What causes a grey colored TIG weld?

blueeyeddevil

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So I'm welding on a miller 250 squarewave. I'm cleaning, grinding, sanding, brushing, and wiping down with acetone. I can't get a "clean" weld to save my life. It's been a while since I did any TIG ( Been an ironworker for awhile, got my G3 & G4 certs.) What am I missing?
CFH= 15-20
DCEN
AMPS= 80-100 or so....
3/32 tungsten and 1/16 70-s2
Thanks in advance
 

tomahawkracefab

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too hot outside of your gas shield , amp down and slow down movement maintain penetration , try a larger gas lens on your torch for better gas shielding , binzel make a cheap and easy flowmeter to check cfm @ torch tip , some times you can lose a few cfm's through long/faulty leads
 

blueeyeddevil

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Re: What causes a gray colored TIG weld?

I'm welding everything from 18-16ga plate, basic 1/8" tabs, and .083"-.095" tubing;both DOM and ERW.
The weld will look nice and clean some colors. By the end of the post flow (about 6 secs or so), it turns gray.
 

Demp

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tmathews

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Try taking the cylinder back to your gas supplier and see if they can run a purity analysis on the gas. Also, see if they will exchange it for another cylinder of gas.

Also, try turning up your CFM to 25 to 30.
 

blueeyeddevil

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maybe???? We did get a new bottle a couple weeks ago. I hate to blame problems on tools or the like, because most of the time it is an operator error.;)
 

tmathews

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Just thought of something else... Check all of you lines for leaks... Gas hoses.. tig torch. etc.. One little pin hole can make a difference.
 

Chase 2

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Although I don't think that it is the problem in this case, but sometimes too high a gas flow can actually cause problems.

If its not the gas, then most likely you're too hot and too fast.
 

atomicjoe23

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I would second the opinion that is a gas problem somewhere. . .either bad gas or a leak in your line somewhere since you have good post flow. . .I like to run a slightly higher CFM than what you are but not more than 25. . .but that was inside a 4x7 weld booth not out in an open shop.
 

Scott_F

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If a gray colored weld is caused by welding too hot and too fast, how does that affect the quality of the weld?
 

atomicjoe23

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The gray is caused because the metal is too hot after the shielding gas is removed from it and the weld has absorbed impurities from the atmosphere. . .so it will still be a strong weld, but metallurgically there are impurities in the weld and depending on what impurities are in there, it will not be as strong as one that doesn't have impurities in it. Also. . .it just doesn't look as nice.

Normally this is a bigger problem with stainless steel, aluminum, etc. (ESPECIALLY titanium) and is not as much of a problem with mild steel. . .which is why a gas lens isn't normally necessary for use on DOM, mild steel, etc.
 

blueeyeddevil

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O.K. fellas...
I adjusted the CFH to about 22. I added a gas lens or "diffuser" and a bigger cup.
I checked the regulator fittings and gave the torch a once over. Nothing out of the ordinary.
I ran a pass on some 16ga tickets; in a lap position, at about 90 amps. The welds came out a helluva lot better than they have been for the past week or so. BUT, I was way hot by the end of the pass. Not hot like I was burnin' it in, but like I was loosing gas coverage or something.
I guess the best way to describe it was almost like a flash point. The temp was ok, ok, ok, ok, ok, then wham!!! Glowing red hot. It just seems weird.
Maybe I should STICK to hanging out in the air several stories up and burning that 7018:D
 

Brian Mapes

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Go back and search there is some good advice myself and others have left on tig welding. But from what you are describing you might not have the post flow on long enough. General rule of thumb is one second post flow for every ten amps. The cfh should be 12 to 18. Your problem with getting red hot at the end is because you are not moving fast enough at the end, or backing off the pedal enough if you have a pedal. In the beginning the metal is cold so you need more heat/slower travel speeds. Then towards the end the metal is much hotter and you need to have less heat input/faster travel speeds. You can use a gas lens or not. Its up to you. I almost always use a gas lens for everything if i can. After welding alot with and without a gas lens you can tell the difference and it is worth it to me.
 

atomicjoe23

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Your welding coupons. . .it's to be expected that all of the sudden the weld will be WAY hot at the end of the coupon. . .

