DECREASING MECHANICAL PROPERTIES OF THE SUPERHEATER STEEL GRADE P22 HEATED AT ELEVATED TEMPERATURE UNDER CONSTANT STRESS

This paper investigated change of the mechanical properties superheater pipe steel grade P22 (ASTM A335) under constant stress 9.68 MPa and various temperatures 500-700 oC. The specimens were prepared from new taken a coal-fired power plant in Vietnam, then heated to given temperature held for predetermined time as 24, 48 72 hours atmosphere. results showed that decreased with increased time. deterioration strength was caused by redistribution carbide subjected elevated stress. Although microstructure including phase grain size not observed, SEM micrographs accumulated on boundaries triple regions when holding increased. phenomenon attributed reduce number steel, resulting decrease properties. obtained indicated can occur early period working practice.