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Title:
PRODUCTION METHOD FOR HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2017/154494
Kind Code:
A1
Abstract:
[Problem] To provide a production method for a high-strength hot-dip galvanized steel sheet having excellent plating adhesion, workability, and resistance to fatigue. [Solution] In this invention, a steel sheet is subjected to oxidation processing comprising: in an early stage, heating at a temperature of 400 to 750°C in an atmosphere of O2 at a concentration of 1000 ppm by volume or more and H2O at a concentration of 1000 ppm by volume or more; and, in a later stage for oxidative treatment, heating at a temperature of 600 to 850°C in an atmosphere of O2 at a concentration of less than 1000 ppm by volume and H2O at a concentration of 1000 ppm by volume or more. Next, the steel sheet is subjected to reduction-annealing comprising: in a heating zone, heating at a temperature rising speed of 0.1°C/sec or faster to a temperature of 650 to 900°C in an atmosphere wherein the H2 concentration is 5 to 30% by volume, the H2O concentration is 10 to 1000 ppm by volume, and the remainder comprises N2 and unavoidable impurities; and then, in a soaking zone, maintaining a uniform heat within ±20°C temperature variation for 10 to 300 seconds, in an atmosphere wherein the H2 concentration is 5 to 30% by volume, the H2O concentration is 500 to 5000 ppm by volume, and the remainder comprises N2 and unavoidable impurities.

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Inventors:
MAKIMIZU YOICHI (JP)
SUZUKI YOSHITSUGU (JP)
TAKEDA GENTARO (JP)
HASEGAWA HIROSHI (JP)
Application Number:
PCT/JP2017/005603
Publication Date:
September 14, 2017
Filing Date:
February 16, 2017
Export Citation:
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Assignee:
JFE STEEL CORP (JP)
International Classes:
C23C2/02; C21D9/46; C21D9/56; C22C18/04; C22C38/00; C22C38/60; C23C2/06; C23C2/28; C23C2/40
Domestic Patent References:
WO2015087549A12015-06-18
Foreign References:
JP4791482B22011-10-12
JP2012251192A2012-12-20
JP2014019935A2014-02-03
Other References:
See also references of EP 3428303A4
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
Download PDF:
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