CHAPA DE AÇO LAMINADA A QUENTE PARA UMA CHAPA DE AÇO ELÉTRICO NÃO ORIENTADO
Patent Information
- Authority / Receiving Office
- BR · BR
- Patent Type
- Patents
- Current Assignee / Owner
- NIPPON STEEL CORPORATION
- Filing Date
- 2021-02-19
- Publication Date
- 2026-08-04
Abstract
Description
[001] The present invention relates to a hot-rolled steel sheet for a non-oriented electrical steel sheet with excellent magnetic characteristics that is mainly used as a ferrous core material for electrical equipment. Priority is claimed in Japanese Patent Application No. 2020-027503, filed in Japan on February 20, 2020, the contents of which are incorporated herein by reference. [Fundamentals of the Technique]
[002] Recently, in the field of electrical equipment, in particular rotating machines, small and medium-sized transformers, electrical components and the like, in which non-oriented electrical steel sheet is used as ferrous core material, in response to the environmental conservation movement represented by the global energy economy, CO2 reduction and the like, the demand for high efficiency and size reduction has intensified. Under such a social environment, naturally, improving the performance of non-oriented electrical steel sheets is an urgent problem.
[003] The characteristics that are required for non-oriented electrical steel sheets, in relation to improving motor characteristics, are iron loss and magnetic flux density. In the related technique, the grain diameters before cold rolling are increased by winding at high temperatures after hot rolling, whereby the textures of the non-oriented electrical steel sheets, which are products, are controlled and their characteristics are improved.
[004] Patent Document 1 describes that an electrically non-oriented steel sheet capable of achieving excellent magnetic characteristics in all directions in the sheet plane is obtained by controlling the crystal rate. Petition 870250119774, dated 12 / 26 / 2025, page 10 / 79 / 25 columnar and average crystal grain diameter in the casting or rapid solidification of molten steel, controlling the reduction of cold rolling and controlling the threading stress and cooling rate during final annealing. [Citation List] [Patent Document]
[005] Unexamined Japanese Patent Application, First Publication No. 2019-157247 [Summary of the Invention] [Problems to be Solved by the Invention]
[006] As the demand for non-oriented electrical steel sheets (hereinafter also referred to simply as electrical steel sheets) intensifies, a reduction in costs is also required. As one of the methods to reduce manufacturing costs, a method is conceivable in which annealing after hot rolling is bypassed by increasing the hot rolling temperature in a hot rolling process. However, compared to normal steel sheets, a large amount of Si is added to electrical steel sheets to decrease iron loss, which causes the onset of cracking in the end portions of the steel sheets and fracturing of the steel sheets in a pickling process after hot rolling following bending and non-bending in a continuous line. The simple skip of annealing after hot rolling degrades the stiffness and increases the risk of fracturing of the steel sheets.
[007] The present invention was made in consideration of the circumstances described above, and an objective of the present invention is to provide a hot-rolled steel sheet for a non-oriented electrical steel sheet in which, even when annealing after hot rolling is ignored, fracture due to bending and non-bending in the subsequent pickling process can be suppressed, in addition, the magnetic characteristics are. Petition 870250119774, dated 12 / 26 / 2025, page 11 / 79 / 25 excellent in a case where an electrical steel plate is produced and the rigidity improves. [Means to Solve the Problem]
[008] The present inventors have repeated intensive studies regarding a method for, in a hot-rolled sheet for a non-oriented electrical steel sheet, bypassing annealing in a hot rolling process and satisfying both the stiffness of the hot-rolled sheet high enough to suppress the occurrence of fracture of the end portion of the steel sheet during pickling and the magnetic characteristics of the electrical steel sheet.
[009] As a result, it was found that when the temperature and immersion time during the self-annealing of hot-rolled sheet by high-temperature winding, after hot rolling and the cooling rate in subsequent cooling are controlled, it is possible to increase the amount of C segregation that is present in the grain boundaries in the end portion in the sheet width direction of a hot-rolled steel sheet relative to the amount of P segregation, which degrades stiffness and, as a result, fracture due to bending and non-bending can be prevented by improving the stiffness of the hot-rolled steel sheet, thus, excellent magnetic characteristics can be achieved when an electrically non-oriented steel sheet is produced.
[0010] The present invention was made based on the discovery described above, and the essence thereof is as described below.
