Oriented Electromagnetic Steel Sheet and its Manufacturing Method

Abstract

This invention provides a scheme to improve the adhesion of the coating during magnetic domain subdivision processing. The method involves setting the Mn+Fe concentration in the ceramic substrate coating of the oriented electromagnetic steel sheet to 0.05% by mass or more, and setting the Young's modulus of the substrate coating to 108–144 GPa.

Description

Technical Field

[0001] This invention relates to an orientation-oriented electromagnetic steel sheet, specifically to an orientation-oriented electromagnetic steel sheet for magnetic domain subdivision processing and a method for manufacturing the same, and more specifically, to an orientation-oriented electromagnetic steel sheet with excellent magnetic and coating properties and a method for manufacturing the same. Background Technology

[0002] Since oriented electromagnetic steel sheets are mainly used as core materials for transformers, they are required to have excellent magnetic properties, especially low iron loss. Therefore, oriented electromagnetic steel sheets have traditionally been manufactured using the following method: cold-rolled Si-containing steel sheets undergo decarburization annealing, which also involves primary recrystallization annealing; after coating with an annealing separating agent with MgO as the main agent, secondary recrystallization is induced in fine annealing, resulting in a high degree of uniformity of grains in the {110}<001> orientation (the so-called Goss orientation).

[0003] The aforementioned fine annealing combined with secondary recrystallization and purification treatment at a maximum temperature of approximately 1200°C requires about 10 days. Therefore, batch annealing, which is performed while the steel is wound into coils, is typically used.

[0004] Here, in the above-mentioned fine annealing, a magnesium olivine film is formed on the steel plate surface by causing the secondary oxide scale, which is mainly composed of SiO2 formed on the surface of the steel plate during decarburization annealing, and the annealing separating agent, which is mainly composed of MgO, to be coated on the surface of the steel plate after decarburization annealing, to react MgO + SiO2 → Mg2SiO4.

[0005] In addition to providing insulation and corrosion resistance to the steel plate, this forsterite coating also improves the magnetic properties by instilling tensile stress on the steel plate surface. Therefore, the forsterite coating must be uniform and have excellent adhesion.

[0006] In recent years, with the increasing demand for energy conservation, there has been a need to further improve the iron loss characteristics of oriented electromagnetic steel sheets. Therefore, after planarization annealing, oriented electromagnetic steel sheets are irradiated with lasers, electron beams, plasma, etc., and heated to apply localized deformation, thereby improving iron loss.

[0007] However, if such localized heating is performed, the coating may sometimes peel off partially due to thermal deformation. Such peeling can lead to a deterioration in corrosion resistance and insulation. Therefore, to prevent this, the coating must be recoated and sintered.

[0008] Implementing too many processes is a major factor in reducing costs, but it also leads to the release of the hard-won localized thermal deformation, resulting in insufficient reduction of iron loss.

[0009] Various solutions have been proposed to address this problem. For example, Patent Document 1 discloses a method of irradiating an electron beam with a Se thickened portion at the interface between the coating and the iron substrate, while controlling the proportion of the thickened portion at a predetermined level.

[0010] Patent document 2 discloses a method for performing magnetic domain subdivision treatment on the surface of a oriented electromagnetic steel sheet after final fine annealing by irradiating it with an electron beam, wherein the oriented electromagnetic steel sheet is heated to above 50°C before the magnetic domain subdivision treatment is performed.

[0011] Patent document 3 discloses a method for quantitatively analyzing the Ti and Al intensities and the FX (Al) and Fe intensities on the surface of a steel plate using fluorescence X-ray analysis, thereby controlling the final fine annealing within a specific thermal mode.

[0012] Patent document 4 discloses a substrate coating containing 0.02 g / m³ of nitrogen. 2 The above-mentioned nitrogen compounds, and the method of controlling the contact between the substrate coating and the steel plate within a specific range.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 2012-52232

[0016] Patent Document 2: Japanese Patent No. 6465054

[0017] Patent Document 3: Japanese Re-registration No. 2015-40799

[0018] Patent Document 4: Japanese Patent Application Publication No. 2012-92409 Summary of the Invention

[0019] Among these existing technologies, firstly, regarding Patent Document 1, it is based on the following insight: improving the coating thickens Se, which makes the coating easily damaged during magnetic domain subdivision, but electron beams do not do this. Therefore, methods other than electron beams cannot be used, such as magnetic domain subdivision based on lasers or plasma jets.

[0020] Furthermore, in addition to the thickening of Se, the thickening of S, Al, etc. also needs to be considered. Since the thickening states of each element are different, it is difficult to control them all within a specified range.

[0021] It should be noted that although Patent Document 1 mentions thickening of S and Al in addition to Se, regardless of which method is used, because the fine annealing is performed in the coil state, it is impossible to make the temperature and atmosphere uniform across the entire length and width, making it difficult to control the entire area of ​​the coil within the specified range. Therefore, it is difficult to control it within the limited range described in Patent Document 1.

[0022] Furthermore, even when using an electron beam, the problem of film peeling still exists when the irradiation energy is increased during magnetic domain subdivision to improve the iron loss reduction effect.

[0023] The method described in Patent Document 2 is similarly limited to domain subdivision based on electron beams; no effect was observed for domain subdivision based on plasma jets or lasers. Furthermore, the heating and cooling of the vacuum section before and after electron beam irradiation results in high equipment and operating costs. Moreover, the same problems as those in Patent Document 1 exist when using electron beams.

