TIG porosity issue

[stevemfreeman]

Just got an old Miller TIG unit that I cleaned up and is working well. Bought new torch. Have 40 yrs experience with Oxy/Ace and about 20 yrs using a Miller MIG unit. Decided to teach myself TIG. The welds look OK for a beginner but at the end of each weld there is a crater about the same diameter as the width of the weld and the bottom of the crater looks very porous. I have tried leaving the torch in place longer after I stop the weld but that does not seem to help. Any suggestions as to what I am doing wrong. Flowmeter is set to 30 on the straight argon. Not sure you can see it well but I have uploaded a photo of the problem.

[Cgotto6]

Are you gradually rolling off the pedal as you sit still at the end of the bead? This helps

[cruizer]

Likely porosity all the way through, just out of curiousity, are you in the correct polarity, cause when I blow your pic up, the shape of the arc looks kinda odd. + turn your gas down to around 20CFH. Could just be that your freezing your weld.

[H80N]

Likely porosity all the way through, just out of curiousity, are you in the correct polarity, cause when I blow your pic up, the shape of the arc looks kinda odd. + turn your gas down to around 20CFH. Could just be that your freezing your weld.

+1 on this...

Polarity should be DCEN for steel

and gas flow (pure Argon) was way high.. somewhere between 15-20 Cubic Feet per Hour should be good...(depending on amperage, cup and tungsten sizes)
Too high a gas flow rate will cause turbulence and draw in air...
And..should be done in a shop with no breezes or puffs of air... even seemingly insignificant puffs of air can affect your weld..

here is a booklet with the basic parameters and settings

http://www.millerwelds.com/pdf/gtawbook.pdf

and the TIG resources section

http://www.millerwelds.com/resources/improving-your-skills/tig/

BTW... which machine?? pedal.. water cooled torch, cooler??.. or??
pics of your welder..

[Old Skool]

Backstep, add a dab of filler & ease off the pedal until your post flow stops.

[Portable Welder]

well, I guess I don't get to add much to this thread because you guys covered all the bases, The only thing I can comment about is you should clean the mill scale off the metal, The mill scale has a tendency to spit up onto your tungsten which causes you to have to regrind it clean and to a point a lot more often then normal.

What I commented about wont fix your problem, However make sure you have argon coming out a couple seconds after you let off the pedal.

If its a transformer machine you want to run 2% Thoriated tungsten that typically has a red band, Pure tungsten which has a green band for aluminum.

Make sure when grinding your tungsten that the grooves go length wise and not around in a circle.

Make sure the cup isn't to small, if it is and your gas is to high it will cause turbulence that will pull in outside atmosphere which will contaminate.

Definitely, make sure to ease off the pedal at the end of the weld.

[cope]

+1 on this...

Polarity should be DCEN for steel

and gas flow (pure Argon) was way high.. somewhere between 15-20 Cubic Feet per Hour should be good...(depending on amperage, cup and tungsten sizes)
Too high a gas flow rate will cause turbulence and draw in air...
And..should be done in a shop with no breezes or puffs of air... even seemingly insignificant puffs of air can affect your weld..

here is a booklet with the basic parameters and settings

http://www.millerwelds.com/pdf/gtawbook.pdf

and the TIG resources section

http://www.millerwelds.com/resources/improving-your-skills/tig/

BTW... which machine?? pedal.. water cooled torch, cooler??.. or??
pics of your welder..

30SCFH of Argon would make it act like a cutting torch with a scarfing tip.

[stevemfreeman]

Thanks for the advice. More photos just in case not set up correctly.

Thanks for all the great responses. I think the majority of the problem is just inexperience. I have uploaded photos of my TIG unit and the torch in case I have the electrode too far out etc. That is what the electrode looks like after about 4 welds like the one in the original photo. Also included a photo of the gate I am making and the water cooler. Welding mild steel. Here are my responses to most of the comments.

Are you gradually rolling off the pedal as you sit still at the end of the bead?
Probably not. Was just lifting foot off quickly I think. Starting holding torch in place after foot off pedal for post flow of argon but not sure I did that on the weld I sent in the photo.

are you in the correct polarity
I think so but have uploaded photo of my welder exactly as it was set up for weld in photo. Steel is about 3/16.

turn your gas down to around 20CFH
Will try that first thing tomorrow. Am using pure argon and in a shop with the fan turned off before I start welding.

If its a transformer machine you want to run 2% Thoriated tungsten that typically has a red band
Using red band electrode and ground in line with length of rod. Does it make any difference that I am using my belt sander rather than a grinder to shape the tungsten?

If you see anything else you think I am doing wrong in the new photos I am definitely up for any advice. I think I will go back to just practicing and use the mig for the rest of the welding on the gate.

[griff01]

Just got an old Miller TIG unit that I cleaned up and is working well. Bought new torch. Have 40 yrs experience with Oxy/Ace and about 20 yrs using a Miller MIG unit. Decided to teach myself TIG. The welds look OK for a beginner but at the end of each weld there is a crater about the same diameter as the width of the weld and the bottom of the crater looks very porous. I have tried leaving the torch in place longer after I stop the weld but that does not seem to help. Any suggestions as to what I am doing wrong. Flowmeter is set to 30 on the straight argon. Not sure you can see it well but I have uploaded a photo of the problem.

Your picture looks like you are running rg60 filler rod which is a gas rod. Your need er70-s_ rod.
Let us know.

Griff

[stevemfreeman]

Your picture looks like you are running rg60 filler rod which is a gas rod. Your need er70-s_ rod.
Let us know.

Griff

You are probably right. Did not know I needed a special filler rod. Just picked up a rod from my oxy acel rig. Will add to my list of things to change and try tomorrow.

[griff01]

You are probably right. Did not know I needed a special filler rod. Just picked up a rod from my oxy acel rig. Will add to my list of things to change and try tomorrow.

Don't bother asking how I knew.


Griff

[Portable Welder]

Your machine should be on High freq. start for steel and continuous for aluminum, your cup looks good but you have your tungsten sticking out to far, I typically keep mine out about 3/16".

Its best if you have a dedicated wheel for your tungsten grinding, I have what is known as a green wheel designed for hardened tungsten.
When out in the field and I don't have my green wheel I do get by with my hand grinder with a sanding disc. ( Not the best but does work )


Good luck.

[Cgotto6]

Yes, at the end of the bead, while still powered up, I come to a stop at the bead end, maybe dab once more with filler then sit still over the last portion of the weld and roll off power slowly and keep the torch still while post flow is running to make sure the bead stays enveloped in gas while it's solidifying.