[TheForge] Stainless steel Welding

[MRScherm at aol.com]

It's not the welding itself that can be a problem with stainless, but the  
corrosion resistance of the weld in service.  The "L" grades; 304L, 316L  etc 
are "Low" Carbon (less that .025) usually and they are designed for  welding.  
The problem goes like this; when you weld the 300 series  stainless, the carbon 
from the base metal migrates into the grain boundaries  around the weld.  
They then appear as carbides which can corrode - rust as  the passive film that 
makes stainless stainless cant form.  So, the low  carbon grades dont have 
enough "spare" carbon to make these carbides and so no  problem.  If you can 
anneal (1800F water quench) the part after welding, it  does not matter what grade 
you use as the carbon will go back into solution and  be just like it was 
before welding.  But if you cant post-anneal, use an L  grade or:  type 321 or 347 
stainless, both are stabilized (one with  Titanium and the other with 
Columbium (Niobium) and will not rust because of the  stabilization.  The high carbon 
400 series can be real tricky to weld and  440 very nasty and should be 
avoided.  Then, follow the other  suggestions regarding proper weld rod/filler rod 
if used.
Best regards,
Mike Schermerhorn
In a message dated 9/3/2004 12:42:01 PM Eastern Daylight Time,  
rniemi at fidalgo.net writes:

I have a  quick question on this stainless steel topic.  Recently at 
> work  I
> had the engineering department basically call me stupid when I asked  
> them to
> weld something that was stainless steel.  I took  a year of welding in 
> High
> School and if I remember correctly  it can be done.  You mentioned that 
> you
> TIG weld parts  together...  I never got to work with TIG, only MIG...  
>  How
> does a person weld stainless steel?  Does it require a  special welder 
> or
> just a special filler rod?
>
>  Blake