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Old 09 November 2021, 13:32   #1
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Trying to learn to TIG weld.

I should start by saying this is a learning journey for me.
My goal - to be half decent @ TIG welding.

As part of this, I'm making a new exhaust for my boat, which as it's a V8, will have an internal (inside the boat) crossover & secondary air injection. This is to reduce exhaust reversion, hopefully meaning I can run a wet exhaust, which is easy to then silence properly.

I'm using a Parweld XTT-202P welder
1.6-2mm 304 & 316 stainless
1-1.6mm filler rods
anywhere between 5 and 15 lpm argon to give shielding
Typically 55 amps seems to be about right.
Seperate bottle or argon for purging the inside of the exhaust.

I welded up the Tee's first, feeling all gung ho. However, despite only welding an inch at a time, I wasn't happy with the welds. They'll do the job, but I decided to go back top basics and practice more.

The general annoyance - cooking the stainless. I want a nice colour on the final weld, not a baked, overheated look. I have found I can get a nice colour - but at the cost of amps, which means I don't get enough penetration.

But when I increase the amps, I'm literally welding stupidly fast - I can hardly dab fast enough. Get a smaller HAZ, but still almost impossible to avoid cooking the metal.

The general message is "weld faster", but if I go faster, the puddle doesn't coalesce properly. If I add more amps, the HAZ is smaller, but I still get the cooked weld.

I think gas coverage might be part of the issue?
This is a few of my most recent attempts, and that last pic is my attempt today with the biggest cup I have @ 55amps - which I think has adequate penetration and it not too bad.

So anyway, got a mooseknuckle gas lens on order to try.

It's not easy!
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Old 09 November 2021, 14:56   #2
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There's a difference between laying down a bead and doing a weld. You'll get far less penetration practising a bead because there is no gap and no edges. Fewer amps will work when you've got edges. Leave a gap when welding and use tacks to hold everything in place. If the metal is too thick and you need big amps then chamfer the edges so as to have a V to weld into.

You may need to set a gap wider at the final end than at the start end before you start tacking because each tack will contract. The hot tack metal is expanded and will shrink on cooling. Each tack will pull the edges together as you add more of them. If there's no gap when you start the edges will pull hard together and distort. How much gap is tricky, there are rules of thumb and theory but in my experience it's not quite so exact. Perhaps it would become so if I welded all day every day but even experienced welders discuss it. However, if I was welding 3mm (10g) steel using 1.6mm (16g) rod I'd start with a rod's width gap winged out to about 3 times that at 300mm distant.

However, breezeblock is a Ribnet member and he's a welder, I'm sure he knows far more than me and it might be worth a pm to him.

I've seen a gas pipe welder use a technique where he bent a piece of welding rod into a V and placed it between the tube ends to set the gap then tacked the tubes in multiple places then pulled out the bent V. Worked nicely for him.

Anyway, some gap will let you use fewer amps and therefore have a more controllable puddle but too wide a gap will blow through and you'll have difficulty keeping the puddle.
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Old 09 November 2021, 15:25   #3
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I “know” those facts, but I’m just not very good at putting it all together in to a nice weld. I’ll keep practicing. It’s a shame argon is so expensive.
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Old 09 November 2021, 15:40   #4
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RIBase
Quote:
Originally Posted by Matt View Post
Itís a shame argon is so expensive.
I'll be interested to see how this turns out. I tend to turn to Youtube when contemplating adding Tig to the list of things I need more practice at.

Unfortunately Mr Argon seems to have you by the short and curlies if you are doing Tig.

Good luck.
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Old 09 November 2021, 15:59   #5
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Quote:
Originally Posted by Matt View Post
... It’s a shame argon is so expensive.
He-he, if you're going to use lots of argon it might be worth giving BOC a year's rental and getting a seriously large cylinder.
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Old 09 November 2021, 16:07   #6
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I use SGS Gases actually, 20 litre bottles. I have a two of them. One as the primary and a 2nd for purging. 50 litres starts to be a bit tricky to move
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Old 10 November 2021, 13:06   #7
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Making some progress
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