Welding Stainless to Mild

I am not sure what you mean by "which process to use" but it sounds like you are going with SMAW/stick welding.

In any case, 309 filler material is appropriate for welding carbon steel to stainless with the following two assumptions:

1. The carbon steel is not a low alloy steel such as Cr-Mo - I gather so because you said a tank
2. Assuming the SS is an austenitic grade 304L/316L/..... and not duplex or ferritic

I would recommend going with the manufacturer's spec for amps and polarity - usually on the packaging or could be found from a datasheet.

Exactly what type of rod do you intend to use?

Oh yeah - have you also given any thought to galvanic corrosion due to coupling the stainless to the mild steel? It could accelarate the corrosion on the mild steel side of the weld. Will this nozzle be submersed? What liquid/atmosphere will it see?

Lastly, to avoid any galvanic corrosion issues, could you not just as easily install a mild steel nozzle (pipe/flange) and bolt on to the rest of the, presumably stainless, pipe?

Because if the rest of the tank is fine being carbon steel, why do you want to install a stainless nozzle?

the liquid it will see is hot water and crude oil (bituman),i believe that is the correct spelling.It will not be submersed but will just be an outlet of some sort.Would you happen to know where i could look for a data sheet on 309 rods on the net?Thanks for your help and time

thank you that was what i was looking for

Galvanic corrosion between any dissimilar metals will not be created in the absence of electrolyte.

Replying to Forum Thread by Kenny Jr.: (Use Copy & Paste or drag text to quote the original text.)

i need to weld a stainless steel pipe onto a carbon steel tank.I understand i need to use 309 1/8 stainless rod but not sure the prosses in witch to use the rod or temp settings.it will be a 8 to 10 inch stainless pipe with stainless flange to a 1 inch carbon plate shell of a tank.Can anyone give me some advise on the prosess

YOU NEED TO KEEP THE ROD IN A PORTABLE OVEN AND MAINTAIN A TEMPERATURE OF 150 DEGREE F FOR AT LEAST 3 HOURS BEFORE YOU START WELDING

thank you Lorenzo

If you are welding the SS nozzle keeping it's bevelled (outer wall thickness) outer edges matching with inside wall thickness of the MS shell plate, it is better to go for GTAW welding process using same filler wire i.e.ER 309 which will give you a better quality weld joing.Don't forget giving the local purging with an inert gas at the weld joint. Purging is possible by taking an extra precaution at the weld joint inside the shell.

If you are welding the SS nozzle keeping it's bevelled (outer wall thickness) outer edges matching with inside wall thickness of the MS shell plate, it is better to go for GTAW welding process using same filler wire i.e.ER 309 for root welding and SMAW for further passess, using E-3091/8,which will give you a better quality weld joing.Don't forget giving the local purging with an inert gas at the weld joint. Purging is possible by taking an extra precaution at the weld joint inside the shell.

The proper way to weld this nozzle is to get a Boilermaker from Lodge 146 and a Qc person from C.B.I. and an inspector from Canspec and quit messing around with which you know not. seriously folks, this is not a game we are playing at school here. This is life and death if it is done wrong.

Clint Price

I was just wondering, why didn't anyone inquire about the power source Kenny Jr. had? or just presumend that its sufficient.

You MUST follow API specifications and standards for making this connection. There are specific designs for reinforcement pads, weldnecks, etc. You MUST make the tank connection with mild steel per API requirements with CS flange. Then bolt the SS pipe flange to the 'approved method' CS tank flange. Piping caused stress loads have to be calculated and managed to keep within the allowable values. Not fully complying with the API standards may result in connection failure and all sorts of legal complications. This is NOT a place to cut corners. Stresses in tank shell walls are VERY high (that is why the shell is 1" think) and proper reinforcement is critically vital.

You did not say what schedule pipe, but anyway, I would consider "Tigging" rather than sticking this thing out. At least the roots. Run a good pass(s) on the outside, and back groove the inside until you get to good metal. Run a few passes from the inside ( careful you don't sugar the outside) then go ahead and cap it off with stick if you so desire. But again, I would tig the whole thing.

I had a BBBAAAADDDD experience (no not isolated either) with 309 on some dbl-pads out in California and ever since I have been using 308L for dissimilar metals. Yes, I have an approved WP for both. It is just my experience has been much more consistent with 308L. Also, you do not say what grade of SS. If it is hot water service it may be 316 or 2205 or some other duplex. Better check. 316 needs moly and 309 provides no moly where as 308l does.

Lastly, I agree with just about everyone else, the GC, QA/QC, PM or even your formen responsible on site, should provide a WP from the QA/QC department. API or worse yet, ASME Sect. VII violations could lead to legal as well as safety issues. If the tank is code, you may need an A.I. inspector for hold points and insurance issues.

If your with the BM check with the hall or the NTL guys.

DO NOT TAKE CHANCES...It's your life, your career, and your reputation. Be safe, remember you confined space requirements.

Good Luck

It's called Super Missle Rod made by Lincon look at the specks Ithink you'll be impressed.

you need a qualified WPS (welding procedures specification) to make the weld. There are many factors, variables that you have to control to make a good weld....

S.

corrosion prevention