Title of invention: grain-oriented electrical steel sheet
Technical field
[0001]
　The present invention relates to a grain-oriented electrical steel sheet having a high magnetic flux density and an extremely low iron loss, which is used as an iron core material for a transformer or a generator.
　The present application claims priority based on Japanese Patent Application No. 2018-010203 filed in Japan on January 25, 2018, and the content thereof is incorporated herein.
Background technology
[0002]
　The grain-oriented electrical steel sheet is a soft magnetic material and is used for an iron core of electric equipment such as a transformer. The grain-oriented electrical steel sheet is a steel sheet containing Si in an amount of about 7% by mass or less and in which crystal grains are highly integrated in the {110}<001> orientation by a Miller index. In the production of grain-oriented electrical steel sheet, controlling the crystal grain orientation is an important process, and is controlled by utilizing an abnormal grain growth phenomenon called secondary recrystallization.
[0003]
　In order to properly control the secondary recrystallization, the structure obtained by the primary recrystallization before the secondary recrystallization (the primary recrystallization structure) is appropriately formed, and the fine precipitates or grain boundaries called inhibitors are formed. It is important to properly adjust the segregation element.
[0004]
　In the secondary recrystallization, the inhibitor suppresses the growth of crystal grains other than the {110}<001> orientation in the primary recrystallization structure, and has the function of preferentially growing the crystal grains in the {110}<001> orientation. As such, adjustment of the type and amount of inhibitor is particularly important.
[0005]
　Many studies have been disclosed regarding inhibitors. Among them, as a characteristic technique, there is a technique of utilizing B as an inhibitor. For example, Patent Documents 1 and 2 and Non-Patent Document 1 disclose that solid solution B that functions as an inhibitor is effective in developing the {110}<001> orientation.
[0006]
　In Patent Documents 3 and 4, fine BN is formed by nitriding a material to which B is added in a step after cold rolling, and the formed fine BN functions as an inhibitor. , {110}<001> orientation is disclosed.
[0007]
　In Patent Document 5, while precipitating BN by hot rolling is suppressed as much as possible, extremely fine BN is precipitated in the subsequent temperature rising process of annealing, and the fine BN thus precipitated serves as an inhibitor. Functioning is disclosed.
　Patent Documents 6 and 7 disclose a method of functioning as an inhibitor by controlling the precipitation morphology of B in the hot rolling step.
[0008]
　These documents disclose a technique of adding B as a steel component and utilizing it as an inhibitor. According to these documents, after the secondary recrystallization, the {110}<001> orientation is highly developed to reduce the hysteresis loss by these techniques, so that a grain-oriented electrical steel sheet with low iron loss can be obtained. It is disclosed. However, these documents do not disclose anything about achieving both high magnetic flux density and extremely low iron loss by controlling the precipitation state of B after secondary recrystallization.
Prior art documents
Patent literature
[0009]
Patent Document 1: U.S. Pat. No. 3,905,842
Patent Document 2: U.S. Patent No. 3,905,843 Pat
Patent Document 3: Japanese Patent Laid-Open 01-230721 discloses
Patent Document 4: Japanese Patent Laid-Open 01-283324 discloses
JP 5: Japanese Unexamined Patent Publication No. 10-140243
Patent Document 6: International Publication No. 11/007771
Patent Document 7: International Publication No. 11/007817
Summary of the invention
Problems to be Solved by the Invention
[0010]
　In the prior art disclosed in the prior art document, since the precipitation morphology of B in the steel sheet after secondary recrystallization cannot be sufficiently controlled, the hysteresis loss is increased by the B precipitation and a grain-oriented electrical steel sheet with an extremely low iron loss is obtained. Hard to get.
[0011]
　Based on the current state of the art, the present invention provides a grain-oriented electrical steel sheet that utilizes a B compound as an inhibitor, which has a high magnetic flux density and an extremely low iron loss, and provides a grain-oriented electrical steel sheet that solves the problems. The purpose is to
Means for solving the problem
[0012]
　In order to stably produce a grain-oriented electrical steel sheet with a high magnetic flux density and an extremely low iron loss by adding B as a steel component, the crystal grains are highly oriented in the {110}<001> orientation by secondary recrystallization. It is important to orient it to increase the magnetic flux density and to appropriately control the precipitation form of B in the steel sheet.
[0013]
　When BN is used as an inhibitor, if the precipitation morphology of B after finish annealing is fine, fine BN precipitates in the steel sheet, so it is difficult to achieve both high magnetic flux density and extremely low iron loss, and It is difficult to realize an extremely low iron loss due to an increase in hysteresis loss due to a large BN.
[0014]
　Based on the above, the present inventors diligently studied a method for solving the above problems. As a result, if the precipitation morphology of B after finish annealing is Fe 3 B and/or Fe 2 B, the effect on the hysteresis loss can be minimized, so that both high magnetic flux density and extremely low iron loss are achieved. It has been found that the grain-oriented electrical steel sheet can be obtained.
[0015]
　The present invention has been made based on the above findings, and the summary thereof is as follows.
[0016]
　(1) A grain-oriented electrical steel sheet according to one aspect of the present invention is formed by a base material steel sheet, a lower layer coating formed on the base material steel sheet in contact with the lower layer coating, and a phosphate and a colloid. An insulating coating film containing silica as a main
　component, the base material steel sheet as a chemical component in mass%
　　C: 0.085% or less;
　　Si: 0.80 to 7.00%;
　　Mn: 0 0.05 to 1.00%;
　　Al: 0.010 to 0.065%;
　　N: 0.0040% or less;
　　Seq=S+0.406·Se: 0.015% or less;
　　B: 0.0005 to 0.0080 %
, and the
　balance Fe and impurities. The
　base steel sheet contains a B compound having a major axis length of 1 μm or more and 20 μm or less at a number density of 1×10 to 1×10 6 pieces/mm 3. The
　lower layer coating is a glass coating mainly composed of forsterite or an intermediate layer mainly composed of silicon oxide.
