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Guest Editorial

Defining specifications

By Peter Schlafly & Viktor Pocajt

(First in a three-part series)

July 2010- In today’s global market--where a product can be designed in the United States, manufactured in India and recycled in Europe--companies need to be familiar with metals specifications. Consulting these standards helps designers and metallurgists find a common definition for a product’s properties, making it easier to communicate and convert from one material to another.

However, specifications are difficult to decipher, even for large companies. There are thousands of ferrous, nonferrous and alloy materials, and there is no common global standard or classification system.

key to metalsFerrous and nonferrous materials from around the world are grouped on the basis of chemical composition or mechanical properties and then further grouped into product type or delivery conditions, such as flat-rolled, bars or pipes. There are many classification and specification systems accepted and used worldwide, which standards development organizations, specific vertical industries or suppliers develop and standardize either nationally or internationally. Each standards development organization defines the metal products, delivery conditions and the properties of metals in its own way.

U.S. standards
The American Society for Testing and Materials is a common standard for steel specifications in the United States. These steel specifications represent a consensus from producers, fabricators and users of steel mill products. In many cases, the dimensions, tolerance limits and restrictions in the ASTM specifications are the same as the corresponding items of the standard practices in the American Iron and Steel Institute steel product manuals.

The American Society of Mechanical Engineers has adopted many of the ASTM specifications with slight or no modification. ASME uses the prefix S with the ASTM specifications. For example, ASME SA 213 and ASTM A 213 are the same.

Sometimes SAE/AISI designations for the chemical compositions of carbon and alloy steels are included in the ASTM specifications for bars, wires and billets for forging. Some ASTM specifications for sheet products incorporate SAE/AISI designations for chemical composition.

Even though the AISI standards no longer are maintained and increasingly have been replaced by SAE, ASTM and other U.S. standards, they still are used worldwide.

International standards
Euronorm is a harmonized system of metal and steel standards in European countries. Although it is accepted and effectively used across Europe, often obsolete national systems, such as Germany’s DIN, Britain’s BS, France’s AFNOR and Italy’s UNI, are found in many documents.

The Japanese Industrial Standards Committee in Tokyo develops the JIS standard. The specifications begin with the prefix JIS, followed by a letter G for carbon and low-alloy steels. They are used in the Asian and Pacific regions. JIS steel specifications also have been used as a base for other national systems, such as Korean, Chinese and Taiwanese standards.

Because of global sourcing, several other standards, such as China’s GB and YB, India’s IS and Brazil’s NBR, increasingly are being used. However, they are often less comprehensive. Russia’s GOST is the de facto standard for the whole Community of Independent States.

Industry-specific standards
Vertical industrial steel standards include SAE for automotive, aerospace and more; ASME for pressure vessels and many other applications; and AWS for welding consumables and related materials. The U.S. ABS, Lloyds British Testing, Italy’s RINA and others cover shipbuilding specifications.

In addition to the many standards described above, various steel manufacturers and suppliers have developed their own proprietary, commercial names for designating steels.

Some of these designations have, after decades of use, become widely used within the industrial community and are referred to as common names or trade names without actually referring to the particular supplier. In most cases, these common names are not standardized, and properties may vary substantially. MM

The Key to Metals database brings together global metal properties and standards into one integrated and searchable database. Quick and easy access to mechanical properties, chemical composition, cross-reference tables and more gives users useful information for more than 150,000 alloys.

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