Abstract
Seamless steel pipes for the petroleum industry are produced by a hot-extrusion process. Extrusion processing deforms the material in three dimensions with a very high deformation ratio. In one operation the deformation ratio may sometimes reach 100:1, higher than in any other hot-working process. During this process grains are heavily deformed and recrystallization will take place depending on the finishing temperature; grain growth may sometimes be expected. Full-scale plant experiments have been carried out with various low-alloy carbon steels in a horizontal Davy-Loewy press of 30 MN capacity to produce tubes of 108mm i.d. and 5·6mm wall thickness. To analyse all aspects of the hot-extrusion process, mechanical properties have been determined in accordance with API specifications. Effects of sulphide and oxide inclusions on the workability and final properties of the material have been investigated. The effects ofprocess parameters on yield strength and grain size have been determined. Recommendations have been made to the manufacturer on selecting the suitable composition and cleanness, and on setting the parameters.
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