This specification covers the 8 and 9% nickel-alloy steel forged or rolled flanges, fittings, valves, and parts intended for use in welded pressure vessels for low-temperature service. Two types of materials are specified according to the chemical composition: type I and type II. Materials for forgings shall consist of ingots, or either forged or rolled blooms, billets, or bars. Except for all types of flanges, elbows, return bends, tees, and header tees, other parts including NPS 4 may be machined from hot-rolled or forged bar. The steel shall conform to the specified chemical requirements for carbon, manganese, phosphorus, sulfur, silicon, and nickel. The following methods of heat treatment shall be used: quenched and tempered and double normalized and tempered. Two tests shall be done to meet the mechanical requirements of the material: tension test and Charpy impact test.

1.1 This specification covers 8 and 9 % nickel-alloy steel forged or rolled flanges, fittings, valves, and parts intended for use in welded pressure vessels for low-temperature service. The specification is applicable to forgings with maximum section thickness of 3 in. [75 mm] in the double normalized and tempered condition and 5 in. [125 mm] in the quenched and tempered condition. Forgings under this specification are intended for service at operating temperatures not lower than −320 °F [−196 °C] for Type I or −275 °F [−170 °C] for Type II or higher than 250 °F [121 °C].