[0024] In Patent Document 3, rapid heating to 400–650°C for fine annealing followed by slow heating to 700–850°C is required. This necessitates an unnatural thermal cycle, resulting in significant costs for heat dissipation in the annealing furnace to anneal the coiled steel. Furthermore, meeting this condition across the entire length and width of the coil is difficult, and achieving uniform coating under favorable conditions remains problematic.

[0025] In Patent Document 4, the length of the interface between the substrate coating and the base iron is adjusted. In addition, it is necessary to determine the gas supply amount for fine annealing to form nitrides, the coil winding tension, and the moisture content in the annealing separator. However, since there are places where moisture is easily retained and places where moisture is not easily retained, and there are parts that are easily subjected to winding tension and parts that are not, it is difficult to obtain a uniform coating on the entire surface of the coil.

[0026] As mentioned above, methods for preventing coating stripping caused by domain subdivision processing remain insufficient. Furthermore, the demand for energy conservation has surged in recent years, leading to a trend where the irradiation energy for domain subdivision processing needs to be increased to further improve iron loss. Even measures previously considered effective in preventing coating stripping have become less effective in recent years.

[0027] The present invention was made in view of the above circumstances. It provides an oriented electromagnetic steel sheet and a method for manufacturing the same, which improves physical properties by adjusting the composition of the substrate coating, thereby ensuring coating adhesion during magnetic domain subdivision processing.

[0028] The main structure of this invention is as follows.

[0029] 1. An oriented electromagnetic steel sheet, wherein the Mn+Fe concentration of the oriented electromagnetic steel sheet having a ceramic coating and containing Mn is 0.05% by mass or more, and the Young's modulus is 108 to 144 GPa.

[0030] 2. A method for manufacturing a grain-oriented electromagnetic steel sheet, comprising the method described in 1 above, wherein a grain-oriented electromagnetic steel sheet containing Mn is hot-rolled from a steel billet, followed by cold rolling to a final sheet thickness in one or more cold rolling passes with intermediate annealing, and then subjected to decarburization annealing that also involves recrystallization, followed by coating the surface of the steel sheet with an annealing separating agent containing 50% by mass or more of MgO and fine annealing, and, if necessary, removing the unreacted separating agent after fine annealing and then performing planarization annealing.

[0031] By adjusting the above decarburization annealing conditions to an annealing temperature of 700–900°C, a soaking time of 30–300 seconds, and a dew point of at least the initial stage of the soaking process in the wet hydrogen atmosphere of 45–60°C, the absorbance of the steel plate surface after decarburization annealing, measured by Fourier transform infrared spectroscopy (FTIR), and the absorbance of fir olivine, pyroxene, and silica, respectively, are set to A1, A2, and A3, respectively, such that {(A1+A2) / (A1+A2+A3)}×100 is set to 45% or higher.

[0032] Furthermore, in the aforementioned fine annealing, the temperature range from at least 950°C to 1100°C is set to an atmosphere containing H2, and the gas flow rate within the aforementioned temperature range is set at a rate per 1m² of the steel plate surface area. 2 1.0×10 －5 ~7.6×10 －5 The range of (NL / min).

[0033] Invention Effects

[0034] According to the present invention, an orientation-type electromagnetic steel sheet with excellent coating adhesion can be provided. In particular, by preventing coating peeling during the magnetic domain subdivision process, the corrosion resistance and insulation properties based on the coating can be maintained, and the magnetic domain subdivision process can be performed at a higher energy density, thereby effectively reducing iron loss. Detailed Implementation

[0035] The following section discusses the experiment that led to the development of this invention.

[0036] <Experiment 1>

[0037] Steel containing 0.06% by mass of C, 3.3% by mass of Si, 0.07% by mass of Mn, 0.03% by mass of Al, and 0.01% by mass of N was smelted and formed into billets using continuous casting. The billets were then heated to 1400°C and hot-rolled to produce a 2.2mm thick hot-rolled plate. After annealing the hot-rolled plate at 1000°C for 60 seconds, it underwent a single cold rolling process to reduce the intermediate plate thickness to 1.7mm. After intermediate annealing at 1100°C for 80 seconds, it was then warm-rolled at 200°C to produce a final 0.23mm thick cold-rolled plate.

[0038] Next, under an atmosphere of 50 vol% H2–50 vol% N2, various changes were made to the dew point, and decarburization annealing was carried out at 830°C for 100 seconds, thereby changing the oxide formation on the steel plate surface. Then, an annealing separating agent mainly composed of magnesium oxide was applied to the steel plate surface and dried.

[0039] For this steel sheet, as a fine annealing process, heat treatment was performed under N2 atmosphere up to 700°C, and under a 75 vol% H2 + 25 vol% N2 atmosphere, with the temperature increased from 700°C to 1200°C at a rate of 25°C / h. This was followed by purification at 1200°C for 10 hours under an H2 atmosphere. It should be noted that this fine annealing was carried out by varying the gas flow rate during the heating process.

[0040] For finely annealed plates with various forsterite coatings obtained in this way (in the case of ceramic coatings, hereinafter referred to as forsterite coatings), the Young's modulus of the substrate coating is evaluated by nanoindentation, and the concentrations of Mn and Fe in the substrate coating are quantified by Auger electron spectroscopy.

