Need some help TIGing 4130

[Nikolai]

Quick background: I bought a Diversion 165 this past spring so I could start making my own snowmachine parts. So far everything I've done has been aluminum and I'm fairly decent. I'm currently trying to weld up a 4130 chromoly steering post and would like some input on the proper tungsten and filler sizes.


I'm using 2% ceriated tungsten and ER70S2 filler, straight Argon at 20 CFH with a #6 cup(I use a 7 cup for the 3/32). I achieve nicer welds with 1/16 tungsten and filler but is this enough for the 1/4"? The 3/32 seems like it puts a lot of heat into the metal. I try to keep the tungsten as close to the base metal as possible to reduce heat input.


Here's a pic of what I'm welding up...
The main tube is .065 4130, the top and bottom pieces are 1/4" mild steel, and the middles pieces are all 1/8" mild steel. Everything has been cleaned extremely well(all mill scale removed) and acetoned before welding. I made one post but wasn't happy with the welds so I'm making another.




I've practiced a lot already, but I want to make sure I'm practicing with the correct size tungsten and filler.

Thanks for any input. I've done a ton of reading on the internet and already read through the Miller TIG manual and weldingtipsandtricks.com website, along with the multiple welding books I own, but haven't been able to find the info I need.

[Rolox]

Post a close up of your welds. 1/16" tungsten should be able to weld 1/8" steel no problem. 1/4" should be possible if you are patient on your machine. As long as you are pushing the puddle from the 1/4" to the tubing the penetration should be good. 1/16" filler should be adequate. What kind of problems have you been having?

[Nikolai]

The first pic was of the first steering post. Here are a few close up pictures of the new one I just fit up tonight so you can see exactly what I'm working with. I'm not sure how big the weld bead should be? You can google aluminum welds all day long but there aren't very many pics if steel TIG welds. When I look at 4130 weld pics it seems like the heat affected zone(steel that turns blue) is always smaller than I can get it which tells me I'm putting too much heat into the part.





How long should it be taking me to get the puddle established? Is it better to just crank up the amps and stomp on the pedal and start welding? Or should I be using lower amps and taking 5-6 second to get a puddle? Everything I've read about 4130 says to weld slow.

I'll lay a few more welds on the old post tomorrow and take some pictures.

[shovelon]

Looks like you are doing fine to me.

From my experience with 4130, is the the weld usually needs to be no larger than the the thinnest section as minimum weld size. So weld can be as small as 1/16".

I personally like to weld as fast as possible. Time is money. I also like to weld from the ends of the gussets to the corner. And keep from overheating the joints is essential to me. The other sides of the plates you may need to scrape the blisters off the surface, or even bead blast clean before welding it.

ER80 filler is what I like to use. But in your case, I think I would go for ER90 because you are basically going to near penetrate the tube and dilute the weld.

A purge of the tube should not be necessary if you don't overheat your welds. The blister scale produced on the opposite side acts somewhat to shield atmosphere, but don't take it to the extreme.

Good luck, and post pics when you are done.

[wronghand]

Sounds like you're on the right track. Weld slow, let the material heat up. 1/4" to the .065" could be a little tricky but the other guys seemed to cover that really well. Start heating the plate first, then wash your puddle up the tubing.
As for weld size 1/16" to 3/32" bead is plenty. Rule of thumb is never run a bead any bigger than your material thickness-- you risk overheating the base metal and changing its structure if you make your weldment too big.
ER70S-2 is a great choice for 4130, second choice being ER80S-D2.

[DORNBOX]

Filler rod

Try an 880 or 880T rod. It's for welding dissimilar materials but it flows really nicely and has great strength. I've had really good luck with it and I'm able to get smaller beads and smaller heat effected zones when I use it over a standard ER70.

Good luck!
Chris

[Nikolai]

Finally got around to welding it up after a few days of practice. Still having a hard time maneuvering the torch around the pipe and keeping it steady at the same time. I think I need to take more time to better position myself. Some of the welds turned out ok and others not so much. I actually had the easiest time welding the 1/4" and 1/8". The small thin braces underneath the top flat plate gave me the hardest time. I'm going to have to practice...a lot! Aluminum is way easier to weld.




The weld on the 1/4" plate turned out really good but the thin stuff gave me some trouble. I can lay good beads on flat .058 plate but the tube was another story. Oh well, it gets a little easier each time.