tig stainless heat tint +penetration

[jamrobo]

I am a student competitng in the skillweld competiton in which i make a design out of stainless steel and have to weld with full penetrations which is purged on the inside.

My question is how do i achieve fully penetration whilst keeping good heat tint (weld colours) on the surface as it just turns grey.

The butts have to be square butted on 2mm stainless steel and have full pen. There is also corner joints all in horizontal, vertical and overhead.
i am using a large diameter pyrex cup with gas flow of 25lpm
50-70A and tryed 1.6mm filler rod ,and 2.4mm filler rod
is there anything i can do better to keep the colours on the outside of the vessel as it keeps going grey.whilst getting the penetration correct.

Any tips or anything that might help will be gratefull.

 

[Tinbasherdan]

Grey means there's too much heat/too slow travel. Personally 50 amp is probably the highest id go, but others will probably tell me I'm wrong !

 

[jamrobo]

I used 50 A today with 1.6mm filler rod on a vetical but and it was gold with penetration with a really slow travel speed to push the metal through but the rest was still grey. Im thinking i might have to pulse.

 

[Tinbasherdan]

Also 25lpm sounds very high, I'd drop it down to around 7-10

 

[jamrobo]

Ok just everything i read its better to have more gas pressure, i did a overhead stainless t joint 3mm and it was gold with flowof 25 lpm maybe a bit high for a square butt gasmight be bouncing off??

 

[Tinbasherdan]

There comes a point where you are just wasting gas though. For 2 mm I'd try 40-45 amps see how that goes

 

[jamrobo]

Ok thank you for the help ill try tomorow. Much appreciated.

 

[Richard.]

Rough rule of thumb 25amps per 1mm on SS
25lpm is just ludicrous. Your just throwing money away and probably is part of the reasons things ain't looking that great. Too much gas flow has the same effect as not enough. Turbulence is created and air is sucked in. Depending on your cup size is say the max you need is 12 and with a normal size cup 8 should be more than enough.
You will fully penetrate 2 mm butt joint with 50amps no problem. Travel speed has the most impact on your heat input so rather than playing with the settings leave it at 50 and play with the travel speed till your beads become shiny. A grey stainless weld is useless and under alloyed due to too much heat input.

 

[Tinbasherdan]

There you go, a far more eloquent person than me

 

[Richard.]

There you go, a far more eloquent person than me

Not really. I've only repeated every thing you said which IMO was accurate.

 

[AndersK]

I agree with all Richard said but will add a tip.

If you arent using a gas lens you can improve the gas coverage by stuffing some scotch brite cloth in the cup.
Look at Monster or DogFab cups.

You still need to attend to what Richard wrote but this will help you get there.

Over head joint will require more gas flow since Argon is heavier than air but even here 25 lpm sounds a bit high. But again, if it worked thats fine.

With a 8 cup and a gas lens you should be fine below 10 lpm on a butt weld.

 

[Richard.]

Why are you looking for colour in the weld. You should be aiming for shiny. The colour may or may not appear but it's not important as these are just surface oxides. Why do you suggest a pulse.
Yes I might be tempted to pulse weld it but it would not be to enhance appearence. I'd only pulse weld it if I needed to speed up and reduce heat input from a distortion point of view only. If distortion is not an issue then weld it normally

 

[biffa]

Tilting the torch back gives greater gas coverage especially with a long stick out I find that often helps with colour. Also are your getting a good purge coming out silver if your using 25lpm you might me starving your purge

 

[Richard.]

But why do you want colour?????

 

[jamrobo]

It purely a competition weld and it requires penetration and weld appereance the colours are purely for asthetics to make me stand out from other competitors. there was a vessel done by a korean welder in the world skills competition and its clean and full of colours and has good penetration, im just trying to get the closest to the vessel he did to score the most points to win my competiton. I have pictures but dont know how to put them on as i am new to the forum and how to do thinks haha , thanks for help and advice .

 

[Richard.]

Ok so the oxides is what they are looking for.
Fair enough. Pick up the travel speed, use a lens , good size cup, keep the heat input low. Long post gas time and keep the gas flowing over the weld for quite some time after you've stopped.

 

[langy]

I still don't understand the poll at the top ???

 

[jamrobo]

I didnt understand what poll ment so i just put numbers didnt no wt is was for to be honest as im new to this haha.

 

[eSCHEn]

I think the answer to the poll might be one hundred though

 

[Maker]

I voted 100, who was the only other person to vote?

It seems like a competition of weld colour is teaching the entrants the wrong thing to focus on.