Effect of fabrication procedure and metal quality of pipes formed from chromium-magnesium steel on their service properties

This paper examines the effect of fabrication procedure and metal quality on the service properties of pipes fashioned from chromium-magnesium steel DI59. The kinetics of the development of creep strain of the metal in the temperature region from 650 to 730°C is investigated. It is indicated that vigorous strain begins to develop after 90% of the expected life has been exhausted. It is established that in the steel under investigation, the content of σ-phase over the entire period corresponding to 30–90% exhaustion of expected life varies negligibly from 1.8 to 2.5%, and cannot be a criterion for estimation of exhaustion of the metal’s expected life. The investigations that we conducted on steel DI59 tubes fabricated in accordance with a new procedure indicated a significant increase in the long-term ductility of the steel, which dictates the high quality of the metal. __________ Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 30–34.