EP0266422B2 - Verfahren zur herstellung von dünnen silizium-stahlblechen mit goss-textur mit niedrigen wattverlusten sowie mit ausgezeichneten oberflächeneigenschaften - Google Patents

Verfahren zur herstellung von dünnen silizium-stahlblechen mit goss-textur mit niedrigen wattverlusten sowie mit ausgezeichneten oberflächeneigenschaften Download PDF

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EP0266422B2
EP0266422B2 EP86902022A EP86902022A EP0266422B2 EP 0266422 B2 EP0266422 B2 EP 0266422B2 EP 86902022 A EP86902022 A EP 86902022A EP 86902022 A EP86902022 A EP 86902022A EP 0266422 B2 EP0266422 B2 EP 0266422B2
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steel sheet
annealing
steel
subjected
cold rolling
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EP0266422A4 (de
EP0266422B1 (de
EP0266422A1 (de
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Yukio Kawasaki St. Corp. Techn. Res. Di. Inokuti
Yoh Kawasaki St. Corp. Techn. Res. Div. Ito
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JFE Steel Corp
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Kawasaki Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1233—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a localized treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1227—Warm rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest

Definitions

  • the grain oriented silicon steel sheets can be utilized as a core for transformer and other electrical machinery and equipment, and are required to have a high magnetic flux density (represented by B 10 value) and a low iron loss (represented by W 17/50 value).
  • Japanese Patent Application Publication No. 57-2,252 Japanese Patent Application Publication No. 58-53,419, Japanese Patent Application Publication No. 58-5,968, Japanese Patent Application Publication No. 58-26,405, Japanese Patent Application Publication No. 58-26,406, Japanese Patent Application Publication No. 58-26,407 and Japanese Patent Application Publication No.
  • an artificial grain boundary is introduced into the surface of the grain oriented silicon steel sheet by utilizing an AIN precipitation phase as an inhibitor for inhibiting the growth of crystal grains in an unsuitable direction on finish annealing and irradiating a laser beam onto the steel sheet surface at an interval of several mm in a direction substantially perpendicular to the rolling direction to thereby reduce the iron loss through the artificial grain boundary.
  • a silicon steel material having a high Si content of Si: 3.1 ⁇ 4.5% is essentially a material suitable for obtaining a high magnetic flux density, low iron loss product, and have found that the surface properties can be made good even at the high Si content by enriching the surface layer of the steel material with Mo before the hot rolling, as a means for solving the degradation of surface properties.
  • the surface properties of the product are greatly improved as compared with the former case, but if it is particularly intended to thin the gauge of the product to 0.23 ⁇ 0.17 mm for obtanining low iron loss, there remains a large problem in that the improving effect on surface properties is small.
  • Japanese Patent laid open No. 59-126,722 has disclosed that in order to stably manufacture thinned products by utilizing the AIN precipitation phase at high Si content, a two-stage cold rolling process largely different from the conventional strong one-stage cold rolling process is particularly applied to a hot rolled material containing small amounts of Cu and Sn in addition to AlN.
  • This is effective for stably reducing the iron loss of the thinned product, but has yet many problems in that it is difficult to obtain products having excellent surface properties because high-temperature heating of the slab is usually required under a state of increasing Si and in that the cost of the product becomes considerably higher because of the small amounts of Sn and Cu which are added for stabilizing secondary recrystallized grains.
  • the development of the improvement of steel purity 3 or orientation 4 is considered to be marginal at the present.
  • the Goss orientation of secondary recrystallized grains in the existing products is aligned within 3° ⁇ 4° on average with respect to the rolling direction, so that it is very difficult in metallurgy to make the crystal grain small under such a highly aligned state.
  • the present invention provides a method of producing low iron loss grain oriented silicon thin steel sheets comprising subjecting a steel slab consisting of 0.030 to 0.080 wt % C, 3.1 to 4.5 wt % Si, 0.003 to 0.1 wt % Mo, 0.005 to 0.06 wt % acid soluble Al, at least one of S and Se in a total amount of not more than 0.005 to 0.1 wt %, optionally 0.005 to 0.2 wt % Sb, and optionally one or more of Sn, Cu and B in a total amount of not more than 0.5 wt %, the remainder being Fe and incidental impurities to a hot rolling to form a steel sheet, and subjecting said steel sheet to
  • the optional incidental elements include one or more of : 0.030-0.080 wt % C, one or more of Sn, Cu and B in a total amount of not more than 0.5 wt %.
  • the steel sheet is subjected to a treatment which causes the formation at the high temperature finish annealing, of heterogeneous microareas on the steel sheet surface.
  • heterogeneous microareas are formed on the surface of the steel sheet after the high temperature finish annealing.
  • the inventors have found that when a grain oriented silicon steel thin sheet is produced by utilizing the AIN precipitation phase at a high silicon content of 3.1 ⁇ 4.5 wt% products having excellent surface properties are obtained by adding a small amount of Mo to a steel material. Also the production of grain oriented silicon steel sheets having a low iron loss is made possible at very stable steps by the adoption of a two-stage cold rolling process including an intermediate annealing with rapid heating and rapid cooling, and as a result the above invention and embodiments thereof have been accomplished.
  • the hot rolled steel sheet was subjected to a primary cold rolling at a reduction of not more than 70% and further to an intermediate annealing at 1,050°C for 3 minutes.
  • the intermediate annealing the heating from 500°C to 900°C was carried out by a rapid heating treatment of 10°C/s, and the cooling from 900°C to 500°C was carried out by a rapid cooling treatment of 15°C/s.
  • the steel sheet was subjected to a secondary cold rolling at a reduction of 70% ⁇ 91% to obtain a cold rolled steel sheet having a final gauge of 0.20 mm, which was then subjected to decarburization and primary recrystallization annealing at 850°C in a wet hydrogen atmosphere.
  • an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, which was subjected to a secondary recrystallization annealing by raising temperature between 850°C ⁇ 1,100°C at 8°C/hr and further to a high-temperature finish annealing or a purification annealing in a dry hydrogen atmosphere at 1,200°C for 10 hours.
  • the magnetic properties of the resulting product and the ratio of surface defect produced (the ratio of the surface defect block existing on the steel sheet surface is represented by %) are shown in Fig. 1.