　(2) In the grain-oriented electrical steel sheet according to (1), the lower coating film is the glass coating film, the insulating coating film and the glass coating film are removed, and the base material steel plate is measured by glow discharge emission spectrometry. The glass coating side from the plate thickness center of the base material steel plate is divided into two, a surface layer region on the glass coating side and a center region between the surface layer region and the plate thickness center, and reaches the center region. When the sputter time until the temperature is set to t (center) and the sputter time to reach the surface layer region is set to t (surface), the emission intensity I B — t (center) of B at the time t (center) and the The emission intensity IB_t (surface) of B at time t(surface) may satisfy the following formula (1).
　　I B_t (center) > I B_t (Surface) · · · · · · (1)
　oriented electrical steel sheet according to (3) above (1), the lower film is the An intermediate layer, in which the total thickness of the base material steel sheet and the intermediate layer is d, and the emission intensity of B is measured from the surface of the intermediate layer by glow discharge emission analysis (GDS), B emission intensity I B (d/2) at a depth of d/2 from the surface and B emission intensity I B (d/10) at a depth of d/10 from the surface of the intermediate layer. And may satisfy the following formula (2).
　　IB (d/2)> IB (d/10) ...(2)
[0017]
　(4) In the grain-oriented electrical steel sheet according to any one of (1) to (3) above, the B compound may be at least one of Fe 2 B and Fe 3 B.
Effect of the invention
[0018]
　According to the present invention, in the grain-oriented electrical steel sheet that utilizes the B compound as an inhibitor, the hysteresis loss can be reduced by appropriately controlling the precipitation morphology of the B compound, so that both high magnetic flux density and extremely low iron loss are achieved. The grain-oriented electrical steel sheet can be provided industrially stably.
Brief description of the drawings
[0019]
FIG. 1 is a schematic diagram showing a layer structure of a grain-oriented electrical steel sheet according to a first embodiment.
FIG. 2 is a graph showing an example of a result when GDS is performed on the grain-oriented electrical steel sheet according to the first embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0020]
　The grain-oriented electrical steel sheet of the present invention (hereinafter sometimes referred to as “the present invention electrical steel sheet”) includes a base material steel sheet, a lower layer coating formed on the base material steel sheet, and a lower layer coating formed on the lower layer coating. An insulating coating formed mainly of phosphate and colloidal silica,
　wherein the base steel sheet, as a chemical component, in mass% is
　　C: 0.085% or less;
　　Si: 0.80 to 7
　　% .00;
　　Mn: 0.05 ~ 1.00%; Al: 0.010
　　~ 0.065%; N: 0.012% or
　　less; Seq = S + 0.406 · Se: 0.015% or
　　less; B: 0.0005 to 0.0080%;
and the
　balance Fe and unavoidable impurities, and the
　base steel sheet contains 1×10 to 1×10 6 B compound having an average major axis length of 1 μm or more and 20 μm or less. pieces / mm 3 contained in the number density of,
　the lower layer coating, glass coating forsterite is mainly or an intermediate layer of silicon oxide is mainly.
　Further, in the electromagnetic steel sheet of the present invention, the lower coating is the glass coating, and in the grain-oriented electrical steel sheet, the emission intensity IB of B measured by the glow discharge emission analysis (GDS) of the steel sheet excluding the glass coating is the plate. When the sputter time to reach the thickness center is t(center) and the sputter time of the steel plate surface layer excluding the glass coating is t(surface), the emission intensity IB_t(center) of B at the time t(center) , The emission intensity IB_t (surface) of B at the time t(surface) may satisfy the following formula (1).
　　I B_t (center) > I B_t (Surface) · · · · · · (1)
　Further, when the present invention electrical steel sheet, the lower film is said intermediate layer D is the total thickness of the base material steel plate and the intermediate layer, and d/ is measured from the surface of the intermediate layer when the emission intensity of B is measured from the surface of the intermediate layer by glow discharge emission spectrometry (GDS). The emission intensity I B (d/2) of B at the depth position of 2 and the emission intensity I B (d/10) of B at the depth position of d/10 from the surface of the intermediate layer are expressed by the following formula. (2) may be satisfied.
　　IB (d/2) > IB (d/10)　　　　　····· (2)
[0021]
　Further, in the electrical steel sheet of the present invention, the B compound may be Fe 2 B and/or Fe 3 B.
[0022]
　Hereinafter, the electromagnetic steel sheet of the present invention will be described.
[0023]
　[First Embodiment] A
　grain-oriented electrical steel sheet according to a first embodiment is formed by being in contact with a base material steel sheet, the base material steel sheet, and a glass coating mainly composed of forsterite, and being in contact with the glass coating. And an insulating coating mainly composed of phosphate and colloidal silica. The base steel sheet is, as a chemical component, in mass%,
　　C: 0.085% or less;
　　Si: 0.80 to 7.00%;
　　Mn: 0.05 to 1.00%;
　　Al: 0.010 to
　　% 0.065; N: 0.012% or
　　less; Seq = S + 0.406 · Se: 0.015% or
　　less; B: 0.0005 ~ 0.0080%;
containing,
　and the balance Fe and impurities,
　wherein The base steel sheet contains a B compound having a major axis length of 1 μm or more and 20 μm or less at a number density of 1×10 to 1×10 6 pieces/mm 3 .
　Further, the grain-oriented electrical steel sheet according to the present embodiment, the glass coating side than the plate thickness center of the base material steel sheet, the surface layer region of the glass coating side and the central region between the surface layer region and the plate thickness center. When divided into two, the emission intensity IB of B measured by glow discharge emission spectrometry (GDS) on the base material steel sheet excluding the insulating coating and the glass coating. However, when the sputter time to reach the central region is t(center) and the sputter time to reach the surface region is t(surface), the emission intensity I of B at the time t(center) is B_t(center) and the emission intensity IB_t(surface) of B at the time t(surface) may satisfy the following expression (3).
　　I B_t (Center) > I B_t (Surface) · · · · · · (3)
[0024]
　 First, the reasons for limiting the ingredient composition of the base steel sheet of the electromagnetic steel sheet of the present invention will be described. Hereinafter, "%" means "mass%" unless otherwise specified.
