In most cases, critical parts are field tested to evaluate their performance. While in a molten state, these steels are exposed to a vacuum which removes hydrogen and, to a lesser degree, oxygen and nitrogen. Exceptions are nitrided parts, which have better wear resistance than would be expected from the carbon content alone. Other specifications, such as those issued by ASTM, specify minimum properties for critical structural, pressure-vessel, and nuclear applications. ASTM specifications classify cast alloy steels by relating the steel to the mechanical properties and intended service condition.
Chemical analysis is secondary.
There are ASTM specifications for general use such as A27 or A148 when mechanical properties are critical. A352 or A757 is recommended when toughness is important. For weldability, A216 is specified when fabrication is critical, and for pressure service, A217 or A389 is recommended when a number of properties are important. Still other ASTM alloy steels are available for special applications. Other specifications such as SAE J435 are used for cast steels in automotive applications.