Technical field
[0001]
　The present invention relates to a method for producing a grain-oriented electrical steel sheet.
　The present application, to 04 May 02, 2015, claiming priority based on Japanese Patent Application No. 2015-075839, filed in Japan, the contents of which are incorporated here.
Background technique
[0002]
　Grain-oriented electrical steel sheet is used as a core material for stationary induction apparatus such as mainly the transformer. Therefore, the grain-oriented electrical steel sheet, as its characteristics, the energy loss when excited with an alternating current (i.e., iron loss) is to be less able or magnetic permeability higher easily excited, it magnetostriction causing noise is small is required. Conventionally, in order to produce a grain-oriented electrical steel sheet satisfying these properties, many developers have been made. As a result, for example, as described in Patent Document 1, to improve the {110} <001> orientation integration degree of the steel sheet, in particular revealed that the effect is large.
[0003]
　To improve {110} <001> orientation integration degree of the steel sheet, making it possible to correctly grain growth was suppressed, {110} in the secondary recrystallization subsequent <001> oriented grains only abnormal grain growth in the primary recrystallization is important. This includes the steels in fine precipitates and the grain boundary precipitation elements called inhibitors, it is effective to precisely control.
[0004]
　For achieving such control, and the solution of the inhibitor by slab heating, hot rolling subsequent steps, hot-rolled sheet annealing step, and techniques for uniformly fine precipitation of an inhibitor in the intermediate annealing step are well known. Such inhibitors include, for example, a method of controlling the MnS and AlN in Patent Document 1, a technique in Patent Document 2 for controlling the MnS and MnSe, CuxS in Patent Document 3, CuxSe or Cux (Se, S ) and (Al, Si) technique for controlling the N have been reported.
[0005]
　However, in the technique of Patent Document 1 to 3, a sufficiently excellent magnetic properties was not be obtained stably.
[0006]
　Patent Document 4, in the manufacturing method for getting an ultra-high magnetic flux density grain-oriented electrical steel sheet stably, means for containing Bi is disclosed in the slab. However, when including Bi in the steel, adhesion of the deterioration of the primary film which is considered to be due to Bi which is contained, the problem that the primary coating is difficult to be formed. Therefore, in the technique Patent Document 4, even if good magnetic properties can be obtained, in some cases the formation of the primary film is insufficient.
[0007]
　Further, Patent Document 5 below, the steel sheet after hot rolled sheet annealing containing Bi by the aging treatment at the step of cold-rolled to thickness of the object, a technique for improving the magnetic properties is disclosed ing. However, Patent Document 5 not been studied film adhesion, aging treatment is not clear what influence the primary film.
[0008]
　Patent Document 6, the cold-rolled sheet containing Bi was heated to 100 ° C. / sec or faster 700 ° C. or higher 700 ° C. within heating or 10 seconds to more than one second or more in a subsequent 700 ° C. temperature above 20 subjected to decarburization annealing seconds after applying the pre-annealing for holding less, then TiO added during annealing separator agent applied 2 by increasing the amount of a technique of forming a good primary film is disclosed. However, in the Patent Document 6 techniques, for coating even bend the product along the round bar of 20mmφ is prevented from peeling, TiO 2 must be extremely increased coating amount of the additive amount or annealing separator issues such as there are more.
CITATION
Patent Literature
[0009]
Patent Document 1: Japanese Patent Publication 40-15644 Patent Publication
Patent Document 2: Japanese Patent Publication 51-13469 Patent Publication
Patent Document 3: Japanese Patent Laid-Open 10-102149 discloses
Patent Document 4: Japanese Patent 6-88171 JP
Patent Document 5: Japanese Patent Laid-Open 8-253816 discloses
Patent Document 6: Japanese Patent 2003-096520 JP
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　The present invention has been made in view of the above problems, an object of the present invention, while improving the adhesion of the primary coating, which can be obtained at low cost a grain-oriented electrical steel sheet having excellent magnetic properties is to provide a method for producing a grain-oriented electrical steel sheet.
Means for Solving the Problems
[0011]
　The present inventors, in order to solve the above problems, the slab heating condition, the holding condition of the steel sheet in cold rolling step, and the effect of the heating rate or the like in the decarburization annealing was investigated in detail. As a result, once the temperature is lowered during slab heating, be rolled and re-heat, the cold rolling step, holding the steel sheet at a predetermined temperature range, and appropriately controlling the heating rate in the decarburization annealing step by, found that improved adhesion of the primary coating.
　The present invention to be described below, has been completed based on the above findings and has as its gist is as follows.