[0011] (1) A hot-rolled steel sheet for a non-oriented electrical steel sheet containing, in % by mass, C: 0.0010% to 0.0050%, Si: 1.90% to 3.50%, Al: 0.10% to 3.00%, Mn: 0.05% to 2.00%, P: 0.10% or less, S: 0.005% or less, N: 0.0040% or less, B: 0.0060% or less, Sn: 0% to 0.50%, Sb: 0% to 0.50%, Cu: 0% to 0.50%, REM: 0% to 0.0400%, Ca: 0% to 0.0400%, Mg: 0% to 0.0400%, and a remainder consisting of Petition 870250119774, dated 12 / 26 / 2025, p. 12 / 79 / 25 Fe and impurities, wherein, in an end portion in the sheet width direction of hot-rolled steel sheet for a non-oriented electrical steel sheet, a concentration of C [% of atoms] at a crystal grain boundary is 3.0 or more times a concentration of P [% of atoms], and the concentration of C [% of atoms] at the crystal grain boundary is 3.5 or more times a concentration of C in a crystal grain.
[0012] (2) Hot-rolled steel sheet for a non-oriented electrical steel sheet according to (1), containing, in % by mass, one or two or more of Sn: 0.01% or more and 0.50% or less, Sb: 0.01% or more and 0.50% or less, Cu: 0.01% or more and 0.50% or less, REM: 0.0005% or more and 0.0400% or less, Ca: 0.0005% or more and 0.0400% or less and Mg: 0.0005% or more and 0.0400% or less. [Effects of the Invention]
[0013] According to the present invention, it is possible to provide a hot-rolled steel sheet for a non-oriented electrical steel sheet having sufficient stiffness of hot-rolled sheet, even in the case of ignoring annealing in a hot rolling process and satisfying both low iron loss and high magnetic flux density when a non-oriented electrical steel sheet is produced. [Method for Implementing the Invention]
[0014] Next, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the configuration described in this embodiment and can be modified in various ways within the scope of the essence of the present invention. In the following description, there will be instances where specific numerical or material values are exemplified, but other numerical or material values may also be applied provided the effect of the present invention can be obtained. Furthermore, the individual configuration elements of the embodiment to be described below can be combined among Petition 870250119774, dated 12 / 26 / 2025, page 13 / 79 / 25 si. Furthermore, the numerical limit ranges to be described below include the lower limit value and the upper limit value within the ranges. Numerical values expressed as 'more than' or 'less than' are not included in numerical ranges. [Chemical components of hot-rolled steel sheet for non-oriented electrical steel sheet]
[0015] First, the reasons for limiting the steel components of the present invention will be described. Hereinafter, “%” in relation to the steel sheet components means “% by mass”. C: 0.0010% to 0.0050%
[0016] OC is segregated at grain boundaries to strengthen stiffness, and thus 0.0010% or more of C is preferably added. On the other hand, C is a harmful component that degrades iron loss and also acts as a cause of magnetic aging, and thus the C content is set to 0.0050% or less and preferably set to 0.0040% or less. Yes: 1.90% to 3.50%
[0017] Silicon (Si) is a component that reduces iron loss by increasing electrical resistance to decrease eddy current loss and also improves blanking capacity in ferrous cores by increasing yield rate. To exhibit these effects, 1.90% or more of Si needs to be present. Conversely, when the Si content increases, the magnetic flux density decreases, and in the manufacturing processes of non-oriented electrical steel sheet, the workability for cold rolling and similar processes deteriorates, and the cost increases. Therefore, the Si content is set to 3.50% or less, and preferably to 3.00% or less. solution: 0.10% to 3.00% Petition 870250119774, dated 12 / 26 / 2025, page 14 / 79 / 25
[0018] Al, similar to Si, is also a component that reduces iron loss by increasing electrical resistance to decrease eddy current loss, but it slightly increases hardness compared to Si. Therefore, 0.10% or more of Al needs to be included. On the other hand, when the content increases, the saturated magnetic flux density decreases, a decrease in magnetic flux density is caused, in addition, a decrease in the yield ratio is caused and the blank accuracy is also degraded, and thus the Al content is set to 3.00% or less and preferably set to 2.50% or less. Mn: 0.05% to 2.00%
[0019] Mn has effects of increasing electrical resistance to reduce eddy current loss and improving primary recrystallization texture to develop a {110} crystal orientation. <001> This is desirable for improving magnetic characteristics in a rolling direction. Furthermore, Mn suppresses the precipitation of a fine sulfide, such as MnS, which is detrimental to crystal grain growth. For this purpose, it is necessary to contain 0.05% or more, preferably 0.20% or more of Mn. However, when the content increases, crystal grain growth during annealing deteriorates and iron loss increases; therefore, the Mn content is set to 2.00% or less, and preferably to 1.50% or less. P: 0.10% or less