[0041] It should be noted that nanoindentation refers to the method of pressing an indenter into the object being tested, continuously measuring the load and depth at that time, and calculating the composite elastic modulus based on the relationship between the indentation depth and the load. Compared with the micro-Vickers method, nanoindentation requires a smaller indentation depth, and therefore can be commonly used in the physical property testing of thin films.

[0042] As for the measurement conditions, a diamond triangular pyramid indenter (Berkovich type, vertex angle: 60°) was used to press the substrate film at any three positions with a loading time of 5 seconds, a deloading time of 2 seconds, and a maximum load of 1000 μN. This was a linear load application method at room temperature.

[0043] In addition, Auger electron spectrometry is used to determine the kinetic energy distribution of Auger electrons released when irradiated by an electron beam. The extraction depth of Auger electrons is limited to below a few nanometers, thus enabling the analysis of the concentration of various components in the substrate coating portion alone without being affected by the iron content of the substrate.

[0044] Then, the finely annealed coil steel sheet, which is the purified annealed steel sheet described above, is coated with a coating agent, and after drying, it is subjected to a planarization treatment at 800°C for 20 seconds to produce a finished sheet. For this finished sheet, an irradiation power of 3.0 mJ / mm² is applied. 2 Irradiate with laser to perform magnetic domain subdivision processing, and observe the presence or absence of film peeling on the finished board after irradiation using a microscope.

[0045] It should be noted that the above-mentioned laser irradiation is carried out under the condition that the irradiation spacing is 10 mm and perpendicular to the rolling direction.

[0046] The observations are shown in Table 1.

[0047] [Table 1]

[0048]

[0049] As shown in Table 1, no coating peeling was observed in the region where the Young's modulus of the substrate coating was 108–144 GPa and the concentration of (Mn+Fe) in the substrate coating was 0.05% by mass or higher, indicating that a good coating could be obtained.

[0050] The inventors believe the following are the reasons why such a result can be obtained.

[0051] First, the reason why the peel resistance of the film can be improved if the Young's modulus of the substrate coating is within the above range is as follows.

[0052] Originally, when thermal deformation was applied for magnetic domain subdivision, the film peeled off because local thermal expansion occurred due to heating for a very short time. When the thermally expanded part was cooled, shear stress was generated due to the difference in thermal expansion rate between the steel plate and the film. This stress exceeded the destructive resistance stress of the film, thus causing peeling.

[0053] Therefore, to prevent such peeling, it is effective to consider increasing the resistance to failure caused by the thermal stress of the coating. Furthermore, to increase this resistance, it is effective to decrease the Young's modulus of the coating. This is because the shear stress caused by thermal expansion increases with a higher Young's modulus. On the other hand, a lower Young's modulus is not always better; if it is less than 108 GPa, the tensile tension imparted by the coating to the steel plate decreases, and the iron loss increases, which is therefore undesirable.

[0054] On the other hand, the reason why introducing Fe and Mn into the coating can improve the coating's peel resistance is as follows.

[0055] It is believed that Fe and Mn exist in the coating as metals and other compounds (sulfides, oxides, silicates, etc.). Compared with magnesium olivine, the main component of the substrate coating, these compounds have a relatively large coefficient of thermal expansion, similar to that of iron. Therefore, they are less prone to thermal expansion caused by heating, preventing coating peeling. In addition, Fe and Mn themselves have the effect of reducing the Young's modulus of the coating.

[0056] Next, the inventors investigated the factors that control the Young's modulus and Fe+Mn concentration of the substrate coating. Particular attention was paid to the absorbance of fayalite, pyroxene, and silica, as these react with MgO in the annealing separating agent to form forsterite, which serves as the substrate coating.

[0057] Based on the measured values ​​obtained in this way, the ratio (hereinafter also expressed as the sum of absorbance ratios) of fayalite (A1) and pyroxene (A2) to the total absorbances of fayalite, pyroxene, and silica (A1, A2, and A3) is also marked in Table 1 above. It should be noted that the absorbances of fayalite, pyroxene, and silica on the steel plate surface, measured by FTIR, are designated as A1, A2, and A3, respectively. Furthermore, the method described in Japanese Patent Application Publication No. 2005-69917 is used as the FTIR measurement method and the absorbance measurement method.

[0058] It should be noted that in this invention, the sum of the above absorbance ratios is a value obtained using the following Equation 1.

[0059] That is, the absorbance ratio of fayalite is [A1 / (A1+A2+A3)]×100, and the absorbance ratio of pyroxene is [A2 / (A1+A2+A3)]×100. Furthermore, the sum of the absorbance ratios of fayalite and pyroxene is shown below.

[0060] The sum of absorbance ratios = [A1 / (A1+A2+A3)]×100 + [A2 / (A1+A2+A3)]×100

[0061] ={(A1+A2) / (A1+A2+A3)}×100… Formula 1

[0062] In addition, Table 1 also indicates the gas flow rate per surface area of ​​the coiled steel for the atmospheric gas supplied to the fine annealing furnace within the temperature range of 950 to 1100°C during the fine annealing described above.

[0063] As shown in Table 1, the higher the sum of the absorbance ratios of fir olivine and pyroxene, the greater the Fe+Mn concentration in the substrate film. In addition, there is a trend that the Fe+Mn concentration can be further increased by adjusting the gas flow rate.

