harv... help welding SS...

[gmason]

Harv and anyone else with Stainless Steel welding knowledge.

I'm trying to weld together two 8" dia SS 1/8" pipe for a flue. I'm using my Henrob torch with a carburizing flame <A target="_blank" HREF=http://www.cut-like-plasma.com/info_welding_stainless_steel.htm>http://www.cut-like-plasma.com/info_welding_stainless_steel.htm</A>

I'm using an 1/8" SS rod and I tacked 3 spots around the pipe to start. Problem was that by the time I got around to the first weld spot, that weld had cracked from the heat(my guess). Although, the area of the welding glowed cherry red, the area 1' from the weld remained closs to original temp(unlike mild steel).

After welding several beads around some more of the pipe, I saw where a number of welds had cracked also. I did not have the pipe clamped down. It's way too big for anything clamp system I've got.
Is this normal for SS, was I using too much heat/ too little? The weld beads I ran looked alright, nothing as good as I can weld with a stick, but they looked like good penitration and no slag of course.

Any suggestions? I can't recall off hand the rod number I was using, but I'll look at my welding class tonight to see what bin I got the rod from.

Thanks Harv and others..
gary

 

[Anonymous Poster]

I know you can use a torch, although I'm not sure of the quality. When I was a welder, we used a Tig welder and filler rods. Works extreamly well.

 

[Anonymous Poster]

Sounds like stress is causing the cracks as you work on the other side.
Fixturing may help, use a piece of C chanel and chains with draw bolts to clamp the pipes in line.

 

[RJohnson]

If you are welding any of the austentic stainless steels (300 series) then a 308 rod should be used. Stainless steel is real bad about setting up thermal stresses. Heat does not transfer through it like carbon steel. i would suggest that you make your tack welds bigger and then skip weld the joint. Weld for 2 or 3 inches and then go to the opposite side and weld about the same amount. Return to your first weld and add another 2 or 3 inches then go back to the opposite side. This should help in offsetting your weld stresses.
Any kind of torch welding process will have high heat input, if it continues to crack then you may have to go to an electric arc process to speed up your welding and reduce your heat input.

Randy

 

[wroughtn_harv]

Just got back in from being on the road.......

Thanks Randy,

That was what I was going to suggest. Welding a couple of inches in one spot. And then moving across to weld another couple of inches. Sorta along the principle of torqueing down a wheel on a hub.

 

[gmason]

I tried anchoring it with a rachet tie down and welding a small spot, but within a few seconds of starting the 1" weld, there went a BANG as the weld about 4" from the spot cracked/split for about 5" around the pipe.

This is some tricky stuff, I've seen examples of SS pipe welded at class and they look very nice, I'm going to have my instructor walk me through the process tomorrow night.

gary