Stainless exhaust pipe

[jakeru]

The Solar Flux won't work that great if you need to weld a subsequent pass, including any "touch up" weld pass. When it cools, parts of it can crack and "pop" away as the metal contracts, so it will not reliably protect the metal on any subsequent welding passes or "touch up" work. However it might be a good alternative to purging a very long, relatively large diameter exhaust system (saving you lots of effort getting a large volume purged.)

For tungsten diameter, I would go .040" or "sharp" 1/16" for better arc starts and low-current arc stability. For filler rod size I would go with 1/16, not the 3/32" unless you have some really big gap from really poor fitup you are trying to bridge (and definitely back purge if you are doing that, or better yet, try to avoid it.) You might even try to locate a filler rod smaller than 1/16". (I've got some 3/64")

I like using 309L for most of my stainless welding.

Attached picture is a stainless steel chair .049" diameter, I welded using 1/16" 309L and .040" tungsten. You don't want to use much amperage for welding stainless. I usually control with footpedal, but would guesstimate about 40 amps average or less for exhaust tubing. Keep a tight arc to focus the heat and make a narrow puddle, and minimize overall heat input. Weld in stitches and allow cooling of the part in between. If a large portion is glowing red after you are done welding a stitch, take a break and do something else to allow the work to cool before welding near there again. Stainless is slow cooling. A larger diameter gas lens cup is also adviseable. Using some pulsing to minimize heat input if your machine offers it. (For this I would go with min. pulse freq, min. pulse duty cycle, and minimum background current.)

Oh and almost forgot, use plenty of post-flow to keep the metal shielded, it needs to stay shielded with argon even a little bit longer after it stops glowing. You can re-trigger the post flow by tapping on your footpedal, repeatedly as many times as is needed. Avoid the "dull grey" looking heavily oxidized surface.

[angular]

What's the difference or pros/cons of the 309 filler rod compared to 308? I'm using 308 to get started with... just practicing on 304 pipe (16 ga and schedule 10).

Edit: Reading your posts and seeing you live in WA state, I've had this strange feeling I know you from somewhere. Are you the same Jake that bought a pair of Scirocco 16V seats from me back in 1998?? I had a red 16V Scirocco and lived in West Seattle. Then the car got stolen shortly after having Matrix install a low-boost turbo kit. Talk about twisting the knobs on the "Way Back Machine"! Haha.

[jakeru]

Hey Bradley nice to be back in touch with you - looking forward to more chatting via IM!

Regaring stainless filler rods, I haven't done enough back to back testing of stainless filler rod to be really certain about the differences of 309 vs 308. But here are a few facts I can offer about them based on what I've read and to a limited extent, from my experience.

308 is "technically correct" for welding 304 to 304, so you should be all set to go with it.

309 has a higher nickel (~12%) and chromium (~24%) content than 308, and so generally costs somewhat more per pound. You will see it generally called for when joining "dissimilar" materials (such as mild steel to 304 stainless.) My hunch is that the higher nickel content increases elongation & ductility, and makes it more suitable for joining materials that expand and contract with heat at different rates (such as, stainless to mild, or one stainless alloy to another stainless alloy.) But I think another reason the 309 is called for is the higher alloying ingredients can be "diluted" with a lower alloy parent metal and the resulting diluted weld bead still maintains enough alloying ingredients for acceptable corrosion resistance and ductility.

Now I've used 309L for joining stainless to "same alloy" stainless, as well as for joining mild steel to mild steel, and I can't find anything wrong with it based on the way it welds and holds up. I think the reason its not "recommended" for these application is because simply that other less expensive filler rods are available that do these jobs satisfactorily (such as, 308 for joining 304, or 70S2 or 70S6 for joining mild steel.)

However I've noticed something I like using about 309L to join mild to mild - it seems to dissolve oxides very well, and not leave anything floating on the surface, giving a really fluid, easily controllable molten puddle, as well as a great looking weld deposit. check out the attached picture, 309L joining cold rolled mild steel together. The puddle is really fluid. I've heard the nickel is what gives the oxide dissolving qualities. Sort of like a built-in flux that needn't be cleaned off afterward. 308 might work well for this too but I haven't experimented much with it for welding mild steel yet.

I've heard from others that 309 works really well for welding dirty steel (like hot rolled mill scale), although I haven't had opportunity to try it on that yet. Maybe kind of like a built-in flux that doesn't need to be cleaned off afterwards.

(The "L" suffix means low carbon by the way, and generally increases ductility of the weld deposit at some loss of tensile strength - usually but not necessarily always a desirable thing IMO.)

[presure2]

Hey Bradley nice to be back in touch with you - looking forward to more chatting via IM!

Regaring stainless filler rods, I haven't done enough back to back testing of stainless filler rod to be really certain about the differences of 309 vs 308. But here are a few facts I can offer about them based on what I've read and to a limited extent, from my experience.

308 is "technically correct" for welding 304 to 304, so you should be all set to go with it.

309 has a higher nickel (~12%) and chromium (~24%) content than 308, and so generally costs somewhat more per pound. You will see it generally called for when joining "dissimilar" materials (such as mild steel to 304 stainless.) My hunch is that the higher nickel content increases elongation & ductility, and makes it more suitable for joining materials that expand and contract with heat at different rates (such as, stainless to mild, or one stainless alloy to another stainless alloy.) But I think another reason the 309 is called for is the higher alloying ingredients can be "diluted" with a lower alloy parent metal and the resulting diluted weld bead still maintains enough alloying ingredients for acceptable corrosion resistance and ductility.

Now I've used 309L for joining stainless to "same alloy" stainless, as well as for joining mild steel to mild steel, and I can't find anything wrong with it based on the way it welds and holds up. I think the reason its not "recommended" for these application is because simply that other less expensive filler rods are available that do these jobs satisfactorily (such as, 308 for joining 304, or 70S2 or 70S6 for joining mild steel.)

However I've noticed something I like using about 309L to join mild to mild - it seems to dissolve oxides very well, and not leave anything floating on the surface, giving a really fluid, easily controllable molten puddle, as well as a great looking weld deposit. check out the attached picture, 309L joining cold rolled mild steel together. The puddle is really fluid. I've heard the nickel is what gives the oxide dissolving qualities. Sort of like a built-in flux that needn't be cleaned off afterward. 308 might work well for this too but I haven't experimented much with it for welding mild steel yet.

I've heard from others that 309 works really well for welding dirty steel (like hot rolled mill scale), although I haven't had opportunity to try it on that yet. Maybe kind of like a built-in flux that doesn't need to be cleaned off afterwards.

(The "L" suffix means low carbon by the way, and generally increases ductility of the weld deposit at some loss of tensile strength - usually but not necessarily always a desirable thing IMO.)

great info jake (i assume that is your name? lol)
do you think the 309l would be easier to use on mild for a beginner? i've used it in a mig machine welding both 409 and 304 exhaust tubes with good results, (for me anyway..lol) but dont remember ever trying it on mild..i do remember the 2lb roll of wire costing ~30$ vs the under 10 i normally pay for solid core standard wire (lincoln brand)

[angular]

Thanks for the info, Jake. I bought 308L and 70S2 (and some 4043 for aluminum) to get started with. I'll have to try the 309L some time to see if I can tell the difference.