Zinc plated steel sheet having excellent fatigue strength of electrical resistance spot welds, and manufacturing method thereof

Patent metadata

Field	Value
Publication number	US-12486553-B2
Application number	US-202418661194-A
Country	US
Kind code	B2
Filing date	May 10, 2024
Priority date	Dec 3, 2019
Publication date	Dec 2, 2025
Grant date	Dec 2, 2025

Abstract

The present disclosure relates to a zinc plated steel sheet having excellent fatigue strength of electrical resistance spot welds and a method for manufacturing the same. According to an aspect of the present disclosure, a zinc plated steel sheet includes a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a concentration profile of one or two of oxygen, and silicon and manganese measured in a depth direction from the surface of the base steel sheet has a maximum point in the depth direction from the surface, and an absolute value of a difference between a depth at which the maximum point of the concentration profile of oxygen is formed and a depth at which the maximum point of the concentration profile of one of silicon and manganese is formed is 0.5 μm or less.

First claim

The invention claimed is:

1 . A method for manufacturing a zinc plated steel sheet, the method comprising:
heating a steel slab to a temperature of 950 to 1,350° C.; hot-rolling the steel slab to obtain a hot-rolled steel sheet; coiling the hot-rolled steel sheet at a temperature of 590 to 750° C. to obtain a hot-rolled steel sheet; pickling the hot-rolled steel sheet at a sheet-passing speed of 180 to 250 mpm; cold-rolling the hot-rolled steel sheet at a reduction rate of 35 to 60% to obtain a cold-rolled steel sheet; performing recrystallization annealing on the cold-rolled steel sheet in an atmosphere of a dew point of −10 to 30° C. at 650 to 900° C., wherein a sheet-passing speed during the recrystallization annealing is 40 to 130 mpm; and hot-dip galvanizing the annealed cold-rolled steel sheet, wherein the zinc plated steel sheet comprises: a base steel sheet; and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a concentration profile of oxygen, and a concentration profile of one or two of silicon and manganese measured in a depth direction from the surface of the base steel sheet have a maximum point in the depth direction from the surface, and an absolute value of a difference between a depth at which the maximum point of the concentration profile of oxygen is formed and a depth at which the maximum point of the concentration profile of the one or two of silicon and manganese is formed is 0.5 μm or less.

2 . The method for manufacturing a zinc plated steel sheet of claim 1 ,
wherein the recrystallization annealing is performed in a wet nitrogen gas atmosphere comprising 5 to 10 vol % of hydrogen (H 2 ).

3 . The method for manufacturing a zinc plated steel sheet of claim 1 ,
wherein the hot-dip galvanizing is performed by immersing the steel sheet in a hot-dip plating bath in which an Al concentration is 0.1 to 0.25 wt % at an entering temperature of the steel sheet of 420 to 500° C.

4 . The method for manufacturing a zinc plated steel sheet of claim 3 ,
further comprising, after the hot-dip galvanizing, alloying the steel sheet at a temperature of 480 to 560° C.

5 . The method for manufacturing a zinc plated steel sheet of claim 1 ,
wherein the steel slab has a composition comprising 0.05 to 1.5% of C, 2.0% or less of Si, 1.0 to 30% of Mn, 3% or less of S−Al (acid-soluble aluminum), 2.5% or less of Cr, 1% or less of Mo, 0.005% or less of B, 0.2% or less of Nb, 0.2% or less of Ti, 0.2% or less of V, 0.1% or less of Sb+Sn+Bi, and 0.01% or less of N.

6 . The method for manufacturing a zinc plated steel sheet of claim 2 ,
wherein the steel slab has a composition comprising 0.05 to 1.5% of C, 2.0% or less of Si, 1.0 to 30% of Mn, 3% or less of S−Al (acid-soluble aluminum), 2.5% or less of Cr, 1% or less of Mo, 0.005% or less of B, 0.2% or less of Nb, 0.2% or less of Ti, 0.2% or less of V, 0.1% or less of Sb+Sn+Bi, and 0.01% or less of N.

7 . The method for manufacturing a zinc plated steel sheet of claim 3 ,
wherein the steel slab has a composition comprising 0.05 to 1.5% of C, 2.0% or less of Si, 1.0 to 30% of Mn, 3% or less of S−Al (acid-soluble aluminum), 2.5% or less of Cr, 1% or less of Mo, 0.005% or less of B, 0.2% or less of Nb, 0.2% or less of Ti, 0.2% or less of V, 0.1% or less of Sb+Sn+Bi, and 0.01% or less of N.

8 . The method for manufacturing a zinc plated steel sheet of claim 4 ,
wherein the steel slab has a composition comprising 0.05 to 1.5% of C, 2.0% or less of Si, 1.0 to 30% of Mn, 3% or less of S−Al (acid-soluble aluminum), 2.5% or less of Cr, 1% or less of Mo, 0.005% or less of B, 0.2% or less of Nb, 0.2% or less of Ti, 0.2% or less of V, 0.1% or less of Sb+Sn+Bi, and 0.01% or less of N.

Assignees

• Posco Co Ltd
• Posco

Inventors

• Kang Ki-Cheol
• Lee Chung-Hwan

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C23C2/022

  by heating · CPC title

• C23C2/024

  by cleaning or etching · CPC title

• C23C2/02

  Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence) · CPC title

• C23C2/40

  Plates; Strips · CPC title