[0025]
　
　C: 0.085% or less
　C is an element effective in controlling the primary recrystallization structure, but has an adverse effect on the magnetic properties, and is an element to be removed by decarburization annealing before finish annealing. When it exceeds 0.085%, decarburization annealing time becomes long and productivity is lowered, which is not preferable. The C content is preferably 0.070% or less, more preferably 0.050% or less.
[0026]
　The lower limit includes 0%, but if C is reduced to less than 0.0001%, the manufacturing cost increases significantly. Therefore, 0.0001% is the practical lower limit for practical steel sheets.
[0027]
　Si: 0.80 to 7.00%
　Si is an element that increases the electric resistance of the steel sheet and improves the iron loss characteristics. If it is less than 0.80%, γ transformation occurs during finish annealing, and the crystal orientation of the steel sheet is impaired, which is not preferable. The amount of Si is preferably 1.50% or more, more preferably 2.50% or more.
[0028]
　On the other hand, if the Si content exceeds 7.00%, the workability deteriorates and cracks occur during rolling, which is not preferable. The Si amount is preferably 5.50% or less, more preferably 4.50% or less.
[0029]
　Mn: 0.05 to 1.00%
　Mn is an element that prevents cracking during hot rolling and forms MnS and/or MnSe that functions as an inhibitor by combining with S and/or Se. If the amount of Mn is less than 0.05%, the effect of addition is not sufficiently exhibited, which is not preferable. The Mn content is preferably 0.07% or more, more preferably 0.09% or more.
[0030]
　On the other hand, if the Mn content exceeds 1.00%, the precipitation dispersion of MnS and/or MnSe becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, which is not preferable. The amount of Mn is preferably 0.80% or less, more preferably 0.60% or less.
[0031]
　Acid-soluble Al: 0.010 to 0.065%
　Acid-soluble Al is an element that combines with N to generate (Al,Si)N that functions as an inhibitor. If the amount of acid-soluble Al is less than 0.010%, the effect of addition is not sufficiently exhibited and the secondary recrystallization does not proceed sufficiently, which is not preferable. The amount of acid-soluble Al is preferably 0.015% or more, more preferably 0.020% or more.
[0032]
　On the other hand, when the amount of acid-soluble Al exceeds 0.065%, the precipitation dispersion of (Al,Si)N becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, which is preferable. Absent. The amount of acid-soluble Al is preferably 0.050% or less, more preferably 0.040% or less.
[0033]
　N: 0.012% or less
　Since there is a concern of iron loss deterioration due to the formation of nitrides, it is set to 0.012% or less. As will be described later, N in the slab component is an element that combines with Al to form AlN that functions as an inhibitor. On the other hand, N forms blisters (holes) in the steel sheet during cold rolling. It is also an element to do. If the N content is less than 0.004%, the formation of AlN becomes insufficient, which is not preferable. The N content is preferably 0.006% or more, more preferably 0.007% or more.
[0034]
　On the other hand, when the N content exceeds 0.012%, blisters (holes) may be generated in the steel sheet during cold rolling, which is not preferable. The N content is preferably 0.010% or less, more preferably 0.009% or less.
[0035]
　Seq=S+0.406.Se: 0.015% or less
　Since there is a concern of iron loss deterioration due to sulfide formation, it is set to 0.015% or less. As will be described later, in the slab component, S and Se are elements that combine with Mn to form MnS and/or MnSe that function as an inhibitor. The addition amount is specified by Seq=S+0.406·Se in consideration of the atomic weight ratio of S and Se.
[0036]
　If Seq is less than 0.003%, the effect of addition is not sufficiently exhibited, which is not preferable. Seq is preferably 0.005% or more, more preferably 0.007% or more. On the other hand, if Seq exceeds 0.015%, the precipitation dispersion of MnS and/or MnSe becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, which is not preferable. Seq is preferably 0.013% or less, more preferably 0.011% or less.
[0037]
　B: 0.0005 to 0.0080%
　B is an element that combines with N and forms a complex precipitate with MnS or MnSe to form BN that functions as an inhibitor.
[0038]
　If the amount of B is less than 0.0005%, the effect of addition is not sufficiently exhibited, which is not preferable. The amount of B is preferably 0.0010% or more, more preferably 0.0015% or more. On the other hand, if the amount of B exceeds 0.0080%, the precipitation and dispersion of BN becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, which is not preferable. The amount of B is preferably 0.0060% or less, more preferably 0.0040% or less.
[0039]
　In the base steel sheet, the balance excluding the above elements is Fe and impurities. Impurities are elements that are inevitably mixed from the steel raw material and/or in the steelmaking process, and are allowed if they are contained in a range that does not impair the characteristics of the grain-oriented electrical steel sheet of the present invention.
[0040]
　Further, the magnetic steel sheet of the present invention does not impair magnetic properties and can enhance other properties, Cr: 0.30% or less, Cu: 0.40% or less, P: 0.50% or less, Ni: One or two or more of 1.00% or less, Sn: 0.30% or less, Sb: 0.30% or less, and Bi: 0.01% or less may be contained.
[0041]
　Next, the B compound that is a feature of the electrical steel sheet of the present invention will be described.
[0042]
　 The form of the B compound is not limited, but the form has an average major axis length of 1 μm or more and 20 μm or less.
[0043]
　If the major axis length is less than 1 μm, the frequency of precipitation increases and the hysteresis loss increases, which is not preferable. The average major axis length is preferably 4 μm or more, more preferably 8 μm or more.
[0044]
　On the other hand, the morphology of the B compound is preferably a coarse morphology from the viewpoint of lowering the precipitation frequency, but in order to precipitate the B compound having a major axis length of 20 μm or more, it is necessary to significantly slow down the cooling rate in the purification annealing. However, this is not preferable because it is difficult in industrial production. Therefore, the average major axis length of the B compound is 20 μm or less. The average major axis length is preferably 17 μm or less, more preferably 10 μm or less.
[0045]
　 The number density of the B compound is 1×10 to 1×10 6 pieces/mm 3 . When the number density exceeds 1×10 6 pieces/mm 3 , the B compound becomes small, the frequency of precipitation of the B compound having a major axis length of less than 1 μm increases, and iron loss increases, which is not preferable. The number density is preferably 0.5×10 6 pieces/mm 3 or less, more preferably 1×10 5 pieces/mm 3 or less.
