Cracking issue along side of the weld.

By Lawrence (*****)

Date 06-27-2007 21:19

Ray

If this is an old tank It may have been brazed, and welding over braze material is always a problem. If it is, try extra cleaning on both sides if possible.

If this is the case and you can't prep both sides, than in the end it may need to be rebrazed

By Kix

Date 06-28-2007 12:14

Yeah I don't really know how old these tanks are ad if he is welding over allready welded seams. Thats a very good possibility of what might be happening here. Hey, thanks for the quick response. I'll do some more digging and see what i can find out from him.

By js55

Date 06-28-2007 13:28

Gasoline is a 'hydro' carbon. I wonder if this is an issue.

By ramakant_v (*)

Date 06-28-2007 15:22

hello,

Can you elaborate a little on this issue:
1. what is the parent metal i.e. material of construction of the tanks
2. how old this is
3. what is the thickness of the tank wall..
4. what is the weld joint configuration?

RK

By reddoggoose (**)

Date 06-28-2007 20:53 Edited 06-28-2007 21:01

When I was a kid I use to work in a shop were we occasionally did custom machining and welding for a bike builder down the road. Used to get lots of used gas tanks in for repair or modification. We used to wash them out several times with soap and water then fill them with water and let them sit for a couple of days. After a couple of days the gas smell would go down alot, then we would weld them and never had any cracking problems. Like mentioned before gas is a hydrocarbon and will acutally seep into the steel itself and will sweat out when heat is applied. I don't know if that would cause the cracking, but I've seen stranger things. However we use to soak the tanks as a more of a safety precaution than anything.

By Tommyjoking (****)

Date 06-29-2007 08:14

Sorry no answer on the cracks either-more info.

To go along with reddogoose since we are talking about gas tanks. After washing/soaking it does not hurt a thing to drop a hunk of dry ice inside a tank to push out any residual fumes and remove oxygen before welding. better safe then boom as long as we are on that subject.

By Kix

Date 06-29-2007 12:13

Dry ice huh? That sounds like a pretty safe and cheap way to keep from going boom. Never heard of that so i'll have to throw that in my bag of tricks!!

By Kix

Date 06-29-2007 12:36

Ok i asked him a few more questions. These tanks are fairly new and some are after market and some are just stock Harley tanks. They are mig welded all over and i do not know with what wire. He ended up using a ER309L rod on it and the cracks went away. The tanks are washed and then purged with argon while welding. So what do ya guys think? I think i'm leaning toward the carbon leaching intot the steel theory because i don't know what else it could be.

By Lawrence (*****)

Date 06-29-2007 14:25

I'm kinda surprised some lugnut has not given us a specific on this one.

Your pretty close to Milwaukee anyhow... I wonder if those tanks did not get some sort of corrosion preventative coating inside that doesn't like weld...... hmmph

By Kix

Date 06-29-2007 15:04

This guy is in southern Illinois, but not that it really matters cause they still could use some sort of coating or sealer in production. He knows harleys pretty good so i'm sure he would probably be able to pick up on if there was some kind of coating though. Although companies are getting pretty sneaky these days and the stuff may be clear.

By reddoggoose (**)

Date 06-29-2007 15:30

Very well could be the seepage theory. The low carbon austenetic stainless filler will cut down on the amount of carbon added to the weld pool and also give better ductility for shrinkage stresses during cooling.