Designated as UNS S31254 or DIN W.Nr. 1.4547, 254SMO is an Cr-Ni-Mo alloyed super austenitic stainless steel with deliberate additions of copper and nitrogen content. With high levels of chromium, molybdenum, and nitrogen, 254SMO is especially suited for high-chloride environments and offers chloride resistance superior to Alloy 904L, SS316L, Alloy 20 and Alloy 825. It can be readily welded to other common austenitic stainless steels. The 254 SMO stainless steel provides outstanding resistance to pitting corrosion, crevice corrosion, as well as stress-corrosion cracking. It is widely used in seawater handling & desalination equipment, pulp and paper industry, oil refinery plant, chemical processing equipment, and food processing equipment, etc.

1. Chemical Composition of 254SMO

Element	Wrought	Castings
Carbon	≤0.020	≤0.025
Chromium	19.5-20.5	19.5-20.5
Nickel	17.5-18.5	17.5-19.5
Molybdenum	6.0-6.5	6.0-7.0
Nitrogen	0.18-0.22	0.180-0.240
Copper	0.50-1.00	0.50-1.00
Sulfur	≤0.010	≤0.010
Phosphorus	≤0.030	≤0.045
Silicon	≤0.80	≤1.00
Manganese	≤1.00	≤1.20
Iron	Balance	Balance

2. Mechanical Properties of 254 SMO

Tensile Strength, min.		Yield Strength, min.		Elongation, min.	Hardness, max.
ksi	Mpa	ksi	Mpa	%	Brinell HBW	Rockwell
95	655	45	310	35	223	96 HRBW

*The values are furnished on the basis of 254SMO plates.

3. Physical Properties of 254 SMO

Modulus Elasticity	Thermal Conductivity	Specific Heat	Density	Melting Range	M.P
106psi	Btu/hft°F	Btu/lb°F	g/cm3	°C	-
29	7.5	0.120	8.1	1320-1390	1.003

*All values are measured at room temperature.

4. Product Forms and Relative Standards

Product Form	Standard
Plate, Sheet, Strip	ASTM A240,A480
Bar, Billet	ASTM A276, A479
Seamless and Welded Pipe	ASTM A312, A358, A409, A813, A814
Seamless and Welded Tube	ASTM A249, A269, A270
Fittings, Forgings	ASTM A182, A403, A473
Bolting, Nuts	ASTM A193, A194
Casting	ASTM A351, A743, A744

*254SMO is designated differently in different product forms: for wrought pipe fittings, it is ASTM A403 WPS31254; for forgings, it is ASTM A182 F44; for castings, it should be CK3MCuN or UNS J93254.

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