Stabilised Grade
A stainless steel alloyed with titanium (321) or niobium (347) so that carbon is tied up as a stable carbide and cannot rob the grain boundaries of chromium.
Where stabilised beats low carbon
A low-carbon grade solves sensitisation during welding. It does not solve long exposure in service between 425 and 815 °C, where even 0.030% carbon will eventually precipitate. Stabilised grades do — which is why expansion bellows, exhaust systems and hot refinery vessels specify 321 or 347.
Ti or Nb
321 uses titanium and is the general choice. 347 uses niobium, which survives the welding arc better, so 347 is preferred for welded high-temperature pressure parts.
Related terms
Where this applies
Austenitic Stainless Steel Plate
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