Grain-oriented electromagnetic steel sheet

Abstract

This invention provides an orientation-oriented electromagnetic steel sheet that can sufficiently suppress the process coefficient when used as a core material for transformers. The orientation-oriented electromagnetic steel sheet of this invention comprises a base steel sheet containing at least 0.0001–0.0050% Ga and a substrate coating, such that the Ti content of the orientation-oriented electromagnetic steel sheet is 0.0050–0.0210%, and Wh... 17 With W 17 / 50 The ratio of R17 to Wh 19 With W 19 / 50 The ratio R17 to R19 satisfies R17 ≤ R19 ≤ 0.70.

Description

Technical Field

[0001] This invention relates to oriented electromagnetic steel sheets suitable for transformer core materials. Background Technology

[0002] Oriented magnetic steel sheets are soft magnetic materials used as core materials for transformers, and have the following crystal structure: the easy magnetization axis of iron... <001> The grain structure exhibits a highly consistent orientation along the rolling direction of the steel sheet. This texture is formed through a phenomenon known as secondary recrystallization, which occurs during the purification annealing process in the manufacturing of oriented electromagnetic steel sheets, resulting in a {110} grain with a Goss orientation. <001> The phenomenon that oriented grains preferentially undergo giant growth.

[0003] Regarding this formation method, a common technique involves recrystallizing Goss-oriented grains a second time during purification annealing using a precipitate known as an inhibitor. For example, the method using AlN described in Patent Document 1 and the method using MnS and MnSe described in Patent Document 2 have been industrially applied.

[0004] Using these inhibitors is a useful method to stabilize the development of secondary recrystallized grains, but in order to make the inhibitors finely dispersed in the steel, the slab needs to be heated at a high temperature above 1300°C to dissolve the inhibitor components in one step.

[0005] On the other hand, for example, Patent Document 3 discloses a technique for developing Goss-oriented grains through secondary recrystallization in a billet without inhibitor components. This technique involves maximally eliminating impurities such as inhibitor components, allowing the grain boundary energy of the grain boundaries during primary recrystallization to exhibit a grain boundary orientation difference angle dependence, thus enabling secondary recrystallization of Goss-oriented grains even without inhibitors. This effect is referred to as the texture suppression effect. In this method, it is not necessary to finely disperse the inhibitor in the steel, and therefore, the high-temperature slab heating required when using inhibitors is also eliminated. Thus, this method offers significant advantages in terms of both cost and maintenance.

[0006] Oriented magnetic steel sheets are mainly used as transformer cores, requiring excellent magnetization characteristics, especially low iron loss. Therefore, it is important to ensure that the secondary recrystallized grains in the steel sheet are highly consistent with the Goss orientation and to reduce impurities in the finished sheet. Furthermore, techniques have been developed to reduce iron loss by physically introducing non-uniformity into the surface of the steel sheet and refining the width of magnetic domains. For example, Patent Document 4 proposes a technique that reduces iron loss by irradiating the final product sheet with a laser to introduce a high dislocation density region into the surface of the steel sheet, thereby narrowing the magnetic domain width. Additionally, Patent Document 5 proposes a technique for controlling the magnetic domain width by irradiating with an electron beam.

[0007] It should be noted that by achieving a high degree of consistency between the orientation of the secondary recrystallization and the Goss orientation, and by reducing impurities, hysteresis loss is reduced. In contrast, if magnetic domain refinement technology is applied, eddy current loss is primarily reduced.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Publication No. 40-15644

[0011] Patent Document 2: Japanese Patent Publication No. 51-13469

[0012] Patent Document 3: Japanese Patent Application Publication No. 2000-129356

[0013] Patent Document 4: Japanese Patent Publication No. 57-2252

[0014] Patent Document 5: Japanese Patent Publication No. 6-72266

[0015] Patent Document 6: Japanese Patent Application Publication No. 2008-196016 Summary of the Invention

[0016] As mentioned above, oriented electromagnetic steel sheets are mainly used as transformer cores. Generally, there is a deviation between the iron loss value of the transformer core and the iron loss value of the oriented electromagnetic steel sheet used as the raw material, with the transformer core having a larger iron loss. The ratio of the iron losses of these two is called the building factor.

[0017] That is, even if the iron loss of the billet is good, if the process coefficient is high, the iron loss of the transformer core will increase, resulting in the problem of not being able to perform sufficiently.

[0018] In the era of carbon neutrality, what should be reduced is the iron loss of the transformer, the final product. No matter how low the iron loss of the raw material is, it is meaningless if the process coefficient is high. The process coefficient affects not only the transformer design but also the characteristics of the raw material; therefore, it is necessary to reduce both the iron loss of the raw material and the characteristics of the process coefficient.

[0019] Therefore, the object of the present invention is to provide an orientation-oriented electromagnetic steel sheet that can sufficiently suppress the process coefficient when used as a core material for transformers.

[0020] The inventors conducted repeated and in-depth research, and found that when forming a substrate film with magnesium olivine as the main component on a base steel plate, they focused on the amount of Ga in the base steel plate and the amount of Ti in the overall oriented electromagnetic steel plate with the substrate film. They then discovered that, in particular, by controlling these Ga and Ti amounts within a specified range and satisfying the specified formula (1), an oriented electromagnetic steel plate with a low process coefficient can be obtained.

[0021] The following describes the experiments that successfully implemented this invention. The numerical ranges indicated by “~” in this specification refer to the ranges containing the values ​​before and after the “~” as the lower and upper limits, respectively.