  • the product made from the test steel I containing Mo is good in the magnetic properties when the reduction at primary cold rolling is 10 ⁇ 60% (particularly 20 ⁇ 40%), and the ratio of the surface defect produced in the product is noticed to be not more than 2% (not more than 0.5% when the reduction at primary cold rolling is within a range of 20 ⁇ 25%).
  • the B 10 value and W 17/50 value are somewhat poorer than those of the test steel I as magnetic properties as seen from plots shown by the mark O in the same figure, and particularly the ratio of the surface defect produced in the product is as extremely high as 6 ⁇ 18%.
  • the hot rolled steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,050°C for 3 minutes.
  • the intermediate annealing each of the heating rate from 500°C to 900°C and the cooling rate from 900°C to 500°C was varied within a range of 1°C ⁇ 100°C.
  • the steel sheet after the intermediate annealing was subjected to a secondary cold rolling at a reduction of about 83% to obtain a cold rolled steel sheet having a final gauge of 0.23 mm, which was then subjected to decarburization and primary recrystallization annealing at 850°C in a wet hydrogen atmosphere, an application of an annealing separator mainly composed of MgO onto the steel sheet surface, a secondary recrystallization annealing by raising temperature from 850°C to 1,100°C at 10°C/hr, and a purification annealing in a dry hydrogen atmosphere at 1,200°C for 10 hours.
  • the magnetic properties of the resulting product are shown in Fig. 2.
  • products having considerably improved magnetic properties can be obtained when the heating rate from 500°C to 900°C at the intermediate annealing and the cooling rate from 900°C to 500°C after the intermediate annealing are not less than 5°C/s, particularly not less than 10°C/s.
  • 59-126,722 applies only the AIN micro-precipitation treatment through quenching treatment after normalized annealing in the conventional strong one-stage cold rolling process to the cooling stage of the intermediate annealing after the primary cold rolling, while according to the present invention it is newly elucidated that excellent magnetic properties are obtained only by the combination of rapid cooling at the intermediate annealing with rapid heating at the heating stage of the intermediate annealing and particularly by the addition of Mo.
  • test steel A containing C: 0.046 wt%, Si: 3.36 wt%, Mo: 0.026 wt%, Sb: 0.025 wt%, acid soluble Al: 0.024 wt% and Se: 0.020 wt% and a continuously cast slab (comparative steel B) containing C: 0.049%, Si: 3.45%, acid soluble Al: 0.025 wt%, Sb: 0.023 wt% and Se: 0.022 wt% were each heated at 1,360°C for 3 hours to perform the dissociation and solution of the inhibitor, and then hot rolled each to form a hot rolled steel sheet of 2.2 mm in thickness.
  • each hot rolled steel sheet was subjected to a normalized annealing at 1,050°C for 2 minutes and quenched.
  • each steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,000°C for 2 minutes.
  • the heating from 500°C to 900°C was carried out by a rapid heating treatment of 10°C/s, and the cooling from 900°C to 500°C was carried out by a rapid cooling treatment of 12°C/s.
  • the steel sheets were subjected to a secondary cold rolling at a reduction of 85% to obtain cold rolled steel sheets having a final gauge of 0.20 mm, which were subjected to decarburization and primary recrystallization annealing at 830°C in a wet hydrogen atmosphere.
  • the steel sheets were subjected to a secondary recrystallization annealing by raising temperature from 850°C at a rate of 10°C/hr, a purification annealing in a dry hydrogen atmosphere at 1,200°C for 10 hours, a baking treatment with an insulation coating and a strain relief annealing at 800°C for 3 hours.
  • the magnetic properties of the resulting products and the ratio of the surface defect produced therein are shown in Table 1.
  • Table 1 Steel ingot ingredient (%) Magnetic properties Surface property B 10 (T) W 17/50 (W/kg) Ratio of surface defect block produced (%) (A) C 0.046%, 1.94 0.82 1.8 Si 3.36%, Mo 0.026%, Sb 0.025%, Al 0.024%, Se 0.020%, (B) C 0.049%, 1.93 0.85 8 Si 3.45%, Al 0.025%, Sb 0.023%, Se 0.022%
  • the magnetic properties of the product made from the test steel A containing Mo therein are good in that the B 10 value is 1.94 T and the W 17/50 value is 0.82 W/kg, and it is noted that the ratio of the surface defect produced in the product is 1.8%.
  • the magnetic properties of the product made from the comparative steel B of the conventional composition are bad in that B 10 is 1.93 T and W 17/50 is 0.85 W/kg as compared with those of the test steel B containing Mo therein, and particularly the ratio of the surface defect produced in the product is as extremely high as 8%.
  • a steel ingot (test steel III) containing C: 0.053%, Si: 3.43%, Mo: 0.023%, acid soluble Al: 0.028% and S: 0.027% and a steel ingot (comparative steel II) containing C: 0.056%, Si: 3.46%, acid soluble Al: 0.026%, S: 0.026%, Sn: 0.1% and Cu: 0.1% was heated at 1,430°C for 3 hours to perform the dissociation and solution of the inhibitor, and then hot rolled each to form a hot rolled steel sheet of 2.2 mm in thickness.
  • the hot rolled steel sheets were subjected to a primary cold rolling at a reduction of not more than 70% and further to an intermediate annealing at 1,100°C for 3 minutes.
  • the heating from 500°C to 900°C was carried out by a rapid heating treatment at a heating rate of 13°C/s
  • the cooling from 900°C to 500°C after the intermediate annealing was carried out by a rapid cooling treatment at a cooling rate of 18°C/s.
  • the steel sheets were then subjected to a secondary cold rolling at a reduction of 70% ⁇ 91% to obtain cold rolled steel sheets having a final gauge of 0.20 mm.
  • a warm rolling at 250°C was carried out in the course of the cold rolling.
  • each of these samples was subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere, and after an annealing separator mainly composed of MgO was applied to the steel sheet surfaces, the samples were further subjected to a secondary recrystallization annealing by raising temperature from 850°C to 1,100°C at 10°C/hr and a purification annealing in a dry hydrogen atmosphere at 1,200°C for 10 hours.
  • the test steels III containing Mo therein have good magnetic properties when the reduction at the primary cold rolling is from 10 to 60% (particularly 20 ⁇ 40%), and it is noted that the ratio of surface the defect produced in the product is not more than 3% (particularly not more than 1.0% when the reduction at the primary cold rolling is within a range of 20 ⁇ 50%).