[0012]
(1) A method of manufacturing a grain-oriented electrical steel sheet according to one embodiment of the present invention, in mass%, C: 0.030 ~ 0.150%, Si: 2.50 ~ 4.00%, Mn: 0. 02 to 0.30%, one or two of S and Se: 0.005 ~ 0.040% in total, acid-soluble Al: 0.015 ~ 0.040%, N: 0.0030 ~ 0.0150 %, Bi: 0.0003 ~ 0.0100%, Sn: 0 ~ 0.50%, Cu: 0 ~ 0.20%, 1 kind or two kinds of Sb and Mo: 0 ~ 0.30% in total, containing the slab the balance being Fe and impurities, was heated to T1 ° C. of 1150 ° C. or higher 1300 ° C. or less, after holding for more than 5 minutes to 30 hours or less, the temperature of the slab T1-50 ° C. below T2 ° C. until reduced, then the slab is heated to T3 ° C. of 1280 ° C. or higher 1450 ° C. or less 5 min a heating step of holding 60 minutes or less or more; and a heated the slab was hot-rolled, and hot rolled to obtain a hot-rolled steel sheet; the hot-rolled steel sheet and cold-rolled, giving multiple paths plate a cold rolling step to obtain the following cold-rolled steel sheet thickness 0.30 mm; the cold rolling step before, or, prior to the final pass of the cold rolling process by once interrupting the cold rolling step, at least the hot-rolled steel sheet once the intermediate annealing step carried out intermediate annealing; and annealing separator material application step of applying an annealing separator material to the said cold-rolled steel sheet after decarburization annealing; decarburization annealing step and decarburization annealing the cold-rolled steel sheet ; and finish annealing step performs annealing finishing the cold-rolled steel sheet after the annealing separator material coating step; the cold-rolled steel sheet after the final annealing, a secondary coating application step of applying an insulating coating; has, wherein in the intermediate annealing step, 5 seconds or less at a temperature of 1000 ° C. or higher 1200 ° C. or less Performs the intermediate annealing for holding 180 seconds or less, in the cold rolling process, during the multiple passes, the hot-rolled steel sheet, 130 ° C. or higher 300 ° C. temperature below 3 minutes or more and 120 minutes or less at least once holding performs holding process to, among the holding process, or less 4 times held more than once at a temperature T ° C. satisfying the following formula (a), the heating rate in the decarburization annealing step, 50 ° C. / sec or higher it is.
　170+ [Bi] × 5000 ≦ T ≦ 300 ··· (a)
where, in the formula (1), [Bi] is the content of Bi in mass% in said slab.
(2) A method of manufacturing a grain-oriented electrical steel sheet according to the above (1), the slab contains, by mass%, Sn: may contain from 0.05 to 0.50%.
(3) The method of producing grain-oriented electrical steel sheet according to (1) or (2), the slab contains, by mass%, may contain from 0.01 to 0.20% of Cu.
(4) The method of producing grain-oriented electrical steel sheet according to any one of the above (1) to (3), said slab contains, by mass%, one or two of Sb and Mo, the total in may contain from 0.0030 to 0.30%.
(5) The method of producing grain-oriented electrical steel sheet according to any one of the above (1) to (4), in the finish annealing step, the X value calculated by the following formula (b), 0. 0003Nm 3 / (h · m 2 ) may be more.
　　X = atmosphere gas flow rate / steel plate total surface area ··· (b)
Effect of the invention
[0013]
　According to this aspect of the present invention, while improving the adhesion of the primary coating, it is possible to obtain an inexpensive grain-oriented electrical steel sheet having excellent magnetic properties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
FIG. 1 is a graph showing the relationship between the maximum temperature and the Bi content of the aging process in the embodiment.
It is a graph showing the relationship between aging treatment times in the aging treatment times and 130 ~ 300 ° C. satisfying the formula (1) in FIG. 2 embodiment.
3 is a graph showing a preferable range of heating rates and hot rolled sheet annealing temperature in the decarburization annealing in the embodiment.
DESCRIPTION OF THE INVENTION
[0015]
　Hereinafter, the manufacturing method of the grain-oriented electrical steel sheet according to an embodiment of the present invention (sometimes referred to as the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment) will be described in detail.
[0016]
(Chemical composition of the steel)
　First, the chemical composition of the steel used in the method for producing a grain-oriented electrical steel sheet according to the present embodiment (chemical composition), is described.
[0017]
　In the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment, by mass%, C: 0.030 ~ 0.150%, Si: 2.50 ~ 4.00%, Mn: 0.02 ~ 0.30 %, one or two of S and Se: 0.005 ~ 0.040% in total, acid-soluble Al: 0.015 ~ 0.040%, N: 0.0030 ~ 0.0150%, Bi: containing from 0.0003 to 0.0100%, using a slab balance being Fe and impurities.
[0018]
　Slab for use in grain-oriented electrical manufacturing method according to this embodiment includes the above elements, but the balance is basically that of Fe and impurities, the slab, instead of a part of Fe, further it may contain 0.05-0.50 wt% of Sn. Moreover, the slab, instead of a part of Fe, and may further contain 0.01-0.20 wt% of Cu. Moreover, the slab, instead of a part of Fe, further, one or two of Sb and Mo, may contain from 0.0030 to 0.30 mass% in total. However, Sn, Cu, Sb, since Mo may not be contained, the lower limit is 0%.
[0019]
: [C 0.030 ~
　0.150%] When the content of C (carbon) is less than 0.030% or, when heating the slab prior to hot rolling, the crystal grains grow abnormally grain, that result, secondary recrystallization defect called linear granules in the product. On the other hand, when the content of C is at 0.150% excess, in the decarburization annealing conducted after cold rolling step, required decarburization time long, not only uneconomical, decarburization tends to be incomplete . When decarburization is incomplete, since the magnetic defect called magnetic aging in the product is produced, which is undesirable. Accordingly, the content of C, and 0.030 to 0.150%. The content of C is preferably at from 0.050 to 0.100%.