[0022] <Experiment 1>

[0023] To primarily modify the Ga content in the base steel plate, a billet containing, by mass percent, 0.0500–0.0810% C, 3.15–3.31% Si, 0.07–0.10% Mn, 0.0200–0.0250% Al, 0.0069–0.0085% N, 0.0011–0.0031% Sb, 0.025–0.036% Ti, 0.0080–0.0090% Ga, and 0.0000–0.0058% Sb, with the remainder consisting of Fe and unavoidable impurities, was manufactured by continuous casting. This billet was then subjected to slab heating at 1400°C for 20 minutes and hot-rolled to a thickness of 2.4 mm. The hot-rolled plate was then annealed at 1000°C for 30 seconds in a N2 atmosphere. Next, the annealed hot-rolled sheet is cold-rolled to a thickness of 1.5 mm, and then further annealed at 1000°C for 100 seconds in a 25% H2-75% N2 atmosphere. Then, the annealed intermediate cold-rolled sheet is cold-rolled to a thickness of 0.23 mm. This cold-rolled sheet is then decarburized annealed at 850°C for 150 seconds in a humid atmosphere of 50% H2-50% N2 and a dew point of 50°C. Subsequently, the surface (both sides) of the resulting decarburized annealed sheet is coated with an annealing separating agent mainly composed of MgO, and then purified annealed at 1200°C for 10 hours to form a substrate film mainly composed of magnesium olivine. At this point, the heating rate up to 1200°C is 20°C / h. Furthermore, during the heating process, the atmosphere is N2 from room temperature to 700°C, various atmospheres are obtained by changing the mixing ratio of N2 and H2 from above 700°C to 1100°C, and H2 from above 1100°C to 1200°C. In addition, the atmosphere is H2 during the holding period and Ar during the cooling period.

[0024] The resulting orientation-oriented electromagnetic steel sheet, with a base coating (magnesium olivine coating) formed primarily of magnesium olivine on the surface of the base steel sheet, was used as a sample. Then, the iron loss W of these samples was measured using the method described in JIS C2550-1. 17 / 50 and W 19 / 50 (Iron loss at 50Hz when excited to 1.7T and 1.9T respectively) and hysteresis loss Wh 17 and Wh 19 (Hysteresis loss when excited to 1.7T and 1.9T respectively).

[0025] In addition, to determine the Ga content of the base steel plate, a portion of the obtained sample was immersed in a 10% hydrochloric acid aqueous solution at 80°C for 180 seconds to remove the magnesium olivine coating, and then the sample was determined by the method described in the general rules of high-frequency plasma mass spectrometry in JIS K0133.

[0026] Next, a simulated transformer was fabricated from the obtained sample: a three-phase, three-legged model transformer, 500mm square, with each leg and yoke having a plate width of 100mm. Then, the iron loss (WT) was measured on this model transformer. 17 / 50 (Transformer iron loss when excited to 1.7T at 50Hz). The sample in the model transformer has 50 laminated wafers, with two wafers stacked alternately.

[0027] Based on the results, the process factor F17 of the model transformer was used as the iron loss WT of the model transformer. 17 / 50 Divide by the iron loss W of the sample 17 / 50 The obtained value (WT) 17 / 50 / W 17 / 50 The value of F17 (unitless) was calculated. Then, the relationship between this F17 and the Ga content (unit: mass%) in the base steel sheet was investigated. The results are presented below. Figure 1 .

[0028] Based on the results, no clear correlation was observed between the process factor F17 and the Ga content. However, from... Figure 1 It can be seen that the process coefficient F17 is divided into good values ​​below 1.25 and high values ​​above 1.30.

[0029] Therefore, it was investigated whether the difference in process coefficient F17 could be explained by the relationship between iron loss and hysteresis loss of the samples. The results showed that the hysteresis loss Wh at excitation of 1.7T... 17 With iron loss W 17 / 50 The ratio of Wh 17 / W 17 / 50 Set to R17 (unitless), the hysteresis loss (Wh) under excitation at 1.9T will be calculated. 19 With iron loss W 19 / 50 The ratio of Wh19 / W 19 / 50 When R19 is set as unitless, a general trend is observed in the process coefficient F17 when R17 and R19 are divided into group A, which has the relationship R17≤R19≤0.70, and group B, which is otherwise.

[0030] Figure 2 It is Figure 1 The results were divided into groups A and B and then redrawn. Figure 2 In the diagram, Group A is represented by a white circle, and Group B by a black triangle. Figure 2 The results show that the relationship R17≤R19≤0.70 indicates that the product belongs to Group A and exhibits good process coefficients within the range of 0.0001 to 0.0050% by mass of Ga in the base steel plate.

[0031] <Experiment 2>

[0032] A steel billet containing, by mass percent, 0.0370% C, 3.05% Si, 0.18% Mn, 0.0090% Al, 0.0036% N, 0.0070% Se, 0.062% Sn, and 0.0030% Ga, with the remainder consisting of Fe and unavoidable impurities, was manufactured and used. This billet was then subjected to slab heating at 1300°C for 30 minutes and hot-rolled to a thickness of 2.2 mm. The hot-rolled sheet was then annealed at 1100°C for 30 seconds in a N2 atmosphere. Next, the annealed hot-rolled sheet was cold-rolled to a thickness of 0.23 mm. The cold-rolled sheet was then subjected to decarburization annealing at 840°C for 120 seconds in a humid atmosphere of 40% H2-60% N2 and a dew point of 40°C. Furthermore, the surface of the obtained decarburized annealed plate is coated with an annealing separating agent obtained by mixing TiO2 and MgO in various ways within the range of 0-15 parts by mass. The mixture is then subjected to purification annealing at 1220°C for 5 hours to form a substrate film mainly composed of magnesium olivine. During this process, the heating rate up to 1220°C is 15°C / h. Furthermore, during the heating process, an N2 atmosphere is used from room temperature to 700°C, an atmosphere obtained by varying the mixing ratio of N2 and H2 from above 700°C to 1100°C, and an H2 atmosphere from above 1100°C to 1200°C. Additionally, an H2 atmosphere is used during holding, and an Ar atmosphere is used during cooling.