  • the properties of the comparative steels II of the conventional composition (mark ⁇ , ⁇ ), B 10 value and W 17/50 value are somewhat poorer than those of Mo containing steel, and the ratio of the surface defect produced in the product is as extremely high as 6 ⁇ 20%.
  • the magnetic properties are noteably good in that the W 17/50 value is 0.72 W/kg when the reduction at the primary cold rolling is 30 ⁇ 40% (reduction at secondary cold rolling, 87 ⁇ 85%) as shown in plots of the mark ⁇ of the test steel III, and the ratio of the surface defect produced in the product is as good as not more than 1%.
  • the W 17/50 value of iron loss is as good as 0.75 W/kg when the reduction at the primary cold rolling is 30 ⁇ 40% as shown in plots of the mark ⁇ , but the ratio of the surface defect produced in the product is as high as 6 ⁇ 7%.
  • test steel C containing C: 0.048%, Si: 3.41%, Mo: 0.024%, acid soluble Al: 0.025%, Sb: 0.025% and S: 0.026% and a steel ingot (test steel C) containing C: 0.052%, Si: 3.38%, acid soluble Al: 0.023% and S: 0.025% were each heated at 1,420°C for 3 hours to perform the dissociation and solution of inhibitor and hot rolled each to form a hot rolled steel sheet of 2.0 mm in thickness.
  • each hot rolled steel sheet was subjected to a two-stage cold rolling (reduction at primary cold rolling: 50%, reduction at secondary cold rolling: 80%) with an intermediate annealing at 980°C for 3 minutes to obtain cold rolled steel sheets having a final gauge of 0.20 mm.
  • the heating from 500°C to 900°C was carried out by a rapid heating treatment at a heating rate of 10°C/s, and the cooling from 900°C to 500°C after the intermediate annealing was carried out at a cooling rate of 13°C/s.
  • the steel sheets were subjected to a secondary recrystallization annealing by raising the temperature from 850°C to 1,050°C at 10°C/hr, a purification treatment at 1,200°C for 8 hours, a baking treatment with an insulation coating and a strain relief annealing at 800°C for 3 hours.
  • a grain oriented silicon steel sheet was produced by a method of applying an annealing separator mainly composed of MgO, omitting the adhesion treatment of Al 2 O 3 powder according to the usual manner, which was a comparative example.
  • Table 2 Steel ingot ingredient (wt%) Application method of annealing separator after decarburization and primary recrystallization annealing Magnetic properties Surface property B 10 (T) W 17/50 (W/kg) Ratio of surface defect block produced (%) (C) C 0.048%, Mgo is uniformly applied to steel sheet 1.94 0.84 0.4 Si 3.41%, Mo 0.024%, Sb 0.025%, Al 2 O 3 is locally applied and then MgO is applied 1.94 0.77 0.5 Al 0.025%, S 0.026% (D) C 0.052%, Mgo is uniformly applied to steel sheet 1.93 0.90 9 Si 3.38% Al 0.023%, Al 2 O 3 is locally applied and then MgO is applied 1.93 0.86 10 S 0.0025%
  • the magnetic properties of the product made from the test steel C containing Mo therein are good in that B 10 is 1.94 T and W 17/50 is 0.84 W/kg when the MgO annealing separator is uniformly applied to steel sheet according to the usual manner after the decarburization and primary recrystallization annealing, and the ratio of the surface defect produced in the product is 0.4%.
  • the magnetic properties of the product made from the comparative steel D of the conventional composition are B 10 of 1.93 T and W 17/50 of 0.86 ⁇ 0.90 W/kg depending upon the handling conditions after the decarburization and primary recrystallization annealing and are poorer than those of the test steel C containing Mo therein, and the ratio of the surface defect produced in the product is as extremely high as 9 ⁇ 10%.
  • test steel E containing C: 0.053%, Si: 3.43%, Mo: 0.026%, acid soluble Al: 0.029%, Se: 0.021% and Sb: 0.020% and a steel ingot (test steel F) containing C: 0.058%, Si: 3.49%, acid soluble Al: 0.026%, S: 0.026%, Cu: 0.1% and Sn: 0.05% were each heated at 1,420°C for 5 hours to perform the dissociation and solution of inhibitor and hot rolled each to form a hot rolled steel sheet of 2.0 mm in thickness.
  • the hot rolled-steel sheets were subjected to a normalized annealing at 1,080°C for 2 minutes, quenched and subjected to two-stage cold rolling (reduction at primary cold rolling: 50%, reduction at secondary cold rolling: 80%) through an intermediate annealing at 950°C for 3 minutes to obtain a cold rolled steel sheets having a final gauge of 0.20 mm.
  • the heating from 500°C to 900°C was carried out by a rapid heating treatment at 11°C/s, and the cooling from 900°C to 500°C after the intermediate annealing was carried out at a cooling rate of 12°C/s.
  • the steel sheets were coated at their surface with an annealing separator mainly composed of MgO, and subjected to a secondary recrystallization annealing by raising the temperature from 850°C to 1,050°C at a heating rate of 12°C/hr and further to a purification annealing in a dry hydrogen atmosphere at 1,220°C for 5 hours.
  • an annealing separator mainly composed of MgO
  • the steel sheet after the finish annealing was subjected to the baking treatment with the insulation coating and further to a strain relief annealing at 800°C for 3 hours.
  • Table 3 Steel ingot ingredient (wt%) Treatment after finish annealing Magnetic properties Surface property B 10 (T) W 17/50 (W/kg) Ratio of surface defect block produced (%) (E) C 0.053%, Insulation coating 1.94 0.84 0.2 Si 3.43%, Mo 0.026%, Laser irradiation ⁇ pickling ⁇ immersion in SbC l 3 solution ⁇ insulation coating 1.94 0.76 0.4 Sb 0.029%, Al 0.021%, S 0.020%, (F) C 0.058%, Insulation coating 1.93 0.90 9 Si 3.49% Al 0.026%, Laser irradiation ⁇ pickling ⁇ immersion in SBC l 3 solution ⁇ insulation coating 1.93 0.85 11 S 0.026% Cu 0.1%, Sn 0.05%
  • the magnetic properties of the product from the test steel E containing Mo therein are good in that B 10 is 1.94 T and W 17/50 is 0.84 W/kg when the insulation coating is formed according to the usual manner after the finish annealing, and the ratio of the surface defect produced in the product is 0.2%.
