ASTM International

Standard Specification for Steel Castings, Creep-Strength Enhanced Ferritic Alloy, for Pressure-Containing Parts, Suitable for High Temperature Service
 N A1091/A1091M

Annotation

This specification covers creep-strength enhanced alloy steel castings for valves, flanges, fittings, and other pressurecontaining parts intended primarily for high-temperature service (see Note 1). However, they are not restricted to such applications, and the castings may be used for other applications for which the attributes of the material, as defined by this specification, are suitable

One grade of martensitic alloy steel, Grade C91, is covered (see Note 2). It is provided in two classes, differentiated by the type of heat treatment after weld repairs. This and similar steels are characterized by a predominantly tempered martensitic or tempered Bainitic microstructure that is stabilized by the precipitation of temper-resistant particles at various precipitate nucleation sites in the microstructure. Such steels are designed to have creep-rupture strengths significantly superior to those of alloys of nominally similar compositions, but in which the precipitates or nucleation sites are absent. Since this crucial difference cannot be revealed by roomtemperature mechanical property tests, these alloys require tighter controls on manufacturing and processing

NOTE 1—The grades covered by this specification represent materials that are generally suitable for assembly with other castings or wrought steel parts by fusion welding. It is not intended to imply that these grades possess equal degrees of weldability; therefore, it is the responsibility of the purchaser to establish a suitable welding technique. Since these grades possess varying degrees of suitability for high-temperature service, it is also the responsibility of the purchaser to determine which grade shall be furnished, due consideration being given to the requirements of the applicable construction codes