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How far back do I need to grind this tungsten?

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How far back do I need to grind this tungsten?

Postby smig » Mon Mar 20, 2017 9:05 pm

Hello. New to the forum. I have been attempting to teach myself scratch start tig with my DC Thunderbolt and a 17v torch.

Being new to tig, I am contaminating my tungsten on a regular basis. Sometimes my tungsten will get contaminated just at the tip, and other times it will have a blue heat discoloration about 1/4" from the point.

My question is: how far back do I need to grind the discolored one? Do I need to get rid of all the discoloration, or just grind a new point? The one on the left has obvious contamination at the tip, the one on the right has a lot of discoloration, but not so much contamination.

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Re: How far back do I need to grind this tungsten?

Postby nelson » Mon Mar 20, 2017 11:04 pm

Good Q. I'll be watching the answers. I've been doing it both ways but don't know which is correct.
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Re: How far back do I need to grind this tungsten?

Postby Poland308 » Mon Mar 20, 2017 11:35 pm

99% of the time I just regrind the tapered end. Unless it's food grade or some specialty part.
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Re: How far back do I need to grind this tungsten?

Postby weldin mike 27 » Tue Mar 21, 2017 2:48 am

Remind the taper and go again. The blue discoloration is from not keeping the gas flow going long enough after welding finishes. Called post flow. Just keep your gas valve open a little longer (up to 10 seconds) it will make your electrodes last longer as well. The colour of the electrode won't effect the weld, but it indicates something isn't right in gas shielding land.
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Re: How far back do I need to grind this tungsten?

Postby cj737 » Tue Mar 21, 2017 7:18 am

After you re-grind the tungsten, use a Red ScotchBrite pad and wipe the tungsten. It cleans and polishes it up nicely (will even remove the discoloration). Just wipe from middle to tip. And turn up your gas CFH and allow a longer post-flow. It helps protect the tungsten, and loitering over your weld with Argon only helps keep your puddle clean.

Preventing contaminating your tungsten can be "improved" using a few tricks:
1 - Rest your arm/hand holding the torch and slide it along. This eliminates you from "air welding" and moving closer and farther from the puddle as you move along.

2 - Rest your cup directly on what you're welding, tipping/tilting it forward to point the tungsten at your rod/puddle. Then just slide the cup along the metal. This virtually eliminates any distance variance, and allows you to get and maintain a very tight arc.

3 - As you dab, adopt a technique of: add, slide, hold, add, slide, hold, add, slide, hold...
What this means is once you have your puddle established, dip the rod, then slide the cup, hold the cup still, add some rod, then slide again. This helps you dip the same amount of rod each time, and move the puddle/torch without introducing wire and making too large a puddle.

Using a #7 or #8 alumina cup with a gas lens helps immensely with your welding and arc distance. The stubby #8 cup is a wide body and enables you to rely on it as a resting surface and positioning prop. All that, and a good Flexible head torch! That is the other really advatageous trick.
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Re: How far back do I need to grind this tungsten?

Postby exnailpounder » Tue Mar 21, 2017 7:33 am

That discoloration is common for gas mizers. My machine will set the post flow automatically or I can set it. I hate to hear gas coming out of the cup for 15 seconds after the arc is off so I shorten it down to save gas and get a little color on the tungsten. I usually keep the post flow on the weld bead to keep it covered til it cools off.
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Re: How far back do I need to grind this tungsten?

Postby AndersK » Tue Mar 21, 2017 9:14 am

I usually get away with 4-6 s post flow but remember to keep the torch steady during that time.
If you move the torch away directly after killing the arc air will push the argon off and you'll get the blue tip anyway.
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Re: How far back do I need to grind this tungsten?

Postby Olivero » Tue Mar 21, 2017 9:51 am

Just grind and go. If you dipped it and picked up some metal, make sure to get it all off or it just reblobs the tip.

Post flow is important, I doubt it will ever do much for the tungsten as it never reaches a molten state where the shield is needed, I don't think you can contaminate the tungsten that way. The whole concept of post flow is to keep the puddle shielded while it cools back down to a solid state and as soon as that's all done, it should re-passivate. Tungsten on the other hand with the very high melting point should not reach its melting point while welding.
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Re: How far back do I need to grind this tungsten?

Postby Oscar » Tue Mar 21, 2017 7:33 pm

Olivero wrote:Tungsten on the other hand with the very high melting point should not reach its melting point while welding.


....unless you're welding on AC. Then it's common for the tungsten tip to reach melting temperature.

Unless you're doing pro-level work according to some WPS, don't waste tungsten. Grind the point back into shape, and polish out the rest. I doubt you'll tell the difference.
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Re: How far back do I need to grind this tungsten?

Postby smig » Tue Mar 21, 2017 8:45 pm

Thanks for the tips guys. I have been snapping out to end the arc, then quickly bringing the torch back to the weld and leaving it there to cool.

I will just regrind the blue tungstens. About half of my tungstens were turning blue, and I was not sure why.
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