Zinc plated steel sheet having excellent spot weldability and manufacturing method thereof

Patent metadata

Field	Value
Publication number	US-12344923-B2
Application number	US-201917415543-A
Country	US
Kind code	B2
Filing date	Dec 18, 2019
Priority date	Dec 19, 2018
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

Provided is a zinc plated steel sheet having excellent spot weldability and a manufacturing method thereof. The zinc plated steel sheet includes a steel sheet and a zinc plated layer formed on the surface of the steel sheet, wherein the ratio (a/b) between a widthwise average value (a) of thickness of an internal oxidized layer and a widthwise standard deviation (b) of thickness of the internal oxidized layer in the steel sheet may be 1.5 or more.

First claim

The invention claimed is:

1. A zinc plated steel sheet having excellent spot weldability, comprising:
a steel sheet; and
a zinc-based plated layer formed on a surface of the steel sheet,
wherein a ratio (a/b) between a widthwise average value (a) of thickness of an internal oxidized layer and a widthwise standard deviation (b) of thickness of the internal oxidized layer in the steel sheet is 1.5 or more, and
wherein the widthwise average value (a) of the thickness of an internal oxidized layer and the widthwise standard deviation (b) of thickness of the internal oxidized layer are obtained by dividing the overall width of the steel sheet at equal intervals, measuring the thickness of the internal oxidized layer at each divided point, and calculating the average and standard deviation of these values.

2. The zinc plated steel sheet having excellent spot weldability of claim 1 , wherein the widthwise average value (a) of the thickness of the internal oxidized layer is 3.0 μm or more.

3. The zinc plated steel sheet having excellent spot weldability of claim 1 , wherein the widthwise standard deviation (b) of the thickness of the internal oxidized layer is 2.0 μm or less.

4. The zinc plated steel sheet having excellent spot weldability of claim 1 , wherein a plating adhesion amount of the zinc-based plated layer is 30 to 70 g/m 2 .

5. The zinc plated steel sheet having excellent spot weldability of claim 1 , wherein the zinc-based plated layer is a galvannealed (GA) layer having an alloying degree of 8 to 13% by weight.

6. The zinc plated steel sheet having excellent spot weldability of claim 1 , wherein the steel sheet has a composition including 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. A method of manufacturing a zinc plated steel sheet having excellent spot weldability, comprising steps of:
hot rolling a 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;
heating an edge portion of the coiled hot-rolled steel sheet at 600 to 800° C. for 5 to 24 hours;
pickling the hot-rolled steel sheet with a 5-25% hydrochloric acid solution at a plating speed of 180 to 250 mpm;
cold rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet;
annealing the cold-rolled steel sheet in an atmosphere with a dew point of −10 to 30° C. at 650 to 900° C.; and
hot-dip galvanizing the annealed cold-rolled steel sheet.

8. The method of manufacturing a zinc plated steel sheet having excellent spot weldability of claim 7 , further comprising
a step of galvannealing the hot-dip galvanized cold-rolled steel sheet.

9. The method of manufacturing a zinc plated steel sheet having excellent spot weldability of claim 8 , wherein the galvannealing treatment is performed at a temperature of 480 to 560° C.

10. The method of manufacturing a zinc plated steel sheet having excellent spot weldability of claim 7 , wherein the steel slab has a composition including 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.

11. The zinc plated steel sheet having excellent spot weldability of claim 2 , wherein the steel sheet has a composition including 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.

12. The zinc plated steel sheet having excellent spot weldability of claim 3 , wherein the steel sheet has a composition including 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.

13. The zinc plated steel sheet having excellent spot weldability of claim 4 , wherein the steel sheet has a composition including 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.

14. The zinc plated steel sheet having excellent spot weldability of claim 5 , wherein the steel sheet has a composition including 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.

15. The method of manufacturing a zinc plated steel sheet having excellent spot weldability of claim 8 , wherein the steel slab has a composition including 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
• Posco Co Ltd

Inventors

• Kang Ki-Cheol
• Lee Sea-Woong
• Lee Kyoo-Young
• Kim Jong-Ho
• Im Young-Roc

Classifications

• C21D8/02

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

• C23C2/0222

  in a reactive atmosphere, e.g. oxidising or reducing atmosphere (C23C2/024 takes precedence) · 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

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• C23C2/0224

  Two or more thermal pretreatments · CPC title