US 12,459,049 B2
Method for welding a zinc coated steel sheet
Gyu-Yeol Bae, Incheon (KR); and Ho-Soo Kim, Incheon (KR)
Assigned to POSCO CO., LTD, Pohang-si (KR)
Appl. No. 17/289,537
Filed by POSCO, Pohang-si (KR)
PCT Filed Oct. 8, 2019, PCT No. PCT/KR2019/013207
§ 371(c)(1), (2) Date Apr. 28, 2021,
PCT Pub. No. WO2020/091254, PCT Pub. Date May 7, 2020.
Claims priority of application No. 10-2018-0129810 (KR), filed on Oct. 29, 2018.
Prior Publication US 2021/0394294 A1, Dec. 23, 2021
Int. Cl. B23K 9/23 (2006.01); B23K 9/09 (2006.01); B23K 9/095 (2006.01); B23K 9/10 (2006.01); B23K 9/16 (2006.01); B23K 101/34 (2006.01); B23K 103/04 (2006.01)
CPC B23K 9/23 (2013.01) [B23K 9/092 (2013.01); B23K 9/095 (2013.01); B23K 9/1006 (2013.01); B23K 9/16 (2013.01); B23K 2101/34 (2018.08); B23K 2103/04 (2018.08)] 3 Claims
OG exemplary drawing
 
1. A lap-joint welding method of welding a first zinc coated steel sheet and a second zinc coated steel sheet stacked to partially overlap the first zinc coated steel sheet using a welding wire, to reduce a porosity defect of welded metal, comprising:
welding, wherein the welded metal has a pore area ratio of 0.97% or less and have a tensile strength of 700 MPa or more,
wherein a gap of a welded joint formed by the method is 0 mm,
wherein the welding current is supplied as a bidirectional pulse current in which positive direct current and negative direct current are of equal and constant absolute value in a range from 200 A to 270 A, and
wherein a welding polarity is alternately altered to satisfy a welding polarity fraction, in a range of 0.25 to 0.35, the welding polarity being defined by
ENR,%/(EPR,%+ENR,%)
where, ENR, % is a fraction of time for which current through the welding wire is negative direct current, and EPR, % is a fraction of time for which current through the welding wire is positive direct current.