Granted Patent B2

US 12,194,560 · App. 16/770,295 · Granted Jan 14, 2025

Inventor: Jai-Hyun Kwak (Gwangyang-si, KR)

Assignee: POSCO CO., LTD

B23K11/11B23K11/16B23K11/34C23C2/06B23K2103/04

Abstract

Claims (15)

1. A method for preventing spot welding cracking of a galvanized steel sheet, comprising:

preparing a galvanized steel sheet on which including a base steel sheet and a plating layer formed on at least one surface of the base steel sheet;

press molding the galvanized steel sheet thereby changing the galvanized steel sheet for obtaining a desired shape to form a molded galvanized steel sheet;

heating a welding spot of the molded galvanized steel sheet to a temperature of 770° C. to 950° C. directly before welding thereby increasing a concentration of Fe in an interface between the plating layer and the base steel to be 65 wt % or more; and

spot welding the heated welding spot,

wherein the heating is performed using a current in the range from 0.4 times of an exclusion-occurring current to the exclusion-occurring current,

the heating is performed an area over 1.2 times a nugget diameter, and

the spot welding is conducted without cooling the heated welded spot.

2. The method of claim 1 , wherein the heating is performed using a tungsten or copper electrode.

3. The method of claim 1 , wherein an average Fe concentration in an entire area of the plating layer is 50 wt % or more.

4. The method of claim 1 , wherein, when measuring glow discharge spectrometry (GDS) of the plating layer, an average Fe concentration, represented by Equation (1) below, is 0.5 or more:

Average Fe concentration=Fe (%)/(Fe (%)+Zn (%)).  Equation (1)

5. The method of claim 1 , wherein the base steel sheet is an advanced high strength steel (AHSS) having tensile strength of 980 MPa or more.

6. The method of claim 1 , wherein the base steel sheet is an advanced high strength steel (AHSS).

7. The method of claim 1 , wherein the plating layer is a zinc-based alloying plating layer.

Assignments (3)

Priority Claims (1)

Continuity (1)

References Cited (27)