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Title:
METHOD FOR PRODUCING HIGH-STRENGTH HOT DIPPED GALVANIZED STEEL SHEET
Document Type and Number:
WIPO Patent Application WO/2016/013144
Kind Code:
A1
Abstract:
Provided is a method for producing a hot dipped galvanized steel sheet having low annealing temperature dependence of the surface appearance and the material quality, which uses steel containing C, Si, Mn and the like necessary for achieving a high strength of TS ≥ 1,180 MPa. A method for producing a high-strength hot dipped galvanized steel sheet by subjecting a steel slab having a specific composition to hot rolling, cold rolling, first annealing, acid pickling and second annealing, wherein: the steel structure comes to have an area ratio of ferrite of 10-60% and a total area ratio of martensite, bainite and residual austenite of 40-90% by carrying out the first annealing under predetermined conditions; and during the second annealing, a steel sheet is heated to an annealing temperature within the annealing temperature range of 750-850°C, kept within the annealing temperature range for 10-500 seconds, subsequently cooled at an average cooling rate of 1-15°C/second, and then cooled to 150°C or less at an average cooling rate of 5-100°C/second after having been subjected to hot dip galvanization, so that the steel sheet comes to have a steel structure that contains ferrite in an area ratio of 10-60% and martensite in an area ratio of 40-90%.

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Inventors:
KIMURA HIDEYUKI (JP)
FUJITA KOICHIRO (JP)
HASEGAWA HIROSHI (JP)
AOYAMA MAI (JP)
Application Number:
PCT/JP2015/002876
Publication Date:
January 28, 2016
Filing Date:
June 09, 2015
Export Citation:
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Assignee:
JFE STEEL CORP (JP)
International Classes:
B21B1/26; C21D9/46; B21B1/28; B21B3/00; C22C38/00; C22C38/14; C22C38/58; C23C2/02; C23C2/06; C23C2/28; C23C2/40; C22C18/00
Foreign References:
JP2013177673A2013-09-09
JP2012012703A2012-01-19
JP2013221198A2013-10-28
JP2004263271A2004-09-24
JP2002294397A2002-10-09
JP2015117403A2015-06-25
Other References:
See also references of EP 3173494A4
Attorney, Agent or Firm:
KUMASAKA, Akira et al. (JP)
Akira Kumasaka (JP)
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