  • the magnetic properties are very good in that B 10 is 1.94 T and W 17/50 is 0.76 W/kg, and it is noted that the ratio of the surface defect produced in the product is 0.4%.
  • the magnetic properties of the product made from the comparative steel F of the conventional composition are B 10 of 1.93 T and W 17/50 of 0.85 ⁇ 0.90 W/kg depending upon the handling conditions after the finish annealing and are poorer than those of the test steel E containing Mo therein, and the ratio of the surface defect produced in the product is as extremely high as 9 ⁇ 11%.
  • a part of the construction of the above method is a method wherein iron loss is reduced by irradiating with laser the surface of the grain oriented silicon steel sheet after the finish annealing in a direction substantially perpendicular to the rolling direction to introduce artificial grain boundary thereinto as disclosed in Japanese Patent Application Publication No. 57-2,252, Japanese Patent Application Publication No. 57-53,419, Japanese Patent Application Publication No. 58-5,968, Japanese Patent Application Publication No. 58-26,405, Japanese Patent Application Publication No. 58-26,406, Japanese Patent Application Publication No. 58-26,407 and Japanese Patent Application Publication No. 58-36,051.
  • the low iron loss grain oriented silicon steel sheet can advantageously be produced by a method wherein microstrain is introduced through laser irradiation, and the base metal is completely exposed through pickling to react with Sb at a high temperature, and recovery and recrystallization of local areas is accelerated to form heterogeneous microareas onto the steel sheet surface.
  • the latter method is an epock-making method that the degradation of iron loss is not caused even when being subjected to high-temperature heating treatment, which is different from the laser irradiated product sheet as mentioned above, and a part of the construction of this method is disclosed in Japanese Patent laid open No. 60-255,926.
  • the invention makes possible the production of grain oriented silicon steel sheets having good iron loss and surface properties at stable steps by the addition of Mo to the steel material, the adoption of a two-stage cold rolling process, a restriction of heating and cooling rates at the intermediate annealing, and the further formation of heterogeneous microareas onto the steel sheet in the decarburization and primary recrystallization annealing or after the finish annealing, which is different from the aforementioned conventional techniques in the fundamental idea and is fairly superior in the effect obtained by the adoption of these steps as compared with the conventional techniques.
  • Si is an element effective for increasing the electrical resistance of silicon steel sheet to reduce eddy current loss as previously mentioned, and is particularly required to be not less than 3.1 wt% for reducing the iron loss of the thinned product.
  • Si amount exceeds 4.5 wt%, brittle fracture is probe to be caused in the cold rolling, so that the Si amount is limited to a range of 3.1 ⁇ 4.5 wt%.
  • the Si amount in the conventional grain oriented silicon steel sheet utilizing AIN as an inhibitor is about 2.8 ⁇ 3.0 wt%, but if the Si amount is increased, the surface properties of product as in the comparative steels I, III of Figs. 1, 3 are considerably degraded.
  • the prevention of the occurrence of surface defects is made possible by adding 0.003 ⁇ 0.1 wt% of Mo to the steel material.
  • the amount of Mo added to the steel material is less than 0.003 wt%, the force improving the magnetic properties and preventing the occurrence of surface defect is weak, while when it exceeds 0.1%, the decarburization in the steel is delayed at the decarburization step, so that the amount should be limited to a range of 0.003 ⁇ 0.1 wt%.
  • Al forms a fine precipitate of AIN by bonding to N contained in steel and acts as a strong inhibitor.
  • acid soluble Al is necessary to be within a range of 0.005 ⁇ 0.06 wt%.
  • the amount of acid soluble Al is less than 0.005 wt%, the precipitated amount of AIN fine precipitates as an inhibitor is lacking and the growth of secondary recrystallized grains in ⁇ 110 ⁇ ⁇ 001> orientation is insufficient, while when it exceeds 0.06 wt%, the growth of secondary recrystallized grains in ⁇ 110 ⁇ ⁇ 001> orientation is also considerably degraded.
  • the S amount is less than 0.005 wt%, or if the Se amount is less than 0.003 wt%, the inhibitor effect is lacking, while if either of the amounts exceeds 0.05 wt%, the hot and cold workabilities are degraded, so that it is desirable that the S amount is within a range of 0.005 ⁇ 0.05 wt% and the Se amount is within a range of 0.003 ⁇ 0.05 wt%.
  • Sb exerts control of the primary recrystallized grain growth.
  • the amount is less than 0.005 wt%, the effect is small, while when it exceeds 0.2 wt%, the magnetic flux density is lowered to reduce the magnetic properties, so that the amount should be within a range of 0.005 ⁇ 0.2 wt%.
  • the steel material adapted for the method of the invention should contain 3.1 ⁇ 4.5% of Si and small amounts of Mo, Al, S and Se and further Sb as mentioned above, but there is no obstacle to the presence of other well-known elements added to ordinary silicon steel.
  • C is required to produce ⁇ transformation in a part of the steel sheet during the annealing of the hot rolled steel sheet in connection with the fine precipitation of AIN.
  • the C amount is suitably within a range of about 0.030 ⁇ 0.080 wt% when the Si amount is within a range of 3.1 ⁇ 4.5 wt % according to the invention.
  • At least one of Sn, Cu and B added to ordinary silicon steel as a well-known inhibitor for primary recrystallized grain growth may be contained in a total amount of not more than 0.5 wt%, and also it is generally accepted to contain a slight amount of inevitable elements such as Cr, Ti, V, Zr, Nb, Ta, Co, Ni, P, As and so on.
  • LD converter open hearth and other well-known steel making processes can be used as the means for melting the steel material used in the method according to the invention. It is a matter of course that the above means may be used together with vacuum treatment or vacuum dissolution.
  • the usual ingot making-bloom rolling as well as continuous casting may preferably be used.
  • the thus obtained silicon steel slab is heated in the well-known method and then subjected to a hot rolling.
  • the thickness before hot rolling obtained by the hot rolling is different by the reduction of the subsequent cold rolling step, but it is usually desirable to be about 1.5 ⁇ 3.0 mm.
