| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.25 ( September 1991 ) Special Issue on 'H-Shapes with Fixed Outer Dimension' and 'Steel Pipe' ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| Production and Properties of Seamless Modified 9Cr-1Mo Steel Boiler Tubes Terufumi Sasaki, Kunihiko Kobayashi, Teruo Yamaura, Toshiaki Kasuya, Toshikazu Masuda |
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Synopsis : The production of seamless modified 9Cr-1Mo steel tube by the Mannesmann process was studied regarding the hot workability and heat-treatment conditions. The mechanical properties of the base metal and welded joints, and the Charpy absorbed energy and precipitation behavior after long-time aging were also investigated. The hot workability of modified 9Cr-1Mo(T91) steel was found to be inferior to that of low-alloy steel, but the steel tube and pipe can be produced by optimizing the rolling conditions and by reducing the S content. The tensile strength at elevated temperatures and the creep rupture strength of T91 steel pipe were excellent and satisfied ASME specifications. The tensile, impact, and bending properties of mechanized GTAW girth welded joints were sufficiently good. The Charpy absorbed energy of T91 steel pipe decreased after aging at 550-650, but retained a good enough value, this decrease being most marked at 600 due to the increase in coarse (FeCr)2Mo precipitates identified by SEM observation. Hot-finished tube produced by the Mannesmann process showed equivalent properties to those of cold-finished tube, with sufficient dimensional accuracy. |
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