Method for controlling dew point of reduction furnace, and reduction furnace

Patent metadata

Field	Value
Publication number	US-2016363372-A1
Application number	US-201515119022-A
Country	US
Kind code	A1
Filing date	Feb 18, 2015
Priority date	Feb 25, 2014
Publication date	Dec 15, 2016
Grant date	—

Abstract

Provided are a method for controlling a dew point in a reducing furnace and a reducing furnace in which, even in the case of galvanizing Si-added steel, coating adhesion can be secured, alloying treatment can be performed without increasing the alloying temperature excessively, and it is possible to obtain a hot-dip galvanized steel sheet having an excellent coating appearance. When a steel sheet is subjected to annealing and hot-dip galvanizing treatment using continuous hot-dip galvanizing equipment including at least a radiant tube-type reducing furnace, a mixed gas of a dry gas and a humidified gas by a humidifying device having a water vapor permeable membrane is used as a gas to be supplied into the reducing furnace. The mixed gas is supplied into the reducing furnace, thereby controlling the dew point in the reducing furnace.

First claim

1 . A method for controlling a dew point in a reducing furnace which is at least a radiant tube-type and which is provided in continuous hot-dip galvanizing equipment, the method comprising steps of:
applying annealing and hot-dip galvanizing treatment to a steel sheet in the continuous hot-dip galvanizing equipment; and supplying a gas into the reducing furnace in the applying to control the dew point in the reducing furnace, by using a mixed gas of a dry gas and a humidified gas by a humidifying device having a water vapor permeable membrane as the gas to be supplied into the reducing furnace.

2 . The method according to claim 1 , wherein the dew point in the reducing furnace is controlled to −20° C. to 0° C.

3 . A reducing furnace which is a part of continuous hot-dip galvanizing equipment, the reducing furnace comprising:
a humidifying device having a water vapor permeable membrane and configured to humidify part of a dry gas to be supplied into the reducing furnace; a circulating constant temperature water tank configured to supply to the humidifying device water that is controlled to a predetermined temperature and that has a predetermined flow rate; a gas mixing device configured to mix the humidified gas by the humidifying device with a dry gas; a gas supply pipe configured to supply a gas mixed by the gas mixing device into the reducing furnace; and a supply gas dew point meter that measures the dew point of the gas to be supplied into the reducing furnace.

4 . The reducing furnace according to claim 3 , further comprising:
a gas distributing device configured to distribute a part of the dry gas to be supplied into the reducing furnace to the humidifying device and supply the rest of the dry gas to the gas mixing device.

5 . The reducing furnace according to claim 3 , wherein,
the humidifying device has a pipe through which the gas after humidification passes, and the pipe is maintained at a temperature equal to or higher than the dew point of the gas after humidification.

6 . The reducing furnace according to claim 4 , wherein,
the humidifying device has a pipe through which the gas after humidification passes, and the pipe is maintained at a temperature equal to or higher than the dew point of the gas after humidification.

Assignees

• Jfe Steel Corp

Inventors

• Takeda Gentaro
• Takahashi Hideyuki
• Miyake Masaru
• Makimizu Yoichi
• Suzuki Yoshitsugu

Classifications

• C21D9/46

  for sheet metals · CPC title

• C21D9/0012

  Rolls; Roll arrangements · CPC title

• F27D7/02 Primary

  Supplying steam, vapour, gases or liquids · CPC title

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• C23C2/40

  Plates; Strips · CPC title