  • the addition of a small amount of Mo to the steel material is an essential feature for obtaining silicon steel sheets having good surface properties.
  • a means for enriching Mo in the surface layer of the steel sheet by applying an Mo compound to the surface up to the completion of the hot rolling may naturally be used.
  • the hot rolled steel sheet after the completion of the hot rolling is subjected to a primary cold rolling.
  • the steel sheet is subjected to a normalized annealing within a temperature range of 900 ⁇ 1,200°C and a quenching treatment for obtaining a finely uniformized dispersion of C into the hot rolled steel sheet before the primary cold rolling.
  • the reduction at primary cold rolling is somewhat different in accordance with the gauge of the product, but it is limited to 10 ⁇ 60% (desirably 20 ⁇ 50%) for obtaining the thinned product having good properties according to the invention as seen from Figs. 1 and 3.
  • the intermediate annealing is carried out at a temperature of 900 ⁇ 1,100°C for about 30 seconds ⁇ 30 minutes.
  • the heating from 500°C to 900°C and the cooling from 900°C to 500°C after the intermediate annealing are carried out at a rate of not less than 5°C/s, preferably not less than 10°C/s.
  • Such rapid heating and rapid cooling treatments may be performed by a well-known means such as a continuous furnace, a batch furnace or the like.
  • the secondary cold rolling is adapted at a reduction of 75 ⁇ 90% as seen from Figs. 1 and 3, whereby a cold rolled steel sheet having a final gauge of 01. ⁇ 0.25 mm is finished.
  • the invention is to produce high magnetic flux density electromagnetic steel thin sheets.
  • the steel sheets having good properties are obtained by finishing the hot rolled steel sheet of about 1.5 ⁇ 3.0 mm in thickness at the reduction of each of the cold rolling and secondary cold rolling shown in Figs. 1 and 3 into a cold rolled steel thin sheet having a final gauge of 0.1 ⁇ 0.25 mm.
  • an ageing treatment at 50 ⁇ 600°C may be performed through a plurality passes as disclosed in Japanese Patent Application Publication No. 54-13,866.
  • the thus cold rolled thin sheet of 0.1 ⁇ 0.25 mm in gauge is subjected to a decarburization annealing serving as a primary recrystallization within a temperature range of about 750 ⁇ 870°C.
  • the decarburization annealing may be usually performed in a wet hydrogen atmosphere having a dew point + about 30 ⁇ 65°C or in a mixed gas atmosphere of hydrogen and nitrogen for several minutes.
  • the steel sheet after the decarburization annealing is coated with an annealing separator mainly composed of MgO and subjected to a finish annealing to grow secondary recrystallized grains in ⁇ 110 ⁇ ⁇ 001 > orientation.
  • the concrete conditions for the finish annealing may be the same as in the well-known ones, but it is usually desirable that the secondary recrystallized grains are grown by raising the temperature up to 1,150 ⁇ 1,250°C at a heating rate of 3 ⁇ 50°C/hr and then a purification annealing is carried out in a dry hydrogen atmosphere for 5 ⁇ 20 hours.
  • a treatment for forming heterogeneous microareas onto the steel sheet surface through subsequent high-temperature finish annealing is previously performed in the decarburization and primary recrystallization annealing, i.e. before or after this annealing and then the high-temperature finish annealing is performed as previously mentioned in the second embodiment, or the laser irradiation is performed as mentioned in the third embodiment, whereby low iron loss grain oriented silicon sheets can be produced.
  • the treatment for the formation of heterogeneous microareas can use the following methods:
  • the decarburization promotion area and decarburization delay area are alternately formed on the steel sheet surface at substantially an equal width at intervals of 1 ⁇ 50 mm as previously disclosed in Japanese Patent laid open No. 60-39,124.
  • the narrower the width of these areas the finer the primary recrystallized texture, and hence the secondary recrystallized grain becomes finer.
  • the secondary recrystallized grain size of the product is usually within a range of 1.5 ⁇ 25 mm, when the primary recrystallized texture is varied on the steel sheet surface at a width corresponding to not more than 2 times of the secondary recrystallized grain size or a width of 3 ⁇ 50 mm, it is possible to obtain finer secondary recrystallized grains.
  • the effect of applying the coating agent to the steel sheet surface is sufficiently developed even at the one-side surface, but it is more enhanced when being applied to both-side surfaces of the steel sheet.
  • As the application method to the steel sheet surface it is considered that the application with a grooved or uneven rubber roll is optimal, but a spraying method after the covering of unnecessary areas with a making plate may be used.
  • the coating solution for forming the decarburization promotion area and decarburization delay area on the steel sheet surface may be prepared according to the teaching published by the inventors (Y. Inokuti: Trans. ISIJ, Vol. 15 (1975), P. 324), which is quoted below by way of precaution.
  • Decarburization promotion agent MgCl 2 ⁇ 6H 2 O, Mg(NO 3 ) 2 ⁇ 6H 2 O, CaCl 2 ⁇ 2H 2 O, Ca(NO 3 ) 2 ⁇ 4H 2 O, SrCl 2 ⁇ 2H 2 O, Sr(NO 3 ) 2 ⁇ 4H 2 O, BaCl 2 ⁇ 2H 2 O, Ba(NO 3 ) 2 , KCI, KMnO 4 , K 2 P 2 O 7 , KBr, KClO 3 , KBrO 3 , KF, NaCl, NalO 4 , NaOH, NaHPO 4 , NaH 2 PO 4 ⁇ 2H 2 O, NaF, NaHCO 3 ⁇ Na 2 O 5 , Na 4 P 2 O 7 ⁇ 10H 2 O, Nal ⁇ (NH 4 ) 2 Cr 2 O 7 , Cu(NO 3 ) 2 ⁇ 3H 2 O, Fe(NO 3 ) 3 ⁇ 9H 2 O, Co(NO 3 ) 2
  • Decarburization delay agent K 2 S, Na 2 S 2 O 3 ⁇ 5H 2 O, Na 2 S ⁇ 9H 2 O, MgSO 4 , SrSO 4 , Al 2 (SO 4 ) 3 ⁇ 18H 2 O, S 2 Cl 2 , NaHSO 3 , FeSO 4 ⁇ 7H 2 O, KHSO 4 , Na 2 S 2 O 8 , K 2 S 2 O 7 , Ti(SO 4 ) 2 ⁇ 3H 2 O, CuSO 4 ⁇ 5H 2 O, ZnSO 4 ⁇ 7H 2 O, CrSO 4 ⁇ 7H 2 O, (NH 4 ) 2 S 2 O 8 , H 2 SO 4 , H 2 SeO 3 , SeOCl 2 , Se 2 Cl 2 , SeO 2 , H 2 SeO 4 , K 2 Se, Na 2 Se, Na 2 SeO 3 , K 2 SeO 3 , Na 2 SeO 4 , K 2 SeO 4 , H 2 TeO 4 ⁇ 2H 2 O, Na 2 TeO 3 , K 2
  • the non-treated area is formed as a delay area in the treatment using only the former agent or as a promotion area in the treatment using only the latter agent.