　Further, if the number density of the B compound is less than 1×10 5 /mm 3 , B is remarkably nonuniformly deposited and does not function as an inhibitor for controlling secondary recrystallization, which is not preferable. The number density of the B compound is preferably 1×10 2 /mm 3 or more, more preferably 1×10 2 /mm 3 or more.
[0046]
　Quantitative evaluation of the number density of the B compound is carried out, for example, by performing B mapping by EPMA on the sample Z plane (plane perpendicular to the rolling direction) in the steel plate polished to the center of the plate thickness. Another method is to polish the cross section of the sample and perform B mapping by EPMA.
[0047]
　 The
　B compound is preferably Fe 2 B or Fe 3 B. The compound B is a compound in which BN functioning as an inhibitor was decomposed by purification annealing and re-precipitated during cooling.
[0048]
　If N dissolved in a high temperature is not released into the atmosphere and exists in a supersaturated state inside the steel sheet, during dissolution of the refinement annealing, the dissolved B is combined with the dissolved N, and BN is finely and frequently reprecipitated. Then, the hysteresis loss is increased. In the purification annealing, when the annealing temperature is high and solid solution N is released out of the system, Fe 2 B or Fe 3 B precipitates coarsely and infrequently, and the adverse effect on iron loss is reduced.
[0049]
Identification of 　Fe 2 B and/or Fe 3 B can be performed using analysis by EPMA and electron diffraction by a transmission electron microscope. Fe 2 B and/or Fe 3 B has a tetragonal crystal system and is characterized in that 562.1 pm>a=b>459.9 pm, 467.4 pm>c>382.4 pm.
[0050]
　 In
　the distribution of B in the depth direction of the steel sheet, the B concentration (strength) at the surface layer portion of the base material steel sheet is higher than the B concentration (strength) at the center portion of the base material steel sheet. It indicates that fine BN exists in the surface layer of the steel sheet. In such a case, iron loss increases, which is not preferable.
[0051]
　FIG. 1 is a schematic diagram showing a layer structure of a grain-oriented electrical steel sheet according to this embodiment. As shown in FIG. 1, a grain-oriented electrical steel sheet 100 according to this embodiment includes a base material steel sheet 10, a glass coating film 20, and an insulating coating film 30. Further, the region on the surface side (interface between the glass coating 20 and the base material steel plate 10) with respect to the plate thickness center C of the base material steel plate 10 is divided into two, and the surface side is defined as the surface layer region 12, and the plate thickness center C The side is called the central region 14.
　The emission intensity I B of B measured by glow discharge emission analysis (GDS) on the steel sheet from which the insulating coating and the glass coating have been removed is defined as t(center), which is the sputtering time for reaching the central region 14, and the sputtering is for reaching the surface region 12. When the time is t(surface), it is preferable that IB_t(center) and IB_t(surface) satisfy the following expression (4).
　　I B_t (center) > I B_t 　　　　　　　　　　　　　(Surface) · · ·
　　　(4) I B_t (center) : the emission intensity of B in t (center)
　　　I B_t (Surface) : the emission intensity of B in t (Surface)
[0052]
　When performing the above measurement, the insulating coating 30 is removed with an alkaline aqueous solution such as sodium hydroxide, and the glass coating 20 is removed using hydrochloric acid, nitric acid, sulfuric acid, or the like.
　Further, the above-mentioned t (surface) means a position immediately below the glass film, and t (center) is defined as a position from immediately below the glass film to the plate thickness center.
　FIG. 2 is an example showing the measurement result of GDS in the present embodiment. Specifically, t(surface) is defined as 300 seconds to 400 seconds after the start of measurement, and t(center) is defined as the time corresponding to a position of 400 seconds or more.
　I B — t (surface) is the average value of the emission intensity of B in 300 to 400 seconds from the start of measurement. I B — t(center) is the average value of the emission intensity of B from 400 to 900 seconds (until the end of measurement) from the start of measurement. However, the times of t(surface) and t(center) can be arbitrarily changed depending on the film thickness of the glass and the GDS measurement conditions, and are examples.
[0053]
　When IB_t(center) ≤ IB_t(surface) , the B concentration (strength) of the base material steel plate surface layer portion is equal to or higher than the B concentration (strength) of the base material steel plate central portion, and the base material steel plate surface layer portion is finely divided. The presence of BN increases iron loss, which is not preferable.
[0054]
　 In the
　grain-oriented electrical steel sheet according to the present embodiment, the glass coating is formed in contact with the base material steel sheet. The glass film contains a complex oxide such as forsterite (Mg 2 SiO 4 ). The glass coating film is formed by a finish annealing treatment described below, in which an oxide layer containing silica as a main component reacts with an annealing separator containing magnesia as a main component.
[0055]
　 In the
　grain-oriented electrical steel sheet according to the present embodiment, an insulating coating formed on and in contact with the glass coating and mainly composed of phosphate and colloidal silica is formed.
[0056]
　Next, a manufacturing method for manufacturing the electromagnetic steel sheet of the present invention from the silicon steel of the present invention will be described.
[0057]
　 As
　a silicon steel slab component of the electromagnetic steel sheet of the present invention, C: 0.085% or less, Si: 0.80 to 7.00%, Mn: 0.05 to 1.00% by mass%. , Acid-soluble Al: 0.010 to 0.065%, N: 0.004 to 0.012%, Seq=S+0.406·Se: 0.003 to 0.015%, B: 0.0005 to 0. Contains 0080%.
[0058]
　C: 0.085% or less
　C is an element effective in controlling the primary recrystallization structure, but has an adverse effect on the magnetic properties, and is an element removed by decarburization annealing before finish annealing. If it exceeds 0.085%, the decarburization annealing time becomes long and the productivity decreases, so C is made 0.085% or less. It is preferably 0.070% or less, more preferably 0.050% or less.
