Continuous annealing furnace for annealing steel strip, method for continuously annealing steel strip, continuous hot-dip galvanizing facility, and method for manufacturing hot-dip galvanized steel strip

Patent metadata

Field	Value
Publication number	US-9759491-B2
Application number	US-201615177940-A
Country	US
Kind code	B2
Filing date	Jun 9, 2016
Priority date	May 24, 2012
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A continuous annealing furnace for annealing steel strips that is a vertical-type annealing furnace is configured so that part of gas inside the furnace is drawn and introduced to a refiner disposed outside the furnace including an oxygen removing apparatus and a dehumidifying apparatus, oxygen and moisture contained in the gas are removed to lower the dew point of the gas, and the gas having a lowered dew point is put back into the furnace. At least one gas inlet through which gas is drawn from the furnace into the refiner is disposed in the vicinity of the entry side of the furnace at a distance of 6 m or less in the vertical direction and 3 m or less in the furnace-length direction from the steel-strip-introduction section located at the lower part of the heating zone.

First claim

What is claimed:

1. A method for continuously annealing a steel strip, the method comprising, when a steel strip is continuously annealed using a continuous annealing furnace having a steel-strip-introduction section located at a lower part of a heating zone of the furnace and a refiner disposed outside the furnace, the refiner including an oxygen removing apparatus and a dehumidifying apparatus, oxygen and moisture contained in gas from the furnace are removed to lower the dew point of the gas, and gas having a lowered dew point is put back into the furnace,
wherein at least one gas inlet through which gas is drawn from the furnace into the refiner is disposed in the vicinity of an entry side of the furnace at a distance of 6 m or less in a vertical direction and 3 m or less in a furnace-length direction from the steel-strip-introduction section located at the lower part of the heating zone,
the method comprising controlling an upper limit of an amount of gas drawn through the at least one gas inlet disposed in the vicinity of the entry side of the furnace so that an increase in the dew point of the gas inside the furnace in the vicinity of the at least one gas inlet compared with a condition where gas is not drawn through the inlet is less than 3° C.,
wherein the condition where gas is not drawn through the inlet is maintained while the refiner is operated at the same flow rate.

2. A method for manufacturing a hot-dip galvanizing steel strip, the method comprising continuously annealing a steel strip by the method according to claim 1 and subsequently performing hot-dip galvanizing.

Assignees

• Jfe Steel Corp

Inventors

• Takahashi Hideyuki

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C23F17/00

  Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25 (coating for obtaining at least two superposed coatings either by methods not provided for in a single one of main groups C23C2/00 - C23C26/00, or by combinations of methods providedfor in subclasses C23C and C25D, C23C28/00) · CPC title

• C23C2/40

  Plates; Strips · CPC title

• F27B9/045

  Furnaces with controlled atmosphere · CPC title

• C23C2/26

  After-treatment (C23C2/14 takes precedence) · CPC title