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ajmuller
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    Tue Nov 21, 2017 11:01 am

Hello All:

I am new to TIG welding and the forum. I have been practicing on 1/8 stock and seem to be doing pretty well. I had the occasion to weld a Stainless Exhaust tip to 15-16 Gauge mild steel exhaust aluminized tubing. The Stainless tip seemed to be a slightly thinner at 16-18. It was a lap joint where the SS exhaust tip went over the steel exhaust tube. I practiced butt and lap welds on just the steel tubing (after grinding off the AL) and had no issues. The practice run was with ER70S2 1/16 rod and had the amperage at 60 amps but was not maxing out the pedal. I used 309L 1/16" rod on the steel to stainless. Both were 1/16 2% thoriated tungsten.

When I went to weld the real thing, I made a mess. The stainless would constantly burn through, but the mild steel would not puddle without more heat. I tried moving the heat to the thicker steel like I would with mig and as soon as I tried to wipe the puddle to the stainless, it would just melt and pull away. I tried multiple amperage settings and pulse, nothing seemed to work. It seemed I exceeded my current ability to tig weld. I did not back purge, but assumed with the steel backing the stainless I would not need to do so.

Any tips on how to complete a weld like this?

Drew.
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Hello Drew and welcome to the forum.

was the sst exhaust tube a tight fit over the steel tube? the larger the gap here, the harder it will be to complete this weld.

also if your arc length isn't tight the arc will melt the sst back as you described. you'll also need to keep the puddle full, torch angle will either hurt or help especially in this situation.

can you post a pic?
Richard
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ajmuller
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In the end, I was able to get them welded together after some pretty ugly passes. Queue the 1" belt sander and a pass with just the tig torch with no filler over the really rough spots and I had it smoothed out so it was presentable. After cleaning it up it looks like there is no weld vs a nice stack of dimes.

I guess I should have taken pictures to help with the correction, unfortunately I did not think of it.

Yes, they were very tight together. After I got them placed, I inserted an exhaust expander and expanded the inner pipe to take up any slack. Stretched the from the inside until they were so tight, they probably did not need to be welded to stay together.

One thing I read today was that the long taper to sharp point I was using on the tungsten may have been to my disadvantage. I thought the long sharp point would concentrate the heat. From what I read, it was spreading it out wider. Would the shape of the tungsten point have a huge impact?
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ajmuller wrote: One thing I read today was that the long taper to sharp point I was using on the tungsten may have been to my disadvantage. I thought the long sharp point would concentrate the heat. From what I read, it was spreading it out wider. Would the shape of the tungsten point have a huge impact?
I don't think it would be huge, plus at lower amps you're not going to be able to get away with too blunt of a tungsten. I think keeping a tight arc, filler in the puddle, moving fast and the torch angle focused on the steel tube would win the day.

You got it done so that counts! :D
Richard
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ajmuller
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    Tue Nov 21, 2017 11:01 am

Thanks.

Me, Tig, and Fast in the same sentence is going to take a lot more practice :D
motox
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if you have to think about moving fast you will have lost.
watch the puddle and keep up with it without letting it
widen and oh yes, tight arc and good torch angle.
craig
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ajmuller
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    Tue Nov 21, 2017 11:01 am

Thx.

I practiced the heck out of feeding the rod like Jody suggested, the people at work thought I was nuts. That just started to happen one day while welding. The same happened with using the pedal vs flat out.

This sounds like more seat time and experience. I guess I will just keep practicing.
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