[0033] It should be noted that by changing the mixing ratio of N2 and H2 in the atmosphere in the temperature range of over 700°C to 1100°C, the Ti content in the whole of the oriented electromagnetic steel sheet with the base coating, i.e., the steel sheet composed of the base steel sheet and the base coating, was controlled.

[0034] The oriented electromagnetic steel sheet with a magnesium olivine coating formed on the surface of the base steel sheet obtained in this way was used as a sample. Then, for these samples, the iron loss W was measured by the method described in JIS C2550-1. 17 / 50 and W 19 / 50 (Iron loss at 50Hz when excited to 1.7T and 1.9T respectively) and hysteresis loss Wh 17 and Wh 19 (Hysteresis loss when excited to 1.7T and 1.9T respectively).

[0035] In addition, the Ti content of oriented electromagnetic steel sheets having a substrate coating mainly composed of forsterite was determined by the method described in JIS G1223.

[0036] Furthermore, to determine the Ga content of the base steel plate, a portion of the obtained sample was immersed in a 10% hydrochloric acid aqueous solution at 80°C for 180 seconds to remove the forsterite coating, and then measured using the same method as in Experiment 1. The result showed that the Ga content was 0.0030% by mass, the same as that in the steel billet.

[0037] Based on the obtained magnetic properties, similar to Experiment 1, the hysteresis loss Wh under excitation at 1.7T is... 17 With iron loss W 17 / 50 The ratio of R17 to the hysteresis loss Wh under excitation at 1.9T. 19 With iron loss W 19 / 50 The ratio R19 was divided into group A, which had a relationship of R17 ≤ R19 ≤ 0.70, and group B, which had no other relationships. Then, for samples belonging to these groups A and B, the results corresponding to the Ti content (in mass%) in the oriented electromagnetic steel sheet with a substrate film mainly composed of magnesium olivine formed on the surface of the base steel sheet are shown in the figure. Figure 3 .

[0038] Depend on Figure 3 The results show that when the Ti content in the aforementioned oriented electromagnetic steel sheet is between 0.0050% and 0.0210% by mass, it tends to belong to Group A. The reason for belonging to Group A when the Ti content is within this range is believed to be that the nitriding of the steel sheet during purification annealing is suppressed, thus reducing hysteresis loss. Cases that do not belong to Group A are those with too much or too little Ti. With too much Ti, it is believed that hysteresis loss increases due to domain wall pinning. Conversely, with too little Ti, it is believed that hysteresis loss increases due to the formation of nitrides in the steel sheet during purification annealing.

[0039] Then, a three-phase, three-legged model transformer with the same shape as in Experiment 1 was constructed: 500mm square with each leg and yoke having a plate width of 100mm. Then, the iron loss WT measured on this model transformer was... 17 / 50Calculate the process coefficient F17 (WT) 17 / 50 / W 17 / 50 (Units not specified). The relationship between the calculated process coefficient and the Ti content in the oriented electromagnetic steel sheet is shown in... Figure 4 .

[0040] Depend on Figure 4 The results show that the process coefficient is high when the Ti content in the oriented electromagnetic steel sheet is less than 0.0050 wt% and more than 0.0210 wt%. In other words, it was found that the process coefficient is low and good when the Ti content in the oriented electromagnetic steel sheet with a base film mainly composed of forsterite formed on the surface of the base steel sheet is 0.0050 to 0.0210 wt%. Although this is an inference, it is believed that the film properties are improved by the presence of a certain amount of Ti in the forsterite film. For example, if the film tension of the base film is increased due to the presence of Ti, magnetostrictive vibration can be suppressed, thus suppressing the magnetostrictive vibration that increases due to the addition of Ga. As a result, the vibration of the steel sheet caused by magnetostriction is suppressed, and the transmission of magnetic flux at the transformer joint becomes smoother, thus it is believed that the process coefficient can be reduced.

[0041] As described above, the mechanism by which the process coefficient of the model transformer is good by controlling the Ga content of the base steel plate and the Ti content of the orientation electromagnetic steel plate on which a base film with magnesium olivine as the main component is formed on the surface of the base steel plate is not yet clear, but the inventors have considered the following.

[0042] Because the yoke and legs of a transformer have a certain width, the magnetic circuit, like a track in an athletics competition, has different distances on the inner and outer sides. Therefore, during excitation, there is a tendency for the magnetic flux to shift towards the inner side, where the magnetic circuit is shorter. Even when the entire steel plate is excited to 1.7T, the magnetic flux density on the inner side exceeds that of the steel plate. Therefore, it is inferred that the higher the magnetic field characteristics, the better the transformer characteristics, as represented by the process coefficient.

[0043] In secondary recrystallization, Ga functions as an inhibitor of normal grain growth, suppressing grains deviating from the Goss orientation. However, Ga is not completely removed during purification, remaining in the steel in a finely dispersed state. It is speculated that this appropriate amount of finely dispersed Ga does not impair iron loss but serves as a starting point for rotating magnetic flux, thus optimizing the process coefficient.

[0044] On the other hand, the process coefficient deteriorates when excessive Ga is added. It is believed that the increased magnetostriction due to excessive Ga addition means that Ti's effect on magnetostriction is greater than its effect on improving the film properties. As a result, when assembled into a transformer, vibration of the steel plate occurs due to magnetostriction, hindering the smooth transmission of magnetic flux, thus increasing the process coefficient.

[0045] Furthermore, Patent Document 6 discloses a manufacturing technique for Ga-containing oriented electromagnetic steel sheets. However, this document mentions a manufacturing method that exhibits high magnetic flux density along the entire length of the electromagnetic steel sheet. Therefore, this is a completely different technique from the present invention, which uses a technique of including Ti in oriented electromagnetic steel sheets with a magnesium olivine coating to reduce the process coefficient.

