Device for producing coated steel sheet and method for producing coated steel sheet

A device for producing a coated steel sheet, comprising:

• a blowing-off unit which sprays a gas onto and removes excessive coating that accumulates along a first side edge of a steel sheet that threads along one direction;
• and
• a coating-collection unit which collects the excessive coating removed by the blowing-off unit,
• wherein the blowing-off unit comprises:
• a first spray nozzle extending from a gas supply member, the first spray nozzle directed in a direction from an inside to an outside in a sheet-width direction of the steel sheet and directed toward the first side edge, and
• the gas supply member supplying the compressed gas to the first spray nozzle,
• wherein the coating-collection unit includes a duct having an inlet that receives the excessive coating and an outlet that discharges the received excessive coating, and a coating container having an opening that receives the excessive coating discharged from the outlet, the container being below the inlet to the duct,
• wherein, in a case where the duct is seen in a plan view, the outlet is disposed to fit in and overlap an inside of the opening of the coating container, and in a case where the duct is seen in a side view, a gap is provided between the outlet and the opening of the coating container and the gap is 60 mm to 100 mm,
• wherein an opening area of the inlet of the duct is larger than an opening area of the outlet of the duct, and an opening area of the opening of the coating container is larger than the opening area of the outlet of the duct,
• wherein the inlet of the duct is located below a surface of the steel sheet and is positioned to be oblique with respect to the surface of the steel sheet and the sheet threading direction of the steel sheet, and the inlet of the duct faces a discharge direction of the compressed gas that is discharged from the first spray nozzle to receive the excessive coating which is blew-off from the surface of the steel sheet,
• wherein an angle β of a center axis of the first spray nozzle and the surface of the steel sheet is between 30 and 60 degrees,
• wherein an angle α of a projection of the first spray nozzle onto the surface of the steel sheet in a direction perpendicular to the surface of the steel sheet and the first side edge of the steel sheet is between 30 and 60 degrees,
• wherein a length d along the center axis of the first spray nozzle between an end of the first spray nozzle and the surface of the steel sheet is between 10 mm and 55 mm, and
• wherein the discharge direction is oblique with respect to all of the sheet threading direction of the steel sheet, a direction perpendicular to the surface of the steel sheet and a width direction of the steel sheet.