Fracturing of Seam Welded G60 IF Steel
Fracturing of Seam Welded G60 IF Steel
(OP)
When a seam-welded 5-gallon body is flanged (to accept top and bottom), the nugget on the flange fractures sometimes. The sample I have has one flange cracked and the other OK. The steel is .005 C, .13 Mn, .008 S, .043 Al, .058 Ti, .0039 N. Base metal ASTM grain is 9-10. Zinc coating weight is high at 1.2 oz/ft.sq. The properties of the base steel blank are uniform edge to edge, good DDS. The grain in the HAZ is blown to ASTM 2 to 4 and no failure. The grain in the fusion zone is ASTM 7 to 8 around the contact region with surface grain ASTM 4 to 5. In the failed nugget, the grain boundaries of surface grains have separated and there is mainly transgranular cracking through the nugget. No obvious collections of zinc in the joint. The fracture is brittle, not ductile.
Seems like some sort of embrittlement? What is the cause? Is this a form of CW embrittlement? Has increasing the welding current to accommodate the heavy zinc coating caused problems?
Seems like some sort of embrittlement? What is the cause? Is this a form of CW embrittlement? Has increasing the welding current to accommodate the heavy zinc coating caused problems?





RE: Fracturing of Seam Welded G60 IF Steel
RE: Fracturing of Seam Welded G60 IF Steel
RE: Fracturing of Seam Welded G60 IF Steel
I don't think you'll find the Zn via etching.
RE: Fracturing of Seam Welded G60 IF Steel
RE: Fracturing of Seam Welded G60 IF Steel
ASTM is based on single polygonal ferrrite grain, in weld you have high speed coled ferrite grains which has various shape and dimension,
If -Ti has an higher graingrowth tendecy in HAz but not necessarly in FZ, IF-Boron,has no grain graowth tendency in HAZ as well as at weld junction.
I do not think that zinc can couse those probelm may be dicontiounty but not transgranuler crack which is more for high stregth hardenabil steel;
good luck
alex