[0020]
[Si: 2.50 ~
　4.00%] Si (silicon) is in reducing the eddy current loss by increasing electrical resistance of the steel forms a part of the iron loss, a very effective element. However, when the content of Si is less than 2.50% can not suppress the eddy current loss of product. On the other hand, when the content of Si is 4.00% past is to workability remarkably deteriorates the steel, cold-rolled at room temperature is difficult. Accordingly, the content of Si, and 2.50 to 4.00%. The content of Si is preferably between 2.90 to 3.60%.
[0021]
[Mn: 0.02 ~
　0.30%] Mn (manganese) forms MnS and / or MnSe is a compound known as affecting inhibitor secondary recrystallization, is an important element. When the content of Mn is less than 0.02% is due to the lack of the absolute amount of MnS and / or MnSe required to cause secondary recrystallization, it is not preferred. On the other hand, when the content of Mn is 0.30% exceeded, it becomes difficult to solid-solved Mn during slab heating, not only the amount of MnS and / or MnSe is then precipitated is decreased, deposit size is the optimal size distribution is impaired as inhibitors makes it easier to coarse. Accordingly, the content of Mn, and 0.02 to 0.30 percent. The content of Mn is preferably 0.05 to 0.25%.
[0022]
[S and / or Se: total ~ 0.040%
　0.005] S (sulfur), by reacting with the Mn, is an important element that forms MnS an inhibitor, Se (selenium) is , by reacting with the Mn, it is an important element that forms MnSe is an inhibitor. Since the MnS and MnSe has the same effect as an inhibitor, and S and Se, may, if the total content within the range of 0.005 to 0.040%, also be contained in only one both of S and Se may be contained. On the other hand, and when the total content of S and / or Se (total of one or content of S and Se) is less than 0.005%, the total content of S and Se 0 If it is .040% excess it can not obtain a sufficient inhibitor effect. Accordingly, the total content of S and / or Se, is required to be from 0.005 to 0.040%. Total content of S and / or Se is preferably between from 0.010 to 0.035 percent.
[0023]
[Acid-soluble Al: 0.015 ~ 0.040%]
　acid-soluble aluminum (sol. Al) is a constituent element of AlN which is the main inhibitor to obtain a high magnetic flux density grain-oriented electrical steel sheet. If the content of acid-soluble Al is less than 0.015%, the inhibitor is insufficient in quantity, the inhibitor strength is insufficient. On the other hand, when the content of acid-soluble Al is 0.040% past is, AlN to be precipitated are coarsened as inhibitors, resulting in inhibitor strength is lowered. Accordingly, the content of acid-soluble Al, and from 0.015 to 0.040%. The content of acid-soluble Al is preferably a 0.018-.035%.
[0024]
[N: 0.0030 ~
　0.0150%] N (nitrogen), form an AlN reacts with the acid-soluble Al, which is an important element. And when the content of N is less than 0.0030% or, when the content of N is 0.0150% excess it can not obtain a sufficient inhibitor effect. Accordingly, the content of N, to limit the 0.0030 to 0.0150 percent. The content of N is preferably 0.0050 to 0.0120 percent.
[0025]
[Bi: 0.0003 ~
　0.0100%] Bi (bismuth), in the manufacture of grain-oriented electrical steel sheet according to the present embodiment, is an essential element to be contained in the slab in order to obtain good magnetic flux density . When the content of Bi is less than 0.0003%, not be sufficiently achieved a magnetic flux density improving effect. On the other hand, when the content of Bi is at 0.0100% excess, not only the magnetic flux density improving effect is saturated, increases adhesion possibility of failure of the primary film. Accordingly, the content of Bi and 0.0003 to 0.0100%. The content of Bi is preferably between from 0.0005 to 0.0090 percent, more preferably 0.0007 to 0.0080%.
[0026]
[Sn: 0 ~ 0.50%] Sn
　(tin) is not necessarily to be contained, is an element effective to stably obtain the secondary recrystallization of thin products. Further, Sn is also an element having an effect of reducing the secondary recrystallization grains. To obtain these effects, it is necessary to contain 0.05% or more of Sn. Therefore, if the inclusion of Sn, the content of Sn, is preferably 0.05% or more. Further, the effect is saturated as 0.50% exceeds the content of Sn. Therefore, from the viewpoint of cost, even if to be contained, the content of Sn is preferably set to 0.50% or less. Sn content is more preferably 0.08 to 0.30%.
[0027]
[Cu: 0 ~
　0.20%] Cu (copper) is not necessarily to be contained, an element effective in primary film improve steel containing Sn. When the content of Cu is less than 0.01%, since the primary film improvement effect is small, the case of obtaining this effect, the content of Cu preferably 0.01% or more. On the other hand, when the content of Cu is 0.20% excess, since the magnetic flux density is lowered, which is undesirable. Therefore, even if to be contained, the content of Cu, preferably 0.01 to 0.20%. The content of Cu is more preferably 0.03 to 0.18%.