[0046] This invention is based on the above insights. That is, the main structure of this invention is as follows.

[0047] [1] A grain-oriented electromagnetic steel sheet comprising a base steel sheet and a substrate coating, wherein the base steel sheet comprises Si: 1.50–8.00 wt%, Mn: 0.02–1.00 wt%, and Ga: 0.0001–0.0050 wt%, with the remainder being Fe and unavoidable impurities; the substrate coating is formed on the surface of the base steel sheet and is mainly composed of magnesium olivine; the Ti content in the above-mentioned grain-oriented electromagnetic steel sheet is 0.0050–0.0210 wt%, and the hysteresis loss Wh under excitation at 1.7T is [not specified]. 17 With iron loss W 17 / 50 The ratio of Wh 17 / W 17 / 50 Assuming R17, the hysteresis loss Wh during excitation at 1.9T will be calculated. 19 With iron loss W 19 / 50 The ratio of Wh 19 / W 19 / 50 When R19 is set, the following equation (1) is satisfied.

[0048] R17≤R19≤0.70 (1)

[0049] [2] According to the orientation electromagnetic steel sheet described in [1] above, the Ti content of the base steel sheet is less than 0.0030% by mass.

[0050] [3] The oriented electromagnetic steel sheet according to [1] or [2] above, wherein the surface of the substrate film has an insulating film.

[0051] [4] The orientation-oriented electromagnetic steel sheet according to any one of [1] to [3] above, wherein the base steel sheet further contains an amount selected from Sn: 0.005 to 0.500 wt%, Cr: 0.005 to 0.500 wt%, Cu: 0.01 to 0.50 wt%, Ni: 0.01 to 0.50 wt%, Bi: 0.005 to 0.500 wt%, P: 0.005 to 0.500 wt%, Sb: 0.005 to 0.500 wt%, and Mo: 0.005 to 0.500 wt%. One or more of the following: 0% by mass, B: 0.1–25.0 ppm by mass, Nb: 0.001–0.020% by mass, V: 0.001–0.020% by mass, As: 0.0010–0.0200% by mass, Zn: 0.001–0.020% by mass, Pb: 0.0001–0.0100% by mass, Co: 0.002–0.050% by mass, W: 0.0010–0.0100% by mass, and Ge: 0.0001–0.0050% by mass.

[0052] According to the present invention, by appropriately controlling the amount of Ga in the base steel sheet and the amount of Ti in the oriented electromagnetic steel sheet having a substrate coating on the surface of the base steel sheet, and satisfying a specified loss relationship, an oriented electromagnetic steel sheet capable of reducing the process coefficient can be obtained. Attached Figure Description

[0053] Figure 1 This is a coordinate graph showing the relationship between the Ga content in the base steel plate and the process coefficient.

[0054] Figure 2 It is a coordinate graph showing the relationship between the Ga content in the base steel plate and groups A and B, as well as their relationship with the process coefficient.

[0055] Figure 3 This is a coordinate graph representing the Ti content in the oriented electromagnetic steel sheets of groups A and B.

[0056] Figure 4 This is a coordinate graph showing the relationship between the Ti content in oriented electromagnetic steel sheets and the process coefficient. Detailed Implementation

[0057] <Oriented Electromagnetic Steel Sheet>

[0058] The oriented electromagnetic steel sheet of the present invention comprises: a base steel sheet containing a specified amount of a specified element including Ga, and a base coating formed on one or both surfaces of the base steel sheet, the base coating being primarily composed of magnesium olivine. Furthermore, the oriented electromagnetic steel sheet of the present invention contains a specified amount of Ti. Moreover, the oriented electromagnetic steel sheet of the present invention satisfies the specified formula (1) regarding losses. Because the oriented electromagnetic steel sheet of the present invention possesses these characteristics, it can achieve a good process coefficient when used as a core material for transformers.

[0059] The oriented electromagnetic steel sheet of the present invention can be obtained, for example, according to the manufacturing method described later.

[0060] [Composition of the base steel plate]

[0061] Next, the reasons for limiting the constituent elements of the present invention will be explained. First, the amounts of each element in the composition will be explained. It should be noted that, unless otherwise stated, the designations “%” and “ppm” for the composition hereafter refer to “mass %” and “mass ppm”.

[0062] Si: 1.50–8.00%

[0063] Si is an element required to increase the resistivity of steel and improve iron loss, but if the content is less than 1.50%, it has no effect. On the other hand, if the Si content exceeds 8.00%, the workability of the steel deteriorates, and rolling becomes difficult. Therefore, the Si content in the base steel sheet is limited to the range of 1.50% to 8.00%. Preferably, the Si content is 2.50% or more. On the other hand, it is preferable that the Si content is 4.50% or less.

[0064] Mn: 0.02~1.00%

[0065] Mn is an element required to improve hot workability, but if it is less than 0.02%, there is no effect. On the other hand, if the Mn content exceeds 1.00%, the magnetic flux density of the oriented electromagnetic steel sheet used as the product plate decreases. Therefore, the Mn content in the base steel sheet is in the range of 0.02% to 1.00%. Preferably, the Mn content is 0.04% or more. On the other hand, it is preferable that the Mn content is 0.20% or less.

[0066] Ga: 0.0001~0.0050%

[0067] For the reasons mentioned above, Ga needs to be present in the base steel sheet in the range of 0.0001% to 0.0050%. The Ga content is preferably 0.0005% or more, more preferably 0.0010% or more. On the other hand, the Ga content is preferably 0.0040% or less, more preferably 0.0030% or less. A Ga content of 0.0001% or more is an amount exceeding the content of unavoidable impurities that may be mixed into the base steel sheet in general.

