Steel plate and its manufacturing method

Abstract

To provide a steel sheet that has excellent chemical conversion treatment properties even when having a Trump element and has high corrosion resistance. The steel sheet contains a predetermined element in a predetermined amount, and by GDS, in the emission intensity profile of the wavelength indicating Ni obtained by measuring in the depth direction from the surface of the steel sheet, the average intensity of Ni is I ave , the peak intensity of Ni is I max , the depth (μm) indicating the I max is D max , the Ni concentration (mass%) converted from the I max is [Ni] max , (I max - I ave ) / 2 + I ave is defined as the depth (μm) of the intensity shown as D 1 / 2 , when the Cu content (mass%) in the steel sheet is defined as [Cu], the Sn content (mass%) is defined as [Sn], and the Cr content (mass%) is defined as [Cr], it is a steel sheet that satisfies the following formulas (1) to (3). 0.00 ≦ [Ni] max - 2.5[Cu] ≦ 6.00 ··· (1) 0.020 ≦ D 1 / 2 ··· (2) 10[Sn] + 5[Cr] ≦ 1.81 ··· (3)

Claims

1. In mass percent, Cu: 0.01 to 0.50%, Ni: 0.04-1.00%, Sn: 0.001 to 0.100%, Cr: 0.01-0.20%, Mo: 0.001 to 1.000%, Zn: 0 to 0.500%, Pb: 0 to 0.500%, As: 0 to 0.500%, Sb: 0 to 0.500%, Bi: 0-0.500%, V: 0 to 0.500%, C: 0-0.50%, Si: 0-3.000%, Mn: 0 to 5.00%, B: 0-0.0100% P: 0-0.100%, S: 0-0.020%, Al: 0-0.100% and A steel sheet having a composition in which N: 0 to 0.0100% is present, with the remainder being Fe and unavoidable impurities. By glow discharge emission spectroscopy (GDS), the emission intensity profile of Ni at a wavelength obtained by measuring from the surface of the steel plate in the depth direction, The average intensity of Ni is I ａｖｅ , The peak intensity of Ni is I ｍａｘ , The above I ｍａｘ The depth (μm) that indicates this is D ｍａｘ , The above I ｍａｘ The Ni concentration (mass%) converted from [Ni] ｍａｘ , (I ｍａｘ -I ａｖｅ ) / 2 + I ａｖｅ The depth (μm) indicating the intensity of １／２ is defined as D In the aforementioned steel plate, The Cu content (mass%) is denoted as [Cu]. The Sn content (mass%) is indicated as [Sn]. When the Cr content (mass%) is defined as [Cr], A steel plate that satisfies the following equations (1) to (3). 0.00 ≦ [N+] ｍａｘ -2.5[C] ≦ 6.00・・・(1) 0.020 ≦ D １／２ ・・・(2) 10[Sn]+5[Cr]≦1.81...(3)

2. The steel sheet according to claim 1, wherein the steel sheet is a steel sheet having a chemical conversion treatment coating.

3. A method for manufacturing a steel sheet according to claim 1, A heating step of heating a slab that satisfies the component composition and formula (3) described in claim 1, A descaling step is performed on the heated slab, A hot rolling process is performed on the slab after descaling. A method for manufacturing steel plates, including The heating step includes a first heat treatment in which the slab is held at 1100 to 1300°C for 30 to 120 minutes in an atmospheric environment, and a second heat treatment in which, after the first heat treatment, the slab is held at 1100 to 1300°C for 30 to 120 minutes in a controlled nitrogen atmosphere. A method for manufacturing steel plates.

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