[0064] Furthermore, the Young's modulus of the substrate coating is also significantly affected by the sum of the absorbance ratios of fir olivine and pyroxene, as well as the gas flow rate. This was mitigated by controlling these ratios to be above 45% and the steel plate's unit surface area to be 1.0 × 10⁻⁶. －5 ~7.6×10 －5 The range of NL / min allows for an increase in the Fe+Mn concentration of the substrate coating, thereby controlling the Young's modulus within the range of 108–144 GPa.

[0065] Here, the inventors consider the reasons for obtaining the above results as follows.

[0066] Fir olivine and pyroxene are shown as Fe₂SiO₄ and FeSiO₃, respectively, but in fact, in steel plates containing Mn, Fe and Mn substitute for each other, becoming (Fe₂SiO₄ and FeSiO₃). x ,Mn 1－x )2SiO4、(Fe x ,Mn 1－x SiO3 exists in this form. During fine annealing, they further dissolve with Mg to form...

[0067] (Fe x ,Mn 1－x )2SiO4+MgO→(Fe y ,Mn z Mg 1―y－z )2SiO4+(Fe x－y ,Mn 1―x－z Mg y+z )O

[0068] (Fe x ,Mn 1－x SiO3 + MgO → (Fe y ,Mn z Mg 1―y－z SiO3+(Fe x－y ,Mn 1―x－z Mg y+z )O

[0069] In this form, Mg is infiltrated into the compound, and Fe and Mn are released from the oxide, ultimately remaining as Fe and Mn compounds in the substrate coating. That is, by ensuring that the amount of fir olivine and pyroxene is sufficient, the amount of Fe+Mn in the substrate coating can be ensured.

[0070] Furthermore, regarding the atmosphere conditions during fine annealing, the temperature range of 950–1100°C within the fine annealing temperature zone is extremely important for film formation. This is because the magnesium olivine formation reaction truly begins within this temperature range. Additionally, the introduction of H2 into the atmosphere is crucial within this temperature range. This promotes the bulk diffusion of MgO, or the movement of silica from the internal oxide film to the steel surface, thereby facilitating film formation. It should be noted that the concentration of the introduced H2 is not particularly limited, but is preferably in the range of approximately 5 vol% or higher. Furthermore, the upper limit can be 100 vol%.

[0071] Here, with a higher gas flow rate, the diffusion tendency of MgO caused by H2 in the atmosphere becomes stronger. This means that the aforementioned substitution reaction between Mg and Mn / Fe is also promoted. As a result, Mn and Fe trapped in the coating diffuse into MgO. That is, the amount of Fe and Mn in the coating decreases. On the other hand, if the gas flow rate is moderately reduced, it is possible to simultaneously allow the surface movement of silica from internal oxidation caused by H2 to proceed while suppressing the diffusion of Mn and Fe into MgO, effectively retaining Mn and Fe in the coating.

[0072] It should be noted that if the gas flow rate is high, the forsterite-forming ability becomes excessively high. This results in coarser grains in the resulting forsterite coating, or a decrease in porosity, thereby increasing Young's modulus. From this perspective, the gas flow rate needs to be moderately reduced. On the other hand, if the gas flow rate is reduced excessively, the effect of adding gas itself diminishes. This results in poor coating formation, deterioration of the coating morphology, and a degree to which the coating peels off even without domain refinement.

[0073] In this invention, controlling the gas flow rate per unit surface area of ​​the steel plate is crucial. Typically, the fine annealing of oriented electromagnetic steel sheets is performed in a batch annealing furnace in the form of coiled steel. The gas flow rate is set to suit the number of gas replacement cycles based on the internal volume of the furnace hood. For example, if the furnace internal volume is 10 m³... 3 In this case, the gas flow rate is typically 1.5 to 6 NL / min. However, in this invention, the optimal flow rate varies depending on the oxides on the steel plate surface and the amount of MgO applied. Therefore, as described later, it needs to be set to a range approximately 10 to 60% lower than the gas flow rate calculated from the furnace volume.

[0074] Next, the preferred composition of the steel billet (slab) for the oriented electromagnetic steel sheet to which the present invention is applied will be described. It should be noted that the remainder of the composition described below consists of Fe and unavoidable impurities.

[0075] C: 0.020~0.080% by mass

[0076] When the carbon content is less than 0.020% by mass, the grain boundary strengthening effect provided by carbon is lost, potentially leading to defects that hinder manufacturing, such as cracking of the slab. On the other hand, if it exceeds 0.080% by mass, it may be difficult to reduce it to below 0.005% by mass without magnetic aging through decarburization annealing. Therefore, carbon is preferably set in the range of 0.020 to 0.080% by mass. More preferably, the lower limit is 0.025% by mass and the upper limit is 0.075% by mass.

[0077] Si: 2.50–4.50% by mass

[0078] Si is an element needed to increase the relative resistance of steel and reduce iron loss. This effect cannot be sufficiently obtained when the content is less than 2.50% by mass. On the other hand, if it exceeds 4.50% by mass, the workability decreases, and rolling may become difficult. Therefore, Si is preferably set in the range of 2.50 to 4.50% by mass. More preferably, the lower limit is 2.80% by mass and the upper limit is 4.00% by mass.

[0079] Mn: 0.03–0.30% by mass

[0080] Mn is an element required to improve the hot workability of steel. This effect is not sufficiently observed when the concentration is less than 0.03% by mass. On the other hand, if it exceeds 0.30% by mass, the magnetic flux density of the finished plate may decrease. Therefore, the preferred concentration of Mn is in the range of 0.03 to 0.30% by mass. More preferably, the lower limit is 0.04% by mass and the upper limit is 0.20% by mass.

