Alloy 254 SMO 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.

APPLICATIONS:

Due to its high levels of molybdenum and nickel, Alloy 254 SMO is frequently used in high chloride environments. Examples of applications that call for the used of Alloy 254 SMO include:

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

254SMo  is an austenitic stainless steel, developed for use in halide-containing environments such as seawater. The superiority of this steel manifests itself especially in halide-containing acids. 254SMo also features good resistance to uniform corrosion. As its carbon content is less than 0.02%, it is called pure austenitic stainless steel; when its carbon content is less than 0.01% , it can also be called super austenitic stainless steel.

Features of Inox 254SMo

Super stainless steel is a type of special stainless steel. First of all, unlike ordinary stainless steel, it is a high-alloy stainless steel containing high nickel, high chromium and high molybdenum. The most well-known one is 254SMo with 6% Mo. Due to high molybdenum content, this stainless steel features very good local corrosion resistance. Plus, it features good resistance to pitting corrosion (PI ≥ 40) and stress corrosion when used in harsh conditions like seawater, aeration, gap and low speed scouring. Therefore, it can be a great substitute to nickel-based alloys and titanium alloys. Secondly, it embodies excellent high-temperature resistance and corrosion resistance, which 304 stainless steel cannot match. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenitic metallurgical structure.

According to the results of a large number of field experiments and extensive experience, 254SMo has high crevice corrosion resistance in seawater, even at slightly higher temperatures. Only a few types of stainless steel embody this property. In acidic solutions and oxidizing halide solutions necessary for paper bleaching, 254SMo demonstrates strong corrosion resistance, comparable to that of the most corrosion-resistant nickel-based alloys and titanium alloys.

Due to the high nitrogen content, 254SMo features better mechanical strength than other types of austenitic stainless steel. In addition, 254SMO features high ductility, impact strength and good weldability. The high molybdenum content contained within allows 254SMO to acquire a high oxidation rate during annealing, resulting in a rougher surface than common stainless steel after pickling. However, this does no harm to the corrosion resistance of this stainless steel.

Specification

Chemical properties

Th e chemical composition of stainless steel grade 254 SMO™ is outlined in the following table.

Mechanical properties

The following table shows mechanical properties of stainless steel grade 254 SMOTM.

• 254SMo Applications
• 1)  Ocean:  marine structures in the sea environment, seawater desalination, marine aquaculture, seawater heat exchange, etc.;
• 2)  Environmental Protection:  flue gas desulfurization device for thermal power generation, wastewater treatment, etc.;
• 3)  Energy:  atomic power generation, comprehensive utilization of coal, and ocean wave power generation.;
• 4)  Petrochemical Industry:  refining, chemical equipment;
• 5)  Food:  salt making, soy sauce brewing, etc.;
• 6)  High concentration chloride ion environment:  paper industry, various bleaching devices;
• 7) Others.

STANDARDS:

• ASTM/ASME: UNS S31254
• EURONORM: FeMi35Cr20Cu4Mo2
• DIN :  2.4660

• ORROSION RESISTANCE

• 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
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