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TIG thick steel to thinner mild steel

Posted: Sun Sep 15, 2019 10:19 am
by fakky
Trying to tig a bracket onto frame of truck. Just tacked right now.

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Truck is around 3/8 thick ....... the bracket steel is around 1/8th.

Whats the right way to approach this ? In terms of setup (Amps) .... and preheat or not etc ......
Started out setting to around a split of 150A .... and really it just soaked into the larger metal and blew out the thinner metal.

Re: TIG thick steel to thinner mild steel

Posted: Sun Sep 15, 2019 4:23 pm
by cj737
No preheat. Clean bare metal. Enough amps to weld the thinner piece.

Re: TIG thick steel to thinner mild steel

Posted: Sun Sep 15, 2019 4:45 pm
by Simclardy
Are you using a foot pedal? I would focus the heat into the thick metal and then once you get a puddle add your filler and creep over to the thin metal. With the pedal you can pump it just before each dip.
Make sure you have a tight, clean fit up. Otherwise you will be fighting to join the two. You can almost use the rod as a heat shield by using a lay wire technique. 3/32 or even 1/8" would be good. I would probably go with 3/32 and a good sharp point on my tip (not too long, you lose penetration).
Cheers

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Re: TIG thick steel to thinner mild steel

Posted: Mon Sep 16, 2019 2:35 am
by tweake
Simclardy wrote:Are you using a foot pedal? I would focus the heat into the thick metal and then once you get a puddle add your filler and creep over to the thin metal. With the pedal you can pump it just before each dip.
+1

tho you don't need the foot pedal. you can simply wash over to the thin metal.

Re: TIG thick steel to thinner mild steel

Posted: Mon Sep 16, 2019 9:53 am
by Simclardy
tweake wrote:
Simclardy wrote:Are you using a foot pedal? I would focus the heat into the thick metal and then once you get a puddle add your filler and creep over to the thin metal. With the pedal you can pump it just before each dip.
+1

tho you don't need the foot pedal. you can simply wash over to the thin metal.
Agree, just thought it would be easier for him. On second thought the switch can be easier sometimes for out of position welding.

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Re: TIG thick steel to thinner mild steel

Posted: Mon Sep 16, 2019 10:09 am
by Oscar
I would first tack the corners with a nice blog of filler metal. Usually buy the time you get to a corner, the smaller piece will be so hot you'll have a good chance of blowing it out. With a nice plump tack, it will be able to absorb the heat just a little bit better for you to terminate the weld.

These are the corners I mean.
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As long as the corner is touching, a quick high amperage blast while quickly feeding in 1/16" filler is what I would do. Amperage? I'd probably max out my 220A TIG and use the foot-pedal to aim the arc towards the frame and wash it up toward the 1/8" plate and jam the filler rod in there. It's one of those things that if you haven't practiced in the past, it can get tricky because it has to be done kinda fast. Try to practice on some parts before you go in there. Once you blow away metal, it's hard to build it back up with such little reinforcement. If it were me, I would definitely be using my MIG, or even SMAW'ing it before I tried to TIG it.

Re: TIG thick steel to thinner mild steel

Posted: Mon Sep 16, 2019 2:13 pm
by Simclardy
220 sounds high. You would have to really work that pedal. imho

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Re: TIG thick steel to thinner mild steel

Posted: Tue Sep 17, 2019 9:57 am
by Oscar
Simclardy wrote:220 sounds high. You would have to really work that pedal. imho

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That's exactly what it's for, working it. :) I like to tack at high amperages/low durations. For me, it makes for "neater" tacks.

Re: TIG thick steel to thinner mild steel

Posted: Tue Sep 17, 2019 11:14 am
by Simclardy
Oscar wrote:
Simclardy wrote:220 sounds high. You would have to really work that pedal. imho

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That's exactly what it's for, working it. :) I like to tack at high amperages/low durations. For me, it makes for "neater" tacks.
Sorry, i thought you where talking about running the weld. For tacks i agree get in and out with high heat

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