Most of the data in MatWeb has been supplied directly by companies in the supply chain - most often the manufacturers, or, less commonly, distributors or fabricators. Other data has been taken from standards organizations or from similar materials/known relationships by the MatWeb staff. For more information about this specific material, see the following source(s):
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ASM Specialty Handbook - Carbon and Alloy Steels, edited by J.R. Davis, Davis & Associates, ASM International, Metals Park, OH, (1996).
Engineering Properties of Steels, Philip D. Harvey, editor, American Society for Metals, Metals Park, OH, (1982).
Metals Handbook, Vol.1 - Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International 10th Ed. 1990.
Metals Handbook, Howard E. Boyer and Timothy L. Gall, Eds., American Society for Metals, Materials Park, OH, 1985.
Physics for Scientists and Engineers with Modern Physics, 2nd ed., Douglas C. Giancoli, Prentice Hall Publishers, Englewood Cliffs, NJ (1989)
SAE Ferrous Materials Standards Manual, 1999 ed., HS-30, Society of Automotive Engineers, Inc., Warrendale, PA, (1999).
For ASTM A572 Grade 42
http://www.matweb.com/search/DataSheet.aspx?MatID=14023
Four grades are avaiable - 42, 50, 60 and 65, which represent min RT YS in ksi. The material's strength depends on composition and thermo-mechanical processing (e.g. controlled rolling and accelerated cooling methods).
ASTM materials standards are intended to provide some specifications for manufacturing and product acceptance in order to assure quality and uniformity of product. The ASTM standards do not provide performance criteria or characteristics. That must be determined by the end user.