Tig trouble - blistering in welds

Date 04-07-2007 12:21

Hey berntd,
Your description of blistering and volcano appearance indicate moisture and vaporing in the metal along with perhaps dirt residue. The oxy/acet. application and remelting has heated the metal to dissipate this moisture. Brown deposits indicate dirt and rust forming on the welded area. Your statement of getting "reasonable welds" should also tell you that you need to do some serious practicing and learn welding techniques to improve your skills. You must make a mindset that "reasonable" is not acceptable...."excellent" is acceptable. Consider some schooling in a Vo-Tech school, college class, or even a high school class to enhance your welding education and proficiency. With experience, you will find the answers to problematic issues as this and will be better prepared to understand welding parameters to avoid these conditions. Learning will not be acquired overnight....it takes work, practice, and the thought that you will learn and get better with each mistake....there is no room for frustration and anger....simply walk away, think, and start another time.....Denny

By berntd Date 04-07-2007 22:54

Hi, thanks for that.

I cannot understand how moisture would get into the weld puddle unless it comes out of the argon cylinder perhaps?
How do I prevent this?

The symtoms certainly appear like there is something in there that boild. These craters bubble and pop open like there is something boiling in them and never stop as long as I keep heating or reheating later or whatever. In fact, they often end a pin holes through the sheet.

When using the oxy, they never even bubble again, they simply melt shut immediately.

I read all the fine print on my filler rods' packet yesterday and although the large print state CIGWELD TIG & GAS WELDING RODS Comweld, the small print at the bottom states "not suitable for TIG welding".

They are annealed low carbon mild steel rods with a black coating and maybe I need copper coated ones instead?

I wonder if this has anyting to to with it?

Can it be that the old steel I am welding to contains something that makes it unsuitable for TIG?

Kind regards
Bernt

By yorkiepap (***)

Date 04-08-2007 00:34

Hey berntd,
Moisture is simply condensation caused by the sudden mix of heat and cold. The metal frame is cold and your welding is hot. When using TIG, the heat is instantaneous and when it meets the cold frame, condensation forms, thus the bubbling as the moisture tries to evaporate. The oxy/acet. application heats the metal to the point that the condensation is evaporated before the metal reaches its melting point. Just as a warm air mass meets a cold air mass.....rain. You would be best to preheat a cold frame to dissipate the moisture prior to TIG. That may cure your issue with bubbling & cratering. I don't believe the steel you are trying to weld is any different than any other frame steel. The only difference in steels is the grade. Hope that helps a bit....Denny

By billvanderhoof (****)

Date 04-08-2007 03:10

Each molecule of rust comes with several molecules of water adsorbed onto it so if any rust remains the tig arc will drive out the adsorbed water giving problems. There are special rods for TIG somewhat different chemically from gas rods. Other schmutz (technical word) on the surface will also outgas and cause trouble. Sometimes contamination can be under the surface of the steel (especially true for ground engaging parts like cultivator shoes). Try different material and correct rods (or mig wire) and see if the problem goes away. Then work back until you find the problem.
Bill

By berntd Date 04-08-2007 22:32

Hi Denny, Bill.

Thanks for all the suggestions!
As soon as this easteris over, I will get the proper welding rods.
I will see if I can preheat the metal a bit maybe with the oxy to overcome the potential moisture problems.

Unfortunately the rust particles are not that easy to get rid off. Since I am welding sheet patches into existing old panels form 1955, there will always be some rust at the rear of the panels ehich is not accessible for cleaning.

On a different note, what is the best way is to get rid of such bubbles once they have formed?
The oxy method works but the panel distortion comes into it and this nullifies the advantages of using the TIG in the first place.

Maybe there is some sort of flux or something that will aid the removal of these bubbles?

By the way, I did show this to a welder (he uses mig) and he thought that there was too much oxygen in the weld or metal. I never quite understood what he meant and he wasn't very helpful as he was very busy.

Kind regards
Bernt