To manufacture the steel tube having excellent seam quality and surface without performing bead cutting and with high productivity by heating the whole main tube of an open tube to a warm area by a first induction heating coil whose oscillation frequency is less than a prescribed value, and heating the end faces of both edge parts to the temperature area of solid phase pressure welding by a second induction heating coil whose oscillation frequency is a prescribed value or over.
In a steel tube manufacturing device 10, after heating the whole main tube of the open tube 1 to the warm area by the first induction heating coil 11, and heating the end faces of both edge parts of the open tube 1 to the temperature area of the solid phase pressure welding by the second induction heating coil 12, the end faces of both edge parts are abutted by squeeze rolls 13, and seaming by the solid phase welding with pressure is performed. Since the whole main tube of the open tube 1 is heated by the first induction heating coil 11, the first induction heating coil 11 is limited to a frequency of less than 100KHz whose penetrative depth of a current is deep and with satisfactory heating efficiency compared with a high frequency, and since the only edge part on both sides of the open tube 1 is heated by the second induction heating coil 12, the second induction heating coil 12 is limited to a frequency of 100KHz or over whose penetrative depth of the current is shallow and with satisfactory heating efficiency.
HASHIMOTO YUJI
ITAYA MOTOAKI
YORIFUJI AKIRA
ONISHI TOSHIO
TANAKA NOBUKI
Next Patent: APPARATUS FOR CONTINUOUSLY FORMING METALLIC THIN STRIP