Steel Grades and Specifications Explained (Part 1): Standards Organizations

Bethlehem Steel, photo by Michael LaMartin Bethlehem Steel, photo by Michael LaMartin[/caption]

Did you know there are over 3,500 different grades of steel? While all steel is composed of iron and carbon, each grade is comprised of unique physical, chemical, and environmental properties. But it’s the amount of carbon, and additional alloys, as well as the level of impurities, that determine the properties of each steel grade.

Steel Standards Organizations

A number of standards organizations have developed grades to classify various steels by their composition and physical properties.There are two major numbering systems used by the steel industry, the first developed by the American Iron & Steel Institute (AISI), and the second by the Society of Automotive Engineers (SAE). Both of these systems are based on four digit code numbers: the first digit indicates the main alloying element, the second digit indicates the secondary alloying element, and the last two digits indicate the amount of carbon, in hundredths of a percent (by weight). For example, a 1060 steel is a plain-carbon steel containing 0.60 wt% C.

There is also the American Society for Testing and Materials (ASTM), which is different from AISI. One main difference is that AISI is a North American association while ASTM is an international one. AISI is concerned only with steel and iron products; ASTM is concerned with several other products including plastics, rubber, textiles, petroleum, and more.

The largest concern of AISI is to make the North American steel and iron industry more profitable and safer. ASTM, on the other hand, is concerned with regulating the development and production of different materials used worldwide.

Then, there is the American Institute of Steel Construction (AISC). It is a not-for-profit technical institute and trade association for the use of structural steel in the construction industry in the U.S. AISC supplies specifications, codes, technical assistance, quality certification, standardization, and market development for its member. Their mission is to make structural steel the material of choice for new structures.

Other countries have their own grading systems, including JIS (Japan), DIN (Germany), and GB (China).

Steel Specifications for Pallet Rack

ANSI MH16.1: 2012, Specification For The Design, Testing And Utilization Of Industrial Steel Storage Racks states:

1.2 MATERIALS

This Specification assumes the use of steel of structural quality as defined by the specifications of the American Society for Testing and Materials (ASTM) that are listed in the American Iron and Steel Institute (AISI) North American Specification for the Design of Cold-Formed Steel Structural Members [1]1, and the American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings [2].

Steels not listed in the above specifications are not excluded provided they (a) conform to the chemical and mechanical requirements of either reference [1] or [2] or other published specifications, which establish their properties and structural suitability and (b) are subjected either by the producer or the purchaser to analyses, tests, and other controls in the manner prescribed by either reference [1] or [2] as applicable.

1.3 APPLICABLE DESIGN SPECIFICATIONS

Except as modified or supplemented in this Specification, the AISI [1] shall be used for the design of cold-formed members and the AISC [2] shall be used for the design of hot-rolled members. These specifications shall be used to determine the available strength and stiffness of industrial steel storage racks.

Stay tuned; our next post in  this series will explore the exciting world of Steel Categories and Classifications!

Photo Credit: Michael LaMartin via Flickr. Click here to view source.

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