Stainless Steel: Alloys and Product Forms-00-780

Stainless steels are iron-based alloys containing 10.5% or more chromium. Other elements are added and the chromium content increased to improve the corrosion and heat resisting properties, enhance mechanical properties, and/or improve fabricating characteristics.

Reference is often made to stainless steel in the singular sense as if it were one material. Actually there are well over 100 stainless steel alloys. Three general classifications are used to identify stainless steels. They are:

1. Metallurgical Structure.
2. The AISI numbering system: namely 200, 300, and 400 series numbers.
3. The Unified Numbering System, developed by the American Society for Testing Materials (ASTM) and Society of Automotive Engineers (SAE), to apply to all commercial metal and alloys.

ALLOYS

The following grades of stainless steel 304 have an austenitic metallurgical structure. It is the basic “18-8” alloy (18% chromium, 8% nickel UNS S30400), is the most readily available grade, and is often specified for “all purpose” applications. It has excellent corrosion resistance and unusually good formability.
316 is basically a 304 grade with the addition of 2 to 3% molybdenum (UNS31600). It has greater corrosion resistance than 304 and is unusually preferred for long-term service in aggressive industrial, chemical and seacoast atmospheres.
409 has a ferritic metallurgical structure. It is a straight chrome alloy (11 to 12% chromium UNS S40900). It has good ductility and corrosion resistance. It is mainly used for internal applications. 410-3 is a dual phase alloy (UNS S41003) with micro alloy element control that permits welding in up to 1 ¼ inches (30 mm).
2205 has a duplex structure which is typically about equal parts of austenite and ferrite (21% chromium, 4.5% nickel, 2.5% molybdenum UNS 32304). It has excellent about twice the yield strength as conventional grades.

CONDITION

Stainless steel is usually available in the “Hot Rolled and Annealed” condition and has yield strength of about 42 ksi. The austenitic grades can be hardened by cold working the material. 301 (UNS S30100), a modification of 304,(with the chromium and nickel lowered slightly to increase the work hardening rate), can be supplied in various “tempers” up to full hard with a yield strength of 140 ksi.
The American Society of Civil Engineers (ACSE) has a standard ANSI/ASCE 8-90, “Specification for the Design of Cold Formed Stainless Steel Structural Members”, which details the design information on “cold formed” stainless steel.

PRODUCT FORMS

The forms of stainless steel used in structural applications are: plate and sheet (often fabricated into structural shapes), extrusions, forgings, preformed products (tubes and angles), bar and rod, wire and castings.

Plate is defined as material that has a thickness of 3/16” or greater. It is usually available in widths of 48, 60, 72 and 96 inches. It can be supplied as individual flat plates or in “coil” form (some limits on thickness and width).
Many structural shapes are produced by fabricating the plate into beams, angles and other components.
Sheet is defined as material that has a thickness of less than 3/16” and is usually supplied in either 48 or 60 inch wide coils.

Shanti Foils Private Limited deals in the manufacturing and trading of all types of stainless steel sheets (patta and patti), sheet cuttings, hot and cold rolled coils, rods, wires, utensils, kitchenware, cutlery and scrap ( stainless steel, HMS - I, HMS - II, aluminum and copper). For more information, detailed specifications, sale and purchase of these items, visit the site: http://www.shantifoils.com/

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