Blue tungsten burn-back

[Mr Otford]

I have a question relating to trouble with 2.4mm blue tungsten. It burnt back almost as soon as the arc was established unlike the red tungsten which performed perfectly. Maximum current was 100A but I've no idea of the actual figure because I was using the pedal. DCEN on 3 - 4mm steel. R-Tech TIG161. It's, undoubtedly, operator error 'cos this is the first time of using blue tungsten and the last time I touched the machine was over 2 years ago!

TA

Richard

 

[Misterg]

...the last time I touched the machine was over 2 years ago!

Out of gas?

(If not, what flow rate & post flow are you using?)

 

[Munkul]

Your sharp tungsten with the pretty colours on it suggests that you don't have enough post flow of gas. You start between 6 to 8 seconds of post flow and work from there.
If you don't fix it, you'll always blunt your tungsten prematurely.

Regarding the blue tungsten melt back, that's very strange. Is it actually tungsten? Have you changed anything else?

Blue (lanthanated) and red are pretty much interchangeable in the way they weld, so something is way off.

 

[AdventuresInMetal]

I'm a TIG newbie myself but just to point out, that blueing of the tungsten could also be from overheating during sharpening?, i've done it myself on the belt grinder.

I'm also using lanthanated tungstens and you should easily be able to do over 200A on a 2.4mm!

 

[Mr Otford]

Out of gas?

(If not, what flow rate & post flow are you using?)

~10l/mim and 10s post-flow

 

[Mr Otford]

Your sharp tungsten with the pretty colours on it suggests that you don't have enough post flow of gas. You start between 6 to 8 seconds of post flow and work from there.
If you don't fix it, you'll always blunt your tungsten prematurely.

Regarding the blue tungsten melt back, that's very strange. Is it actually tungsten? Have you changed anything else?

Blue (lanthanated) and red are pretty much interchangeable in the way they weld, so something is way off.

Post-flow is ~10sec

The box is marked as 2% Lanth. (pcket anonymised 'cos the vendor is being helpful and I see no reason to alienate them)

Nothing changed apart from swapping from blue to red. Red performed exactly as I would expect.

 

[Mr Otford]

I'm a TIG newbie myself but just to point out, that blueing of the tungsten could also be from overheating during sharpening?, i've done it myself on the belt grinder.

I'm also using lanthanated tungstens and you should easily be able to do over 200A on a 2.4mm!

The colouring on the red arose during use, i.e. it was shiny before I used it.
I too thought that Lanthanated were good for greater currents than my machine can deliver. I'd try them in another machine but my nearest is in Suffolk!

 

[Mr Otford]

This is what I achieved after swapping from blue to red.

 

[Munkul]

Post-flow is ~10sec

The box is marked as 2% Lanth. (pcket anonymised 'cos the vendor is being helpful and I see no reason to alienate them)

Nothing changed apart from swapping from blue to red. Red performed exactly as I would expect.

You have a gas issue somewhere then. Possibly the flowrate is incorrect, in spite of 10lpm reading. Or the tungsten is sticking out too far. It should stay nice and silver when everything is right.

Not meaning to be patronising, but could you have dipped the blue tungsten straight away and not realised? It certainly looks like a blob from a material dip, and not a melt back.

 

[Mr Otford]

You have a gas issue somewhere then. Possibly the flowrate is incorrect, in spite of 10lpm reading. Or the tungsten is sticking out too far. It should stay nice and silver when everything is right.

Not meaning to be patronising, but could you have dipped the blue tungsten straight away and not realised? It certainly looks like a blob from a material dip, and not a melt back.

Would I not experience problems with the red tungsten too if the flow rate was wrong? I'm using a "rising ball" stick-type of flow meter.

Do not have qualms about the risk of being patronising - remote diagnosis is very difficult when the complainant is under-informed and no suggestions are invalid :-) I did wonder about dipping on the first occurrence and was very careful on subsequent attempts to not dip it. The sequence is this: HF arc is established and nothing happens as the current rises (pedal pressed) until the tip of the tungsten glows white hot and melts. I initially thought that, as it's suitable for AC and DC operation, I had the wrong polarity and swapped it round but that made no difference.

Mysterious.

 

[Hopefuldave]

Someone been having a laugh, dipping the ends of SS filler rods in blue paint?

 

[Munkul]

Would I not experience problems with the red tungsten too if the flow rate was wrong? I'm using a "rising ball" stick-type of flow meter.

Yes you're right, it would be the same on both tungsten types, but there's something wrong with the set up or some form of contamination causing the colour on the tungsten end.
I'm with Dave here. Maybe its either not tungsten at all, or maybe its just a bad one. Or bad batch.

 

[Mr Otford]

Tried the blue tungsten again today. No changes to the settings from last week except that the test piece has not been cleaned.