[0028]
[Sb and / or Mo: a total of 0 ~
　0.30%] Sb (antimony) and Mo (molybdenum) is necessarily need not be contained, enable secondary recrystallization thin product as a stable obtained element it is. To obtain the above effect more reliably, it is preferable that the Sb and / or total content of Mo and (total of one or content of Sb and Mo) 0.0030% or more. The Sb and Mo, or may be one of being contained, both Sb and Mo may be contained. On the other hand, when the total content of Sb and / or Mo is 0.30% excess, the effect is saturated. Therefore, even if to be contained, the total content of Sb and / or Mo is preferably set to 0.30% or less. The total content of Sb and Mo is more preferably 0.0050 to 0.25%.
[0029]
(Process for manufacturing grain-oriented electrical steel sheet)
　Next, a manufacturing step of the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment comprises will be described in detail. According to the manufacturing method including a manufacturing process to be described below, it is possible to provide inexpensively an excellent grain-oriented electrical steel sheets of the magnetic properties for use in the core material such as transformers.
[0030]
　
　Prior to hot rolling, heating the slab to adjust the components within the above range. Slab is obtained by casting a molten steel having an adjusted component within the above range but application, casting method is not particularly limited, a method of casting a general unidirectional molten steel for electromagnetic steel sheet production can do.
[0031]
　In the production method of the grain-oriented electrical steel sheet according to the present embodiment, when heating the slab having components described above, the slab was heated to a T1 ° C. 1300 ° C. 1150 ° C. or higher, more than 5 minutes at T1 ° C. 30 hours or less to hold (soak). Thereafter, T2 ° C. of T1-50 ° C. below the temperature of the slab (i.e., T1-T2 ≧ 50) is reduced to. Thereafter, again the slab was heated to T3 ° C. of 1280 ° C. ~ 1450 ° C., held for 5 minutes to 60 minutes or less to T3 ° C.. T1 is lower than 1150 ° C., T3 is lower than 1280 ° C., or, if the retention time at T1 ° C. and / or T3 ° C. and less than 5 minutes, not obtained the desired magnetic properties. In particular, magnetic properties, the influence of the retention temperature after reheating is large, T3 is preferably 1300 ° C. or higher. On the other hand, if the heating temperature is too high it requires special equipment, the manufacturing cost is increased. Therefore, T3 is preferably 1400 ° C. or less.
　Further, T1 ° C., or productivity and a long holding time at T3 ° C. is deteriorated, the manufacturing cost is increased. Therefore, the holding time at T1 ° C., or less 30 hours, preferably not more than 25 hours. The holding time at T3 ° C. is not more than 60 minutes, preferably not more than 50 minutes.
　Further, T1-T2 is of less than 50 ℃ (T1-T2 <50 ), the coating adhesion is deteriorated. The mechanism is not clear, that the behavior of the scale formation and descaling of slab heating and hot rolling is changed, is believed to be due to the surface properties of the steel sheet is changed. On the other hand, if the T1-T2 too large, it requires special equipment to heat the T3 ° C. from T2 ° C.. Therefore, preferably the T1-T2 is 200 ° C. or less. That is, it is preferable that 50 ≦ T1-T2 ≦ 200.
　In this embodiment, the temperature of the slab is the surface temperature. A decrease in the temperature of the T2 ° C. from T1 ° C. is water cooled, but may be carried out by any method of air cooling or the like, it is preferable that the air cooling (cooling).
[0032]

　The above was heated in the heating step the slab to hot rolling to obtain a hot-rolled steel sheet. Conditions of hot rolling need not be particularly limited, it may be adopted conditions applicable to the general grain-oriented electrical steel sheet.
[0033]

　In the cold rolling step, performed cold rolling containing multiple passes, the plate thickness is obtained following cold-rolled steel sheet 0.30 mm. The plate thickness after cold rolling step is 0.30mm exceeded, the iron loss is deteriorated. Therefore, the thickness after cold rolling step is less 0.30 mm. Thickness after cold rolling step is preferably not more than 0.27 mm. The lower limit of the plate thickness after cold rolling step is not particularly limited, for example, preferably be at least 0.10 mm, more preferably 0.15mm or more.
[0034]
　In the cold rolling step, in between passes, steel plate, 130 ° C. or higher 300 ° C. and holding process of holding more than three minutes 120 minutes or less at a temperature (aging process) one or more times. However, among the holding, the following equation (1) 120 minutes following retention process 3 minutes or more at a temperature T ° C. satisfying the (aging treatment), it is necessary to perform the following four or more times.
　　　　　　　170+ [Bi] × 5000 ≦ T ≦ 300 ··· (1)
where, in the above formula (1), [Bi], the content of Bi in the slab: a [unit mass%.
[0035]
　Does not perform an aging treatment, the temperature of the aging treatment is below 130 ° C., or, if the retention time is less than 3 minutes is not obtained the desired magnetic properties. On the other hand, when the aging temperature and 300 ° C. Excess, requires special equipment, since manufacturing cost increases undesirably. Further, when the retention time 120 minutes excess is not preferable because the production cost is increased productivity is deteriorated.