[0020] OP has the effect of increasing the accuracy of the blank space and can be added, but an increase in P content makes steel sheets containing more than 2% Si extremely brittle. Therefore, the P content is set to 0.10% or less and preferably set to 0.05% or less. The lower limit of the P content is not particularly restricted, but is Petition 870250119774, dated 12 / 26 / 2025, page 15 / 79 / 25 preferably defined to 0.005% or more from the point of view of the deterioration of magnetic flux density due to P reduction. S: 0.005% or less
[0021] OS is finely precipitated as a sulfide, such as MnS, and thus impairs recrystallization and crystal grain growth during final annealing or similar processes, and therefore the S content is set to 0.005% or less and preferably set to 0.004% or less. The lower limit of the S content is not particularly restricted, but is preferably set to 0.0005% or more from the point of view of increased costs due to desulfurization. N: 0.0040% or less
[0022] N reduces the coating rate of an inner oxide layer on the surface of hot-rolled sheet by fine precipitation of a nitride, such as AlN, which is formed during hot band annealing or final annealing and, moreover, impairs recrystallization and crystal grain growth during final annealing or similar and, therefore, the N content is set to 0.0040% or less and preferably set to 0.0030% or less. The lower limit of the N content is not particularly restricted, but is preferably set to 0.0005% or more from the point of view of an increase in N reduction costs. B 0.0060% or less
[0023] OB impairs recrystallization and crystal grain growth during final annealing or similar due to fine precipitation of a nitride, such as BN, and therefore the B content is set to 0.0060% or less and preferably set to 0.0040% or less. The lower limit of the B content is not particularly restricted, but is preferably set to 0.0001% or more from the point of view of increased costs to reduce B. Sn: 0% to 0.50% Petition 870250119774, dated 12 / 26 / 2025, p. 16 / 79 / 25 Sb: 0% to 0.50%
[0024] Sn and Sb are not essential elements, but they have the effect of improving the primary recrystallization texture of the steel sheet to develop the texture in the {110} texture. <001> , which is desirable to improve the magnetic characteristics in the lamination direction, and suppress a texture {111} <112> or similar, which is not desirable for the magnetic characteristics and therefore may be added as needed. For such purposes, 0.01% or more of each of Sn and Sb is preferably contained. On the other hand, even when the contents of these increase, the actions described above are saturated and, conversely, there are cases in which the stiffness of the hot-rolled sheet is degraded and, therefore, even in the case where Sn and Sb are contained, the contents of Sn and Sb are set, each, to 0.50% or less. Cu: 0% to 0.50%
[0025] Copper (Cu) is not an essential element, but it acts as a precipitate in steel to improve strength and can therefore be added as needed. To achieve this effect, 0.01% or more of Cu is preferably contained. On the other hand, when more than 0.50% of Cu is contained, there are instances where cracking and defects are initiated during rolling. Therefore, the Cu content is preferably between 0.01% and 0.50%. Even when Sn, Sb, or Cu is contained as an impurity, the effects of the basic elements described above are not impaired. REM: 0% to 0.0400% or less Ca: 0% to 0.0400% or less Mg: 0% to 0.0400% or less
[0026] REM, Ca, and Mg are not essential elements, but they are elements that accelerate grain growth and therefore can be added as needed. To achieve this effect, the content of each is preferably set to 0.0005% or more. The content of any of the Petition 870250119774, dated 12 / 26 / 2025, p. 17 / 79 / 25 The content of rare earth metals is preferably 0.0010% or more, and more preferably 0.0050% or more. On the other hand, when the content of rare earth metals, calcium, and magnesium exceeds 0.0400%, the magnetic characteristics deteriorate, and therefore the content is set to 0.0040% or less. The content of any of the elements is preferably 0.0300% or less, and more preferably 0.0200% or less. Rare earth metals is an abbreviation for rare earth metals and refers to Sc, Y, and elements belonging to the lanthanide series. Industrially, lanthanides are added in a mischmetal form.
[0027] The components other than the components described above are Fe and impurity elements.
[0028] When hot-rolled steel sheet for a non-oriented electrical steel sheet is required to contain components as described above, it is possible to produce a non-oriented electrical steel sheet having excellent magnetic characteristics when the electrical steel sheet is produced.