[0068] The orientation-oriented electromagnetic steel sheet of the present invention has a base steel sheet whose composition includes at least the above-mentioned basic components, with the remainder being Fe and unavoidable impurities.

[0069] In addition to the basic components mentioned above, the base steel plate may also contain any of the elements described below as needed.

[0070] Selected from Sn: 0.005–0.500%, Cr: 0.005–0.500%, Cu: 0.01–0.50%, Ni: 0.01–0.50%, Bi: 0.005–0.500%, P: 0.005–0.500%, Sb: 0.005–0.500%, Mo: 0.005–0.500%, B: 0.1–25 One or more of the following elements are permitted: 0.0 ppm, Nb: 0.001–0.020%, V: 0.001–0.020%, As: 0.0010–0.0200%, Zn: 0.001–0.020%, Pb: 0.0001–0.0100%, W: 0.0010–0.0100%, and Ge: 0.0001–0.0050%. These arbitrary elements can be added to further improve the magnetic properties of the oriented electromagnetic steel sheet. When the amount added is less than the lower limit, there is no improvement in magnetic properties. Furthermore, when the amount added exceeds the upper limit, the development of secondary recrystallized grains is suppressed, and the magnetic properties deteriorate.

[0071] Co: 0.002~0.050%

[0072] In addition to the elements that can be appropriately contained as described above, or in addition to the elements that can be appropriately contained as described above, if the Co content in the base steel plate is in the range of 0.002% to 0.050%, the process coefficient of the model transformer is further improved. Therefore, it is preferable to further add Co within this range. The mechanism of such improved process coefficient is not yet clear, but if Co is dissolved in iron, it is expected that the saturation magnetic flux density of iron will increase, and the high magnetic field characteristics will be improved. Therefore, it is speculated that the process coefficient of the model transformer can be further optimized. The Co content in the base steel plate is preferably 0.002% or more, more preferably 0.006% or more, and even more preferably 0.008% or more. In addition, the Co content in the base steel plate is preferably 0.050% or less, more preferably 0.020% or less, and even more preferably 0.015% or less. The Co content is preferably 0.006% to 0.020%, more preferably 0.008% to 0.015%.

[0073] Ti: below 0.0030%

[0074] The Ti content in the base steel plate is preferably 0.0030% or less, more preferably 0.0010% or less, and can be 0% (not containing Ti). This is because if the Ti content in the base steel plate exceeds 0.0030%, Ti precipitates are easily formed in the steel, which can sometimes significantly deteriorate iron loss.

[0075] The above-mentioned composition refers to the composition of the base steel sheet in which no forsterite film is formed on the surface. When confirming the above-mentioned composition from an orientation-oriented electromagnetic steel sheet formed with a forsterite film on the surface of the base steel sheet, for example, as shown in Experiment 1, the content of each element can be determined after removing the forsterite film from the orientation-oriented electromagnetic steel sheet.

[0076] [Composition of Oriented Electromagnetic Steel Sheet and Substrate Coating]

[0077] For the reasons mentioned above, the Ti content in oriented electromagnetic steel sheets formed by forming a substrate coating with forsterite as the main component on the surface is limited to 0.0050–0.0210%. The Ti content in the oriented electromagnetic steel sheet is preferably 0.0060% or more. The lower limit of 0.0050% for the Ti content in the oriented electromagnetic steel sheet with the substrate coating is because, as mentioned above, it is believed that the presence of a certain amount of Ti in the forsterite coating can improve the coating properties, reduce magnetostriction, and improve eddy current losses, but if it is less than 0.0050%, the effect is poor.

[0078] Furthermore, the Ti content in the oriented electromagnetic steel sheet is 0.0210% or less, preferably 0.0150% or less. Excessive Ti content is not preferred due to increased cost. Additionally, excessive Ti can infiltrate the base steel sheet from the annealing separation material used to form the magnesium olivine coating.

[0079] The Ti content in oriented electromagnetic steel sheets refers to the ratio (mass %) of the total amount of Ti present in the base steel sheet and the substrate coating to the total mass (solid composition conversion) of the base steel sheet and the substrate coating. Regardless of whether the substrate coating is formed on only one side or on both sides of the base steel sheet, the Ti content in oriented electromagnetic steel sheets can be determined according to JIS G1223.

[0080] Based on the above viewpoints, the Ti content in the forsterite coating is preferably 0.0020% or more, more preferably 0.0050% or more, and even more preferably 0.0060% or more. Furthermore, the Ti content in the forsterite coating is preferably 0.0210% or less, more preferably 0.0150% or less.

[0081] Here, when the Ti content in the steel sheet (oriented electromagnetic steel sheet) having a substrate coating is limited to 0.0050 to 0.0210%, as described above, the Ti content in the base steel sheet is preferably 0.0030% or less.

[0082] [Magnetic properties of oriented electromagnetic steel sheets]

[0083] As explained above, the parameters calculated from hysteresis loss and iron loss for the oriented electromagnetic steel sheet used as the product steel plate must meet the specified range. Specifically, the hysteresis loss Wh at excitation of 1.7T must be within the specified range. 17 With iron loss W 17 / 50 The ratio R17 (=Wh) 17 / W 17 / 50 ) and hysteresis loss Wh when excitation is at 1.9T 19 With iron loss W 19 / 50 The ratio of R19 (=Wh) 19 / W 19 / 50 The relationship shown in equation (1) must be satisfied, i.e., R17≤R19≤0.70. If the orientation-oriented electromagnetic steel sheet does not satisfy the above equation (1), it cannot achieve a low process coefficient.

[0084] These values ​​can be determined using the method described in JIS C2550-1. It should be noted that, in order to match the iron loss at 50 Hz, the hysteresis loss can be obtained by multiplying the energy loss of the iron core caused by one rotation of the hysteresis loop by the excitation frequency of 50.

