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Stainless Steel Specialty Products

Stainless steel is essentially a low carbon steel which contains chromium at 10% or more by weight. It is this addition of chromium that gives the steel its unique stainless, corrosion resisting properties.

The chromium content of the steel allows the formation of a rough, adherent, invisible, corrosion-resisting chromium oxide film on the steel surface. If damaged mechanically or chemically, this film is self-healing, providing that oxygen, even in very small amounts, is present. The corrosion resistance and other useful properties of the steel are enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel and nitrogen.

There are more than 60 grades of stainless steel. However, the entire group can be divided into five classes. Each is identified by the alloying elements which affect their microstructure and for which each is named.

Stainless Steel Benefits

Aesthetic Appearance

The bright, easily maintained surface of stainless steel provides a modern and attractive appearance.

Corrosion Resistance

Lower alloyed grades resist corrosion in atmospheric and pure water environments, while high-alloyed grades can resist corrosion in most acids, alkaline solutions, and chlorine bearing environments, properties which are utilized in process plants.

Ease of Fabrication

Modern steel-making techniques mean that stainless can be cut, welded, formed, machined, and fabricated as readily as traditional steels.

Fire and Heat Resistance

Special high chromium and nickel-alloyed grades resist scaling and retain strength at high temperatures.

Hygiene

The easy cleaning ability of stainless makes it the first choice for strict hygiene conditions, such as hospitals, kitchens, abattoirs and other food processing plants.

Impact Resistance

The austenitic microstructure of the 300 series provides high toughness, from elevated temperatures to far below freezing, making these steels particularly suited to cryogenic applications.

Long-term Value

When the total life cycle costs are considered, stainless is often the least expensive material option.

 

Stainless Steel Type 304

This is the most versatile and one of the most widely applied of the 300 series stainless steels. It has excellent forming and welding characteristics. It is easily brake or roll formed into a variety of parts for application in the industrial, architectural and transportation industries.

Type 304 also has outstanding welding characteristics. Post-weld annealing is not required to restore the excellent performance of this grade in a wide range of mildly corrosive conditions.

Type 304L does not require post-weld annealing and finds extensive use in heavy gauge components, where freedom from carbide weld precipitation is often required.

Corrosion Resistance

The corrosion resistance of Type 304 is excellent in a wide variety of corrosive media including hot petroleum products, steam combustion gases.

Typical Applications

The list of applications for this general purpose grade is extensive and includes:

• Beer barrels
• Bulk milk coolers
• Food processing equipment
• Fire extinguisher parts
• Wine storage tanks
• Chemical containers
• Heat exchangers
• Winding Wire
• Truck Accessories

Welding

Weldability is excellent, by all standard methods. Heavy welded sections in Type 304 may require post-weld annealing for maximum corrosion resistance. This is not required if Type 304L is used.

Stainless Steel Type 316

Type 316 is a molybdenum bearing grade. This addition gives this grade better overall corrosion resistance properties than Types 301 and 304. In addition, this type also has a higher creep strength at elevated temperatures. Type 316 gives useful service at room temperature in sulphuric acid of concentration lower than 15% and higher than 85%. It also resists chloride attack and is often selected for use in marine atmospheres.

Heat Resistance

Good oxidation resistance in intermittent service to 1600° F and in continuous service to 1700° F. Continuous use of 316 in 800 – 1575° F range not recommended but often performs well in temperatures fluctuating above and below this range. Type 316L is more resistant to carbide precipitation and can be used in the above temperature range.

Heat Treatment

Annealing-heat to 1850 – 2050° F and cool rapidly. These grades cannot be hardened by thermal treatment.

Corrosion Resistance

Good resistance to a wider range of chemicals than Type 304. Highly resistant to the complex sulphur compounds used in pulp and paper processing. Also resists attack of marine and corrosive industrial atmospheres.

Typical Application

The list of applications for this grade includes:

• Pulp & paper equipment
• Heat exchangers
• Potash Development
• Propeller shafts
• Fittings
• Exterior architectural components in marine coastal equipment areas

Welding

Good characteristics suited to all standard methods.

Stainless Steel Type 430

Type 430 is a straight chromium, non-hardenable grade combining good corrosion resistance and formability characteristics with useful mechanical properties. Its ability to resist nitric acid attack permits its use in specific chemical applications but automotive trim represents its largest field of applications.

Heat Resistance

Resists scaling in intermittent service to 1700° F and in continuous service to 1600° F

Heat Treatment

Annealing-heat to 1150 – 1225° F for 12 to 24 hours and air cool. Hardening-hardened by heating to 1800 – 1900° F, quenching in oil and tempering to suit mechanical requirements. See accompanying table and chart.

Typical Application

The list of applications for this general purpose grade is extensive and includes:

• Automotive trim
• Lashing
• Wire
• Element supports
• Stove trim rings
• Fasteners
• Chimney liners

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