Nippon Steel Corporation

Yasunari Yoshitomi

Nobuyuki Takahashi

Yoshiyuki Ushigami

Yozo Suga

Katsuro Kuroki

Takehide Senuma

Kenzo Iwayama

Tadashi Nakayama

Hiroaki Masui

Satoshi Arai

Maremizu Ishibashi

Tsutomu Haratani

Koji Yamasaki

Takeo Nagashima

Tsuyoshi Kawano

Kenichi Yakashiro

Yoshio Nakamura

Yoichi Mishima

Kuniteru Ohta

Shuichi Funaki

Yukio Matsuo

A grain-oriented electrical steel sheet comprising 2.5-4.5% Si by weight and measuring 0.36-1.00 mm in thickness is imparted with a good core loss value for its thickness by controlling its C content, flux density, grain boundary configuration, and deviation degree of crystal orientation in the grains.

Thick grain-oriented electrical steel sheet exhibiting excellent magnetic properties

A decarburization-annealed steel strip as an intermediate material for grain-oriented electrical steel strip having good secondary recrystallization and excellent electrical properties is provided by causing a steel strip to possess a micro-structure in which the primary recrystallization grains have an average diameter d of not less than 15 .mu.m and a coefficient of diameter deviation .sigma.* of not more than 0.6.

Decarburization-annealed steel strip as an intermediate material for

The present invention relates to the provision of a process for producing a grain oriented electrical steel sheet having excellent magnetic properties, and comprises heating a slab comprising by weight 0.021 to 0.075% of C, 2.5 to 4.5% of Si, 0.010 to 0.060% of acid sol. Al, 0.0030 to 0.0130% of N, 0.014% or less of (S and 0.405 Se) and 0.05 to 0.8% of Mn with the balance being Fe and unavoidable impurities to a temperature below 1280.degree. C. to hot-roll the slab, subjecting the hot rolled sheet to cold rolling with a draft of 80% or more and subjecting decarburization annealing and then finish annealing, characterized in that, after the hot rolling, the hot strip is taken up at a temperature of 600.degree. C. or below and subjected to nitriding at any stage from after the hot rolling to the completion of the secondary recrystallization in the finish annealing without annealing of the hot rolled sheet.

Process for producing grain oriented electrical steel sheet having

In the present invention, a slab of a silicon steel comprising usual components is hot-rolled while adjusting the hot rolling-finish temperature at 750.degree. to 1150.degree. C. and the cumulative reduction ratio of final three passes to at least 40%, or the above-mentioned silicon steel slab is hot-rolled at the above-mentioned hot rolling-finish temperature, the hot-rolled steel sheet is held at a temperature not lower than 35.degree. C. lower than the finish temperature for at least 1 second, and the steel sheet is wound at a winding temperature lower than 700.degree. C. Successively, the hot-rolled steel sheet is subjected, without annealing of the hot-rolled steel sheet, to cold rolling at a reduction ratio of at least 80%, decarburization annealing, and final finish annealing. According to this process, a grain oriented electrical steel sheet having superior magnetic properties can be prepared.

Process for production of grain oriented electrical steel sheet having

In the present invention, grain oriented electrical steel sheets provided by heating a slab comprising, by weight percent, 0.025 to 0.075% of C, 3.4 to 5.0% of Si, 0.015 to 0.080% of sol. Al, 0.0030 to 0.013% of N, 0.014% or less of (S+0.405 Se) and 0.05 to 0.8% of Mn, sol. Al (%)/Si (%) being 0.0080 or more, the balance consisting of Fe and unavoidable impurities at a temperature below 1280.degree. C., hot-rolling the heated slab, subjecting the hot-rolled steel sheet to cold rolling, subjecting the cold-rolled steel sheet to decarbonization annealing with regulating the average diameter of primary recrystallized grains of the steel sheet subjected to decarbonization annealing to 18 to 35 .mu.m in a period between the completion of the decarbonization annealing and the initiation of final annealing, coating the decarburized steel with an annealing separator and subjecting the coated steel sheet to final annealing, wherein the final annealing is effected in such a manner that the partial pressure of nitrogen, P .sub.N2 (%), in the annealing atmosphere is 12.5% or more in a steel sheet temperature range of from 900.degree. C. to 1150.degree. C. in the heating stage of the final annealing, and subjecting the steel sheet to nitriding to cause the steel sheet to absorb 0.0010% by weight or more of nitrogen in a period between the completion of the hot rolling and the initiation of secondary recystallization in the final annealing.

