Problems with tungsten

[hotrodder]

Just out of interest what could be the other possible cause of grey welds and a heat tinted tungsten?

The only cause is oxidation.

Lots of things can result in that happening to welds as the torch is moving so the hot weld is only under argon for a little while. Stainless turns golden/straw at around 280C, as the temp goes up it gets darker through browns, mottled purple/brown, purple then blues at around 600C and then grey. If heat and speed aren't balanced (too hot/too slow), arc length is too long (heat input goes up) then you get grey welds. As long as there's enough postflow* and no leaks etc then the tungsten will remain clean and shiney

As Paul, a gas lens won't fix this. They provide better shielding but only tend to fix problems when lots of stick out is needed or weld geometry creates vortexes that pull air in messing with shielding (in the later case it typically effects only the work, not the tungsten)

* 1 sec/10 amps is a very rough guide for postflow (watercooled torches need less than air cooled typically from the tungstens POV). You can see the tungsten oxidise if you're watching it and counting out the post flow


Oh, random thought... not something daft like welding in the 'firing line' of the welders fan or any other breeze/draft etc?

 

[Mid Wales welder]

So, a bit of an update. Still haven't opened up the machine to check inside yet but i had a spare 15mins and ran these two welds, they were slightly grey but after a wire brush they looked ok (the two long beads in the middle, please excuse the wobble, they were done with the metal on the floor and me kneeling down!). I have realised that i have no post flow on my machine, the gas delay is just a pre flow (haven't done much tig with this machine, just stick. Its a Giant 200amp inverter) So the post flow is set to about 2-3 seconds, so as hotrodder says (thanks btw) when i'm welding above say 40 amps the tungsten isn't being sheilded.
Should i try a larger tungsten as it can take more heat, or will this not make a differance?
Anywho, i will check inside the machine over the weekend. Thanks for all the replies, very helpfull!!

 

[Paul.]

The knob on the right is the post flow, there is no adjustable pre flow on that machine, a bigger tungsten is not the answer here, at lower amps you will just find that the arc is unstable, (playing around with tip prep can help with that, but one thing at a time) stick with the 1.6 and eliminate any mechanical problems with the set, do a spot test as linked to earlier and stick a photo up here, welding on the floor? not direct onto concrete I hope, on thin sheet you will just drag contamination up through the sheet into the pool, also worth checking the back of the sheet is clean too.

 

[Mid Wales welder]

Yeh I thought the knob on the right was post flow too, but actually all it does I'd delay how long after you press the button until it arcs up, so the gas starts flowing straight away hence it being a 'gas time delay' weird, not sure why you would even need that!
Yeh I have herd of putting a very fine point on a larger tungsten to weld thinner stuff (a guy I work with does that).
I didn't have time to get my welding table I made out to weld on, hense welding on the floor, I had the earth clamp on the piece on 3mm stainless sheet so it wasn't directly on the concrete.
I have tried a few spot test on different gas settings, with & without a gas lens & on mild & stainless steels (both clean) but only has minimal success. When I used a gas lens set at about 10lpm on mild steel with a brand new tungsten I only has a slight heat tint on one part of the outer circle, if u get what I mean lol?! I will post a pic when I get a chance tomorrow.

 

[hotrodder]

Yeh I thought the knob on the right was post flow too, but actually all it does I'd delay how long after you press the button until it arcs up

If that's the case then it must have been a Friday afternoon effort as (chinglish writing aside) the front panel is clearly showing it labelled post flow i.e. the knob is at the end of the pictorial description and 'arrowed' along with amps/background (valley) amps/pulse frequency. Have you actually counted out the post flow i.e. turn to look at the flowmeter after breaking the arc?

 

[gavuk]

I wonder if its controlling pre and post flow gas times?,as Paul and HR say it shows postflow

 

[Mid Wales welder]

Opened up the machine this morning & sure enough the connection at the back of the machine was leaking slightly, sorted thanks for the help!
So now onto the pre/post flow thing. I tried the 'gas time delay' switch all the way up and down, the pre flow was the same, just a short purge of gas before it arcs up. The post flow also stayed the same at roughly 4seconds. So it looks like the pre/post flow can't be altered. The thing that does get altered however is the length of time it takes for the amps to taper off, so when I had the switch at zero I let go of the button & the arc stopped straight away but when I had the switch all the way up it tapped off slowly to nothing.
So I think it's just a case of as Hotrodder says the 'chinglish' doesn't make sense lol! Also the diagram on the front meaning amps tapering off (not sure of the correct term) not a post flow.

 

[chrismac]

Amps tapering of is usualy called slope down, on some machines the slope up/down, in/out are adjustable, the slope down is adjustable to let the pool cool down slower to stop pores apearing at then end of a run, hense the higher the amps the longer time needed on the slope down.

Chris

 

[Mid Wales welder]

Yes, slope down, thank you! I did know what it was just couldn't remember lol!

 

[Mid Wales welder]

This how the welds have ended up now. Opinions welcome

 

[Seano]

There ya go, 100% better already, you really should get off the floor, comfort and ease of positioning are paramount in tig work if possible, the more comfortable you feel while welding the better they will turn out, only my opinion of course.

 

[Mid Wales welder]

Yes its defo more comfortable off the floor
I do have a welding table that folds down, just didn't have time to dig it out. Living with the mrs parents at the mo as we're in the process of saving & buying a house so my stuff is all over the place!

Thanks for all the replies!

Regards Dave.