[0081] For components other than C, Si, and Mn, the cases are divided into those that utilize inhibitors to induce secondary recrystallization and those that do not.

[0082] Firstly, when using inhibitors to induce secondary recrystallization, for example, when using AlN-based inhibitors, it is preferable to contain Al and N in the ranges of Al: 0.010–0.040 wt% and N: 0.003–0.012 wt%, respectively. Furthermore, when using MnS·MnSe-based inhibitors, it is preferable to contain the aforementioned amounts of Mn, and one or both of S: 0.002–0.030 wt% and Se: 0.003–0.030 wt%. If the added amount is less than the aforementioned lower limit, the inhibitory effect cannot be sufficiently obtained; on the other hand, if the upper limit is exceeded, the inhibitory component remains undissolved during slab heating, resulting in a decrease in magnetic properties. It should be noted that AlN-based and MnS·MnSe-based inhibitors can be used simultaneously.

[0083] In the absence of inhibitors, it is preferable to inhibit in the range of Al: less than 0.010 wt%, N: less than 0.005 wt%, S: less than 0.005 wt%, and Se: less than 0.005 wt%.

[0084] In addition to the above-mentioned components, to improve magnetic properties, the following components may be appropriately added: Ni: 0.010–1.500 wt%, Cr: 0.01–0.50 wt%, Cu: 0.01–0.50 wt%, P: 0.005–0.200 wt%, Sb: 0.005–0.200 wt%, Sn: 0.005–0.500 wt%, Bi: 0.005–0.050 wt%, Mo: One or more of the following: 0.005–0.100 wt%, B: 0.0002–0.0025 wt%, Te: 0.0005–0.0100 wt%, Nb: 0.001–0.030 wt%, V: 0.001–0.010 wt%, W: 0.002–0.050 wt%, Ti: 0.001–0.050 wt%, and Ta: 0.001–0.050 wt%.

[0085] It should be noted that among these components, Cu is prone to surface cracking when its upper limit is exceeded, while P and Sn are less prone to fracture during rolling when their upper limits are exceeded. Furthermore, Mo and Bi exhibit excessively strong inhibitory forces when their upper limits are exceeded, leading to instability in secondary recrystallization. Nb and Ti, when their upper limits are exceeded, may remain in the steel until they become the final product, worsening iron loss. Moreover, other elements are degraded by the film when their upper limits are exceeded. From these perspectives, the upper limits are preferably limited. On the other hand, the lower limits are specified based on the viewpoint of achieving the desired additive effect.

[0086] Next, the manufacturing method of the oriented electromagnetic steel sheet of the present invention will be described.

[0087] Steel with the above-mentioned composition can be smelted using common refining methods, and then steel billets (slabs) can be manufactured using conventional agglomeration-segmentation rolling or continuous casting methods. Alternatively, thin castings with a thickness of 100 mm or less can be manufactured using direct casting. The aforementioned slabs are heated to approximately 1350°C using common methods, for example, when containing inhibitors; conversely, when not containing inhibitors, they are heated to a temperature below 1300°C before hot rolling. It should be noted that when not containing inhibitors, hot rolling can be performed immediately after casting without post-casting heating. Furthermore, in the case of thin castings, hot rolling can be performed or omitted, proceeding directly to subsequent processes.

[0088] Next, the hot-rolled sheet or thin casting obtained by hot rolling is annealed as needed. The annealing temperature is preferably in the range of 800–1150°C to obtain good magnetic properties. Below 800°C, the residual bonding structure formed during hot rolling makes it difficult to obtain a uniform primary recrystallized structure, hindering the development of secondary recrystallization. On the other hand, if the temperature exceeds 1150°C, the grain size of the annealed hot-rolled sheet becomes too coarse, making it difficult to obtain a uniform primary recrystallized structure.

[0089] A cold-rolled sheet of final thickness is produced by cold rolling a hot-rolled sheet or a thin casting after hot rolling or annealing, either once or twice or more with intermediate annealing. The annealing temperature for the intermediate annealing is preferably in the range of 900–1200°C. Below 900°C, the recrystallized grains become finer after intermediate annealing, leading to a reduction in Goss nuclei of the primary recrystallized structure and a decrease in the magnetic properties of the finished sheet. On the other hand, if the temperature exceeds 1200°C, similar to the annealing of hot-rolled sheets, the grains become too coarse, making it difficult to obtain a uniform primary recrystallized structure.

[0090] In addition, for cold rolling to produce the final plate thickness (final cold rolling), raising the temperature of the steel plate during cold rolling to 100-300°C, or performing one or more aging treatments at a temperature of 100-300°C during cold rolling, is very effective in improving the primary recrystallization aggregate structure and enhancing magnetic properties.

[0091] The cold-rolled sheet with the final thickness is then subjected to decarburization annealing, which also involves a recrystallization annealing. In this invention, for the steel sheet after decarburization annealing, it is important to set the sum of the absorbance ratios (Equation 1 above) of fayalite (Fe2SiO4) and pyroxene (FeSiO3) in the FTIR measurement of the steel sheet surface to be 45% or more.

[0092] The decarburization annealing conditions for this purpose are an annealing temperature of 700–900°C and a holding time of 30–300 seconds. If the annealing temperature is below 700°C or the holding time is less than 30 seconds, decarburization is insufficient, or the primary recrystallization particle size becomes smaller, thus deteriorating the magnetic properties. On the other hand, if the temperature exceeds 900°C and the holding time exceeds 300 seconds, the primary particle size becomes too large, and the magnetic properties still deteriorate.