[0036]
　Further, even when subjected once or more to an aging treatment of conditions as described above, does not include the aging treatment satisfying the equation (1), or, if it exceeds carried four times aging treatment that satisfies the formula (1), film adhesion sex is degraded. Preferred aging conditions are as shown in the following (1 ').
[0037]
　In the holding process of the cold rolling step (aging treatment), in place of the above conditions is preferably carried out in the following conditions. That is, the aging treatment of holding at a temperature 300 ° C. 140 ° C. over 5 minutes to 120 minutes or less performed more than once, and that of the aging process, or 5 minutes at a temperature T ° C. satisfying the following formula (1 ') it is preferably not more than 4 times more than once to an aging treatment of holding 120 minutes or less. By satisfying this condition, it is more stably improved coating adhesion.
　　　　　　　175+ [Bi] × 5000 ≦ T ≦ 300 ··· (1 ')
[0038]

　(between the hot rolling step and cold rolling step) cold rolling step prior to, or during multiple passes of cold rolling steps, prior to the final pass of the cold rolling process by once interrupting the (cold process a) performing the intermediate annealing at least once (preferably once or twice) the hot-rolled steel sheet. That is, the cold rolling after annealing (so-called hot-rolled sheet annealing) in the hot-rolled steel sheet before cold rolling, or, perform cold rolling of a plurality path including intermediate annealing without performing hot-rolled sheet annealing or it would be carried out cold rolling of a plurality path including intermediate annealing after hot rolled sheet annealing.
[0039]
　The intermediate annealing step is subjected to annealing for holding 1000 ° C. or higher 1200 ° C. or less at a temperature of 5 seconds to 180 seconds. When the annealing temperature is lower than 1000 ° C. is not obtained the desired magnetic properties and coating adhesion. On the other hand, when the temperature is 1200 ° C. exceeded, the production cost becomes necessary special equipment increases. Therefore, the annealing temperature to 1000 ° C. or higher 1200 ° C. or less. Annealing temperature is preferably, 1170 ° C. or less 1030 ° C. or higher.
　Further, if the annealing time is less than 5 seconds it can not be obtained the desired magnetic properties and coating adhesion. On the other hand, if the annealing time is exceeded 180 seconds, the production cost becomes necessary special equipment increases. Accordingly, in the present embodiment, the annealing time is 180 seconds or less than 5 seconds. Annealing time is preferably 120 seconds or less 10 seconds or more.
[0040]

　against cold-rolled steel sheet after cold rolling step is subjected to decarburization annealing. Here, during the heating of decarburization annealing, the heating rate and 50 ° C. / sec or higher. The heating temperature of the decarburization annealing, the time, etc., may be adopted the terms applicable to common grain-oriented electrical steel sheet.
　When the heating rate during decarburization annealing is less than 50 ° C. / sec, it is impossible to obtain desired magnetic properties and coating adhesion. Therefore, the heating rate, and 50 ° C. / sec or higher. Heating rate is preferably 80 ° C. / sec or more. The upper limit of the heating rate is not particularly limited, because it requires special equipment is unduly increase the heating rate, preferably in the 2000 ° C. / sec or less.
[0041]

　to cold-rolled steel sheet after the decarburization annealing, an annealing separator material is applied, performs finish annealing. Thus, the coating (primary coating) is formed on the surface of the cold rolled steel sheet.
　Atmosphere gas used during finish annealing is not limited in particular, nitrogen gas and is contained hydrogen and the like, may be used generally atmospheric gas used. Further, the annealing separator material coating, and finish annealing methods and conditions may be employed a method and conditions that apply to common grain-oriented electrical steel sheet. Annealing separator material, for example, may be used with an annealing separator material mainly composed of MgO, in this case, the coating film formed after the finish annealing, forsterite (Mg 2 SiO 4 becomes including).
[0042]
　In the finish annealing step, the X value calculated by the following equation (2), 0.0003Nm 3 / (h · m 2 is preferably a) above. X value 0.0003Nm 3 / (h · m 2 If it is) above, to further improve the coating adhesion.
　　　　　　　X = ambient gas flow rate / steel total surface area (2)
　Here, the atmospheric gas flow rate, a charging amount of the atmosphere gas in the case of performing the box annealing. Further, the steel sheet total surface area is the area of the steel plate in contact with the atmosphere, in the thin steel sheet is the sum of the areas of the front and back surfaces of the steel sheet.
[0043]
　X value calculated by the above formula (2) is more preferably 0.0005 3 / (h · m 2 at) or more. On the other hand, the upper limit of X values, but are not particularly limited, from the viewpoint of production cost 0.0030Nm 3 / (h · m 2 is preferably set to) or less.
[0044]

　the primary coating formed steel plate (cold-rolled steel sheet) is coated with an insulating coating. Thus, the secondary coating is formed on the steel plate. The method for coating is not particularly limited, may be employed a method and conditions that apply to common grain-oriented electrical steel sheet.
[0045]

　in steel sheet secondary coating formed may optionally be subjected to laser irradiation. By irradiation of a laser to form grooves in the coating, or by giving a strain to the film, the magnetic domain refining, it is possible to further improve the magnetic properties of grain-oriented electrical steel sheet.
