Welding Tips and Tricks

Hi Jody,

I discovered the existance of your superb website way too late. It is absolutely awesome for a non-professional guy who enjoys welding (like me) and much appreciated!

Short introduction: I am a hobbyist welder who got taught basic TIG techniques during a 3-day workshop and pretty much selftaught everything else i know from being an formula SAE team member and having to do all the fabrication jobs. Most of the stuff was welding up various spaceframes and suspension parts, mostly made of 4130 (25CrMo4). For 4130 a filler rod called WCrMo1Si was used, mild steel was welded with a rod called FGMO.

Every now and then, the weld has blown out on me while cooling down. Can you please make a Video on this subject?
I understand that closing up a weld around some kind of tubing can cause this problem due to the air inside the tube expanding under heat. However, this problem has happened to me many times right in the middle of a weld where the gas inside the tube would have had lots of space to escape elsewhere. Cleaning the joint thoroughly with a wire brush and brake cleaner didn't help. After grinding out the faulty bit of weld and rewelding, the problem occured again, most of the time even worse. This has happened to me both on welding cold drawn seamless 4130 and mild steel tubing joints, as well as welding on brackets and tabs to such tubing.

Best regards from germany!
Carsten

Welcome, Carsten!

I recently had the experience of TIG welding on steel tube that was coated with zinc rustproofing inside and out. Although I cleaned the exterior to bright shiny steel, the zinc on the interior of the tube corrupted the weld and would boil out of the weld while cooling, creating porosity. Is this what you're seeing, and is it possible there is some contamination that you are not aware of?

Just a note: "Cleaning the joint thoroughly with a wire brush and brake cleaner..."
Please be careful with brake cleaner: if you weld over liquid brake cleaner you'll create phosgene gas, a highly toxic lung irritant. May I suggest you avoid using brake cleaner: another useful alternative is acetone.

Welcome, Carsten,

If, as you said, there is plenty of room for gas to escape, then I think Artie has the right idea... There's some sort of contamination on the back of the weld boiling it's way out.

Or, perhaps, some inclusions in very poor quality steel, or what you're welding on is actually "pot metal", which is a very random alloy of leftovers.

Steve S

Uuuh phosgene... NOT NICE! Thanks for that advice, I will definately use acetone from now on! Brake cleaner was just convenient because it comes in a spray can, but to hell with convenience in that case.

The tubing that i have been welding was never zinc coated. That cold drawn stuff (new and bought directly from thyssen krupp, by the way, so I think potmetal is out of the question) has a passive surface, no idea what exactly it is though. It welds fine on the outside. Perhaps there was some corrosion protection oil or something like that on the inside of the tube.

Here's another question: when you have already tacked the spaceframe together and can't reach the inside of the tube for cleaning purposes anymore: How do the professionals deal with a blown out weld?

Speaking of health hazards pertaining to chemicals,'' acetone can be absorbed through the skin and damage the kidneys, use gloves."'.......ron

One time I was having fits with the weld continually blowing out, it was frustrating.
I was (trying to) weld some (about) 3/16" wire to some (about) 1/4" sq rod.
Turns out, the 1/4 rod was 'key-way' stock. I dont know what was in it, and it was HARD. And for all practical purposes, unweldable. -c-

(Also a very weak weld, it was in a NOT critical situation, eventually, I changed things)