couple of Tig questions

ER80S-B2 You can buy it here.

Great stuff, I also use it for welding bandsaw blades.
It does work, but there are problems with using 308L SS filler on 4130. 308 is basically 304 after welding, and 304 is a pretty weak SS alloy. 309, and 312 have been used for 4130, and are both stronger and better at dealing with carbon steel.
Low strength SS alloys have a problem with repeated flexing, in that they tend to stress fracture much sooner than carbon steel alloys. As long as the frame joints aren't flexing much it should be OK, but use 309 or 312.
ER80S-B2 is the best, but I have used nickle base alloys in the past like Hastelloy W and Inconel 625 with great success.
1% Lanthanated (black) and 1.5% Lanthanated (gold) are both fine. 2% Lanthanted (blue) is better, but harder to find. 1% Ceriated (orange) is also OK on AC and DC, but Ceriated is better on low amperage and Lanthanated is better on high amperage
Get yourself a box of 3/32" 1.5% Lanthanted tungstens.

Ernie Leimkuhler wrote in news:071220040049514103% snipped-for-privacy@stagesmith.com:
I've used these exclusively for all of my TIG welding so far on the advice of the guy who has been teaching me. Although it was noted above that these have a gold band, mine are actually grey (Sylvania brand I think).
So far I've used these for mild steel (1018), stainless sheetmetal, and aluminum (5052 and 6061), all