This specification covers 8 and 9% nickel alloy steel plates for use in the water quenched and tempered condition intended for the fabrication of welded pressure vessels. The materials shall be available in two types, namely Type I and II, having different chemical compositions. The maximum thickness of plates is limited only by the capacity of the material to meet the specified mechanical property requirements. The material is susceptible to magnetization and the use of magnets in handling after heat treatment should be avoided if residual magnetism would be detrimental to subsequent fabrication or service. The steels shall be killed and shall conform to the fine austenitic grain size requirement specified. The plates shall be tempered and hardened by heat treatment. The specimens shall be subjected to tension and Charpy V-notch impact tests.