# US 12,000,008 B2 · Advanced high strength zinc plated steel sheet having excellent surface quality and electrical resistance spot weldability

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,000,008 B2
- Document ID: US12000008B2
- Status: Granted
- Kind: B2
- Application number: 17/787,174
- Filed: 2020-12-18
- Published: 2023-01-26
- Granted: 2024-06-04
- Earliest claimed: 2019-12-20
- Assignees: Posco
- Applicants: Posco
- Inventors: Ki-Cheol Kang; Chung-Hwan Lee; Yong-Joo Kim; Kang-Min Lee; Kyoo-Young Lee
- Web page: https://patentgrep.com/patent/US12000008B2

## CPC

- C21D 9/46: for sheet metals
- B32B 15/01: 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)}
- B32B 15/013: {one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium}
- B32B 15/04: 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)}
- B32B 15/043: {of metal (B32B15/01 takes precedence)}
- B32B 15/18: comprising iron or steel {(B32B15/011, B32B15/012 and B32B15/013 take precedence)}
- C21D 1/19: by interrupted quenching
- C21D 1/25: Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
- C21D 1/76: Adjusting the composition of the atmosphere
- C21D 1/84: Controlled slow cooling (cooling-beds for metal rolling B21B43/00)
- C21D 3/04: Decarburising
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C21D 8/0236: {Cold rolling}
- C21D 8/0257: {with diffusion of elements, e.g. decarburising, nitriding}
- C21D 8/0263: {following hot rolling}
- C21D 8/0273: {Final recrystallisation annealing}
- C21D 8/0278: involving a particular surface treatment (C21D8/0294 takes precedence)
- C21D 9/562: {Details}
- C22C 38/001: {containing N}
- C22C 38/008: {containing tin}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/18: containing chromium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/34: with more than 1.5% by weight of silicon
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/58: with more than 1.5% by weight of manganese
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/022: {by heating}
- C23C 2/0224: {Two or more thermal pretreatments}
- C23C 2/024: {by cleaning or etching}
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath
- C23C 2/29: {Cooling or quenching}
- C23C 2/40: Plates; Strips
- C23C 28/025: {with at least one zinc-based layer}
- C23C 28/3225: {with at least one zinc-based layer}
- C23C 28/345: {with at least one oxide layer}
- C23C 30/00: Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process (C23C26/00, C23C28/00 take precedence)
- C23C 30/005: {on hard metal substrates}
- B32B 2307/732: Dimensional properties
- Y10T 428/12583: Component contains compound of adjacent metal
- Y10T 428/1259: Oxide
- Y10T 428/12597: Noncrystalline silica or noncrystalline plural-oxide component [e.g., glass, etc.]
- Y10T 428/12611: Oxide-containing component
- Y10T 428/12618: Plural oxides
- Y10T 428/1266: O, S, or organic compound in metal component
- Y10T 428/12667: Oxide of transition metal or Al
- Y10T 428/12799: Next to Fe-base component [e.g., galvanized]
- Y10T 428/12958: Next to Fe-base component
- Y10T 428/12965: Both containing 0.01-1.7% carbon [i.e., steel]
- Y10T 428/12972: Containing 0.01-1.7% carbon [i.e., steel]
- Y10T 428/12993: Surface feature [e.g., rough, mirror]
- Y10T 428/24942: including components having same physical characteristic in differing degree
- Y10T 428/2495: Thickness [relative or absolute]
- Y10T 428/24967: Absolute thicknesses specified
- Y10T 428/24983: Hardness
- Y10T 428/26: Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
- Y10T 428/27: Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.]
- Y10T 428/273: of coating
- 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 (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

The galvanized steel sheet of claim 1, wherein a coating weight of the zinc-based plating layer is 30 to 70 g/m2.

### Claim 3 (depends on 2)

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.

### Claim 4 (depends on 3)

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

### Claim 5 (depends on 2)

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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 6)

The galvanized steel sheet of claim 6, wherein a thickness of the base steel sheet is 1.0 to 2.0 mm.

### Claim 8 (depends on 1)

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.