Jfe Steel Corporation

Yuiko Ehashi

Masanori Takenaka

Takeshi Imamura

Yasuyuki Hayakawa

Minoru Takashima

Soshi Yoshimoto

Hirokazu Sugihara

Makoto Watanabe

Hiroi Yamaguchi

Yukihiro Shingaki

A grain oriented electrical steel sheet is produced by heating a steel slab containing, by mass %, C:0.02-0.10%, Si:2.0-5.0%, Mn:0.01-1.00%, sol. Al:0.01-0.04%, N:0.004-0.020% and S+Se:0.002-0.040% to a temperature of higher than 1280° C., and subjecting the sheet to a hot rolling, a hot-band annealing, a single cold rolling or two or more cold rollings having an intermediate annealing between each cold rolling and a primary recrystallization annealing combined with a decarburization annealing, applying an annealing separator onto a steel sheet surface, and subjecting the sheet to a finish annealing and a flattening annealing, a rapid cooling is conducted at an average cooling rate of not less than 200° C./s from 800° C. to 300° C. in the cooling process from a maximum achieving temperature in at least one annealing of the hot-band annealing and the intermediate annealing.

Method for producing grain-oriented electrical steel sheet

When a grain-oriented electrical steel sheet is produced by heating a steel slab containing, by mass %, C: 0.020 to 0.10%, Si: 2.0 to 4.0%, Mn: 0.005 to 0.50%, Al: less than 0.010%, N, S and Se: less than 0.0050% each to a temperature of not higher than 1280° C., subjecting slab to hot rolling, hot-band annealing, single cold rolling or two or more cold rollings having intermediate annealing between each cold rolling and a primary recrystallization annealing combined with decarburization annealing, applying annealing separator onto steel sheet surface, and subjecting steel sheet to finish annealing and a flattening annealing, a rapid cooling is conducted at an average cooling rate of not less than 200° C./s from 800° C. to 300° C. in cooling process from maximum achieving temperature in at least one of hot band annealing and intermediate annealing, whereby grain-oriented electrical steel sheet having excellent magnetic properties is stably produced.

With a hot-rolled steel sheet for electrical steel sheet production having a scale layer on the surface, where the surface of the steel sheet has a lightness L* as defined in JIS Z 8781-4: 2013 satisfying 30&#x2264;L*&#x2264;50, and chromaticities a* and b* as defined in JIS Z 8781-4: 2013 satisfying &#x2212;1&#x2264;a*&#x2264;2 and &#x2212;5&#x2264;b*&#x2264;3 respectively, and with one end portion in the longitudinal direction of a coil as a reference, a color difference &#x394;E* as defined in JIS Z 8781-4: 2013 at the central portion and at the opposite end portion satisfies &#x394;E*&#x2264;8, it is possible to obtain a grain-oriented electrical steel sheet where the variation of properties in a product coil is small.

Hot-rolled steel sheet for electrical steel sheet production and method of producing same

In a production of a grain-oriented electrical steel sheet by subjecting a steel slab containing a particular composition and further including an inhibitor-forming ingredient to hot rolling, hot-band annealing, cold rolling, primary recrystallization annealing combined with decarburization annealing and finish annealing, the steel slab satisfies a given relation between a content ratio of sol. Al to N and a final sheet thickness, and, in the finish annealing, the steel sheet is kept at a temperature zone of higher than 850&#xb0; C. but not higher than 950&#xb0; C. in heating process for 5 to 200 hours, heated to a temperature zone of 950 to 1050&#xb0; C. at 5 to 30&#xb0; C./hr and further subjected to purification treatment of keeping a temperature of not lower than 1100&#xb0; C. for not less than 2 hours to provide a secondary recrystallization structure that has an average value of a diameter equivalent to a circle of 10 to 100 mm.

Low-iron-loss grain-oriented electrical steel sheet and production method for same

To improve and stabilize magnetic properties, a steel sheet is soaked in a temperature range of 1000&#xb0; C. or more and 1120&#xb0; C. or less for 200 sec or less and then soaked in a temperature range of 650&#xb0; C. or more and 1000&#xb0; C. or less for 200 sec or less in annealing before final cold rolling, and the amount of Al in precipitates after the annealing before the final cold rolling is limited to 50% or more of the total amount of Al contained in the steel slab.

Method of producing grain-oriented electrical steel sheet

To provide a grain-oriented electrical steel sheet that has better magnetic property than conventional ones without requiring high-temperature slab heating, in the case of not performing intermediate annealing, the hot rolled steel sheet obtained by a predetermined step is subjected to hot band annealing, and, in a heating process in the hot band annealing, heating is performed at a heating rate of 10&#xb0; C./s or less for 10 sec or more and 120 sec or less in a temperature range of 700&#xb0; C. or more and 950&#xb0; C. or less, and in the case of performing the intermediate annealing, in a heating process in final intermediate annealing, heating is performed at a heating rate of 10&#xb0; C./s or less for 10 sec or more and 120 sec or less in a temperature range of 700&#xb0; C. or more and 950&#xb0; C. or less.

In a grain-oriented electrical steel sheet which is manufactured from a thin slab without using an inhibitor forming component, excellent magnetic properties are stably achieved. In a method for manufacturing a grain-oriented electrical steel sheet, a slab heating and annealing are performed under specific conditions.

Method for manufacturing grain-oriented electrical steel sheet

To provide a grain-oriented electrical steel sheet that has better magnetic property than conventional ones, in hot band annealing of the hot rolled steel sheet obtained by a predetermined step, an average heating rate from ordinary temperature to 400&#xb0; C. is set to 50&#xb0; C./s or more, and a time to reach 900&#xb0; C. from 400&#xb0; C. is set to 100 sec or less.

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Tokyo, Japan

Yuiko Ehashi