[0093] Furthermore, the decarburization annealing consists of a heating step to the aforementioned annealing temperature range and a homogenization step to maintain the temperature range after heating for the aforementioned holding time. This homogenization step can be divided into a pre-stage for controlling the thickness of the secondary oxide scale and a post-stage for adjusting the reactivity of the secondary oxide scale and the annealing separating agent; at least the pre-stage is set to a wet hydrogen atmosphere, and the dew point of the atmosphere is set to 45–60°C.

[0094] The reason for setting the dew point of the atmosphere in at least the initial stage of the homogenization process to 45–60°C is that at temperatures lower than 45°C, a sufficient amount of secondary oxide scale cannot be obtained, or even the formation of the substrate film becomes insufficient. Furthermore, if the dew point of the atmosphere is higher than 60°C, the amount of substrate film formed becomes excessive, and the adhesion of the substrate film may deteriorate.

[0095] The H2 concentration of the aforementioned wet hydrogen atmosphere can be maintained within a range of 40% to 80%, as is commonly done. Furthermore, by varying the dew point and H2 concentration within the aforementioned range, and adjusting the oxidizing pH2O / pH2 ratio, the absorbance of A1, A2, and A3 can be adjusted. The pH2O / pH2 ratio is preferably in the range of 0.3 to 0.55.

[0096] Alternatively, a wet hydrogen atmosphere can be used except for the initial stage of the soaking process in the preferred decarburization annealing, and the dew point of the atmosphere is preferably in the range of 45–60°C. Alternatively, the atmosphere can be changed at different stages of the heating and soaking processes. Furthermore, a dry hydrogen atmosphere can be used for the final stage of the soaking process.

[0097] As described above, the homogenization zone can be divided into two sections: a front section and a rear section. Preferably, the homogenization temperature and the oxidizing pH of the annealing atmosphere (pH2O / pH2) are different in both the front and rear sections. This allows for more precise control of the secondary oxide scale.

[0098] Specifically, when changing the homogenization temperature, it is preferable to set the temperature difference between the first and second stages to be 20°C or more. On the other hand, when changing the oxidizing power, the change in the pH2O / pH2 difference should be 0.2 or more. In either case, the amount of change is not particularly limited; generally, regarding temperature, the second stage is hotter than the first stage, and regarding oxidizing power, the second stage often has a lower pH2O / pH2 ratio than the first stage. In this invention, these conditions can be followed.

[0099] Furthermore, the aforementioned front section can be further divided into multiple sections. In this case, the temperature and / or pH2O / pH2 difference between the rear section and the front section can be set to the conditions described above.

[0100] The absorbance ratios A1, A2, and A3 mentioned above may vary due to material composition and pre-decarburizing annealing processes. Therefore, depending on the manufacturing process, the annealing conditions need to be further adjusted within the range of the aforementioned decarburizing annealing conditions.

[0101] For example, if the Si content in the steel billet is low, below 3% by mass, the absorbance ratio tends to decrease, therefore the dew point is set higher. In addition, if the surface cleanliness of the steel plate before decarburization annealing (e.g., oxygen weight per unit area before decarburization annealing) is 0.1 g / m², [further details needed]. 2For conditions described above that are high, setting the dew point to low is also effective. In addition, to improve the absorbance ratio, the dew point of the decarburization annealing heating process can be set to high, and the dew point of the soaking process can be set to low.

[0102] These treatments are not particularly limited. If the absorbance ratio can be controlled within the range desired by the present invention, any of the above-described decarburization annealing conditions may be used.

[0103] Next, after decarburization annealing, an annealing separating agent is applied and fine annealing is performed. In this fine annealing, an H2-containing atmosphere is obtained at a temperature range of at least 950°C to 1100°C, and the gas flow rate in this temperature range is set to 1.0 × 10⁻⁶ per surface area of ​​the steel plate. －5 ~7.6×10 －5 The range of NL / min, as described above, is an important aspect of this invention. It should be noted that this temperature range refers to the temperature range at which Fe and Mn are thickened in the film through the displacement reaction between the MgO of the annealing separating agent and the (Fe,Mn)2SiO4 on the steel plate surface.

[0104] Typically, the gas flow rate for fine annealing can be determined based on the furnace volume. However, in this invention, as mentioned above, it is important to set the gas flow rate range based on the surface area of ​​the steel plate. This is because the gas flow rate becomes excessive within the furnace volume, i.e., the gas flow rate is less than 1.0 × 10⁻⁶. －5 At NL / min, the effect of gas introduction itself decreases, leading to poor membrane formation. On the other hand, if the gas flow rate exceeds 7.6 × 10⁻⁶... －5 If NL / min, Fe and Mn will move into MgO, thus the peel resistance of the film in the magnetic domain subdivision process will still deteriorate.

[0105] It should be noted that the H2 concentration in the atmosphere within the above temperature range can be low, but is ideally 0.1 vol% or higher, and more preferably 0.5 vol% or higher. The upper limit can be 100 vol%. It should also be noted that, in the case of less than 100 vol%, N2, Ar, etc., can be primarily used as the gas for balancing the atmosphere.