  • the method of forming the microareas on the steel sheet surface after the decarburization and primary recrystallization annealing with a secondary recrystallization promoting or controlling agent may be performed according to the teaching of Japanese Patent laid open No. 60-89,521, which is quoted below by way of precaution.
  • a YAG laser pulse generating multimode is optimal.
  • the method 3 i.e. the formation of temperature differences on the steel sheet surface through heat treatment may be performed according to the teachings of well-known articles (Japanese Patent laid open No. 60-103,132 and the like).
  • the preferred conditions are mentioned as follows. Difference between temperature of high-temperature treated steel sheet and usual annealing temperature 15 ⁇ 100°C High-temperature area of steel sheet surface width of 2 ⁇ 25 mm Area treated at usual annealing temperature width of 2 ⁇ 25 mm
  • the method for non-uniform heat treatment through these repeated annealing treatments may be performed by any one of conventional well-known means such as local heating with a flash lamp, infrared ray lamp, high frequency induction heating, a pulse type heat treatment and so on.
  • the annealing separator mainly composed of MgO is applied to the treated steel sheet surface and then the high-temperature finish annealing is performed to grows the secondary recrystallized grains strongly aligned in ⁇ 110 ⁇ ⁇ 001 > orientation.
  • the concrete conditions of the finish annealing may be the same as in the conventional well-known annealing method, but it is usually desirable that the temperature is raised up to 1,150 ⁇ 1,250°C at a heating rate of 3 ⁇ 50°C/hr to grow the secondary recrystallized grains and then a purification annealing is carried out in a dry hydrogen atmosphere for 5 ⁇ 20 hr.
  • heterogeneous microareas are formed onto the finish annealed steel sheet surface to produce low iron loss grain oriented silicon steel sheets.
  • the method may be performed according to a method previously disclosed in Japanese Patent laid open No. 60-92,479. By way of precaution, there are mentioned the following four methods:
  • the thermal expansion coefficient of the insulation coating is not more than 8.5 ⁇ 10 -6 1/°C and the coefficient between different coatings is not less than 1.1 as disclosed in Japanese Patent laid open No.60-103,182, which may be achieved by alternately applying and baking the conventionally known different coating solutions at an interval of 1 ⁇ 30 mm.
  • the steel sheet layer is peeled off from the steel sheet surface after the finish annealing by means of a laser or a means for application of stress such as scriber, and a part of the base metal is removed with an acid such as hydrochloric acid, nitric acid or the like, and then the treated steel sheet is immersed in an aqueous solution of an inorganic compound containing a semi-metal, a metal or the like to fill in the removed portion, which is thereafter subjected to recovery and recrystallization annealing serving as a strain relief annealing to form non-uniform areas.
  • an insulation coating composed mainly of phosphate and colloidal silica is applied and baked to the above treated sheet. It is naturally required for use in transformers having a capacity as large as 1,000,000 KVA.
  • the formation of such an insulation coating may be performed by using the conventionally well-known process as it is.
  • the strain relief annealing is carried out at a temperature of not lower than 600°C.
  • the method according to the invention has a characteristic that the degradation of magnetic properties is not caused even after such a high-temperature annealing.
  • a continuously cast slab containing C: 0.059%, Si: 3,49%, Mo: 0.024%, acid soluble Al: 0.034%, S: 0.029% was heated at 1,430°C for 3 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Thereafter, the steel sheet was subjected to a primary cold rolling at a reduction of about 50% and further to an intermediate annealing at 1,100°C for 3 minutes. In the intermediate annealing, a rapid heating treatment of 12°C/s was performed from 500°C to 900°, and a rapid cooling treatment of 15°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a cold rolling at a reduction of about 80% to obtain a cold rolled steel sheet having a final gauge of 0.20 mm, which was then subjected to a primary recrystallization annealing serving as a decarburization in a wet hydrogen atmosphere at 830°C.
  • the magnetic properties were B 10 : 1.93 T and W 17/50 :0.80 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 0.8%.
  • a continuously cast slab containing C: 0.064%, Si: 3.39%, Mo: 0.019%, acid soluble Al: 0.029%, Se: 0.020%, Sb: 0.022% was heated at 1,420°C for 4 hours and hot rolled to a thickness of 2.2 mm. Thereafter, the steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,100°C for 2 minutes. In the intermediate annealing, a rapid heating treatment of 12°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 18°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a secondary cold rolling at a reduction of about 83% to obtain a cold rolled steel sheet having a final gauge of 0.23 mm, which steel sheet was then subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C.
  • a secondary recrystallization was performed by raising the temperature from 850°C to 1,100°C at 10°C/hr, and then a purification annealing was performed in a dry hydrogen at 1,200°C for 15 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.93 T and W 17/50 : 0.80 w/kg, and the surface properties were very good as the ratio of the surface defect block produced was 0.6%.
  • a steel ingot containing C: 0.058%, Si: 3.59%, Mo: 0.035%, acid soluble Al: 0.033%, S: 0.023%, Cu: 0.15%, Sn: 0.11% was hot rolled to form a hot rolled steel sheet of 2.0 mm in thickness which was then subjected to a primary cold rolling (reduction: about 40%). Thereafter, the steel sheet was subjected to an intermediate annealing at 1,050°C for 5 minutes, wherein the heating from 500°C to 900°C was performed by a rapid heating treatment of 18°C/s and the cooling from 900°C to 500°C was performed by a rapid cooling treatment of 20°C/s.
