This is why you need a big gap for stainless

admin

A few weeks ago i posted a 750mm 304 pipe weld, and a few people were surprised that i liked a 5mm gap, so i though i might illistrate why i do.This is a 6" sch 10 304 stainless welded with 316L wire, 4 mm root gap (when i started) knife edge, root welded at 65-80 amps, cap at 85, this  is the root gap halfway through welding the root, about 3mm (1/8), root gap as im closing the root is down to .020, if id started with 5mm gap, id have at least 1.5 while closing.Welded free-hand for the root, walking the cup for the cap.Sent from my LG-P716 using Tapatalk
Reply:Sent from my LG-P716 using Tapatalk
Reply:Very nicely done! I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Good explanation as to your procedure. Good explaining that you're not filling a 5mm gap all around.   Might be a bit concerned about a dog-leg with the gap changing from 5mm to next to nothing.  I'd probably scatter a few more tacks so the change isn't so drastic.  Like your heat selection.  Hear so often that .130 wall would require 125 amps.
Reply:Looks good
Reply:Originally Posted by OldSparksGood explanation as to your procedure. Good explaining that you're not filling a 5mm gap all around.   Might be a bit concerned about a dog-leg with the gap changing from 5mm to next to nothing.  I'd probably scatter a few more tacks so the change isn't so drastic.  Like your heat selection.  Hear so often that .130 wall would require 125 amps.
Reply:Am guessing that some will question the HAZ coloring.  Reason being that if the gap was tighter then less weld would be required, the amps could go up, faster welding speed and less heat input.   I used to make job notes and for a similar project... 3" tube with a .115 wall...I recorded tight 3/32" (<2.4mm) gap with 1/16" filler, 50-60 amps.  This would allow for a cap almost half as wide as on a 5mm gap.  More of a beaded stringer then a weave.  Remember could get decent shiny colors through a pass but would lose it on the breakaways.  Never came out like the automobile header people produce but still got excepted by QC.   Who knows at what point HAZ coloring becomes critical?  Only ever had to worry about x-rays.
Reply:You may not believe this, but if you weld the top half first it doesn't close up near as much. Also cuts way down on the heat distortion pulling your pipe up.
Reply:This  is absolutely true, and good info! Originally Posted by TimmyTIGYou may not believe this, but if you weld the top half first it doesn't close up near as much. Also cuts way down on the heat distortion pulling your pipe up.
Reply:Originally Posted by TimmyTIGYou may not believe this, but if you weld the top half first it doesn't close up near as much. Also cuts way down on the heat distortion pulling your pipe up.