[0106] After fine annealing, the steel sheet coils undergo water washing, brushing, pickling, etc., to remove unreacted annealing agents adhering to the surface of the steel sheet. Then, a coating liquid is applied, and after drying, sintering is carried out for planarization annealing to produce steel sheets for magnetic domain subdivision treatment.

[0107] The resulting steel plate has a Young's modulus of 108–144 GPa and a Mn+Fe concentration of 0.05–5.0% by mass in the substrate coating.

[0108] It should be noted that when the Young's modulus of the substrate coating is less than 108 GPa, the coating adhesion itself deteriorates. On the other hand, when the Young's modulus of the substrate coating exceeds 144 GPa, the coating is damaged through magnetic domain subdivision.

[0109] When the Mn+Fe concentration in the substrate coating is less than 0.05% by mass, these elements cannot absorb the thermal stress generated by magnetic domain subdivision, leading to coating damage. On the other hand, there is no particular upper limit to the Mn+Fe concentration, but considering factors such as productivity, around 5.0% by mass is preferred.

[0110] Here, the analytical methods for analyzing the concentrations of Mn and Fe in the substrate coating can be any of the analytical methods commonly used for analyzing the concentrations of Mn and Fe in steel plates, such as EPMA, Auger electron spectroscopy, and SIMS.

[0111] As a method for magnetic domain subdivision processing, a commonly implemented method can be used to introduce thermal deformation or impact deformation into the final product board in a linear or point-like manner using laser irradiation, electron beam irradiation, plasma jet, or other methods.

[0112] The oriented electromagnetic steel sheet manufactured in this way has high coating adhesion, which not only provides excellent corrosion resistance and insulation, but also prevents coating peeling even when the irradiation energy for magnetic domain subdivision is sufficiently increased. Therefore, by increasing the irradiation energy to the ideal intensity, the iron loss can also be improved.

[0113] Furthermore, in the manufacturing method based on the present invention, items not described in this specification can be handled using common methods.

[0114] It should be noted that the composition of the orientation-oriented electromagnetic steel sheet based on the present invention is the composition of the steel sheet obtained by applying the above-described manufacturing method to steel having the above-described composition.

[0115] Specifically, it contains C: less than 0.005% by mass, Si: 2.5 to 4.5% by mass, Mn: 0.03 to 0.30% by mass, Al: less than 0.010% by mass, N: less than 0.005% by mass, S: less than 0.005% by mass, Se: less than 0.005% by mass, with the remainder being Fe and unavoidable impurities.

[0116] Additionally, it may further comprise an amount selected from Ni: 0.010–1.500 wt%, Cr: 0.01–0.50 wt%, Cu: 0.01–0.50 wt%, P: 0.005–0.200 wt%, Sb: 0.005–0.200 wt%, Sn: 0.005–0.500 wt%, Bi: 0.005–0.050 wt%, and Mo: 0.005–0. One or more of the following: 100% by mass, B: 0.0002–0.0025% by mass, Te: 0.0005–0.0100% by mass, Nb: 0.001–0.030% by mass, V: 0.001–0.010% by mass, W: 0.002–0.050% by mass, Ti: 0.001–0.050% by mass, and Ta: 0.001–0.050% by mass.

[0117] Example

[0118] [Example 1]

[0119] A steel billet containing C: 0.070 wt%, Si: 3.43 wt%, Mn: 0.08 wt%, Al: 0.005 wt%, N: 0.004 wt%, S: 0.002 wt%, and Sb: 0.02 wt%, with the remainder consisting of Fe and unavoidable impurities, was manufactured using continuous casting. After being heated to 1250°C, it was hot-rolled to produce a hot-rolled plate with a thickness of 2.4 mm. After annealing the hot-rolled plate at 1000°C for 50 seconds, it was cold-rolled once to produce an intermediate plate thickness of 1.8 mm. After intermediate annealing at 1100°C for 20 seconds, it was cold-rolled a second time to finish it into a cold-rolled plate with a final thickness of 0.27 mm. The cold-rolled plate was then decarburized and annealed. Decarburization annealing was carried out in a humid atmosphere of 50 vol% H2-50 vol% N2 and a dew point of 57 °C, and held at 840 °C for 100 seconds, thereby adjusting the sum of the absorbance ratios of fir olivine and pyroxene to 60%. Then, an annealing separating agent with magnesium oxide as the main component was coated on the surface of the steel plate and dried.

[0120] For this steel sheet, as a fine annealing process, an atmosphere combining various H2+Ar mixtures with N2 atmospheres up to 950°C and then varying H2+Ar mixtures from 950°C to 1100°C was used. The temperature was further increased from 1100°C to 1170°C in an H2 atmosphere at a rate of 25°C / h, and then maintained at 1170°C in an H2 atmosphere for 10 hours for purification. During the heating process of this fine annealing, the H2 gas flow rate was set at 3.0 × 10⁻⁶ m / s² for the steel sheet surface area. －5 NL / min.

[0121] For finely annealed plates with such a forsterite substrate coating, the Young's modulus of the substrate coating portion was evaluated by nanoindentation, and the concentrations of Mn and Fe in the substrate coating were quantified by Auger electron spectroscopy.

[0122] Then, the finely annealed steel coil is coated with a coating solution, dried, and then subjected to a planarization treatment at 800℃ for 20 seconds to produce a finished sheet. Then, the finished sheet is subjected to a planarization treatment at 90mA / mm... 2 Electron beam irradiation power was used, and the coating was observed under a microscope to determine whether the substrate coating had peeled off. The results of this investigation are shown in Table 2.

