Continuous annealing furnace for steel strip, continuous annealing method, continuous galvanizing apparatus and method for manufacturing galvanized steel strip (as amended)

Patent metadata

Field	Value
Publication number	US-9593401-B2
Application number	US-201314402556-A
Country	US
Kind code	B2
Filing date	May 20, 2013
Priority date	May 24, 2012
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

Provided is a vertical annealing furnace, in which a heating zone and a soaking zone are communicated with each other in the upper part of the furnace, in which a part of the furnace other than the communicated parts is separated by a dividing wall, in which part of the furnace gas is suctioned into a refiner having a deoxidation device and a dehumidification device which is placed outside the furnace to decrease the dew point of the gas by removing oxygen and moisture from the gas and such that the resultant gas having a decreased dew point is returned into the furnace, in which a gas suction port into the refiner is located in the lower part of the connection part between the soaking zone and the cooling zone and in which one or more gas suction ports are located in the parts of the heating zone and/or the soaking zone outside of an area within 6 m in the vertical direction and 3 m in the longitudinal direction of the furnace from the steel strip entrance in the lower part of the heating zone.

First claim

The invention claimed is:

1. A continuous annealing furnace for a steel strip, the furnace being a vertical annealing furnace comprising a heating zone, a soaking zone, a cooling zone located in this order through which a steel strip is transferred in the up-and-down direction, the connection part between the soaking zone and the cooling zone being located in the upper part of the furnace, the heating zone and the soaking zone being communicated with each other in the upper part of the furnace, a dividing wall being placed in a part of the furnace other than the communicated parts in the upper part of the furnace to physically separate the heating zone and the soaking zone, an atmospheric gas being fed into the furnace from the outside of the furnace, and the furnace gas being discharged through a steel strip entrance in the lower part of the heating zone while a refiner having a deoxidation device and a dehumidification device which is placed outside the furnace such that part of the furnace gas is suctioned into the refiner to decrease the dew point of the gas by removing oxygen and moisture from the gas and the resultant gas having a decreased dew point is returned into the furnace through a gas delivery port, wherein a gas suction port from the furnace into the refiner is located at a position where a flow channel narrows at a throat part or a position in the vicinity of seal rolls in the lower part of the connection part between the soaking zone and the cooling zone and wherein one or more gas suction ports are located in the parts of the heating zone and/or the soaking zone outside of an area within 6 m in the vertical direction and 3 m in the longitudinal direction of the furnace from the steel strip entrance in the lower part of the heating zone.

2. The continuous annealing furnace for a steel strip according to claim 1 , the furnace further comprising a dew point sensing station of a dew point meter for determining the dew point of the furnace gas located in the vicinity of gas suction ports located in the heating zone and the soaking zone.

3. The continuous annealing furnace for a steel strip according to claim 1 , the furnace further comprising a plurality of gas delivery ports located in the connection part between the soaking zone and the cooling zone and the upper part of the heating zone, the gas flowing from the refiner to the furnace therethrough, wherein the delivery width W0 of the gas delivery ports located in the upper part of the heating zone satisfies the relationship with the furnace width W of the heating zone that W0/W is larger than ¼, where the delivery width W0 of the gas delivery ports in the heating zone is the distance in the longitudinal direction of the furnace between the gas delivery port located at a position nearest to the entrance of the heating zone and the gas delivery port located at a position nearest to the exit of the heating zone.

4. The continuous annealing furnace for a steel strip according to claim 2 , the furnace further comprising a plurality of gas delivery ports, the gas flowing from the refiner to the furnace therethrough, that are located in the connection part between the soaking zone and the cooling zone and the upper part of the heating zone, wherein the delivery width W0 of the gas delivery ports located in the upper part of the heating zone satisfies the relationship with the furnace width W of the heating zone that W0/W is larger than ¼, where the delivery width W0 of the gas delivery ports in the heating zone is the distance in the longitudinal direction of the furnace between the gas delivery port located at a position nearest to the entrance of the heating zone and the gas delivery port located at a position nearest to the exit of the heating zone.

5. A continuous galvanizing apparatus for a steel strip, the apparatus comprising a galvanizing apparatus installed downstream of the annealing furnace according to claim 1 .

6. A continuous galvanizing apparatus for a steel strip, the apparatus comprising a galvanizing apparatus installed downstream of the annealing furnace according to claim 2 .

7. A continuous galvanizing apparatus for a steel strip, the apparatus comprising a galvanizing apparatus installed downstream of the annealing furnace according to claim 4 .

8. A method for continuously annealing a steel strip, the method comprising continuously annealing a steel strip using the continuous annealing furnace for a steel strip according to claim 2 , determining the dew point of the furnace gas in the vicinity of the gas suction ports in the heating zone and the soaking zone, suctioning the furnace gas at positions where the dew point is high and delivering the gas returned from the refiner through the gas delivery ports placed in the upper part of the heating zone.

9. The method for continuously annealing a steel strip according to claim 8 , wherein the delivery width W1 of a gas delivered from the upper part of the heating zone satisfying the relationship with the furnace width W of the heating zone that W1/W is larger than ¼, where the delivery width W1 of the gas delivery ports is a distance in the longitudinal direction of the furnace between the gas delivery port delivering the gas from the position nearest to the entrance of the heating zone and the gas delivery port delivering the gas from the position nearest to the exit of the heating zone.

10. A method for manufacturing a galvanized steel strip, the method further comprising performing galvanization after performing the continuous annealing of a steel strip using the method according to claim 8 .

11. A method for continuously annealing a steel strip, the method comprising continuously annealing a steel strip using the continuous annealing furnace for a steel strip according to claim 1 , determining the dew point of the furnace gas in the vicinity of the gas suction ports in the heating zone and the soaking zone, suctioning the furnace gas at positions where the dew point is high and delivering the gas returned from the refiner through the gas delivery ports placed in the upper part of the heating zone.

12. The method for continuously annealing a steel strip according to claim 11 , wherein the delivery width W1 of a gas delivered from the upper part of the heating zone satisfying the relationship with the furnace width W of the heating zone that W1/W is larger than ¼, where the delivery width W1 of the gas delivery ports is a distance in the longitudinal direction of the furnace between the gas delivery port delivering the gas from the position nearest to the entrance of the heating zone and the gas delivery port delivering the gas from the position nearest to the exit of the heating zone.

13. A method for manufacturing a galvanized steel strip, the method further comprising performing galvanization after performing the continuous annealing of a steel strip using the method according to claim 9 .

14. A method for manufacturing a galvanized steel strip, the method further comprising performing galvanization after performing the continuous annealing of a steel strip using the method according to claim 11 .

15. A method for manufacturing a galvanized steel strip, the method further comprising performing galvanization after performing the continuous annealing of a steel strip using the method according to claim 12 .

16. A method for manufacturing a galvanized steel strip, the method further comprising performing galvanization after performing the continuous annealing of a steel strip using the method according to claim 2 .

17. A method for continuously annealing a steel strip, the met

Assignees

• Jfe Steel Corp

Inventors

• Takahashi Hideyuki
• Sato Nobuyuki
• Nakazato Kazuki
• Takada Motoki

Classifications

• C21D1/26 Primary

  Methods of annealing · CPC title

• F27D7/04

  Circulating atmospheres by mechanical means · CPC title

• C21D9/56 Primary

  Continuous furnaces for strip or wire · 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

• C23C2/40

  Plates; Strips · CPC title