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The ASTM A-890 Grade 1B (CD4MCuN) is a duplex stainless steel alloy that is similar to the Grade
1A, but has a controlled nitrogen level
C - 0.04 max,
Cr -
24.5-26.5, Ni - 4.75-6.00,
Cu - 2.75-3.25, Mo - 1.7-2.3,
N - 0.10-0.25,
Mn - 1.00 max, P - .040 max,
S - 0.040 max,
Si
-
1.00 max
Controlled nitrogen in the 1B
increases the fracture toughness of the alloy.
But the ultimate tensile strength and yield strength of the baseline grade 1B are too low.
Spuncast
engineers modified the 1B alloy with a proprietary composition change
which increased the ultimate strength, yield strength, and % elongation,
so that all the mechanical requirements were met.
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