Effect of a pipe-steel killing technology on the composition and number of nonmetallic inclusions

Abstract

Pipes made from steels 19G, 17GS, 17G1S, 10G2FBYu, 13G1S-U, and 20KT of various manufacturers and technologies are studied. Electron microprobe and fractional gas analyses are used to determine the main types and number of nonmetallic inclusions (NIs). The effect of a modification procedure on the oxidic cleanness of steel 20KT (produced at JSC “Volzhskii Pipe Works”) is studied. The use of a silicocalcium-filled wire is shown to increase the total contamination of the steel by nonmetallic, in particular, calcium aluminate and magnesium spinel inclusions, which are conditionally related to corrosion-active nonmetallic inclusions (CANIs). Fractional gas analysis is shown to allow the number of oxide inclusions of various types to be accurately determined in pipe steels. No correlation is found between the volume fraction of oxide inclusions determined by fractional gas analysis and the number of CANIs determined by a metallo-graphic method.