  • the steel sheet was subjected to a strong cold rolling at a reduction of about 89% to obtain a cold rolled steel sheet having a final gauge of 0.17mm, during which a warm rolling at 300°C was performed. Then, the steel sheet was subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C, a secondary recrystallization by raising the temperature from 850°C to 1,100°C at 15°C/hr, and a purification annealing in a dry hydrogen atmosphere at 1,200°C for 15 hours.
  • the magnetic properties were B 10 ; 1.93 T and W 17/50 : 0.76 w/kg, and the surface properties were good as the ratio of the surface defect block produced was 0.9%.
  • a continuously cast slab containing C: 0.064%, Si: 3.45%, Mo: 0.025%, acid soluble Al: 0.025%, S: 0.028% was heated at 1420°C for 4 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 30% and further to an intermediate annealing at 1,080°C for 3 minutes. In the intermediate annealing, a rapid heating treatment of 13°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 18°C/s was performed from 900°C to 500°C.
  • the steel sheet was subjected to a cold rolling at a reduction of about 85% to obtain a cold rolled steel sheet having a final gauge of 0.23 mm.
  • an aqueous diluted solution of MgSO 4 (0.01 mol/l) at 85°C was applied by spraying with a jig of 0.5 mm in width at an interval of 5 mm in a direction substantially perpendicular to the rolling direction to alternately form applied areas and non-applied areas.
  • the steel sheet was then subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C.
  • the steel sheet was slowly heated from 850°C to 1,100°C at 10°C/hr and then subjected to a purification annealing in a hydrogen atmosphere at 1,200°C for 10 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.93 T and W 17/50 : 0.82 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 1.2%.
  • a continuously cast slab containing C: 0.066%, Si: 3.5%, Mo: 0.035%, acid soluble Al: 0.030%, S: 0.026%, Sb: 0.026%, Sn: 0.1%, Cu: 0.1% was heated at 1,430°C for 4 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,050°C for 5 minutes. In the intermediate annealing, a rapid heating treatment of 15°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 20°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a cold rolling at a reduction of about 85% to obtain a cold rolled steel sheet having a final gauge of 0.20 mm, during which a warm rolling at 250°C was performed.
  • the steel sheet was slowly heated from 850°C to 1,100°C at 8°C/hr and subjected to a purification annealing in a hydrogen atmosphere at 1,200°C for 10 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.94 T and W 17/50 :0.73 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 1.2%.
  • a continuously cast slab containing C: 0.058%, Si: 3.40%, Mo: 0.026%, Se: 0.021%, acid soluble Al: 0.030%, Sb: 0.025% was heated at 1,430°C for 3 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 50% and further to an intermediate annealing at 1,100°C for 3 minutes. In the intermediate annealing, a rapid heating treatment of 12°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 15°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a cold rolling at a reduction of about 80% to obtain a cold rolled steel sheet having a final gauge of 0.20 mm, which was then subjected to a primary recrystalization annealing serving as a decarburization in a wet hydrogen atmosphere at 830°C.
  • an annealing separator mainly composed of MgO, Al 2 O 3 powder as a reaction inhibiting substance against the annealing separator and SiO 2 in subscale of steel sheet was linearly adhered to the steel sheet surface under the conditions that the adhesion amount was 0.3 g/m 2 , the adhesion width in a direction substantially perpendicular to the rolling direction of steel sheet was 1.5 mm, and interval was: 8 mm, and thereafter the annealing separator mainly composed of MgO was applied thereto.
  • the steel sheet was subjected to a secondary recrystallization by raising the temperature from 850°C to 1,100°C at 10°C/hr and further to a purification annealing in a hydrogen atmosphere at 1,200°C for 10 hours.
  • the forsterite layer having a thickness thinner by 0.6 ⁇ m was formed on the area coated with Al 2 O 3 powder.
  • strain relief annealing was performed at 800°C for 3 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.94 T and W 17/50 :0.78 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 0.9%.
  • a continuosuly cast slab containing C: 0.054%, Si: 3.36%, Mo: 0.024%, acid soluble Al: 0.025%, Se: 0.020% was heated at 1,420°C for 4 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,100°C for 2 minutes. In the intermediate annealing, a rapid heating treatment of 12°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 18°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a secondary cold rolling at a reduction of about 83% to obtain a cold rolled steel sheet having a final gauge of 0.23 mm, which was then subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C.
  • the steel sheet was irradiated linearly with a pulse laser (line width: 0.3 mm) at an interval of 8 mm in a direction perpendicular to the rolling direction, and thereafter a solution of SbCl 3 (0.01 mol/l, 90°C) was applied at the laser irradiated position.
  • a pulse laser line width: 0.3 mm
  • SbCl 3 0.01 mol/l, 90°C
  • a secondary recrystalliazation was performed by raising the temperature from 850°C to 1,100°C at 10°C/hr, and then a purification annealing was performed in a dry hydrogen atmosphere at 1,200°C for 15 hours.
  • the steel sheet was subjected to a strain relief annealing at 800°C for 2 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.94 T and W 17/50 : 0.79 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 0.8%.
  • a steel ingot containing C: 0.054%, Si: 3.49%, Mo: 0.025%, acid soluble Al: 0.03%, S: 0.022%, Cu: 0.15%, Sn: 0.10% was hot rolled to form a hot rolled steel sheet of 2.0 mm in thickness, which was subjected to a primary cold rolling (reduction: about 40%). Then, the steel sheet was subjected to an intermediate annealing at 1,050°C for 5 minutes, wherein the heating from 500°C to 900°C was carried out by a rapid heating treatment of 18°C/s, the cooling from 900°C to 500°C after the intermediate annealing was carried out by a rapid cooling treatment of 20°C/s.
  • the steel sheet was subjected to a strong cold rolling at a reduction of about 89% to obtain a cold rolled steel sheet having a final gauge of 0.17 mm, during which a warm rolling at 300°C was performed. Then, the steel sheet was subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C, before which an electron beam was scanned at a width of 0.5 mm and an interval of 12 mm in a direction perpendicular to the rolling direction form non-uniform heat areas.
  • a secondary recrystallization was performed by raising the temperature from 850°C to 1,100°C at 15°C/hr, and a purification annealing was performed in a dry hydrogen atmosphere at 1,200°C for 15 hours.