[0085] [Other properties of oriented electromagnetic steel sheets]

[0086] Furthermore, the oriented electromagnetic steel sheet preferably has an insulating film on the surface of the base film. As this insulating film, a film capable of imparting tension to the oriented electromagnetic steel sheet is preferred. In particular, when a transformer core is manufactured by laminating oriented electromagnetic steel sheets, further tension on the steel sheet can further improve iron loss. The insulating film can be well formed, for example, according to the manufacturing method described later.

[0087] [Manufacturing method of oriented electromagnetic steel sheet]

[0088] Next, an example of a method for manufacturing the oriented electromagnetic steel sheet of the present invention will be described. The manufacturing method can utilize general methods for manufacturing electromagnetic steel sheets. For example, slabs can be manufactured from molten steel with the composition specified above using a conventional ingot casting method or continuous casting method. Alternatively, thin castings with a thickness of 100 mm or less can be manufactured from this molten steel using a direct casting method. The molten steel can be manufactured using a blast furnace method or an electric furnace method. Since the aforementioned preferred added components are difficult to add in intermediate processes, it is preferable to add them at the molten steel stage.

[0089] The slab can be heated and hot-rolled using conventional methods. Alternatively, the slab can be hot-rolled immediately after casting without heating. In the case of heating, in composition systems with low inhibitor content, high-temperature heating for dissolving the inhibitor is unnecessary; therefore, heating at a low temperature below 1300°C is effective for cost reduction. The heating temperature of the slab is preferably below 1250°C. Hot rolling conditions can be performed using conventional methods. This yields a hot-rolled plate.

[0090] Next, the obtained hot-rolled sheet can be annealed as needed. The annealing temperature is preferably in the range of approximately 950–1150°C. If the annealing temperature is below 950°C, unrecrystallized portions may remain in the steel. On the other hand, if the annealing temperature exceeds 1150°C, the grain size in the annealed steel may become excessively coarse, thus risking an unsuitable recrystallization texture in subsequent stages. The annealing temperature is preferably 950°C or higher, more preferably 1000°C or higher. Furthermore, the annealing temperature is preferably 1150°C or lower, more preferably 1100°C or lower. This yields a hot-rolled annealed sheet.

[0091] Hot-rolled sheets or annealed sheets after hot rolling can be cold-rolled to obtain a final sheet thickness through a single cold rolling or two or more cold rolling processes with intermediate annealing. The annealing temperature for the intermediate annealing is preferably 900°C or higher, preferably 1200°C or lower, and more preferably in the range of 900 to 1200°C. If the intermediate annealing temperature is less than 900°C, the recrystallized grains tend to become finer after intermediate annealing. This carries the risk of reduced Goss nuclei in the primary recrystallization structure and decreased magnetic properties of the oriented electromagnetic steel sheet used as the product sheet. On the other hand, if the intermediate annealing temperature exceeds 1200°C, similar to hot-rolled sheet annealing, there is a risk of excessive grain coarsening and difficulty in obtaining a primary recrystallization structure with regular grains. This allows for the production of cold-rolled sheets.

[0092] Then, a primary recrystallization annealing, which also serves as decarburization annealing, can be performed on the cold-rolled sheet that becomes the final sheet thickness. When accompanied by decarburization annealing, from the viewpoint of ensuring a rapid decarburization reaction, the annealing temperature in this primary recrystallization annealing is preferably 800°C or higher, preferably 900°C or lower, and more preferably in the range of 800 to 900°C. Furthermore, the atmosphere during the primary recrystallization annealing, which also serves as decarburization annealing, is preferably a humid atmosphere. This yields a primary recrystallization sheet (decarburized annealed sheet).

[0093] Then, an annealing separating agent based on MgO can be applied to one or both sides of the surface of the primary recrystallized plate, followed by secondary recrystallization annealing. The secondary recrystallization annealing can also serve as a purification annealing process for the purified components. This allows the secondary recrystallization structure to develop in the steel and forms a magnesium olivine film on the surface of the steel plate. Thus, an orientation-type electromagnetic steel plate with a substrate film formed on the surface of the base steel plate can be obtained.

[0094] Here, "MgO as the main component" means that the annealing separating agent contains more than 75% by mass of MgO in terms of solid content.

[0095] Here, by adding a Ti compound to the annealing separator and introducing a N2 atmosphere during purification annealing (both during heating and holding), Ti can be effectively present in the forsterite coating. From the viewpoint of containing Ti in the substrate coating and controlling the Ti content in the oriented electromagnetic steel sheet well to 0.0050 to 0.0210% by mass, TiO2 and TiN are preferred as Ti compounds, with TiO2 being more preferred. Furthermore, the content of this compound in the annealing separator is preferably 2 parts by mass or more, and more preferably 15 parts by mass or less, relative to MgO.

[0096] However, the aforementioned requirements for Ti-oriented electromagnetic steel sheets can also be achieved through other methods. For example, if more than 30 ppm of Ti is added to the slab, Ti can be enriched on the surface by annealing under a nitrogen atmosphere during the intermediate annealing process up to the final annealing, and the Ti concentration in the steel sheet can be controlled by descaling.

[0097] Secondary recrystallization annealing is preferably performed at 800°C or above to express secondary recrystallization towards the Goss orientation. Furthermore, from a purification point of view, it is preferable to raise the temperature to 1100°C or above. The longer the holding time, the more thorough the purification; however, if the holding time is too long, shape deterioration due to high-temperature creep may occur. Therefore, the holding time for purification annealing is preferably 3 hours or more, and more preferably 15 hours or less. After secondary recrystallization annealing, to remove the adhering annealing separating agent, it is preferable to perform washing with water, brushing, or acid washing.