[0046]
　Oriented electrical steel sheet is manufactured as described above has a value of magnetic flux density B8 is 1.92T or more, excellent magnetic flux density, the coating adhesion is also improved.
　Heating conditions, the final cold rolling prior to intermediate annealing conditions, aging treatment conditions in the cold rolling, although the reason the coating adhesion is improved by the proper range heating rate or the like in the decarburization annealing is not clear It is presumed to be due to changes in the surface properties of the steel sheet.
[0047]
　The above and the magnetic flux density, the method of measuring the magnetic characteristics, such as various types of iron loss, but the present invention is not particularly limited, for example, a method based on the Epstein test specified in JIS C 2550, the JIS C 2556 defined by that single plate magnetic properties test method (single sheet Tester: SST), such as it can be measured by a known method.
Example
[0048]
　Hereinafter, while showing an embodiment, a method of manufacturing a grain-oriented electrical steel sheet according to the present invention will be specifically described. Examples shown below is only one example of a method for producing a grain-oriented electrical steel sheet according to the present invention. Therefore, the manufacturing method of the grain-oriented electrical steel sheet according to the present invention is not limited to the following examples.
[0049]
(Example
　1) C: 0.080%, Si: 3.20%, Mn: 0.07%, S: 0.023%, acid-soluble Al: 0.026%, N: 0.0090 %, Bi : containing 0.0015% slab the balance of Fe and impurities, at a surface temperature, heated to a temperature T1 ° C. of 1280 ° C. or less 1130 ° C. or higher, and held for 5 hours. It was then reduced to a temperature T2 ° C. below 1220 ° C. 1050 ° C. or higher at a surface temperature slab. Then, holding the slabs was heated to 1350 ° C. at a surface temperature of 20 minutes. Then, to obtain a hot-rolled coil of 2.3mm thickness by performing a hot rolling the slab.
　Then, with respect to the above hot-rolled coils, after being subjected to intermediate annealing (hot-rolled sheet annealing) holding 20 seconds at a temperature of 1120 ° C., to obtain a cold-rolled steel sheet 0.22mm thick by performing the cold rolling. Thereafter, the cold-rolled steel sheet, the heating temperature retention time at 850 ° C. were subjected to decarburization annealing under conditions such that the 120 seconds. Heating rate at this time was set to 300 ° C. / sec.
　Then, after applying the annealing separator material mainly containing MgO to the cold rolled steel sheet, a nitrogen: hydrogen = 3: 1 in an atmospheric gas comprised of a gas flow rate, the atmospheric gas flow rate / steel total surface area 0 .0008Nm 3 / (H · M 2 as), was subjected to finish annealing. This was followed by application of a secondary coating (insulating film).
[0050]
　The resulting steel sheet by utilizing, in conjunction with measuring the magnetic flux density B8 when magnetized at 800A / m by veneer magnetic measurements as defined in JIS C 2556 (SST), was evaluated the adhesion of the coating . Coating adhesion was evaluated by the following grades A ~ D. That is, to evaluate if not peeled at 10φ bending test A, 20Fai bending if not peeling test B, and if not peeled at 30φ bending test C, and when peeled at 30φ bending test with D , it was passed a and B. In addition, the magnetic flux density B8 was as acceptable more than 1.92T.
　The results are shown in Table 1. Steel plate No. 3, 5 and 6 is a manufacturing method which satisfies the range of the present invention, the magnetic flux density, film score, which satisfies the target value. On the other hand, steel sheet No. 1 slab surface temperature during heating (T1) is lower than a predetermined temperature, desired magnetic properties are not obtained. Steel plate No. 2 is lower than the temperature slab surface temperature (T1) is in a predetermined time of heating, and the temperature difference between T1 and T2 was small, not to obtain the desired magnetic properties and the film scores. Steel plate No. 4 is smaller than the range the temperature difference is given between T1 and T2, not obtained the desired coating grade.
[0051]
[Table 1]

[0052]
(Mika Example
　2) C: 0.080%, Si: 3.20%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.024%, N: 0.0080 %, Bi : 0.0007% or 0.015% or less containing wo shi, remnants ga Fe and impuritiesびでthou ru su ra STAB wo, the surface temperatureで, 1200 ℃ (T1 ℃) ma - de shi heating, holding time 5 shi ta. Afterその, su ra STAB wo, the surface temperature ofで1100 ℃ (T2 ℃) Ma - de low Connecticut after se ta, 1350 ℃ (T3 ℃) Ma - de warmed shi after te 30 minutes holding shi ta, to heat-pressure casting ni Yori 2.3mm thickのhot-rolled U test suitableとshi ta.
[0053]
　To the above hot-rolled coil, subjected to hot rolled sheet annealing to hold 30 seconds at a temperature of 1100 ° C., and a cold rolled steel sheet 0.22mm thick by cold rolling including an aging treatment. At this time, the temperature of the aging treatment, time, and the number of changed variously.
　Thereafter, the cold-rolled steel sheet, the holding time at 850 ° C. were subjected to decarburization annealing so that 150 seconds. Heating rate of the decarburization annealing was set at 350 ℃ / sec.