[0123] [Table 2]

[0124]

[0125] *H2: 10% up to 1000℃, 0% up to 1000℃.

[0126] *H2: 0% up to 1050℃, H2: 0% up to 1050℃.

[0127] As shown in Table 2, by using the present invention, it is possible to prevent the substrate from being peeled off during electron beam irradiation.

[0128] [Example 2]

[0129] Steel billets with the composition listed in Table 3, the remainder consisting of Fe and unavoidable impurities, were manufactured using continuous casting. After heating to 1380°C, they were hot-rolled to produce a 2.0 mm thick hot-rolled sheet. This hot-rolled sheet was annealed at 1030°C for 10 seconds, then cold-rolled and finished to a final thickness of 0.23 mm. Decarburization annealing was then performed to produce steel sheets. The initial stage of decarburization annealing was conducted at 840°C for 100 seconds in an atmosphere of 50 vol% H2-50 vol% N2, with the dew point adjusted according to the steel grade. The subsequent stage was conducted at 870°C for 10 seconds in 100 vol% H2, with the dew point fixed at 10°C. The sum of the absorbance ratios of fir olivine and pyroxene was adjusted to 45% or higher. Finally, an annealing separating agent, primarily composed of magnesium oxide, was applied to the surface of the steel sheet and dried.

[0130] For this steel sheet, as a fine annealing process, an Ar atmosphere was used up to 950°C, followed by an H2-containing atmosphere with varying H2 concentrations from 950°C to 1100°C. The temperature was then further increased to 1100–1170°C in the H2 atmosphere at a rate of 25°C / h, and finally maintained at 1170°C in the H2 atmosphere for 10 hours for purification. During the heating process of this fine annealing, the H2 gas flow rate at the steel sheet surface was set to 3.0 × 10⁻⁶. -5 NL / min.

[0131] For finely annealed plates with such obtained forsterite substrate coatings, the Young's modulus of the substrate coating portion was evaluated by nanoindentation, and the concentrations of Mn and Fe in the substrate coating were quantified by Auger electron spectroscopy.

[0132] Next, after applying and drying the coating solution to the finely annealed steel coil, a planarization treatment is performed at 800℃ for 20 seconds to produce the finished sheet. Then, the finished sheet is subjected to a 90mA / mm... 2 The electron beam irradiation power was adjusted, and the coating was observed under a microscope to investigate whether the coating had peeled off. The results of this investigation are shown in Table 3.

[0133]

[0134] As shown in Table 3, by using the present invention, it is possible to prevent the coating from peeling off during electron beam irradiation.

Claims

1. A type of oriented electromagnetic steel sheet having a ceramic coating and containing Mn, wherein, The film has a Mn+Fe concentration of ≥0.05% by mass and a Young's modulus of 108~144 GPa. Furthermore, it is manufactured as follows: Oriented electromagnetic steel sheets containing Mn are hot-rolled from steel billets, followed by cold rolling to the final sheet thickness via one or more cold rolling processes with intermediate annealing. After further decarburization annealing that also induces recrystallization, the steel sheet surface is coated with an annealing separating agent containing 50% by mass or more MgO and then fine annealed. If necessary, unreacted separating agent is removed after fine annealing, followed by planarization annealing. Specifically, by adjusting the decarburization annealing conditions to an annealing temperature of 700~900℃, a soaking time of 30~300 seconds, and a dew point of the wet hydrogen atmosphere in at least the initial stage of the soaking process of 45~60℃, the absorbance of the steel plate surface after decarburization annealing, measured by Fourier transform infrared spectroscopy (FTIR), of fir olivine, pyroxene, and silica is set to A1, A2, and A3, respectively, such that {(A1+A2) / (A1+A2+A3)}×100 is 45% or higher. Furthermore, in the fine annealing, the temperature range from at least 950°C to 1100°C is set to an H2-containing atmosphere, and the gas flow rate within the temperature range is set per 1m² of the steel plate surface area. 2 1.0×10 －5 ~7.6×10 －5 NL / min range.

2. A method for manufacturing an orientation-oriented electromagnetic steel sheet, comprising the method for manufacturing the orientation-oriented electromagnetic steel sheet of claim 1, wherein the orientation-oriented electromagnetic steel sheet containing Mn is hot-rolled from steel billet, followed by cold rolling to the final sheet thickness in one or more cold rolling processes with intermediate annealing, and then subjected to decarburization annealing that also involves recrystallization, the surface of the steel sheet is coated with an annealing separating agent containing 50% by mass or more of MgO and fine annealed, and, if necessary, the unreacted separating agent after fine annealing is removed and then planarization annealing is performed. in, By adjusting the decarburization annealing conditions to an annealing temperature of 700-900℃, a soaking time of 30-300 seconds, and a dew point of the wet hydrogen atmosphere in at least the initial stage of the soaking process of 45-60℃, the absorbance of fir olivine, pyroxene, and silica on the surface of the decarburized annealed steel plate, measured by Fourier transform infrared spectroscopy (FTIR), is set to A1, A2, and A3, respectively, such that {(A1+A2) / (A1+A2+A3)}×100 is 45% or higher. Furthermore, in the fine annealing, the temperature range from at least 950°C to 1100°C is set to an H2-containing atmosphere, and the gas flow rate within the temperature range is set per 1m² of the steel plate surface area. 2 1.0×10 －5 ~7.6×10 －5 NL / min range.

Images