, and N 30 per 10 mu m of Mn oxide having an equivalent circle diameter of 30nm or more exposed on the surface of the steel sheet satisfies N 30 or more.

Inventors

• Xilianchuan Naoto
• Light Zai Zai

Assignees

• 日本制铁株式会社

Dates

Publication Date

20260508

Application Date

20250903

Priority Date

20240905

Claims (8)

1. 1. A steel sheet, characterized in that the chemical composition of the steel sheet comprises in mass%: Mn:1.20~3.00%、 Ni:0.010~1.000%、 Cu:0.010~1.000%、 0.003 to 1.000% Sn, and Si of 0.01 to less than 0.75%, and Satisfies Mn/(Si+Mn) >0.80, The number N 30 of Mn oxides with equivalent circle diameters of more than 30nm, which are exposed on the surface of the steel plate, per 10 mu m can meet the requirement that N 30 is more than or equal to 20.
2. 2. The steel sheet according to claim 1, wherein the number N 30 of Mn oxides having an equivalent circle diameter of 30nm or more per 10 μm exposed on the surface of the steel sheet satisfies N 30 not less than 30.
3. 3. The steel sheet according to claim 1 or 2, wherein the Cu concentration measured by high-frequency glow discharge emission spectrometry from the surface of the steel sheet in the thickness direction satisfies (Cu concentration at depth 5 nm)/(Cu concentration at depth 10 μm). Ltoreq.10.0.
4. 4. The steel sheet according to claim 1 or 2, wherein the Cu concentration measured by high-frequency glow discharge emission spectrometry from the surface of the steel sheet in the thickness direction satisfies (Cu concentration at depth 5 nm)/(Cu concentration at depth 10 μm) +.7.0.
5. 5. The steel sheet according to any one of claims 1 to 4, wherein the steel sheet has a chemical composition comprising, in mass%: Ni:0.040~1.000%、 0.040-1.000% Cu, and Sn:0.004~1.000%。
6. 6. The steel sheet according to any one of claims 1 to 5, wherein the steel sheet has a chemical conversion coating film on a surface thereof.
7. 7. The steel sheet according to claim 6, wherein a ratio of hopeite in the chemical conversion crystals in the chemical conversion coating film is 50% or more as measured by an X-ray diffraction method.
8. 8. A component comprising the steel sheet according to any one of claims 1 to 7.

Description

Steel sheet and component comprising same Technical Field The present invention relates to a steel sheet and a member including the same. Background In order to improve the corrosion resistance of a steel sheet, it is effective to improve the chemical conversion treatability of the surface of the steel sheet and to uniformly form a chemical conversion coating film on the surface of the steel sheet. In connection with this, for example, patent document 1 discloses a method for producing a high-strength cold-rolled steel sheet, which is characterized by continuously annealing a high-strength cold-rolled steel sheet using a continuous annealing furnace in which a cooling zone including a part or all of a steel sheet temperature range of 600 to 250 ℃ after heating for recrystallization is cooled by one or more of gas cooling, diffusion cooling, and cooling tube cooling, or a cold-rolled steel sheet/hot-dip galvanized steel sheet dual-purpose facility having a continuous annealing furnace in which the surface of the steel sheet is exposed to an atmosphere in which iron is oxidized in the steel sheet temperature range, and then performing iron plating or Ni plating of 1 to 50mg/m 2 after pickling on the outgoing side of the annealing furnace. Further, patent document 1 teaches that, in general, oxidation of a steel sheet is prevented by using an inert atmosphere gas having an extremely low concentration of oxygen and/or an extremely low dew point around the steel sheet, and on the contrary, the steel sheet is actively exposed to an oxidizing atmosphere, not only Si and Mn are oxidized to oxidize iron of the steel sheet, but also an oxide film of iron of the steel sheet and an oxide film of Si, mn or the like are eluted by pickling at the time of exiting from an annealing furnace, whereby a high-strength cold-rolled steel sheet excellent in chemical conversion treatability without "uncovered portions" even if the content of Si, mn or the like is high is obtained. Patent document 2 discloses a steel sheet for automobiles, which contains copper (Cu) in an amount of 0.10 mass% or more and 0.50 mass% or less, and has a number of residual oxide scale on the surface of 160,000 pieces/mm 2 or less, and a maximum particle diameter of copper compound particles exposed on the surface of 2 μm or less. Further, patent document 2 teaches that the above-described constitution makes the particle diameter of copper compound particles exposed on the surface of a steel sheet serving as an cathode point 2 μm or less and makes the residual oxide scale a predetermined amount or less in the chemical conversion treatment, and thus can provide a steel sheet excellent in chemical conversion treatability. Prior art literature Patent literature Patent document 1 Japanese patent laid-open publication No. 2008-190030 Patent document 2 Japanese patent application laid-open No. 2020-084238 Disclosure of Invention Problems to be solved by the invention Patent document 2 teaches that elements such as copper (Cu), nickel (Ni), and tin (Sn) reduce mechanical properties such as strength and formability required for an automotive steel sheet, and also reduce chemical stability such as corrosion resistance, and particularly that copper compounds present on the surface of the steel sheet reduce chemical conversion treatability for improving corrosion resistance. Further, the chemical conversion treatment of the steel sheet is usually performed by degreasing the steel sheet with a degreasing agent and immersing the steel sheet in a chemical conversion treatment liquid, and particularly in the case where the steel sheet contains copper (Cu), nickel (Ni) and tin (Sn), it is necessary to control the time from degreasing the steel sheet to performing the chemical conversion treatment in a very strict and short period of time. When a certain time (for example, 10 minutes or more) has elapsed after degreasing, there is a possibility that the chemical conversion treatability is significantly lowered. Accordingly, an object of the present invention is to provide a steel sheet containing Ni, cu and Sn, which has excellent chemical conversion treatability even when a certain time has elapsed after degreasing, and a member including the steel sheet. Means for solving the problems The present invention includes at least the following aspects. (Scheme 1) A steel sheet, characterized in that, The chemical composition of the steel sheet comprises, in mass%: Mn:1.20~3.00%、 Ni:0.010~1.000%、 Cu:0.010~1.000%、 0.003 to 1.000% Sn, and Si of 0.01 to less than 0.75%, and Satisfies Mn/(Si+Mn) >0.80, The number N 30 of Mn oxides with equivalent circle diameters of 30nm or more exposed on the surface of the steel sheet per 10 mu m satisfies N 30 not less than 20. (Scheme 2) The steel sheet according to claim 1, wherein the number N 30 of Mn oxides having an equivalent circle diameter of 30nm or more exposed on the surface of the steel sheet per 10 μm satisfies N 30 not less than