Facility and method for continuously manufacturing hot-dip galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-2015315691-A1
Application number	US-201214649408-A
Country	US
Kind code	A1
Filing date	Dec 4, 2012
Priority date	Dec 4, 2012
Publication date	Nov 5, 2015
Grant date	—

Abstract

A facility for continuously manufacturing a galvanized steel sheet includes a continuous annealing furnace, a snout, and a galvanization bath. The furnace is divided into a heating zone, a soaking zone, and a cooling zone. The bath is directly connected to the furnace through the snout. The facility has a dewpoint meter and a draft port and a suction port for a furnace gas that are provided in at least one of the zones, gas cyclic paths which connect the draft port and the suction port to a refiner, and a dewpoint meter and a humidification device that are provided in the snout. The gas cyclic paths are separately formed for the respective connected zones. The refiner functions so that a measured value of the dewpoint meter is equal to a target dewpoint, and the humidification device functions so that a measured value of the dewpoint meter in the snout is equal to a target dewpoint for the snout.

First claim

1 . A facility for continuously manufacturing a galvanized steel sheet, comprising:
a continuous annealing furnace divided into three zones including a heating zone that heats a steel strip which is a strip-shaped steel sheet to be passed through the furnace, a soaking zone that soaks the heated steel strip, and a cooling zone that cools the soaked steel strip, which are arranged in this order from an upstream side of a transport path; a galvanization bath; a snout that directly connects the furnace to the galvanization bath therethrough, the snout being a closed space through which the steel strip is directly fed into the galvanization bath from the furnace; a first dewpoint meter and a suction port and a spray port for a gas within the furnace that are provided in at least one of the three zones of the furnace; a gas cyclic path that connects the suction port and the spray port to a refiner, which is a moisture removing device provided outside the furnace, separately formed for each of the connected zones; and a second dewpoint meter and a humidification device, which humidifies an inside of the snout, that are provided in the snout, wherein: the refiner functions so that, for each of the gas cyclic paths, a first measured value of the first dewpoint meter in the connected zone is equal to a first target dewpoint; and the humidification device functions so that a second measured value of the second dewpoint meter in the snout is equal to a second target dewpoint for the snout.

2 . The facility for continuously manufacturing a galvanized steel sheet according to claim 1 , wherein the first dewpoint meter and the suction port and the spray port are provided at least in the soaking zone and the gas cyclic path is formed at least for the soaking zone.

3 . The facility for continuously manufacturing a galvanized steel sheet according to claim 1 , further comprising a snout suction port and a snout spray port for a gas within the snout that are provided in the snout, and a snout gas cyclic path formed between the refiner and the snout by connecting the ports thereof to the refiner,
wherein the refiner functions along with the humidification device so that the second measured value of the second dewpoint meter in the snout is equal to the second target dewpoint for the snout.

4 . The facility for continuously manufacturing a galvanized steel sheet according to claim 3 , wherein the first dewpoint meter and the suction port and the spray port are provided at least in the soaking zone and the gas cyclic path is formed at least for the soaking zone.

5 . A method for continuously manufacturing a galvanized steel sheet using the facility for continuously manufacturing a galvanized steel sheet according to claim 1 , wherein a galvanization operation is performed while setting the first target dewpoint of the furnace to −50° C. or lower and −80° C. or higher and the second target dewpoint for the snout to −35° C. or higher and −10° C. or lower.

6 . A method for continuously manufacturing a galvanized steel sheet using the facility for continuously manufacturing a galvanized steel sheet according to claim 2 , wherein a galvanization operation is performed while setting the first target dewpoint for the soaking zone to −50° C. or lower and −80° C. or higher and the second target dewpoint for the snout to −35° C. or higher and −10° C. or lower.

7 . A method for continuously manufacturing a galvanized steel sheet using the facility for continuously manufacturing a galvanized steel sheet according to claim 3 , wherein a galvanization operation is performed while setting the first target dewpoint of the furnace to −50° C. or lower and −80° C. or higher and the second target dewpoint for the snout to −35° C. or higher and −10° C. or lower.

8 . A method for continuously manufacturing a galvanized steel sheet using the facility for continuously manufacturing a galvanized steel sheet according to claim 4 , wherein a galvanization operation is performed while setting the first target dewpoint for the soaking zone to −50° C. or lower and −80° C. or higher and the second target dewpoint for the snout to −35° C. or higher and −10° C. or lower.

Assignees

• Jfe Steel Corp

Inventors

• Sato Nobuyuki
• Nakazato Kazuki
• Fujii Takamasa

Classifications

• C23C2/003

  Apparatus · CPC title

• C23C2/40

  Plates; Strips · CPC title

• C23C2/02 Primary

  Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence) · CPC title

• C21D9/561

  with a controlled atmosphere or vacuum · CPC title

• C21D1/76

  Adjusting the composition of the atmosphere · CPC title