Achieving Sustainability

Austenitic

Austenitic is the most popular stainless steel group, it can be further grouped into three categories—manganese-chromium-nickel-nitrogen 200 series, common chromium-nickel 300 series and specialty alloys. Austenitic stainless steel is used in many consumer and industrial applications, e.g., food processing and equipment, power factory and chemical plants. Properties of Austenitic are:

• High corrosion resistant + good weldability and formability + good creep resistance + good temperature resistance from cryogenic to high heat + easily machined and fabricated to tight tolerances
• Medium to high strength
• Non-magnetic
• Smooth surface finish that can be easily sterilized and cleaned
• Hardenable by cold working
• Contains nickel

Ferritic

Ferritic has lower corrosion resistance than austenitic because it contains less chromium. Some ferritic stainless steel can be used in kitchen sinks, couters, washing machine drums and exhaust systems, such as 409 and 405. Other ferritic steels that low in C and N are more costly, but are high in chloride resistance, such as 444 and 261. Their properties include:

• Good corrosion resistance + good weldability and toughness + high machinability and workability to tight tolerances
• Moderate strength and toughness
• Magnetic
• Smooth surface finish
• Not hardenable by heat treatment or cold working
• Contains low carbon and no nickel

Martensitc

Martensitic stainless steel can be hardened by heat treatment to high strength levels. It has the lowest corrosion withstand abilities comparing to austenitic and ferritic families. Type 410 is the basic alloy in this group, other types including 403, 410, 410NiMo and 420. Their properties are:

• High strength + high wear resistance + high machinability and workability to tight tolerances
• Limited or Good corrosion resistance
• Magnetic
• Smooth surface finish
• Hardenable by heat treatment
• Contains no nickel