Advanced high strength zinc plated steel sheet having excellent surface quality and electrical resistance spot weldability

Patent metadata

Field	Value
Publication number	US-12000008-B2
Application number	US-202017787174-A
Country	US
Kind code	B2
Filing date	Dec 18, 2020
Priority date	Dec 20, 2019
Publication date	Jun 4, 2024
Grant date	Jun 4, 2024

Abstract

The present disclosure relates to a high-strength hot-dip galvanized steel sheet having excellent surface quality and electrical resistance spot weldability, and a method for manufacturing the same. A galvanized steel sheet according to an aspect of the present disclosure is a galvanized steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a ratio (a/b) of a hardness of a surface layer portion (a) to a hardness of an internal portion (b) of the base steel sheet may be less than 0.95.

First claim

The invention claimed is:

1. A galvanized steel sheet comprising:
a base steel sheet; and
a zinc-based plating layer formed on a surface of the base steel sheet,
wherein the base steel sheet includes a surface layer portion and an internal portion,
wherein a ratio (a/b) of a Vickers hardness of the surface layer portion (a) to a Vickers hardness of the internal portion (b) of the base steel sheet is less than 0.95,
wherein during spot welding, a length of a B-type LME crack generated at a shoulder portion of the spot weld is 100 μm or less and a C-type LME crack is not observed,
wherein the galvanized steel sheet has a powdering property in which a length of the plating layer peeled off from the tape is 10 mm or less, and
wherein a peeling does not occur in a sealer bending test.

2. The galvanized steel sheet of claim 1 , wherein a coating weight of the zinc-based plating layer is 30 to 70 g/m 2 .

3. The galvanized steel sheet of claim 2 , wherein the base steel sheet has a composition containing, by weight ratio, 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.

4. The galvanized steel sheet of claim 3 , wherein a thickness of the base steel sheet is 1.0 to 2.0 mm.

5. The galvanized steel sheet of claim 2 , wherein the surface layer portion contains internal oxides containing at least one of Si, Mn, Al, and Fe.

6. The galvanized steel sheet of claim 1 , wherein the base steel sheet has a composition containing, by weight ratio, 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 galvanized steel sheet of claim 6 , wherein a thickness of the base steel sheet is 1.0 to 2.0 mm.

8. The galvanized steel sheet of claim 1 , wherein the surface layer portion contains internal oxides containing at least one of Si, Mn, Al, and Fe.

Assignees

• Posco

Inventors

• Kang Ki-Cheol
• Lee Chung-Hwan
• Kim Yong-Joo
• Lee Kang-Min
• Lee Kyoo-Young

Classifications

• C21D8/02

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

• C21D9/46 Primary

  for sheet metals · CPC title

• B32B15/01

  all layers being exclusively metallic {(making layered metal workpieces by pressure cladding B23K20/22; making coatings with a metallic material characterised by its composition C23C30/00)} · CPC title

• B32B15/013

  one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium · CPC title

• B32B15/04

  comprising metal as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042)} · CPC title