　Then, after applying the annealing separator material consisting mainly of MgO, nitrogen: hydrogen = 3: in an atmosphere gas composed of a 1, a gas flow rate, 0.0006Nm the atmospheric gas flow rate / steel total surface area 3 / (H · M 2 as), it was subjected to finish annealing. This was followed by a secondary coating application.
　Table 2 shows the Bi content, and aging treatment conditions in the cold rolling process.
[0054]
　Using the obtained steel sheets, with measuring the magnetic flux density B8 when magnetized at 800A / m by veneer magnetic measurements (SST), it was evaluated the adhesion of the coating. The method of evaluation, the acceptance criteria were the same as in Example 1.
　The score that indicates the magnetic flux density B8 and coating adhesion are shown in Table 2. Also, the relationship between the maximum temperature and the Bi content of the aging process shown in FIG. 1, showing the relationship between aging treatment times of aging treatment times and 130 ~ 300 ° C. satisfying the formula (1) in FIG.
[0055]
[Table 2]

[0056]
　Steel plate No. As shown in 7, when not subjected to aging treatment, it did not give the desired magnetic properties. Steel plate No. As shown in 8-10, they were not subjected to aging treatment at a temperature satisfying the equation (1), or if the number of times there were many, the coating score was C or D, and the inferior. In addition, the steel sheet No. As shown in 11, when the Bi content exceeds 0.0100%, the film score was C, and the inferior.
[0057]
　On the other hand, steel sheet No. As shown in 12-18, when the aging treatment condition is appropriate, were excellent in both magnetic properties, coating grade.
[0058]
(Example
　3) C: 0.078%, Si: 3.25%, Mn: 0.07%, S: 0.024%, acid-soluble Al: 0.026%, N: 0.0082 %, Bi : a slab containing 0.0024%, was heated to the slab surface temperature becomes 1180 ℃ (T1 ℃), and held for 1 hour. Then, after lowering until the slab surface temperature of 1090 ℃ (T2 ℃), the slab surface temperature was held for 45 minutes then heated to a 1360 ℃ (T3 ℃). Thereafter, the slab was hot-rolled coil of 2.3mm thickness by hot rolling.
[0059]
　To the above hot-rolled coils, after being subjected to hot rolled sheet annealing to hold 50 seconds at a temperature of 950 ° C. or higher 1150 ° C. or less, by cold rolling, and the cold rolled steel sheet having a thickness of 0.22 mm. Incidentally, in the cold rolling, twice aging treatment of holding for 30 minutes at a temperature of 160 ° C., and was carried out once an aging treatment for 30 minute hold at a temperature of 240 ° C..
　Then, for this cold-rolled steel sheet was subjected to decarburization annealing for holding 150 seconds at 820 ° C.. At this time, the heating rate during decarburization annealing, was 20 ° C. / sec or higher 400 ° C. / sec or less. Then, after applying the annealing separator material consisting mainly of MgO, nitrogen: hydrogen = 2: at configured atmosphere gas 1, the gas flow rate, 0.0010Nm the atmospheric gas flow rate / steel total surface area 3 / (H · M 2 was subjected to finish annealing) as a. This was followed by a secondary coating application.
　Table 3 shows the heating rate in the annealing (hot-rolled sheet annealing) temperature and decarburization annealing step.
[0060]
　Further, a coating grade of flux density B8 and the primary coating of the resulting steel sheet, the Example 1 was evaluated in the same manner as in Example 2. The results are shown in Table 3. Also, the preferred range of the heating rate and the hot rolled sheet annealing temperature in the decarburization annealing is shown in FIG.
[0061]
[table 3]

[0062]
　Steel plate No. As shown in 19-20, the hot-rolled sheet annealing temperature is low, the film scores was C, and the inferior. In addition, the steel sheet No. As shown in 21, the heating rate in the decarburization annealing is slow, both the magnetic characteristics and coating scores were inferior.
[0063]
　On the other hand, steel sheet No. As shown in 22-26, when the heating rate in the hot-rolled sheet annealing conditions and decarburization annealing is proper range was superior in both magnetic characteristics and coating grade.
[0064]
(Example 4)
　to Table 4 shows components of the slab (balance Fe and impurities), and heated until the surface temperature becomes 1210 ° C. (T1 ° C.), and held for 2 hours. Then, after lowering the surface temperature of 1100 ℃ (T2 ℃), heating the surface temperature to 1320 ° C. or higher 1450 ° C. temperature below (T3 ° C.), was held 10 minutes, plate thickness is subjected to hot rolling It was 2.4mm or less of hot-rolled steel sheet or 2.0 mm. These hot-rolled steel sheets were subjected to intermediate annealing (hot-rolled sheet annealing) holding 10 seconds at a temperature of 1150 ° C. 1000 ° C. or higher. Some of these annealed steel sheet was a sheet thickness 0.22mm by cold rolling, and the remainder an intermediate thickness of less thickness 1.9mm or 2.1 mm, held 20 seconds at 1080 ° C. or higher 1100 ° C. or less of the temperature It was subjected to intermediate annealing, and a plate thickness 0.22mm by cold rolling. Incidentally, in the cold rolling to final thickness, it was subjected once to an aging treatment which holds 5 minutes aging treatment of holding for 20 minutes at a temperature of 160 ° C. at a temperature of one and 250 ° C.. Then subjected to a decarburization annealing for holding 180 seconds at a temperature of 800 ° C. These cold-rolled steel sheet.
