รายละเอียดเอกสาร

This specification covers creep-strength enhanced alloy steel castings for valves, flanges, fittings, and other pressure-containing 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 (UNS Number J84090), is covered (see Note 2). It is provided in two classes, differentiated by the type of heat treatment after welding. 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 room-temperature mechanical property tests, these alloys require tighter controls on manufacturing and processing.

...