Tig welds to hot in the middle. Help.

[MattH]

Hi Guys,

I'm just practicing some more with my TIG set on some 2mm stainless.
Autogenous seems fine at different amps and tungsten sizes.
But adding filler seems to cause me issues. After running a bead the start and end of the weld look good with a nice shine but the middle is very dull. I put this down to getting the weld pool to hot and then not moving slow enough for the shielding gas to cover that part of the weld until it cools.

I have tried moving slower with lower amps and moving faster but it always seems the same issue.
I was running about 5.5LM gas, I did try upping that to about 8LM but with the same results.
I am keeping a very tight arc, any lower and I'd dip the tungsten. I've tried both 3.2mm and 2.5mm Blue tungsten's.

Any suggestions?:

 

[Richard.]

1.6 tungsten 50amps 1mm filler 8lpm on a GAS LENS. Speed and gas coverage are key to shiny stainless welds.

 

[Richard.]

By speed I mean you need to travel faster. Going slow although gives the gas more time to cover it also has serious heat input issues. Get stainless too hot and you'll burn out the alloys giving the dull grey appearence in the bead.

 

[MattH]

I was cranking the amps down but that's causing me to go slower. I will go back up to 50A and practice on picking the speed up. I think the issue is I'm slowing as I add filler.

Thanks for the input.

FYI, if my Avatar was bigger you'd see a GP2 on my bike ;-).

 

[Richard.]

They beat racefit hands down. My zx10 would spit flames on the roll off

 

[Richard.]

What size filler u using.

 

[MattH]

They beat racefit hands down. My zx10 would spit flames on the roll off

Yep, my S1000rr does to. Running no baffles at a Doney noisy day is epic.

 

[MattH]

What size filler u using.

1.6 with a 2.5 tungsten and 2.4 with a 3.2 tungsten.

 

[Richard.]

Everything wants to come down a size IMO.

 

[MattH]

I have a 1.6 tungsten to try but no filler smaller than 1.6. I'm not really trying to achieve anything specific, just learning.

 

[Richard.]

I have a 1.6 tungsten to try but no filler smaller than 1.6. I'm not really trying to achieve anything specific, just learning.

Then up the plate size to 3mm go about 75amps with the 1.6 tungsten 1.6 filler. No point in learning to not get results. I think your traveling too slow because the 1.6 filler your adding is chilling the pool so your travelling slow to compensate for it which is creating the heat input too high and dulling off the run. I think the reason it's in the middle is because at the beginning the run is cold before the heat builds up and at the end the post flow gas is keeping out the oxides while it cools. The middle is your challenge and getting that heat input down is key. Just my theory I could be way off.

 

[MattH]

Sounds good. I'll give it a try tomorrow.

 

[Richard.]

This is a mix of 1.5,2 and 3mm
It's the sort of thing I do when trying to bring back forgotten settings etc (I don't do a lot of stainless).
There is a 2-3mm butt joint
A 2-3mm fillet joint and a 1.5mm wall pipe to 3mm flat
Then a quick name knock up. Its quite old actually I did it years ago but can't bring myself to throw it out. Ha ha

 

[Tinbasherdan]

Nothing new to add, just agree with all that Richard has said. For the thickness of material id definately be on 1.6 tungsten, and at most 1.2 filler, if not 1mm

 

[langy]

I would agree with Richard, use a 1mm wire 1.6 will cool the puddle on that material, where are you getting these odd size tungstens

 

[Richard.]

Not sure tbh. I don't know what you think but for me SS Tig is a bit of a dark art and seriously intolerant (more so than Alu IMO) if things ain't bang on.
Heat input is crucial and the common misconception is to turn down the current (I know as I did the same thing when starting out) this will only have the opposite effect as you slow right down to compensate for it. I work on a 25amp/mm rule roughly joint depending but it's a good place to start. Distortion is also a pita with ss due to its lack of conductive ways. So heat stays very local and buckles the job if your not on the ball. Tungstens id not bother with a 2.4 below 100amps on dc, a 1.6 will carry that current and direct that arc better at lower current.
Filler should go into the pool with NO resistance at all. If you suddenly see the pool shrink or even feel the filler stick or even hear it make a tut noise as its dabbed or removed then it's too big and chilling the pool. The other end of the scale is if your intervals are not adding reinforcement or your chasing it beyond comfortable pace then maybe go up a size. I'm no expert on SS and don't do enough of it to feel that way but like most welding I get involved with ill strive to get the best results and better them through practice. I find aluminium Tig a breeze compared to SS but others may not so its down to arc time and testing.