304 to unknown stainless what wire

Gentelmen
I will be welding up an exhaust system using mufflers and cats from a
1996 Mercedes Benz SL600. The material for the mufflers and cats is
belived to be stainless but the alloy is unknown.
These parts will be welded to 304 stainless steel tube. It is most
likely that the parts are either 304 321 or 409 stainless. 409 is the
american exhaust system standard.
Which TIG wire do you guys recomend for this unknown application or is
there a way of finding out which stainless it is.
Generally 304 to 304 is welded with 308 wire
304 to mild is welded with 309
321 to 321 is welded with 347
And I have no idea what is used with 409
Thank You
John Roncallo
Reply to
John Roncallo
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309 and 312 are considered to be the best dissimilar metals filler rods. I also like the aerospace alloys if you can find them Hastelloy W, Inconel 625...
Reply to
Ernie Leimkuhler
Most stainless exhaust systems are made with the 400 series alloys and are usually welded using overcompensated 414 to allow for Chromium loss during welding. But as Ernie said, if you're going to introduce 300 series tube into the system, you'll be best to use 309LO. I don't think the 300 series tube will last long, though. It's not very good in reducing environments such as carbonous and sulphurous acid vapours found in exhaust gases.
Reply to
Potblak
Thanks for the replies
It seams kind of strange though. Most high performance exhaust builders use the 304 or else 321 for racing turbo and sometimes Inconel for really extream turbo application. I have seen the 409 refered to at the cheap alloy the automotive industy came out with for production cars. Top exhaust builders dont even give 409 an honerable mension but some of the off the shelf low dollar headers are made with 409. But in any case 309 will be the filler I will use.
Thanks John Roncallo
Potblak wrote:
Reply to
Anonymous
I did find more information on this topic as to why 304 is used over 409 by hot rod shops. The answer is 304 remains nice looking and 409 gets a surface corrosion after a while and looks ugly but will last longer. Now that I know this and looking at my mufferes and cat's it appeares that MB probably used 409 for all the pipes since they are non magnetic and have surface corosion. And they probably used a 300 series for the actual can since they are non magnetic and are still shinny.
Thanks for the info
John Roncallo
Potblak wrote:
Reply to
Anonymous
I agree..if you can get your hands on "hastelloy W" use it.Your weld will be there forever.
Reply to
digitalmaster

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