To manufacture a steel tube having an excellent seam quality and surface skin with high productivity.
The composition of a band steel is defined as 0.005 to 0.19% C, 0.05 to 1.0% Si, 0.2 to 1.2% Mn, 0.01 to 0.1% Al, by weight, and the balance Fe with inevitable impurities. The band steel is continuously formed to obtain an open tube. Both edge parts of the open tube are subjected to edge heating treatment to a temperature area of 1300°C or over and less than a melting point, and are press-welded by squeeze rolls. Further, in addition to the composition, it is acceptable to contain one or two kinds or over selected from at least one group of Ti, Zr group, Nb, V group, Cr, Mo group, REM(rate earth metal), and Ca group. Also, it is preferable that the time tK (sec) keeping joint part at 1300°C or over after press welding is 0.03sec or over, or the joint part is kept for the time determined by an oxygen concentration in an atmosphere or over.
HASHIMOTO YUJI
ITAYA MOTOAKI
YORIFUJI AKIRA
ONISHI TOSHIO
TANAKA NOBUKI
Next Patent: BRAKING DEVICE FOR UNWINDING WIRE BUNDLE