. . .you have to back off the amps at the end as the metal heats up, just like Brian Mapes said. . .this was something that all of us struggled with when I was in weld school, by the end of the quarter we didn't even have to think about it. . .we just got a natural feel for what needed to happen. . .

. . . you need to back off the amps (pedal) at the end of the coupon and add more filler to help keep the metal at a consistent temp. . .it will also help to tap the metal at the end again (after you have completed the weld but before the gas flow has turned off) to increase the amount of time the gas flows at the end of the weld. . .this wouldn't normally be necessary when welding a larger piece, but when welding a 6" coupon I find it more convenient to tap the pedal again to reset the post-flow timer than to wait for an extra long post-flow that may or may-not be necessary depending on the circumstance.

You said you were a little rusty. . .so I'm sure it will all come back to you very quickly!
 

Scott_F

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The gray is caused because the metal is too hot after the shielding gas is removed from it and the weld has absorbed impurities from the atmosphere.

So, would you say if you are welding hot, and moving fast, that the gas shield has "moved on" with the torch before the weld bead has cooled below some threshold temperature?
 

atomicjoe23

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Exactly. . .when I was working in the nuclear field the pipe welders would have the piping system purged on the inside with a flow of argon and depending upon the size of the pipe they would also have following (and sometimes leading) gas cups which would continue to shield the weld after they had already moved beyond it (and in the case of the leading cup would pre-purge the area of atmosphere). . .

. . .obviously for nuclear grade piping the requirements are very strict and very critical. . .much more so than what we do (not saying are requirements aren't critical. . .nothing is more critical than our safety, but in a relative scale of things an off-road truck vs. a nuclear power plant the off-road truck is a little lower on the list) and a leading cup and internal purge would be way overkill. . .and I personally think a following cup should be unnecessary as well. . .especially for the materials we're talking about.

If speed is the problem and not insufficient gas coverage due to leaking lines or gas flow and the gas itself isn't the problem then back off on the amps and slow down. . .depending on the joint you can slow down just by using a circular oscillation as opposed to just a straight push, if you circle just to the front of the puddle you can allow the puddle to cool just slightly without solidifying and you can pre-heat the area just in front of the puddle that you are getting ready to move onto. . .by doing this you can also run a slightly lower amperage as well. . .this also increases the amount of time the weld has shielding gas as it is cooling down. . .just a suggestion and I found it to work very good on stainless steel.

A good rule of thumb is if the weld is still red and in no longer has shielding on it it's going to absorb atmospheric contaminants.
 

Brian Mapes

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Ok, usually a beginner will have the problem of going to slow, not to fast, but it can happen. Going to fast you will move the gas over the weld too quickly and possibly not get proper sheilding. Going to slow you might put too much heat into it, but you will have more gas shielding. Some more tips I would give to a beginner is to start out before you master it do your welds slow. But control the amperage, if you amps are really low, like almost lower than what you need to melt the metal you will be forced to sit for a second and wait, not necessarily a bad thing for beginnners, take you time and go slow and steady, with really low amps as long as you keep a steady even pace you will do good, and get plenty of sheilding as well. I offer Tig lessons to anyone wanting to learn in a one on one enviroment, If anyone is interested. If you are going to fast you will typically want a trailing sheild or at least a bigger lens to cover more area. There is not one correct way to do a weld, there is a million correct ways, and a million incorrect ways as well. Do some practice coupons taking the advice we have gave you on here and then post the pics of the welds and machine setup so we can help you out further.
 

blueeyeddevil

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I shook the machine down and I had a leaky fitting, and the torch needed some maintenance. I did turn down my amps *83-87* and went with a bigger cup and screen. My welds look like they had a dose of Just For Men. The grey is gone! Nice even and uniform beads have been obtained. It takes a while to change mindset back to welding "thin scheiße " after welding 1"thick beam and column moments with the 8 pak and 7018 5/32 or even better the .072 innershield on the LN 25, for quite awhile.
Thank You:)

Now, since you all have been so very helpful...
Any advice or good threads on the "magical and mysterious" [AL]?:D
 
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