316 filler for all stainless??

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thought i red o a site somewhere that "we only have 316 filler in the shop so we dont mix it up." (mix it and weld 316 with 308 and get corrosion)Can i use 316 for all the 3XX stainless or is there a side affect.Looks like the prices are close enough.G
Reply:Like everything in life Gordfraser, it depends on the situation.  In many instances you can use 316 filler with many common grades of stainless steel.  304, 303, and 316 are commonplace, and you could weld all of them with 316 filler.  As a general rule of thumb, you can weld the 300 series stainless steels that are the same or lower in number with a filler metal that is the same or higher in number.  304 base with 316 filler: OK316 base with 308 filler: not OKYou can debate what not OK and OK mean as well.  Using the wrong filler may degrade the corrosion resistance of the weldment.  You could also wind up with a brittle weld, or hot cracking; if the mis-match is severe.  Whether or not these are bad problems depends on the end use of the weldment.There are other grades, like 440 or 17-4PH that would not be good candidates for welding with 316 filler.If you can't consult with an expert, say customer support at a LWS or filler metal manufacturer, the best thing to do is match the filler to the base metal.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Any welding on 303, 304, 316, etc. SS and you'll get corrosion of some form or fashion over time that can include complete 'rust through' at the weld site.  That is of course without chemical (preferred) or mechanical removal of the carbon deposits left behind as a result of the welding process.  Chemical 'passivation' is the preferred method of surface carbon removal that allows formation of the microscopic layer of oxidation that gives SS it's corrosion resistance.  Some grades, such as 303, aren't very corrosive restistant at all but are used for their ease of machining.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Duaneb55,A welder can minimize the corrosion in the vicinity of a stainless steel weld by choosing a low carbon alloy filler.  These usually have an L, as in 308L, in the name.  If you don't add any carbon to the weld, you don't get chromium carbides in the weld HAZ.  If you add carbon to the weld metal it reacts with the chromium in the base metal and prevents the chromium from forming a thin oxide layer on the metal surface.  It's this oxide layer that provides stainless steel with it's corrosion resistance.This is a real issue with the lower chromium grades of stainless, like 409 and 410.  It becomes less likely to occurr in the higher alloy stainless steels.  The L grades of filler metal will sometimes also include small amounts of Titanium, Niobium, or Tantalum(really exotic).  These 3 elements scavenge carbon and act to prevent the chromium-carbon reaction from occurring.  These alloying ingredients play other roles in the alloy, but can also provide some insurance against degradation of the corrosion resistance of the weldment.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thanks for the additional technical facts and in depth explanation A_DAB_will_do.  I am familiar with L vs. non-L grades and I knew there was more than what little I had to offer but would you agree your statement that "A welder can minimize the corrosion..." supports my claim that "you'll get corrosion of some form or fashion over time..." at least to some extent?  I've seen 12gauge 304 and 316 water tanks corrode through at the welds and even non-removed buckshot points in 8-10 years of service.Thanks again for the additional info.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:You can actually completely eliminate the corrosion if you can apply a post weld heat treatment.  The temps are from memory...I think if you heat the weldment and surrounding base metal over 1400C and hold it for a brief soak then slowly cool to 1000C, cool rapidly from 1000C to <600C and then slowly cool to room temp.The Chromium carbides that can form as a result of welding will redisolve at temps over 1400C.  They form and grow most rapidly in the temp range of 600-1000C, hence the rapid quench through this temperature range.  Rapid cooling prevents the atoms from moving around and recombining to form the carbides.Unfortunately, this all has to be done in a vacuum furnace or inert gas atmosphere or you'll get severe scaling on all the exposed ss surfaces.  Most folks don't have access to a furnace that can accomodate large parts and meet the inert atmosphere requirements.Here's a link to an interesting discussion of a related issue, that get's back to the original question of why selection of the correct filler metal for SS is important.  The article the link takes you to is at the high tech end of the spectrum, but if you pick through it you'll find some interesting facts buried in all the mumbo-jumbo.http://www.refmet.net/technical/anch..._failure_3.htmBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:OK, I tried to get through the entire article all but it'll have to wait until I can focus a little better.As for the rest of the information in your post, I would agree, there are few that would have the ability to perform the required procedures to completely eliminate post weld corrosion and certainly for anything or any size.  Chemical passivation tanks however can be of a size required to accomodate large items and I've seen them approximately 8' wide x 20' long x 4' high as an example.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!