This specification covers gray iron for castings suitable for pressure-containing parts at elevated temperatures. Castings shall be stress-relieved by placing them in a suitable furnace and heating them uniformly to the temperatures and for the times specified. Castings to be used at a particular temperature range shall undergo heat treatment and cooling. Chemical analysis shall be performed on each class of castings and shall meet the maximum requirement for carbon, phosphorus and sulfur. Iron used in supplying castings shall conform to the required tensile strength. Separately cast test bars having the required dimensions shall be poured from the same lot as the castings represented. The test bars shall be cast in dried siliceous sand molds maintained at approximately room temperature. Tension test shall be performed on each lot and materials shall conform to the tensile requirements specified.

1.1 This specification2 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.