　Then, after applying the annealing separator material mainly containing MgO to the cold rolled steel sheet, a nitrogen: hydrogen = 1: in an atmospheric gas comprised of 2, the gas flow rate, the atmospheric gas flow rate / steel total surface area 0.0025Nm 3 / (H · M 2 is set to be) subjected to finish annealing.
　Thereafter, it was subjected to magnetic domain refining treatment by secondary coating application and laser irradiation.
[0065]
[Table 4]

[0066]
　Table 5 shows the processing conditions in each step. Further, the magnetic flux density B8 and coatings scores, the results of evaluation in the same manner as in Examples 1-3, shown in Table 5 together.
[0067]
[table 5]

[0068]
　Table 5 reveals that the steel sheet No. 27-34, because the condition of the components and manufacturing processes is within a predetermined range, it was possible to obtain the desired magnetic characteristics and coating grade.
[0069]
　Above, a preferred embodiment of the present invention with reference to the drawings, and have been described in detail for Example, the present invention is not limited to such an example. It would be appreciated by those skilled in the relevant field of technology of the present invention, within the scope of the technical idea described in the claims, it is intended to cover various changes and modifications , also such modifications are intended to fall within the technical scope of the present invention.
Industrial Applicability
[0070]
　According to the present invention, while improving the adhesion of the primary coating, it is possible to obtain an inexpensive grain-oriented electrical steel sheet having excellent magnetic properties.

The scope of the claims
[Claim 1]
　By
　mass%,
　C: 0.030 ~ 0.150%,
　Si: 2.50 ~ 4.00%, Mn: 0.02 ~ 0.30%,
　1 kind of S and Se or two: 0 Total .005 to 0.040%
　acid-soluble
　Al:
　0.015 to 0.040% N: 0.0030 ~ 0.0150% Bi: 0.0003
　~ 0.0100% Sn: 0 - 0.50
　%, Cu: 0 to 0.20%,
　1 kind of Sb and Mo or two: 0 to 0.30% in total,
containing the slab the balance being Fe and impurities, 1150 ° C. or higher 1300 ° C. or less was heated to T1 ° C., was maintained 5 minutes to 30 hours or less, the temperature of the slab is reduced to T1-50 ° C. or less of T2 ° C., after which the slab, the following T3 ° C. 1280 ° C. or higher 1450 ° C. heating, a heating step of holding 5 to 60 minutes;
　heated Serial slabs by hot rolling, and hot rolling to obtain a hot-rolled steel sheet;
　the hot-rolled steel sheet, a cold-rolled to obtain a cold-cold-rolled steel sheet of less thickness 0.30mm performing rolling multipass ;
　the cold rolling step before, or, prior to the final pass of the cold rolling process by once interrupting the cold rolling step, intermediate annealing step and performing at least one of the intermediate annealing the hot-rolled steel sheet;
　the cold a decarburization annealing step of decarburization annealing the steel sheet;
　; annealing separator material applying step and applying an annealing separator material to said cold-rolled steel sheet after the decarburization annealing
　finishing the cold-rolled steel sheet after the annealing separator material applying step and finishing annealing step perform the annealing;
　The cold-rolled steel sheet after the final annealing, a secondary coating application step of applying an insulating coating;
has,
　in the intermediate annealing step, holding 1000 ° C. or higher 1200 ° C. or less at a temperature of 5 seconds to 180 seconds or less the performed intermediate annealing,
　and in the cold rolling process, during the multiple passes, the hot-rolled steel sheet, subjected to the holding process for holding one or more times below 120 minutes 3 minutes or more at a temperature of 130 ° C. or higher 300 ° C. or less ,
　of the holding process, or less 4 times held more than once at a temperature T ° C. satisfying the following formula (1),
　the heating rate in the decarburization annealing step is 50 ° C. / sec or more
, wherein the method for producing a grain-oriented electrical steel sheet to be.
　170+ [Bi] × 5000 ≦ T ≦ 300 ··· (1)
where, in the formula (1), [Bi] is the content of Bi in mass% in said slab.
[Claim 2]
　Said slab contains, by mass%, Sn: method for producing a grain-oriented electrical steel sheet according to claim 1, characterized in that it contains 0.05 to 0.50 percent.
[Claim 3]
　It said slab contains, by mass%, the production method of the grain-oriented electrical steel sheet according to claim 1 or 2, characterized in that it contains Cu 0.01 ~ 0.20%.
[Claim 4]
　Said slab contains, by mass%, one or two of Sb and Mo, according to any one of claims 1 to 3, characterized by containing 0.0030 to 0.30 percent in total method of manufacturing a grain-oriented electrical steel sheet.
[Claim 5]
　In the finish annealing step, the X value calculated by the following formula (2), 0.0003Nm 3 / (h · m 2 according to any one of claims 1 to 4, characterized in that a) above method for producing a grain-oriented electrical steel sheet.
　　X = atmosphere gas flow rate / steel plate total surface area (2)