Method and system for manufacturing metal-plated steel pipe

A steel pipe manufacturing system for manufacturing steel pipe, in which an inner face and an outer face of a steel pipe are subjected to molten metal-plating, the steel pipe being manufactured on a continuous steel pipe manufacturing line from a steel sheet, the steel pipe manufacturing line being arranged horizontal so that the steel pipe horizontally travels from an upstream side to a downstream side, the system comprising:

• an inner-face plating performing part that performs molten metal-plating by pouring molten metal on an upper side of the steel sheet corresponding to an inner face of the steel pipe;
• a steel pipe forming part, which is arranged at the downstream side from the inner-face plating performing part, for obtaining a continuous steel pipe by continuously cold-forming the steel sheet subjected to the inner-face plating into a tubular shape and seam-welding a longitudinal end face joint portion of the steel pipe formed from the steel sheet;
• and
• an outer-face plating performing part, which is arranged at the downstream side from the steel pipe forming part, that performs molten metal-plating by dipping the outer face of the steel pipe into molten metal, wherein
• the inner-face plating performing part includes:
• a pouring part that pours molten metal on the upper side of the steel sheet through a treatment area (TAin), which is defined between an initial treatment position (IPin) and an end treatment position (EPin), the initial treatment position at which the molten metal comes to contact with the steel sheet and being located most upstream in the treatment area, the end treatment position at which the contact between the pouring molten metal and the steel sheet terminates and being located most downstream in the treatment area,
• a molten metal supply part that supplies molten metal to the pouring part, and
• an inner-face wiping part that removes surplus molten metal poured by the pouring part,
• a length from the initial treatment position (IPin) to the inner wiping position (WPin) is defined as a dipping length (DLin), and the dipping length is adjustable along the steel pipe manufacturing line;
• the system further comprises
• a slide base frame that is in a linear shape, being parallel to the steel pipe manufacturing line, to which the pouring part is attached;
• the pouring part is configured to move along the slide base frame;
• and
• the dipping length is adjusted by moving the pouring part along the slide base frame;
• and
• the outer-face plating performing part includes:
• a dipping part that has a treatment area (TAout) for allowing the continuous steel pipe to pass there through and allows the outer face of the continuous steel pipe to be dipped into molten metal when molten metal is introduced into the treatment area, which is defined between an initial treatment position (IPout) and an end treatment position (EPout), the initial treatment position at which the steel pipe first enters a pool filled with the molten metal and being located most upstream in the treatment area, the end treatment position at which the contact between the molten metal and the steel pipe terminates and being located most downstream in the treatment area,
• a molten metal supply part that supplies the molten metal to the dipping part, and
• an outer-face wiping part that removes surplus molten metal from the continuous steel pipe dipped into the molten metal by the dipping part, and being arranged at an outer wiping position (WPout) that is at the downstream side from the pouring part, wherein
• a length from the initial treatment position (IPout) to the outer wiping position (WPout) is defined as a dipping length (DLout), and the dipping length is adjustable along the steel pipe manufacturing line.