To provide a manufacture of a steel tube by means of an induction heating method that enables a steel tube with a superior seam and surface quality to be manufactured with high productivity.
In the steel tube manufacture by forming a strip steel into an open tube 1, with both edges 10 of the open tube 1 heated and butt-welded by a squeeze roll 3, the entire open tube is heated up to warm temperatures of 200-700°C before heating both edges; then, both edges are induction-heated first by a medium/low frequency (frequency ≤100kHz) or as needed by a high frequency (frequency >100kHz) to a preheating temperature range at Curie point or above; and after further heated to a joining temperature range of equal to or higher than 1,3000°C but lower than the melting point through induction heating by high frequencies, the edges are butt-welded.
TANAKA NOBUKI
ITAYA MOTOAKI
YORIFUJI AKIRA
ONISHI TOSHIO
HASHIMOTO YUJI
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