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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 ó-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.Keywords: quality and expected life of metal, steel DI59, service properties, tubes, metal strain, ductility of steel.

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