To provide a manufacturing method of a steel tube which is high in strength and ductility, excellent in tubular shape, high in productivity, and adaptable to production of many kinds in small quantities.
In the manufacturing method of the steel tube in which a steel strip is heated above the Ac3 transformation point, and continuously formed by a forming roll to make an open tube, both edges thereof are heated, and butted to and joined with each other by a squeeze roll, and internal and external beads are removed to from a base tube, and further drawn, the drawing is achieved in the temperature range between 400°C and Ar3 transformation point +50°C and the drawing rolling is carried out with the draft of not less than 30%, and/or the steel tube is cooled at the cooling speed of ≥30°C/s within 0.5 second after the drawing is completed. The base tube is cooled after the internal and external beads are removed, and re-heated to the temperature range between 400°C and Ar3 transformation point +50°C, and the drawing maybe implemented.
YORIFUJI AKIRA
KAWABATA YOSHIKAZU
NISHIMORI MASANORI
ITAYA MOTOAKI
OKABE YOSHITOMO
ARAYA MASATOSHI
NAGAHAMA TAKUYA
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