mig welding 409 stainless steel?

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I have an outdoor wood burning boiler made of 10g 409 stainless and when it was built they used mild steel wire when they welding the flue pipe together.The weld has rust out and it leaks water into the fire box.What would the best wire and gas combo for this job?,The pipe has been heated and cooled many time from the boiler running for 5 years.Any help would be greatthanks Gary
Reply:Try to clean it all up, and if you can, get some 309 filler. If none is available, just use 308 filler.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:A very timely question because US auto manufacturers will be required to have 100.000 mile exhaust systems in the near future.409 is a titanium stabilised ferritic stainless steel.Use 309 filler but for high temperatures use 309Cb. If you light up a Tig torch on the area after it is cleaned and you see little cracks running everywhere like a dried up river bed, that means the corrosion is all thru the metal and it is at the end of its life so to speak.You can just Google 409 stainless of coarse and find even more information.Last edited by Donald Branscom; 08-21-2008 at 10:43 AM.AWS certified welding inspectorAWS certified welder
Reply:And this is a real world example of what happens when the wrong/incompatible filler/wire/rod is used for the base materials.Yes it welded together with the mild steel wire.  But it wasn't right, it didn't last, and now it has to be repaired/replaced because it wasn't done 'right'.As stated, 409 is a ferritic stainless steel, with a little titanium in the alloy.  General welding recommendation for ferritic stainless is to use a filler with matching or greater chromium levels (nominal 11% Cr for 409), minimize heat input, minimal pre-heat (300F-450F for the higher carbon versions like 430 at 0.12% versus 409 at 0.08% C), fused GTAW a generally accepted practice for thin materials (means good fit-up needed, no gaps).Recommended filler is ER409 or ER430 for GTAW/GMAW, E430 for SMAW (I wouldn't stick weld thin-wall stainless tube, though).  ER309 has plenty of chromium, but also adds a lot of nickel.  409 has almost no nickel.Lincoln Outershield MC-409 (a gas-shielded metal-cored wire made for single-pass welding of 409 tube) is one possible choice.  Uses 98-2 Ar-O2, single-pass as stated.  The 33 lb spool of 0.045 wire is Lincoln part number ED031419 (smallest spool and smallest diameter listed, bigger is available).  Parameters are available on the Lincoln website/catalogs/etc, for 0.045 wire and 98-2 it starts at 180 ipm wire feed at 19-21V and ~145A to 320 ipm wire feed at 22-24V and 230A.Lincoln also lists Outershield MC-409W (improved wetting compared to 'plain' 409).  The part number for a 33 lb spool of 0.045 wire is ED031421.  Same parameters as listed above.ESAB Arcaloy 409Ti is another possibilty.  33 lb spool of 0.045 wire, part number/SKU 258076215.  List price $4.659/lb, alloy surcharges possible.  Similar parameters.ESAB Arcaloy 409Cb is another choice.  It has a little niobium for high temperature corrosion resistance  and strength improvements compared to plain 409.  33 lb spool of 0.040 wire is part number/SKU 258080100.All this info available by checking the appropriate websites.  The best laid schemes ... Gang oft agley ...
Reply:Wowwwwwwwwww!!!!!!!! Now that what i call a COMPLETE awnswer MOONRISE.(Makes me feel like i did not even try.) HahahahhahI will copy that and put that in my welding notebook. Thanks Moonrise.AWS certified welding inspectorAWS certified welder
Reply:MoonRise,That was truly a well stated, informative reply.We all learned something from that post.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Moonrise, do you think they have any rolls smaller than 33lb for that 409 filler?? He only needs to do a flue stack. That would leave 32.75lb excess wire, and EXPENSIVE at that!!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:re: the spool size.  The 33 pound spools were the smallest that I saw in the catalogs.  They did list bigger though.    Need a 500 lb drum of 0.045 Lincoln MC-409?  Part number ED027361.  Yet another reason why it sucks to have to redo something not done 'right' in the first place.  A manufacturer would easily use a 33 lb or bigger amount of wire.  One guy fixing a boiler might use one pound of wire or less (unless it's a really big boiler!).Maybe find a shop that does stainless exhaust pipe welding (which is usually 409 stainless).  Have them do it, or maybe you can sweet talk them into changing their partially used 33 lb spool of 409 wire a few pounds early and you buy that off of them?Or start using a lot of 409 stainless material now that you have 32.5 lbs of 409 wire sitting around.    The best laid schemes ... Gang oft agley ...
Reply:ok first a 33lb spool wouldn't fit in my welder...2 will only handle .030 wire...3 it's only a 150amp..will the 308 or 309 filler work?....and yes i'd like to do it by the book,but i have to use what i have....
Reply:Originally Posted by ghitch75ok first a 33lb spool wouldn't fit in my welder...2 will only handle .030 wire...3 it's only a 150amp..will the 308 or 309 filler work?....and yes i'd like to do it by the book,but i have to use what i have....