ASTM A959:2011 255: Duplex (austenitic-ferritic) stainless steel type 255 (UNS S32550) with the composition limits of ASTM A959-11. Carbon up to 0.04% and chromium 24.0-27.0%.
Matched by chemical composition and mechanical properties, not a formal equivalence claim. Always verify against the applicable standard before substitution.
Chemical Composition (%)
C
Cr
Cu
Mn
Mo
N
Ni
P
S
Si
<=0.04
24.0-27.0
1.50-2.50
<=1.50
2.9-3.9
0.10-0.25
4.5-6.5
<=0.040
<=0.030
<=1.00
More data from ASTM A959:2011
From the standard
Other composition limitsfrom Table 1 and its footnotes
UNS number
S32550
Metallurgical class
Austenitic-ferritic (duplex) grade: a mixture of austenitic and ferritic structures, hardenable only by cold working
Type
255 (common type number, not a trademark, widely used; not associated with any one product)
Values
Maximum unless a range or minimum is shown; where two limits are shown for the same element in one grade the more stringent applies
Other elements (as printed)
Cu 1.50-2.50
These are the recommended composition limits of the A959 guide, intended for adoption by standards for stainless steel products; they are not a product specification.
Source: ASTM A959:2011, Table 1 and its footnotes
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