Bubbles in my weld, why?

[Iron Spade Cycles]

Alright well this is just a question for all you TIG welders out there. Although I have been welding most of my life I just recently bought a mid 90's Miller Dial-Arc 300 machine about a year ago. I had had previous exposure to TIG welding on a friends much newer Square-wave machine but I couldn't afford the $7000 price tag just yet. So I bought a very good used machine for just under $1000.

Well last week I spent several hours welding up some 1x1 angle and the welds were coming out wonderful, like a wiggly stack of dimes. My hands shake a little as I get older. LOL, but when I was welding up a couple pieces of 1/2 inch plate the weld puddle began to bubble as the pool cooled leaving pits in the weld. When I went back over the weld with just the torch and no filler a nice pool would form but just as it would cool it would bubble again.

There is a slight chance I mistakenly grabbed welding rod from my Oxy/Ace rig as it sits right next to my TIG welding rod, but could that be the problem? Is there some property of Oxy/Ace specific rod that reacts differently with the TIG process of welding? I'm also running straight Argon for shielding gas if that makes a difference.

Thanks guys for your help. Later Travis

[Rick (madera)]

without seeing pictures, my first guess is you were welding hot rolled steel.

[bill wallace]

yes, you are welding contaminated material. Try cleaning it down to bright shiny finish & dont put in to much heat. Cold rolled steel will have a much better weld apperance than hot rolled or fabricated metal.

[pro70z28]

Also, the only way to get a good weld is to completely grind out the contaminated weld or you just keep chasing it.

[bobadame]

Make sure the tungsten is not contaminated. If it is, re-grind it. And at the end of each weld bead, hold the torch in place until the post purge times out. This helps to prevent oxidation in that area.

[mcreynoldsair]

low gas pressure

[pro70z28]

Open door letting wind blow the argon away.

Too much gas pressure creating too much argon velocity which may suck contaminated air into the argon stream.

[Iron Spade Cycles]

I have this neat little slide rule chart I picked up from my gas supplier that you pick the material your welding and the thickness and it tells you which tungsten size/cup size to use and what gas type, flow cfh and PSI is suggested. I have a question for you guys. When I choose steel, butt joint, 1/4" thick it suggests a flow cfh of 13 and a PSI of 20. If the flow gauge on the tank is to set the cfh, how do I know the PSI or am I getting the gauge confused? It does have a gauge with tank pressure so I know when the tank is low or worse, empty but not line pressure. I'm also using the Red 2% Thoria tungsten.

I am more inclined to think that the metal was contaminated as it was old scrap I had laying around and it was coated in an industrial primer and a little rusty, I didn't have what I needed to clean the surface adaquately before I started the weld. I did scrap it afterward for a new piece of steel the right size but it left me a little concerned and miffed.

Thanks guys for the help.

Later Travis

[pro70z28]

Sounds like contaminated metal as you and others have said. I usually set my PSI at 15-16 + or -, no matter if I am TIGing metal or aluminum and don't usually have argon coverage issues. I could (and maybe should) probably turn it down a little and save gas...? Pressure is important but there is a fairly wide flow window you can safely weld in as long as there's no outside forces blowing the argon off the bead.

[whateg01]

When TIG welding, it is important to have "clean" metal. Oddly as it seems, it is important to grind the cut area clean if it was flame cut or plasma cut. I don't fully understand the reason, but it is.

Dave

[Iron Spade Cycles]

Gary I hope this doesn't sound like an idiot question but can you post a picture of your Argon regulator and explain how you adjust the line pressure? The reason I ask is I think my reg only allows for a flow rate change, does this sound odd?

Thanks for the help guys. Later Travis

[pro70z28]

http://img.photobucket.com/albums/v205/pro70z28/ArgonTank.jpg

Right gauge is bottle pressure. Left is line pressure after the regulator.

[Iron Spade Cycles]

Thanks Gary, mine is totally different. Just a tank gauge with a flow meter tube. I wonder if I can change line pressure or it it remains constant?

[whateg01]

Gary I hope this doesn't sound like an idiot question but can you post a picture of your Argon regulator and explain how you adjust the line pressure? The reason I ask is I think my reg only allows for a flow rate change, does this sound odd?

Thanks for the help guys. Later Travis

You don't adjust for a certain pressure. You are concerned about the flow rate. That's why Gary's gauge is calibrated in CFH, not PSIG, (even though on a flow gauge like that, you are actually adjusting the pressure on the upstream side of a fixed orifice).

If you are adjusting the flow meter for the desired flow, that's all you need to be concerned with, not line pressure.

Dave

[TheRodDoc]

Gary's picture is of a pressure regulator. No flow meter on it. These aren't to accurate as far as the amount of gas at the torch. Since the low side gage is only reading the pressure going in at that end of line, It can be much less flow at torch. Depending on tig valving, hose type and dia., length of hose and size of torch it self. (passages in totch) Ristricting the line somewhere will raise the pressure on the gage while the flow at the torch gets less. Like putting your finger over the end of a garden hose.

Same as a plain air regulator for painting. Depending on hose size and length you might have to set the regulator at 50 lbs. to get 40 at gun.

A flow meter shows the real flow through the line regardless of all the things stated above. And most info for tig welding is listed as flow, not pressure.

[whateg01]

Travis,
You mentioned grabbing the wrong rod. That is a possibility. So is not having enough shielding gas. As far as where to set the shielding gas goes, though, it's not really all that important exactly how much flow you have, as long as it's enough, and not too much. If you are anywhere between 10 CFH and 20 CFH, it is PROBABLY ok, unless you have a stiff breeze through the work area. And if it welded ok before, and you haven't changed it, then it probably still is ok. I would focus on the work piece. Grind the areas down that you are welding and see how it goes.

Dave

[welderboy]

I agree that contaminates...most likely mill scale or some type of oil. you must maintain the cleanest of parts to realize a good tig weld. If we can't take the time to prep than better off to mig weld....it's a little more forgiving

[Bgbkwndo]

TIG wire will have the I.D. stamped on each end. I use ER 70S-6 with excellent results. And as stated here several times........cleanliness is an absolute must! On thin sections, grind the "backside" too.

Bgbkwndo.

[TheRodDoc]

Dirt can cause it but more likely in your case you were boiling the puddle. 1/2" plate is to thick to weld with most peoples tigs in a single pass. trying to get a proper sized bead with a tungsten that is to small and not enough amperage causes you to have to travel way to slow which can cause the puddle to boil. And if it does you get bubbles much like the ones cumming up from the bottom of a pan of boiling water.

Steel like water has it's 3 states. Solid, liquid and a gas. It melts at around 2400 degrees and boils at about 5400 degrees. Depending on its alloy. And with a tig it is quite easy to get the puddle over the boiling point.

To weld your plate you would need a mimum of 300 amps and a size or two bigger tungsten then 1/8" To get the travel speed back up.