UNS Number S31254

SMO 254 is a very high end, molybdenum and nitrogen alloyed super austenitic stainless steel with low carbon content. It demonstrates outstanding resistance to pitting, crevice corrosion stress cracking, and corrosion fatigue uniform corrosion. Alloy 254 SMO is substantially stronger than the common austenitic grades, with strength nearly twice that of 300 series stainless steel. It is also characterized by high ductility and impact strength. With high levels of chromium, molybdenum, and nitrogen, Alloy 254 SMO is frequently used in high chloride environments, such as brackish water, seawater, pulp mill bleach plants, and other chloride process streams. In some applications it has even been found to be a more cost effective substitute for high nickel and titanium alloys.

 

Available Forms of SMO 254 at Rooplaxmi Steels:

•           Sheet
•           Plate
•           Bar
•           Pipe & Tube (welded & seamless)
•           Fittings
•           Wire

Characteristics of SMO 254:

•           Excellent resistance to pitting and crevice corrosion due to its high chromium, molybdenum, and nitrogen content
•           Has a very low carbon content, which means there is very little risk of carbide precipitation during heating
•           Possesses very good resistance in water containing chlorides, therefore, it is suitable for use in seawater as it can be exposed to it for prolonged periods without suffering from crevice corrosion

SMO 254 Chemical Composition, %:

C	Cr	Cu	Mn	Mo	N	Ni	P
0.02 max	19.5-20.0	0.5-1.0	1.0 max	6.0-6.5	0.18-0.20	17.5-18.0	0.03 max

 

Si	S	Fe
0.80 max	1.01 max	Balance

 

Application of SMO 254:

•           Petroleum production
•           Saltwater handling
•           Pulp mill bleach systems
•           Tall oil distillation columns
•           Desalination equipment
•           Food and chemical processing equipment
•           Flue gas desulphurization scrubbers
•           Offshore oil & gas production equipment

Machining and Fabrication with SMO 254:

SMO 254 is quite tough to machine due to the extremely high work hardening rate and lack of sulfur content; however using sharp tools, overpowered machine tools, positive feeds, good amount of lubrication, and slow speeds tend to provide good machining results. Welding of SMO 254 requires filler material without which it results in poor strength properties. Filler metals such as AWS A5.14 ERNiCrMo-3, and alloy 625 are recommended. Electrodes used in the process, have to match with AWS A5.11 ENiCrMo-12. Annealing of this material should be performed at 1149-1204°C (2100-2200°F), which should be followed by a water quench. Forging, upsetting and other operations relating to this material can be performed at 982 - 1149°C (1800 - 2100°F). Cold working can be carried out using all the traditional methods; however the process would be tough due to its high work hardening rate. It does not respond to heat treatment. Hardening is possible only through cold reduction.

SMO 254 ASTM Specification:

Smls Tube & Pipe	Welded Tube & Pipe	Bar	Forging	Fitting
A269, A213, A312	A249, A269, A312, A358, A409	A276	A473	A182

 

Mechanical Properties of SMO 254:
At Room Temperature

Tensile Strength	98600 psi or 680 Mpa
Yield	(0.2 % offset) 43500 psi or 300 Mpa
Elongation at break	50 %