This invention is directed to improve magnetic properties and to stabilize the magnetic properties of a grain oriented electrical steel sheet used as a core of electric appliances. When producing a grain oriented electrical steel sheet by heating a slab containing C, Si, acid-soluble Al, N, not more than 0.014% of S+0.405 Se and 0.05 to 0.8% of Mn and the balance consisting of Fe and unavoidable impurities at a temperature of less than 1,280.degree. C., effecting hot rolling, applying cold rolling, decarbonization annealing and final finish annealing without annealing hot rolled sheet, the production method of the present invention controls the precipitation quantity of AlN in the hot rolled sheet, controls the mean grain size of the primary crystallization grains from completion of decarbonization annealing to the start of final finish annealing, applies nitriding treatment after hot rolling but before the start of secondary recrystallization at final finish annealing, controls the hot rolling condition in accordance with the quantities of acid-soluble Al and N of the slab, and further adds Sn.

Production method of grain oriented electrical steel sheet having

The present invention provides a process for manufacturing a double oriented electrical steel sheet having a high flux density by suppressing the growth of the secondary recrystallization of {110} &lt;uvw&gt; oriented grains from the surface of the steel sheet in the hot-rolling stage or cold-rolling stage, which process comprises subjecting a hot rolled sheet comprised of 0.8-6.7% by weight of Si, 0.008-0.048% by weight of acid soluble Al, 0.010% by weight or less of N, and the balance being Fe and unavoidable impurities to a cold-rolling at a reduction rate of 40-80%, and then subjecting the resulting sheet to another cold-rolling in the direction vertical to the above cold-rolled direction at the reduction rate of 30-70% in the final thickness, followed by the steps of annealing for the primary recrystallization, applying an annealing separator, and applying finishing annealing for the secondary recrystallization and purification of steel, wherein the rolling in the finishing hot-rolling stage is carried out at the accumulated reduction rate of 20% or more under the condition that the friction coefficient between the rolls and the steel sheet is not more than 0.25; and wherein the accumulated reduction rate in the last three passes in the hot-rolling is not more than 80%; and further, wherein material of more than 1/10 of the total thickness is removed from both surfaces of the hot-rolled sheet; or wherein the cold-rolling is carried out using a work roll having a diameter of not less than 150 mm.

Process for manufacturing double oriented electrical steel sheet having

A silicon steel slab comprising 0.05 to 0.8% by weight of Mn and up to 0.014% by weight of S+0.405Se is heated at a temperature lower than 1280.degree. C. and hot-rolled under such conditions that the hot rolling-finish temperature is 700.degree. to 1150.degree. C., the cumulative reduction ratio at the final three passes is at least 40%, and the reduction ratio at the final pass is at least 20%, or this silicon steel slab is hot-rolled at a hot rolling-finish temperature of 750.degree. to 1150.degree. C. while adopting the above-mentioned reduction ratio according to need, is maintained at a temperature not lower than 700.degree. C. for at least 1 second, and wound at a winding temperature lower than 700.degree. C. The hot-rolled sheet is subjected to the hot-rolled sheet annealing, finally cold-rolled at a reduction ratio of at least 80%, subjected to the decarburization annealing, and then subjected to the final finish annealing. According to this process, a grain-oriented electrical steel sheet having superior magnetic properties is obtained.

Process for preparation of grain-oriented electrical steel sheet having

The present invention discloses a process for producing a grain-oriented electrical steel strip having a high magnetic flux density. The process comprises hot-rolling a steel ingot comprising basic ingredients and, added thereto, 0.02 to 0.15% of Sn at a temperature of 1200.degree. C. or below, annealing the hot-rolled strip, cold-rolling the annealed strip with a final rolling reduction of 80% or more and subjecting the cold-rolled strip to decarburization annealing, a nitriding treatment and finish annealing, wherein the temperature, T.degree.C., of annealing of the hot-rolled strip is set so as to fall within the range 1240-2.1.times.Al.sub.R &lt;T&lt;1310-1.8.times.Al.sub.R (wherein Al.sub.R =acid soluble [Al]-27/14.times.[N]) and the strip is soaked for 180 sec or less, maintained at a temperature in the range of from 800.degree. to 950.degree. C. for 30 to 300 sec and then quenched. The grain-oriented electrical steel strip thus produced is not influenced by the variation in the [Al] and [N]. According to the present invention, a grain-oriented electrical steel strip having a very high magnetic density can be stably prepared through the establishment of a proper relationship between the Al and N ingredients and conditions for annealing of a steel strip before final cold rolling and the growth of a primary recrystallized grain to optimize the annealing conditions and the practice of a nitriding treatment after decarburization annealing.

