PURPOSE: To eliminate stripe patterns after a hardening heat treatment by moving a steel pipe axially while rotating this steel pipe and continuously subjecting the steel pipe to a surface cleaning treatment, heating treatment and cooling treatment while successively moving a surface cleaning device, heating device and cooling device.
CONSTITUTION: The cut steel pipe 1 is washed by a brush roll 6 and a spray 7 of a washing liquid. The oil-component on the surface of the steel pipe 1 is preferably confined to ≤50mg/m2. The steel pipe is heated by an induction heater 2 after the washing and is cooled and hardened by the water cooling device 3. The spiral stripe patterns after the hardening heat treatment are not admitted and the surface grade is improved.
TAMURA SOHEI
TAMADA YASUJI
TAKEGUCHI KENICHI