[0098] Then, planarization annealing to correct the shape is effective in reducing iron loss. It should be noted that when using laminated oriented electromagnetic steel sheets, applying an insulating coating to the steel sheet surface (more specifically, the substrate coating surface) before or after planarization annealing is effective in improving iron loss. As this insulating coating, a coating capable of imparting tension to the oriented electromagnetic steel sheet is preferred for reducing iron loss. Methods such as tension coating with an adhesive, or forming a coating by depositing inorganic materials onto the steel sheet surface using physical or chemical vapor deposition, offer excellent coating adhesion and easily improve the iron loss reduction effect, and are therefore preferred.

[0099] Example 1

[0100] Steel billet A, containing C: 0.0700%, Si: 3.55%, Mn: 0.07%, Al: 0.0080%, N: 0.0050%, Ga: 0.0040%, Mo: 0.026%, Ti: 0.0250%, with the remainder consisting of Fe and unavoidable impurities, was manufactured by continuous casting. Steel billet A also contained C: 0.0720%, Si: 3.51%, Mn: 0.07%, Al: 0.0080%, N: 0.0047%. Billet A, B, and C contain the following components: A steel billet containing 0.0720% Ca, 0.0010% Ga, 0.025% Mo, 0.025% Ti, with the remainder consisting of Fe and unavoidable impurities; and billet C containing 0.0720% C, 3.49% Si, 0.07% Mn, 0.0090% Al, 0.0051% N, 0.00001% Ca, 0.025% Mo, 0.0240% Ti, with the remainder consisting of Fe and unavoidable impurities. Billets A, B, and C are subjected to slab heating at 1200°C for 40 minutes. They are then hot-rolled into a 2.2 mm thick sheet. The hot-rolled sheet is then annealed at 1000°C for 60 seconds in a N2 atmosphere. Finally, the resulting annealed hot-rolled sheet is cold-rolled into a 0.23 mm thick sheet. Furthermore, the cold-rolled sheet is subjected to a primary recrystallization annealing process that serves as both a decarburization annealing and a humid atmosphere of 850°C for 90 seconds, 60% H2-40% N2, and a dew point of 60°C.

[0101] Next, the two surfaces of the decarburized annealed base steel sheet (first recrystallized sheet) were coated with an annealing separating agent mainly composed of MgO (MgO: 97%). Then, a purification annealing process was performed, holding at 1100°C for 25 hours followed by holding at 1200°C for 10 hours. During the heating process of this heat treatment, the atmosphere was N2 from room temperature to 700°C, various atmospheres with different N2 / H2 mixing ratios were used from above 700°C to 1100°C, and an H2 atmosphere was used from the start of the holding above 1100°C to the end of the holding at 1200°C. Finally, an Ar atmosphere was used during cooling.

[0102] The resulting base steel sheet with a substrate coating on its surface was used as a sample. Then, for this sample, i.e., the orientation electromagnetic steel sheet with a substrate coating mainly composed of magnesium olivine, the Ti content was determined according to the method specified in JIS G1223. The results are recorded in Table 1.

[0103] An insulating film, primarily composed of magnesium phosphate and silicon dioxide, is coated onto the substrate film of the aforementioned oriented electromagnetic steel sheet. For the sample obtained in this manner, the iron loss W is measured according to the method specified in JIS C2550-1. 17 / 50 and W 19 / 50 (Iron loss at 50Hz when excited to 1.7T and 1.9T respectively) and hysteresis loss Wh 17 and Wh 19 (Hysteresis losses at excitation times of 1.7T and 1.9T respectively). Then, calculate the hysteresis loss Wh. 17 With iron loss W 17 / 50 The ratio of Wh 17 / W 17 / 50 That is, R17 and hysteresis loss Wh 19 With iron loss W 19 / 50 The ratio of Wh 19 / W 19 / 50 That is, R19. The results are shown in Table 1.

[0104] Furthermore, to determine the Ga and Ti content of the base steel sheet, a portion of the obtained sample was immersed in a 10% hydrochloric acid aqueous solution at 80°C for 180 seconds to remove the forsterite coating, and then subjected to determination according to the methods specified in JIS K0133 and JIS G1223. The Ti determination results are also recorded in Table 1. It should be noted that the Si, Mn, and Ga content in the base steel sheet is the same as that in each steel billet.

[0105] Next, a simulated transformer was fabricated from a sample with an insulating film: a three-phase, three-legged model transformer, 500 mm square, with each leg and yoke having a plate width of 100 mm. Then, the iron loss (WT) of this model transformer was measured. 17 / 50 (Transformer iron loss when excited to 1.7T at 50Hz). The sample in the model transformer has 50 laminated wafers, with two wafers stacked alternately.

[0106] Based on the results, the process factor F17 of the model transformer was used as the iron loss WT of the model transformer. 17 / 50 Divide by the iron loss W of the sample 17 / 50 The obtained value (WT) 17 / 50 / W 17 / 50 Find the answer. Record the results in Table 1.

[0107]

[0108] As can be seen from Table 1, good iron loss characteristics (process coefficient) can be obtained under the conditions within the scope of this invention.

[0109] Example 2

[0110] Steel billets containing the elements shown in Table 2, with the remainder consisting of Fe and unavoidable impurities, were manufactured by continuous casting. Each billet was homogenized at 1410°C for 20 minutes and then hot-rolled to a thickness of 2.4 mm. The hot-rolled sheet was then annealed at 1100°C for 20 seconds in a N2 atmosphere. Next, the annealed hot-rolled sheet was cold-rolled to a thickness of 1.5 mm, and further annealed at 900°C for 100 seconds in a 25% H2-75% N2 atmosphere. The annealed intermediate cold-rolled sheet was then cold-rolled to a thickness of 0.23 mm. This cold-rolled sheet was then decarburized and annealed at 825°C for 150 seconds in a humid atmosphere with a dew point of 45°C. Then, the surface (both sides) of the obtained decarburized annealed plate is coated with an annealing separating agent mainly composed of MgO (MgO: 88%). Five parts by mass of superhydrated TiO2 relative to the powdered MgO are added to this annealing separating agent. This superhydrated TiO2 is obtained by immersing TiO2 powder in warm water at 50°C and stirring for 24 hours, followed by filtration.