Process for producing grain-oriented electrical steel strip having high

A method of primary recrystallization annealing grain-oriented electrical steel strip comprises the steps of conducting online measurement of the primary recrystallization grain diameter of the steel after primary recrystallization annealing and, based on the result of this measurement, controlling the primary recrystallization grain diameter of the steel after primary recrystallization annealing by varying either or both of the annealing temperature and the pass velocity during the primary recrystallization annealing. The method enables stable production of grain-oriented electrical steel strip exhibiting good secondary recrystallization and excellent electrical properties.

Method of primary recrystallization annealing grain-oriented electrical

A process for producing a grain-oriented electrical steel sheet having an excellent magnetic characteristic, comprising the steps of: heating to a temperature lower than 1280.degree. C. a steel slab comprising 0.025 to 0.075 wt % C, 2.5 to 4.5 wt % Si, 0.010 to 0.060 wt % acid-soluble Al, 0.0030 to 0.0130 wt % N, 0.014 wt % or less (S+0.405 Se), 0.05 to 0.8 wt % Mn, and the balance consisting of Fe and unavoidable impurities; hot-rolling the thus heated slab to form a hot-rolled strip; cold-rolling the hot-rolled strip to form a cold-rolled strip; decarburization-annealing the cold-rolled strip; applying an annealing separator on the strip; final-annealing the strip; measuring a primary-recrystallized grain size in the stage after completion of a primary recrystallization during the decarburization annealing and before completion of a secondary recrystallization during the final annealing; and controlling in that stage the subsequent grain growth of primary-recrystallized grains by an absorption of nitrogen into the steel strip in accordance with the measured grain size.

Process for producing grain-oriented electrical steel sheet having

A process for producing a grain-oriented electrical steel sheet having a superior magnetic characteristic, comprising the steps of: hot-rolling a silicon steel slab comprising 0.021 to 0.100 wt % C, 2.5 to 4.5 wt % Si, one or more elements for forming inhibitors, and the balance consisting of Fe and unavoidable impurities, to form a hot-rolled sheet; coiling the hot-rolled sheet at a coiling temperature lower than 700.degree. C.; subsequently cold-rolling the hot-rolled sheet at a reduction of 80% or more, effected by a plurality of rolling passes, to a final product sheet thickness; holding the steel sheet at a temperature of from 50.degree. to 500.degree. C. for 1 minute or longer at least once at the stage between the rolling passes of the cold rolling; decarburization-annealing the cold-rolled sheet; and final-annealing the decarburization-annealed sheet.

Procees for producing grain-oriented electrical steel sheet having

The strains in crystals are evaluated by quantifying the sharpness of an electron channeling pattern and determining changes in the quantified sharpness of the electron channeling pattern. There is such a close correlation between the sharpness of the electron channeling pattern and the strains in crystals that the latter can be evaluated in terms of changes in the former. An apparatus for evaluating strains in crystals comprises a scanning electron microscope having a function to form an electron channeling pattern and an image analyzer having a function to quantify the sharpness of an electron channeling pattern.

Method and apparatus for evaluating strains in crystals

A method of producing grain-oriented electrical steel sheet with a very high magnetic flux density, is characterized by increasing the partial pressure of the N.sub.2 in the annealing atmosphere at the intermediate stage between the start and the finish of the secondary recrystallization, and by ensuring the temperature differential in the coil does not exceed 100.degree. C. during changes to the annealing atmosphere. In addition, the rate of temperature increase at the hottest part of the coil is kept to a maximum of 13.degree. C./hr at least part of the time the coolest part of the coil is between 850.degree. C. and 1100.degree. C.

Method for producing grain-oriented electrical steel sheet with very

In the production of a grain-oriented electrical steel sheet by utilizing an AIN main inhibitor and at least twice cold-rolling with a heavy final reduction, improved magnetic properties are stably obtained by controlling the cooling speed (R) in the cooling process of a hot-rolled sheet annealing (R.gtoreq.5.degree.C./sec from 600.degree.-200.degree. C.) and by inter-pass aging (50.degree.-500.degree. C. for 1 minute or more) during the first cold-rolling.

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Kitakyushu, Japan

Yasunari Yoshitomi