[0059]
　The lower limit includes 0%, but if C is reduced to less than 0.0001%, the manufacturing cost increases significantly. Therefore, 0.0001% is the practical lower limit for practical steel sheets. In the grain-oriented electrical steel sheet, decarburization annealing usually reduces the amount to about 0.001% or less.
[0060]
　Si: 0.80 to 7.00%
　Si is an element that increases the electric resistance of the steel sheet and improves the iron loss characteristics. If it is less than 0.80%, γ-transformation occurs during finish annealing and the crystal orientation of the steel sheet is impaired, so Si is set to 0.80% or more. It is preferably 1.50% or more, more preferably 2.50% or more.
[0061]
　On the other hand, if it exceeds 7.00%, workability deteriorates and cracks occur during rolling, so Si is set to 7.00% or less. It is preferably 5.50% or less, more preferably 4.50% or less.
[0062]
　Mn: 0.05 to 1.00%
　Mn is an element that prevents cracking during hot rolling and forms MnS that functions as an inhibitor by combining with S and/or Se. If it is less than 0.05%, the effect of addition is not sufficiently exhibited, so Mn is made 0.05% or more. It is preferably 0.07% or more, more preferably 0.09% or more.
[0063]
　On the other hand, if it exceeds 1.00%, the precipitation dispersion of MnS becomes non-uniform, the desired secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, so Mn is made 1.00% or less. It is preferably 0.80% or less, more preferably 0.06% or less.
[0064]
　Acid-soluble Al: 0.010 to 0.065%
　Acid-soluble Al is an element that combines with N to generate (Al,Si)N that functions as an inhibitor. If it is less than 0.010%, the effect of addition is not sufficiently exhibited and the secondary recrystallization does not proceed sufficiently, so the acid-soluble Al is made 0.010% or more. It is preferably 0.015% or more, more preferably 0.020% or more.
[0065]
　On the other hand, if it exceeds 0.065%, the precipitation dispersion of (Al,Si)N becomes non-uniform, the desired secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, so that the acid-soluble Al is less than 0.1%. It is set to 065% or less. It is preferably 0.050% or less, more preferably 0.040% or less.
[0066]
　N: 0.004 to 0.012%
　N is an element that combines with Al to form AlN that functions as an inhibitor. On the other hand, during cold rolling, blisters (holes) are formed in the steel sheet. It is also an element to do. If it is less than 0.004%, the formation of AlN is insufficient, so N is made 0.004% or more. It is preferably 0.006% or more, more preferably 0.007% or more.
[0067]
　On the other hand, if it exceeds 0.012%, blisters (holes) may be generated in the steel sheet during cold rolling, so N is made 0.012% or less. It is preferably 0.010% or less, more preferably 0.009% or less.
[0068]
　Seq=S+0.406·Se: 0.003 to 0.015%
　S and Se are elements that combine with Mn to form MnS and/or MnSe that function as an inhibitor. The addition amount is specified by Seq=S+0.406·Se in consideration of the atomic weight ratio of S and Se.
[0069]
　If Seq is less than 0.003%, the effect of addition is not sufficiently exhibited, so Seq is set to 0.003% or more. It is preferably 0.005% or more, more preferably 0.007% or more. On the other hand, if Seq exceeds 0.015%, the precipitation dispersion of MnS and/or MnSe becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, so Seq is 0.015. % Or less. It is preferably 0.013% or less, more preferably 0.011% or less.
[0070]
　B: 0.0005 to 0.0080%
　B is an element that combines with N and forms a complex precipitate with MnS to form BN that functions as an inhibitor.
[0071]
　If it is less than 0.0005%, the effect of addition is not sufficiently exhibited, so B is made 0.0005% or more. It is preferably 0.0010% or more, more preferably 0.0015% or more. On the other hand, if it exceeds 0.0080%, the precipitation dispersion of BN becomes non-uniform, the desired secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, so B is made 0.0080% or less. It is preferably 0.0060% or less, more preferably 0.0040% or less.
[0072]
　In the silicon steel slab, the balance other than the above elements is Fe and inevitable impurities. The unavoidable impurities are elements that are inevitably mixed from the steel raw material and/or in the steelmaking process, and are elements that are allowed within a range that does not impair the characteristics of the electrical steel sheet of the present invention.
[0073]
　Further, the silicon steel slab does not impair the magnetic properties of the electromagnetic steel sheet of the present invention and can improve other properties, Cr: 0.30% or less, Cu: 0.40% or less, P: 0.50% Hereinafter, one or more of Ni: 1.00% or less, Sn: 0.30% or less, Sb: 0.30% or less, and Bi: 0.01% or less may be contained.
[0074]
　
　Molten steel having a predetermined component composition, which has been melted in a converter or an electric furnace and subjected to vacuum degassing treatment as necessary, is continuously cast or ingot-cast and then slab-rolled to form the present invention. Obtain a slab of silicon steel (silicon slab). The silicon steel slab is usually a slab having a thickness of 150 to 350 mm, preferably 220 to 280 mm, but may be a thin slab of 30 to 70 mm. In the case of a thin slab, there is an advantage that it is not necessary to perform rough working to an intermediate thickness when manufacturing a hot rolled sheet.
[0075]
　 The
　steel slab is heated to 1250° C. or lower and subjected to hot rolling. When the heating temperature exceeds 1250° C., the amount of molten scale increases, and MnS and/or MnSe completely dissolves into solid solution and finely precipitates in the subsequent steps to obtain a desired primary recrystallized grain size. It is not preferable because the decarburization annealing temperature needs to be 900° C. or higher. The heating temperature is more preferably 1200°C or lower.
[0076]
　The lower limit of the heating temperature is not particularly limited, but the heating temperature is preferably 1100° C. or higher in order to secure the workability of the silicon steel slab.
[0077]
　
　A silicon steel slab heated to 1250° C. or less is subjected to hot rolling to form a hot rolled sheet. The hot-rolled sheet is heated to 1000 to 1150°C (first stage temperature) for recrystallization, and subsequently, heated to 850 to 1100°C (second stage temperature), which is lower than the first stage temperature, to be annealed. The non-uniform structure generated during rolling is made uniform. The hot-rolled sheet annealing is preferably performed once or more in order to make the history of hot-rolling uniform before the hot-rolled sheet is subjected to final cold rolling.