  • a continuously cast slab containing C: 0.057%, Si: 3.35%, Mo: 0.025%, acid soluble Al: 0.020%, Se: 0.022%, Sb: 0.023% was heated at 1,420°C for 4 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 30% and further to an intermediate annealing at 1,080°C for 3 minutes. In the intermediate annealing, a rapid heating treatment of 13°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 18°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel was subjected to a cold rolling at a reduction of about 85% to obtain a cold rolled steel sheet having a final gauge of 0.23 mm, which was then subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 840°C.
  • an annealing separator mainly composed of MgO the steel sheet was slowly heated from 850°C to 1,100°C at 10°C/hr and subjected to a purification annealing in a hydrogen atmosphere at 1,200°C for 10 hours.
  • the steel sheet was subjected to recovery/recrystallization annealing serving as a strain relief annealing at 800°C for 5 hours.
  • the magnetic properties and surface properties of the resulting product were as follows.
  • the magnetic properties were B 10 : 1.94 T and W 17/50 : 0.78 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 1.1%.
  • a continuously cast slab containing C: 0.056%, Si: 3.41%, Mo: 0.025%, acid soluble Al: 0.030%, Se: 0.020%, Sn: 0.1%, Cu: 0.1% was heated at 1,430°C for 4 hours and hot rolled to form a hot rolled steel sheet of 2.2 mm in thickness. Then, the steel sheet was subjected to a primary cold rolling at a reduction of about 40% and further to an intermediate annealing at 1,050°C for 5 minutes. In the intermediate annealing, a rapid heating treatment of 15°C/s was performed from 500°C to 900°C, and a rapid cooling treatment of 20°C/s was performed from 900°C to 500°C after the intermediate annealing.
  • the steel sheet was subjected to a secondary cold rolling at a reduction of about 85% to obtain a cold rolled steel sheet of 0.20 mm in gauge, during which a warm rolling at 250°C was performed. Then, the steel sheet was subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 850°C, coated with an annealing separator mainly composed of MgO, slowly heated from 850°C to 1,100°C at 8°C/hr, and subjected to a purification annealing in a hydrogen atmosphere at 1,200°C for 10 hours.
  • the magnetic properties were B 10 : 1.94 T and W 17/50 : 0.76 w/kg, and the surface properties were very good as the ratio of surface defect block produced was 1.1%.
  • the invention has a remarkable effect that grain oriented silicon steel thin sheets having a low iron loss in that the B 10 value is not less than 1.92 T and W 17/50 value is not more than 0.85 W/kg (0.23 mm thickness) and very excellent surface properties can be produced industrially and stably.
  • products having excellent iron loss properties and surface properties can be produced at stable steps by including Mo and Al into a steel material, subjecting a steel sheet to two-stage cold rolling process to obtain a final cold rolled steel sheet, and forming heterogeneous microareas onto the steel sheet surface in decarburization and primary recrystallization annealing or after finish annealing to grow a non-uniform and fine secondary recrystallized texture in Goss orientation.

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Claims (3)

  1. Verfahren zur Herstellung von dünnen, kornorientierten Siliziumstahl-Blechen mit geringem Eisenverlust enthaltend: Heißwalzen einer Stahlbramme, welche aus 0,030 bis 0,080 Gew.-%C, 3,1 bis 4,5 Gew.-% Si, 0,003 bis 0,1 Gew.-% Mo, 0,005 bis 0,06 Gew.-% säurelösliches A1, zumindest eines von S und Se in einer Gesamtmenge von nicht mehr als 0,005 bis 0,1 Gew.-%, ggf. 0,005 bis 0,2 Gew.-% Sb, und ggf. Sn, Cu und/oder B in einer Gesamtmenge von nicht mehr als 0,5 Gew.-% besteht, wobei der Rest Fe und unwesentlichen Verunreinigungen sind, um ein Stahlblech zu formen, und Unterwerfen dieses Stahlbleches
    (i) einer ersten Kaltwalzung mit einer Dickenabnahme von 10 bis 60%,
    (ii) einer zwischnezeitlichen Temperung, welche eine Erhitzungsstufe von 500° C bis 900° C und eine Kühlungsphase von 900° C bis 500° C einschließt, wobei die Erhitzungs- und Kühlungsgeschwindigkeiten nicht geringer als 5° C s-1 sind,
    (iii) einer zweiten Kaltwalzung mit einer Dickenabnahme von 75 bis 90%, um ein Stehlblech mit einem Endmaß von 0,1 bis 0,25 mm zu bilden,
    (iv) einer Kohlenstoffentziehungs- und ersten Rekristallisationstemperung in einer nassen Wasserstoffatmosphäre, und
    (v) einer Hochtemperatur-Schlußtemperung.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Stehlblech entweder vor oder nach der Kohlenstoffentziehungs- und ersten Rekristallisationstemperung einer Behandlung ausgesetzt wird, welche bei der Hochtemperatur-Schlußtemperung die Bildung von heterogenen Mikroflächen auf der Stahlblechoberfläche verursacht.
  3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß heterogene Mikroflächen nach der Hochtemperatur-Schlußtemperung auf der Oberfläche des Stahlbleches gebildet werden.
EP86902022A 1986-03-25 1986-03-25 Verfahren zur herstellung von dünnen silizium-stahlblechen mit goss-textur mit niedrigen wattverlusten sowie mit ausgezeichneten oberflächeneigenschaften Expired - Lifetime EP0266422B2 (de)

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FR2007129A1 (de) * 1968-04-27 1970-01-02 Yawata Iron & Steel Co
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JPS5832214B2 (ja) * 1979-12-28 1983-07-12 川崎製鉄株式会社 磁束密度の極めて高く鉄損の低い一方向性珪素鋼板の製造方法
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US4545828A (en) * 1982-11-08 1985-10-08 Armco Inc. Local annealing treatment for cube-on-edge grain oriented silicon steel
JPS59126722A (ja) * 1983-01-11 1984-07-21 Nippon Steel Corp 鉄損の優れた薄手高磁束密度一方向性電磁鋼板の製造方法
JPS6151803A (ja) * 1984-08-21 1986-03-14 Kawasaki Steel Corp 鉄損の低い一方向性けい素鋼板
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