TIG Tungsten Angle

[pulser]

Say your going to TIG weld a flat position square butt joint on 1/4" thick 304 stainless steel. Your not going to add any filler, simply fuse the joint and get the best penetration you can. You are limited by your puny power supply to 100 amps.

The only variable you can change is the grind angle on the tungsten electrode, everything else, from travel speed to gas type is fixed.

So, in your experience or gut feeling, which of the following will give the best penetration, and do you have a reason why?

A. Really sharp = 10 - 30 degree included angle.
or
B. Really blunt = 90 - 120 degree included angle.

[zapster]

really really really sharp...
about a 20 degree angle will work...

...zap!

[prop-doctor]

point yes
travel speed on Tig? we on a timer?
i got lost there
ya got to speed up or slow down some way
working temp of the metal, im welding
travel or speed is why we do Tig
MORE CONTROL

[Engloid]

If you go too sharp and too hot, you will burn the tungsten off into the weld...but go as sharp and hot as you can.

[pulser]

OK, didn't get very many bites on this fly, and yeh I suspect 99% of the welders out there will tell you that a sharp tungsten gives the most penetration. Well welding can be a funny thing, there are a bunch of variables that affect TIG weld shape and actual results may not always follow theory, BUT THE THEORY IS, A BLUNT TUNGSTEN WILL IMPROVE PENETRATION OVER A SHARP TUNGSTEN.

Blasphemy you say, no way, I always use a sharp tungsten! Well, have you ever tried a blunt end prep, say 75 to 120 degrees? Probably not, because we are all first shown how to grind the tungsten to a point, the arc starts easy, and it works just fine. For most all welding who cares, grind it sharp, I agree. I would just like to point out the possibility that a blunt tungsten may actually improve penetration, and a reason why.

Take a look at what Pro-Fusion says about electrode tip geometry:
http://www.pro-fusiononline.com/tungsten/geometry.htm

In theory, the arc tends to come off the sides of the conical electrode, and since the sides of a sharp electrode are more perpendicular to the base metal than the blunt electrode, the arc is broader and less concentrated, giving less penetration.

This attached photo, copied from the AWS Welding Handbook, shows what I'm talking about. Note the welds shown are spot welds, so we don't know what the effect of traveling would have on these welds. Also, this is a topic for later, but we don't know the chemistry of this base metal (particularly Sulfur) and this can have a substantial effect on fluid flow and weld shape.

http://i94.photobucket.com/albums/l1...trodeAngle.jpg

Wadda u think?

[Brett]

Funny you should mention this ,
Just yesterday I was fusing 50mm 1.6 wall 316 to a 6mm 316 base plate and this job specified 2 posts with a 3mm wall.
I found that a 45 deg. angle worked much better on the thicker wall.
I was using a PT 185 and a hand amp controller so not sure what amps I was using.
Can you or have you tried the same angle but with a thicker electrode? (just guessing here)

[Engloid]

Originally Posted by pulser

BUT THE THEORY IS, A BLUNT TUNGSTEN WILL IMPROVE PENETRATION OVER A SHARP TUNGSTEN.
Take a look at what Pro-Fusion says about electrode tip geometry

Wadda u think?

I think that I have never had a need to sharpen to a 15 degree point. If I sharpen it down to 7degrees, it will burn away like a mig wire. I also notice that their increments of test angles are pretty great. They go from 15 to 30. That's a 100% jump.

Personally, I like about a 30 degree point, unless high amperage causes me to baby the tungsten a bit by going with a larger angle.

[pulser]

This was a carefully controlled study that explored the extremes of the process. Of course there are logical reasons why you would not use a 15 degree or 180 degree grind.

[Engloid]

Originally Posted by pulser

This was a carefully controlled study that explored the extremes of the process. Of course there are logical reasons why you would not use a 15 degree or 180 degree grind.

I agree. You have to exceed logical limitations to find where they really are.

My point was that, for most practical purposes, we typically say that a sharp point is good...but we're not talking about 15 degree angles.

[Joe H]

Ok, you just lost me...

What does a tungsten with a 180 degree grind look like?

[Engloid]

Originally Posted by Joe H

Ok, you just lost me...

What does a tungsten with a 180 degree grind look like?

I think it's the opposite of having it ground to a 0 degree angle.

[Joe H]

Originally Posted by Engloid

I think it's the opposite of having it ground to a 0 degree angle.

That sounds logical.

I want to see one ground to 150 degrees, and maybe 240 degrees too.

I think you could weld around corners with those!

[pulser]

I know it's bizzar, it's just a flat ended tungsten. Of course there is probably no reason you would actually use it, but it was just one end of the spectrum for this study. Look at the photo, it shows the 180 deg. tungsten and the arc kind of coming off to one side.