[0078]
　In hot-rolled sheet annealing, the first stage temperature greatly affects the precipitation of the inhibitor in the subsequent steps. If the first stage temperature exceeds 1150° C., the inhibitor finely precipitates in the subsequent steps, and the decarburization annealing temperature for obtaining the desired primary recrystallized grain size needs to be 900° C. or higher, which is not preferable. The first stage temperature is more preferably 1120°C.
[0079]
　On the other hand, if the first stage temperature is lower than 1000° C., recrystallization becomes insufficient, and uniformization of the structure of the hot rolled sheet cannot be achieved, which is not preferable. The first stage temperature is more preferably 1030°C or higher.
[0080]
　When the second stage temperature exceeds 1100° C., the inhibitor is finely precipitated in the subsequent steps, which is not preferable, as in the case of the first stage temperature. The second stage temperature is more preferably 1070° C. or lower. On the other hand, if the second stage temperature is lower than 850° C., the γ phase is not generated and the homogenization of the structure of the hot rolled sheet is not achieved, which is not preferable. The second stage temperature is more preferably 880°C or higher.
[0081]
　 The
　steel sheet subjected to the hot-rolled sheet annealing is subjected to one cold rolling or two or more cold rolling steps sandwiching the intermediate annealing to obtain the steel sheet having the final thickness. The cold rolling may be performed at room temperature or may be performed by warming the steel sheet to a temperature higher than room temperature, for example, about 200°C.
[0082]
　
　The steel sheet having the final thickness was subjected to decarburization annealing in a wet atmosphere for the purpose of removing C in the steel sheet and controlling the primary recrystallized grain size to a desired grain size. For example, it is preferable to perform decarburization annealing at a temperature of 770 to 950° C. for a time such that the primary recrystallized grain size becomes 15 μm or more.
[0083]
　If the decarburization annealing temperature is less than 770°C, the desired crystal grain size cannot be obtained, so the decarburizing annealing temperature is preferably 770°C or higher. More preferably, it is 800° C. or higher. On the other hand, if the decarburization annealing temperature exceeds 950° C., the crystal grain size exceeds the desired crystal grain size, which is not preferable. The decarburization annealing temperature is more preferably 920°C or lower.
[0084]
　
　Before the decarburization-annealed steel sheet and the finish annealing, the steel sheet is nitrided so that the N content of the steel sheet is 40 to 1000 ppm. When the N content of the steel sheet after the nitriding treatment is less than 40 ppm, AlN is not sufficiently precipitated and AlN does not function as an inhibitor, which is not preferable. The N content of the steel sheet after the nitriding treatment is more preferably 80 ppm or more.
[0085]
　On the other hand, if the N content of the steel sheet exceeds 1000 ppm, excessive AlN is present even after the completion of secondary recrystallization in the next finish annealing, and iron loss increases, which is not preferable. The N content of the steel sheet is more preferably 970 ppm or less.
[0086]
　
　Subsequently, the annealing separation agent is applied to the steel sheet subjected to the nitriding treatment and subjected to finish annealing. As the annealing separator, a usual annealing separator is used.
[0087]
　
　[Secondary Recrystallization Annealing]
　Among the finishing annealings, in the secondary recrystallization annealing, the inhibitor is strengthened by BN. preferable. It is more preferably 10° C./hour or less. Instead of controlling the heating rate, the steel sheet may be kept in the temperature range of 1000 to 1100° C. for 10 hours or more.
[0088]
　 The
　steel sheet subjected to the secondary recrystallization annealing is subjected to the purification annealing subsequent to the secondary recrystallization annealing. It is preferable to subject the steel sheet after secondary recrystallization to purification annealing because the precipitates used as inhibitors are rendered harmless and the hysteresis loss in the final magnetic properties is reduced. The atmosphere of the purification annealing is not particularly limited, but for example, a hydrogen atmosphere can be mentioned. Further, the purification annealing is performed at a temperature of about 1200° C. and held for 10 to 30 hours. Although the temperature of the purification annealing is not limited, it is preferably 1180°C to 1220°C from the viewpoint of productivity. If the temperature is 1180° C. or lower, it takes a long time to diffuse the elements, and long-time annealing is required, which is not preferable. Further, if it is 1220° C. or higher, maintenance (durability) of the annealing furnace becomes difficult, which is not preferable.
[0089]
　[Cooling condition]
　After the purification annealing, the steel sheet is cooled under a predetermined cooling condition (cooling rate).
　In order to control the major axis length of the compound B within a desired range, the rate of temperature decrease in the temperature range of 1200 to 1000°C is set to less than 50°C/hour. Further, the temperature lowering rate in the temperature range of 1000 to 600° C. is less than 30° C./hour.
[0090]
　The reason for setting such a cooling rate is as follows.
[0091]
　BN becomes a solid solution B and a solid solution N in a high temperature range, and N that cannot be solid solution is released into the atmosphere during the temperature decrease. On the other hand, B, which cannot be solid-dissolved during the temperature decrease, is not released to the outside of the system and precipitates as a B compound, for example, BN, Fe 2 B, and Fe 3 B in the glass coating or inside the base material steel plate . When solid solution N is not sufficiently present inside the base steel sheet, BN does not precipitate, and Fe 2 B or Fe 3 B precipitates.
[0092]
　If the cooling rate is appropriate during cooling from the high temperature range, the solid solution N is released to the outside of the system, Fe 2 B or Fe 3 B precipitates inside the base steel sheet , and the precipitated Fe 2 B or Fe 3 B grows Ostwald and coarsens.
[0093]
　When the cooling rate is high, solute N is not released into the atmosphere, BN is finely precipitated inside the base steel sheet, and Fe 2 B or Fe 3 B is finely precipitated without Ostwald growth. The B compound finely deposited inside the base steel plate increases the hysteresis loss and increases the iron loss of the final product.