[0111] Then, a purification annealing process was performed at 1200°C for 10 hours to form a substrate film mainly composed of magnesium olivine. The heating rate up to 1200°C was 15°C / h. During the heating process, an N2 atmosphere was used from room temperature to 700°C, various atmospheres with different N2 / H2 mixing ratios were used from above 700°C to 1100°C, and an H2 atmosphere was used from above 1100°C to 1200°C. Additionally, an H2 atmosphere was used during holding, and an Ar atmosphere was used during cooling.

[0112] Furthermore, an insulating film primarily composed of magnesium phosphate and silicon dioxide is applied. It should be noted that in Tables 2, 3, and 4, only sample No. 25 is not coated with an insulating film. Additionally, the No. in Tables 3 and 4 indicates the use of the same No. as in Table 2. Therefore, for example, steel plate No. 4 in Table 3 uses steel billet No. 4 in Table 2, and steel plate No. 31 in Table 4 uses steel billet No. 31 in Table 2.

[0113]

[0114]

[0115] The resulting orientation-oriented electromagnetic steel sheet, with a base film mainly composed of magnesium olivine formed on the surface of the base steel sheet, was used as a sample. Then, for these samples, the iron loss W was measured according to the method specified in JIS C2550-1. 17 / 50 and W 19 / 50 (Iron loss at 50Hz when excited to 1.7T and 1.9T respectively) and hysteresis loss Wh 17 and Wh 19 (Hysteresis losses at excitation times of 1.7T and 1.9T respectively). Then, calculate the hysteresis loss Wh. 17 With iron loss W 17 / 50 The ratio of Wh 17 / W 17 / 50 That is, R17 and hysteresis loss Wh 19 With iron loss W 19 / 50 The ratio of Wh 19 / W 19 / 50 That is, R19.

[0116] The results are shown in Tables 3 and 4.

[0117] Furthermore, for the samples obtained in this way, namely, orientation-oriented electromagnetic steel sheets with a substrate film mainly composed of magnesium olivine on the surface of the base steel sheet, the Ti content was determined according to the method specified in JIS G1223. The determination results are recorded in Tables 3 and 4.

[0118] Furthermore, in order to determine the composition of the base steel plate, a portion of the obtained sample was immersed in a 10% hydrochloric acid aqueous solution at 80°C for 180 seconds to remove the forsterite coating, and then subjected to determination in the same manner as in Example 1.

[0119] These measurement results are recorded together in Tables 3 and 4. It should be noted that the amounts of Si, Mn, Ga, Co, and other elements in the base steel plate are the same as those in each steel billet.

[0120] Next, a simulated transformer was fabricated from a sample with an insulating film: a three-phase, three-legged model transformer, 500 mm square, with each leg and yoke having a plate width of 100 mm. Then, the iron loss (WT) of this model transformer was measured. 17 / 50 (Transformer iron loss when excited to 1.7T at 50Hz). The sample in the model transformer has 50 laminated wafers, with two wafers stacked alternately.

[0121] Based on the results, the process factor F17 of the model transformer was used as the iron loss WT of the model transformer. 17 / 50 Divide by the iron loss W of the sample 17 / 50 The obtained value (WT) 17 / 50 / W 17 / 50 Find the answer.

[0122] Record the results together in Tables 3 and 4.

[0123]

[0124]

[0125] As can be seen from Tables 3 and 4, good iron loss characteristics (process coefficient) can be obtained under the conditions within the scope of this invention.

Claims

1. A grain-oriented electromagnetic steel sheet comprising a base steel sheet and a substrate coating, wherein the base steel sheet has a composition containing 1.50–8.00 wt% Si, 0.02–1.00 wt% Mn, and 0.0001–0.0050 wt% Ga, with the remainder being Fe and unavoidable impurities, and the substrate coating is formed on the surface of the base steel sheet and is primarily composed of magnesium olivine. The Ti content in the oriented electromagnetic steel sheet is 0.0050–0.0210% by mass. Hysteresis loss (Wh) at 1.7T excitation 17 With iron loss W 17 / 50 The ratio of Wh 17 / W 17 / 50 Assuming R17, the hysteresis loss Wh during excitation at 1.9T will be calculated. 19 With iron loss W 19 / 50 The ratio of Wh 19 / W 19 / 50 When R19 is set, the following equation (1) is satisfied. R17≤R19≤0.70 (1)。 2. The oriented electromagnetic steel sheet according to claim 1, wherein, The Ti content of the base steel plate is less than 0.0030% by mass.

3. The oriented electromagnetic steel sheet according to claim 1 or 2, wherein, The substrate has an insulating film on its surface.

4. The oriented electromagnetic steel sheet according to any one of claims 1 to 3, wherein, The base steel plate further contains an amount selected from Sn: 0.005–0.500 wt%, Cr: 0.005–0.500 wt%, Cu: 0.01–0.50 wt%, Ni: 0.01–0.50 wt%, Bi: 0.005–0.500 wt%, P: 0.005–0.500 wt%, Sb: 0.005–0.500 wt%, Mo: 0.005–0.500 wt%, and B: 0.1–25.0 wt%. One or more of the following: ppm, Nb: 0.001–0.020 wt%, V: 0.001–0.020 wt%, As: 0.0010–0.0200 wt%, Zn: 0.001–0.020 wt%, Pb: 0.0001–0.0100 wt%, Co: 0.002–0.050 wt%, W: 0.0010–0.0100 wt%, and Ge: 0.0001–0.0050 wt%.

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