1.1 This specification 2 covers gray iron for castings suitable for pressure-containing parts for use at temperatures up to 650 °F [350 °C]. 1.2 Classes of Iron: 1.2.1 Castings of all classes are suitable for use up to 450 °F [230 °C]. For temperatures above 450 °F and up to 650 °F, only Class 40, 45, 50, 55, and 60 castings are suitable. 1.2.2 Castings of all classes are suitable for use up to 230 °C. For temperatures above 230 °C and up to 350 °C, only Class 275, 300, 325, 350, 380, and 415 castings are suitable. 1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.