Hello All, New To The Board

[cnslmva]

I geuss I'm the new guy on the board tonight. Been welding for 10+ years Mig, Tig and stick. Own nothing but Miller equipmemt, Trailblazer 250G, Super S32P, HF251, and waiting on my Spectrum 625 due in on Friday. Enough rambling on, I have a Tig question. When joining stainless to carbon steel I've always used 309 rods. Another weldor in the area told me that I should be using 312 instead. Which one is the right one?

[HAWK]

cnslmva,

I have always used 309 filler. It is great for SS to SS and SS to carbon steel. The the only testing I've ever done welding mild steel to stainless required 309 filler. Both 309 and 312 have a high ferrite content which helps match the ferrite structure of carbon steel. The 312 has a higher ferrite content which makes it more crack resistant than the 309. Both are acceptable unless a procedure specs one over the other.

[ASKANDY]

cnslmva,

Welcome!

Here we go on the dissimilar base material

I prefer the 312. I often use a rod called Tigtectic 680 which seems to be a 312 blend. I think you may need to do your own testing on this one as neither is wrong.
Sorry not much help. I'm sure everyone has done it one way or another and it work fine.

A-

[cnslmva]

HAWK, In my research I have found the same info that you did and thought that both would be acceptable as you said. The application that I ran into that brought up the question doesn't really have a procedure spelled out, it was joining a 304 SS range hood to black iron ducting in a large kitchen at a local university. Thanks for the input. Will have to try 312 sometime and see how it works.

[timw]

Wellcome aboard, There's a lot of good info to be had here. When you have specefic questions use the search feature to pull up old posts, it works great. I bought the 625 in january and I love it! I've only used my Oxy/Act once since I got it and that was a job away from my shop. The instructions are very basic but I learned to try it and see if it works, and it usually does! Here's a simple trick I like to use, to make a straight drag cut, use a 2X4 for a straight edge. It cuts so fast the board dosen't burn and it makes it easy to keep the torch straight up.

[HAWK]

Originally posted by cnslmva
HAWK, In my research I have found the same info that you did and thought that both would be acceptable as you said. The application that I ran into that brought up the question doesn't really have a procedure spelled out, it was joining a 304 SS range hood to black iron ducting in a large kitchen at a local university. Thanks for the input. Will have to try 312 sometime and see how it works.

cnslmva,

Let me know how it works. I am still using 309 1/16" because I have it. Andy has bragged on the Tigtectic 680 more than once. I have been wanting to try it, and will when I find it.

[dmfa200]

This post is a little late but maybe someone may get some use out of it.
I am a certified pipe welder working out at BP chemicals and we do all are testing in the 6g position.
We do 309L testing with 2" sch 80 carbon steel pipe. Filler rod is 309L. The root, and hot pass is done with TIG, the filler passes and cover pass is done with stick. Destructive testing is 4 strips cut from test coupon. 2 root bends, and 2 face bends. If you know how to weld the bends will be flawless.
Go with 309 it's proven!