[0094]
　If the rate of temperature decrease is less than 10° C./hour, the productivity is greatly affected. Therefore, the rate of temperature decrease is preferably 10° C./hour or more. Therefore, the temperature lowering rate in the temperature range of 1200 to 1000° C. is preferably 10 to 50° C./hour, and the temperature lowering rate in the temperature range of 1000 to 600° C. is preferably 10 to 30° C./hour.
[0095]
　The atmosphere during cooling is preferably H 2 100% in a temperature range of at least 1200° C. to 600° C. and N 2 100% in a temperature range of less than 600° C. When the atmosphere for cooling the temperature range of 1200° C. to 600° C. is N 2 100%, the steel sheet is nitrided during cooling, which causes deterioration of hysteresis loss due to formation of nitrides, which is not preferable. It is possible to use Ar instead of H 2 when cooling the temperature range of 1200° C. to 600° C., but this is not preferable from the viewpoint of cost.
[0096]
　 The
　grain-oriented electrical steel sheet after finish annealing may be subjected to magnetic domain refining treatment. By the magnetic domain refining treatment, grooves are formed on the surface of the steel sheet, the magnetic domain width is reduced, and as a result, iron loss can be reduced, which is preferable. The specific method of the magnetic domain subdivision treatment is not particularly limited, and examples thereof include laser irradiation, electron beam irradiation, etching, and a groove forming method using a gear.
　The magnetic domain refining treatment is preferably performed after finish annealing, but may be performed before finish annealing or after forming the insulating coating.
[0097]
　 An
　insulating coating forming solution is applied to the surface of the steel sheet after secondary recrystallization or the surface of the steel sheet after purification annealing, and baked to form an insulating coating. The type of insulating coating is not particularly limited, and conventionally known insulating coatings are suitable. For example, there is an insulating coating formed by applying an aqueous coating solution containing phosphate and colloidal silica.
[0098]
　As the phosphate, for example, phosphates such as Ca, Al and Sr are preferable, and among them, aluminum phosphate is more preferable. The type of colloidal silica is not particularly limited, and its particle size (number average particle size) can be appropriately selected, but if it exceeds 200 nm, it may settle in the treatment liquid. The average particle size) is preferably 200 nm or less. More preferably, it is 170 nm.
[0099]
　Even if the particle size of the colloidal silica is less than 100 nm, there is no problem in dispersion, but since the manufacturing cost increases, 100 nm or more is preferable from the economical point of view. More preferably, it is 150 nm or more.
[0100]
　The insulating coating is formed by applying an insulating coating forming liquid to the surface of the steel sheet by a wet coating method using a roll coater or the like and baking in air at 800 to 900° C. for 10 to 60 seconds.
[0101]
　[Second Embodiment]
　Next, a grain-oriented electrical steel sheet and a method for manufacturing the same according to the second embodiment will be described. Note that detailed description of the same configuration as the grain-oriented electrical steel sheet according to the first embodiment will be omitted.
　The grain-oriented electrical steel sheet according to the second embodiment includes a base steel sheet, an intermediate layer formed on the base steel sheet in contact with silicon oxide, and a contact layer formed on the intermediate layer. An insulating coating film containing colloidal silica as a main
　component is used, and the base steel sheet is, as a chemical component, in mass%
　　C: 0.085% or less;
　　Si: 0.80 to 7.00%;
　　Mn: 0.05 to 1.00%;
　　Al: 0.010 to 0.065%;
　　N: 0.012% or less;
　　Seq=S+
　　0.406.Se : 0.015% or less B: 0.0005 to 0.0080 %
, and the
　balance Fe and impurities. The
　base steel sheet contains a B compound having a major axis length of 1 μm or more and 20 μm or less at a number density of 1×10 to 1×10 6 pieces/mm 3. ..
　In the grain-oriented electrical steel sheet according to this embodiment, when the total thickness of the base material steel sheet and the intermediate layer is d, and the emission intensity of B is measured from the surface of the intermediate layer by glow discharge emission analysis (GDS). Emission intensity I B (d/2) of B at a depth position of d/2 from the surface of the intermediate layer and emission intensity I B of B at a depth position of d/10 from the surface of the intermediate layer of (D/10) may satisfy the following formula (5).
　　IB (d/2) > IB( d/10) ... (5)
[0102]
　The grain-oriented electrical steel sheet of the first embodiment has a glass coating between the base material steel sheet and the insulating coating, whereas the grain-oriented electrical steel sheet of the second embodiment has an intermediate layer between the base material steel sheet and the insulating coating. Equipped with.
[0103]
　
　The grain-oriented electrical steel sheet according to the present embodiment includes an intermediate layer which is formed in contact with the base steel sheet and is mainly composed of silicon oxide. In the present embodiment, the intermediate layer has a function of bringing the base steel sheet and the insulating film into close contact with each other.
[0104]
　The silicon oxide forming the main component of the intermediate layer is preferably SiOα (α=1.0 to 2.0). It is more preferable that α=1.5 to 2.0 because the silicon oxide is more stable. Sufficient oxidation annealing to form silicon oxide on the surface of the steel sheet can form SiO 2 with α≈2.0.
[0105]
　 In
　the distribution of B in the depth direction of the steel sheet, if the B concentration (strength) of the surface layer of the base steel sheet is higher than the B concentration (strength) of the central portion of the base steel sheet, the base steel sheet Fine BN is present in the surface layer portion, which increases iron loss, which is not preferable.
[0106]
　Therefore, the total thickness of the base material steel sheet and the intermediate layer is d, and the depth of d/2 from the surface of the intermediate layer when the emission intensity of B is measured from the surface of the intermediate layer by glow discharge emission spectrometry (GDS). The emission intensity I B (d/2) of B at the position and the emission intensity I B (d/10) of B at the depth d/10 from the surface of the intermediate layer satisfy the following expression (6). Is preferred.
　　IB (d/2) >IB (d/10)　　　　　　　　　　　　　　　　　...(6)
[0107]
　The total thickness d of the base material steel plate and the intermediate layer is measured as follows. First, the insulating coating is removed from the grain-oriented electrical steel sheet produced by the production method described below with an alkaline aqueous solution such as sodium hydroxide. As a result, only the intermediate layer is formed on the base material steel plate, and the total thickness d of the base material steel plate and the intermediate layer in this state is measured with a micrometer or a plate thickness gauge.
