(19)
(11) EP 0 947 597 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
31.01.2001 Bulletin 2001/05

(43) Date of publication A2:
06.10.1999 Bulletin 1999/40

(21) Application number: 99105071.7

(22) Date of filing: 23.03.1999
(51) International Patent Classification (IPC)7C22C 38/02, C21D 8/12
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 30.03.1998 JP 8400798
28.10.1998 JP 30750798

(71) Applicant: NIPPON STEEL CORPORATION
Chiyoda-ku Tokyo-to (JP)

(72) Inventors:
  • Kumano, Tomoji, c/oNIPPON STEEL CORP. YAWATA WORKS
    Kitakyushu City, Fukuoka (JP)
  • Fujii, Norikazu, c/oNIPPON STEEL CORP YAWATA WORK
    Kitakyushu City, Fukuoka (JP)
  • Kuroki, Katsuro, c/o NITTETSU PLANT DESIGNING CORP
    Kitakyushu City, Fukuoka (JP)
  • Yamasaki, Koji, c/oNIPPON STEEL CORP. YAWATA WORKS
    Kitakyushu City, Fukuoka (JP)
  • Ohata, Yoshifumi, NIPPON STEEL CORP. YAWATA WORK
    Kitakyushu City, Fukuoka (JP)
  • Mogi, Hisashi, c/o NIPPON STEEL CORP. YAWATA WORKS
    Kitakyushu City, Fukuoka (JP)

(74) Representative: VOSSIUS & PARTNER 
Siebertstrasse 4
81675 München
81675 München (DE)

   


(54) Method of producing a grain-oriented electrical steel sheet excellent in magnetic characteristics


(57) A method for producing a grain-oriented electrical steel sheet excellent in magnetic characteristics is provided wherein differentiated use of primary and secondary inhibitors enables production without high temperature slab heating, few glass film defects and no lack of uniformity in secondary recrystallization.
A slab containing 0.025 ∼ 0.10% of C, 2.5 ∼ 4.0% of Si as well as acid-soluble Al, Mn, Cu, N, and Seq = (S + 0.406 Se) of 0.008 ∼ 0.05% is reheated to a temperature of more than 1050°C and lower than 1350°C and hot-rolled into a hot-rolled strip. The hot-rolled strip is optionally annealed, subjected to at least one cold rolling with intermediate annealing, whereafter the sheet is decarburization annealed to have primary recrystallization grains after completion of the decarburization annealing of an average diameter of not less than 7 µm and less than 18 µm, nitrided up to the start of secondary recrystallization, coated with an annealing separator composed mainly of MgO, and subjected to final finish annealing.





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