Patent Number: 6,254,697

Title: Cast steel material for pressure vessels and method of making a pressure vessel by using same

Abstract: The present invention provides a cast steel material for pressure vessels which has improved impact resistance (weldability) and toughness while maintaining its creep rupture strength at a level equal to or higher than the excellent creep rupture strength currently possessed by CrMoV cast steel, as well as a method of making a pressure vessel (or cast steel article) by using this cast steel material which permits a pressure vessel to be made without requiring a material working step such as forging. Specifically, the present invention relates to a cast steel material for pressure vessels which contains C, Si, Mn, Ni, Cr, Mo, V, W, Nb and/or Ta, B, Ti, Al, N, O, P and S in predetermined proportions, the balance being Fe and incidental impurities, provided that the contents of Ti, Al, O and N satisfies the following relationship: and to a method of making a pressure vessel wherein the aforesaid cast steel material is cast and then heat-treated under predetermined conditions.

Inventors: Tashiro; Yasunori (Kitakyushu, JP), Ueno; Masakatsu (Kitakyushu, JP), Fujita; Akitsugu (Nagasaki, JP), Kamada; Masatomo (Yokohama, JP)

Assignee: Mitsubishi Heavy Industries, Ltd.

International Classification: C22C 38/48 (20060101); C22C 38/44 (20060101); C22C 38/46 (20060101); C22C 38/54 (20060101); C21D 1/28 (20060101); C21D 9/00 (20060101); C21D 1/26 (20060101); C21D 009/00 ()

Expiration Date: 07/03/2018