[0108]
　 In
　the method for manufacturing a grain-oriented electrical steel sheet according to the first embodiment, a nitriding-treated steel sheet is coated with an annealing separating agent containing magnesia as a main component and subjected to finish annealing to obtain a base steel sheet. A glass film made of forsterite was formed on the surface. On the other hand, in the method for manufacturing the grain-oriented electrical steel sheet according to the second embodiment, the glass coating formed by the above method is removed by means such as pickling and grinding. After the removal, the surface of the steel sheet is preferably finished by chemical polishing or electric field polishing to be smooth.
[0109]
　Alternatively, as the annealing separator, an annealing separator containing alumina as a main component can be used instead of magnesia, which is applied and dried, and after drying, it is wound into a coil and finish annealing (secondary recrystallization ). By finish annealing, it is possible to produce a grain-oriented electrical steel sheet while suppressing the formation of a film of an inorganic mineral substance such as forsterite. After the production, the surface of the steel sheet is preferably finished by chemical polishing or electric field polishing to be smooth.
[0110]
　 In
　the method for manufacturing a grain-oriented electrical steel sheet according to the second embodiment, the intermediate layer forming heat treatment is performed after the finish annealing is performed by the above method.
　Annealing is applied to the grain-oriented electrical steel sheet from which the film of inorganic minerals such as forsterite is removed, or the grain-oriented electrical steel sheet that suppresses the formation of the film of inorganic minerals such as forsterite, and silicon oxide is applied to the surface of the base steel sheet. To form an intermediate layer.
[0111]
　The annealing atmosphere is preferably a reducing atmosphere so that the inside of the steel sheet is not oxidized, and a nitrogen atmosphere mixed with hydrogen is particularly preferable. For example, an atmosphere in which hydrogen:nitrogen is 75%:25% and a dew point is −20 to 0° C. is preferable.
[0112]
　The method of manufacturing the grain-oriented electrical steel sheet according to the second embodiment is the same as the method of manufacturing the grain-oriented electrical steel sheet according to the first embodiment except for the points described above. The magnetic domain refining treatment is the same as in the first embodiment, and the magnetic domain refining treatment may be performed before finish annealing, after finish annealing, or after forming the insulating coating.
Example
[0113]
　Next, examples of the present invention will be described. The conditions in the examples are one condition example adopted for confirming the feasibility and effects of the present invention. It is not limited. The present invention can employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
[0114]
　(Example 1)
　A steel slab having the composition shown in Table 1-1 was heated to 1150°C and subjected to hot rolling to obtain a hot-rolled steel sheet having a plate thickness of 2.6 mm. Annealing, followed by hot-rolled sheet annealing that is annealed at 900° C., then cold rolling once or multiple cold rolling steps with intermediate annealing sandwiched between them to obtain a cold-rolled steel sheet having a final sheet thickness of 0.22 mm. did.
[0115]
[Table 1-1]

[0143]
　In H1 to H10, grain-oriented electrical steel sheets having excellent magnetic properties were obtained. On the other hand, in any of the manufacturing conditions h1 to h6, which are out of the range of the present invention, the magnetic properties were inferior.
Industrial availability
[0144]
　As described above, according to the present invention, in the high magnetic flux density grain-oriented electrical steel sheet (final product) using B as an inhibitor, the precipitation morphology of the B compound is appropriately controlled, and the low iron loss with a small hysteresis loss. The grain-oriented electrical steel sheet can be provided industrially stably. Therefore, the present invention is highly applicable in the electrical steel sheet manufacturing industry.
The scope of the claims
[Claim 1]
　The base steel sheet and,
　a lower layer coating formed over and in contact with said base material steel plate;
　formed over and in contact with the lower film, an insulating film composed mainly of phosphate and colloidal silica;
equipped with,
　said base As a chemical component, the material steel plate is, in mass %,
　　C: 0.085% or less;
　　Si: 0.80 to 7.00%;
　　Mn: 0.05 to 1.00%;
　　Al: 0.010 to 0.
　　% 065; N: 0.0040% or less;
　　Seq = S + 0.406 · Se: 0.015% or
　　less; B: 0.0005 ~ 0.0080%;
containing,
　and the balance Fe and impurities,
　wherein the base material The steel sheet contains a B compound having a major axis length of 1 μm or more and 20 μm or less at a number density of 1×10 to 1×10 6 pieces/mm 3 , and the
　lower layer coating is a glass coating mainly composed of forsterite, or , A grain-oriented
electrical steel sheet comprising an intermediate layer mainly composed of silicon oxide .
[Claim 2]
　The lower coating is the glass coating, the
　insulating coating and the glass coating are removed and measured by glow discharge emission spectrometry, the glass coating side from the center of the thickness of the base steel sheet, the glass coating side Of the surface layer area and the central area between the surface layer area and the center of the plate thickness, and the sputtering time until reaching the central area is t(center), and the time until reaching the surface area is when the sputtering time was set to t (Surface), wherein t (center) B of the emission intensity I in B_t (center) and the t luminous intensity of B in (Surface) I B_t (Surface) and although the following formula (1 ) Is satisfied, the grain-
oriented electrical steel sheet according to claim 1.
　　I B_t (Center) > I B_t (Surface) · · · · · · (1)
[Claim 3]
　The lower coating is the
　intermediate layer, the total thickness of the base material steel sheet and the intermediate layer is d, and the intermediate when the emission intensity of B is measured from the surface of the intermediate layer by glow discharge emission analysis. emission intensity of B at the depth position of d / 2 from the surface of the layer I B (d / 2) and the emission intensity of B at the depth position of the d / 10 from the surface of the intermediate layer I B (d / 10) and the following formula (2) are satisfied
: The grain-oriented electrical steel sheet according to claim 1.
　　IB (d/2) > 　　　　　IB( d/10) ... (2)
[Claim 4]
The grain-oriented electrical steel sheet according to any one of claims 1 to 3, 　wherein the B compound is at least one of Fe 2 B and Fe 3 B.