UNDERSTANDING
MATERIAL SPECIFICATIONS FOR STEEL CASTINGS
The world of specifi cations is wide and can be confusing. Knowing the most critical concerns for cast parts is a necessity for the casting end-user.
A Classifi cation Overview
According to materials information society ASM International, Materials Park, Ohio, car- bon and low alloy steels generally are classifi ed based on composition. T e higher-alloy steels (stainless, heat-resistant, wear-resistant steels, etc.) can be classifi ed according to composition, microstructure, application or specifi cation. Carbon steels contain only carbon as the principal alloying element, but other elements,
AN MCDP STAFF REPORT
number of considerations affect the way a steel part should be specified for a metalcasting facility, including material properties, tolerance limits, inspection and certification. To make things simple, the Steel Founders’ Society of America, Crystal Lake, Ill., recommends
end-users deliver the following to their casting supplier: • Shape of the metal casting (drawing or pattern).
• Number of parts. • Supplementary requirements (test methods and acceptance criteria).
• Material specifi cation and grade. For many designers, the fi nal piece of this
puzzle can be the most diffi cult. What material specifi cations are appropriate for casting alloys, and how should they be delivered to your cast- ing supplier?
such as silicon and manganese may be added for deoxidization. Low alloy steels contain other alloying elements up to a total of 8% alloy content in addition to carbon. Of the three major classifi cation systems used in the U.S., two employ
STEEL SPECIFYING SIMPLIFIED When choosing a material to fulfi ll
other benefi cial characteristics, as well. 1 and weldability.
2 3
28 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2012
your casting needs, the following basic guidelines can help simplify your decision-making process. Choose a material that can develop the necessary strength for your ap- plication, but remember to consider
Make sure the material has suf- fi cient hardenability to allow opti- mum heat treatment response.
Keep your carbon and alloying additions to a minimum to improve part castability
chemical composition as their basis: • T e American Iron and Steel Institute (AISI) and Society of Automo- tive Engineers (SAE) System. T e AISI/ SAE system uses a four- or fi ve-digit code designation (e.g. AISI/ SAE 1040), where the last two or three digits indicate carbon content (three digits are used for steels with 1.00% carbon or more), and the fi rst two digits refer to compositional class. AISI/SAE 1040 refers to carbon steel with 0.4% carbon. (See Table 1 for a full list of compositional classes.)
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