[0029] The steel components described above can be measured by a common steel analysis method. For example, steel components can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). C and S can be measured using an infrared absorption method after combustion, and N can be measured using an inert gas fusion thermal conductivity method. [Concentrations of grain boundary elements of hot-rolled steel sheet for a non-oriented electrical steel sheet]
[0030] Next, the concentrations of elements at the grain boundaries of hot-rolled steel sheet for a non-oriented electrical steel sheet will be described. <Concentração C / Concentração P>
[0031] Next, in the hot-rolled steel sheet for a non-oriented electrical steel sheet of the present embodiment, the ratio TR = C / P Petition 870250119774, dated 12 / 26 / 2025, page 18 / 79 / 25 of the concentration of C (C) to the concentration of P (P) [% of atoms] that are contained in the grain boundaries is 3.0 or more. OP is a representative element that decreases the cohesive force between atoms and degrades stiffness by being segregated at the grain boundaries. Therefore, the amount of P segregated at the grain boundaries is preferably as small as possible, but it is normal for P to inevitably be contained in the steel sheet as an impurity element, and therefore it is difficult to avoid stiffness degradation due to intergranular segregation of P. The fact that the ratio TR = C / P of the concentration of C (C) to the concentration of P (P) [% of atoms] contained in the grain boundaries of hot-rolled steel sheet for a non-oriented electrical steel sheet is 3.0 or more means that, in other words, the concentration of C [% of atoms] at the crystal grain boundaries is 3.0 or more times the concentration of P [% of atoms].
[0032] C is a representative element that improves the cohesive force between atoms and improves stiffness by being segregated at grain boundaries. Therefore, in the hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention, the concentration of C that is segregated at grain boundaries is defined as 3.0 or more times the concentration of P that is segregated at grain boundaries. In this case, the stiffness of the hot-rolled steel sheet improves, and it is possible to avoid fracture of the end portion of the steel sheet due to bending and non-bending in a pickling process.
[0033] In a case where the steel plate fractures due to bending and non-bending, the cracks are initiated at the end portion and the steel plate fractures, and thus the concentration of C and the concentration of P contained in the grain boundaries at the end portion of the steel plate need to have the relationship described above. Specifically, the concentration of C and the concentration of P contained in the grain boundaries are measured by cutting a Charpy test piece, such that a position of 10 Petition 870250119774, dated 12 / 26 / 2025, page 19 / 79 / 25 mm from the end face in the sheet width direction of the steel sheet (hereinafter referred to as the end portion in the sheet width direction) becomes the surface of a cross-section L, by making a notch in the surface on the side surface of the steel sheet, performing a Charpy test in an atmosphere of -50°C or lower and analyzing the intergranular fractured surface by Auger electron spectroscopy (AES). The C concentration and the P concentration are calculated from the ratios between the intensity of the spectrum of the intergranular fractured surface analyzed by AES and the intensities of the spectrum of the quantity of elements present. Here, the cross-section L means a cross-section parallel to the sheet thickness direction of the steel sheet and a rolling direction (or the longitudinal direction of the steel sheet).
[0034] B also has the same effect as C, but B is an element that degrades magnetic characteristics and therefore makes it difficult to satisfy both magnetic characteristics and stiffness and, as described above, B impairs recrystallization and crystal grain growth during final annealing or similar processes due to fine precipitation of a nitride, and thus, in the present invention, C is segregated at the grain boundaries. <Concentração C no contorno de grão / concentração C intragranular>
[0035] In addition to the ratio of C concentration to P concentration at grain boundaries described above, the ratio CR = CGB / CIG of the C concentration (Cgb) [% of atoms] present at the grain boundaries of rolled steel sheet to the C concentration (Cig) [% of atoms] present in the grains of non-oriented electrical steel sheet is set to 3.5 or more, which allows for further improvement in stiffness. The C concentration at the grain boundary and the intragranular C concentration can be measured by the same method as for the C concentration and P concentration described above. The fact that the ratio CR = Cgb / Cig of the C concentration (Cgb) [% of atoms] present at the grain boundaries of the steel sheet Petition 870250119774, dated 12 / 26 / 2025, page 20 / 79 / 25 hot-rolled for a non-oriented electrical steel sheet for the concentration of C (Cig) [% of atoms] present in the grains is defined as 3.5 or more means that, in other words, the concentration of C [% of atoms] at the crystal grain boundaries of the hot-rolled steel sheet for a non-oriented electrical steel sheet is 3.5 or more times the concentration of C in the crystal grains. [Manufacturing method]
[0036] Next, a method for manufacturing hot-rolled steel sheet for a non-oriented electrical steel sheet of the present embodiment will be described.
[0037] The hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention is manufactured by making cast steel having the components described above in a plate by continuous casting, furthermore, performing hot rolling to produce a hot-rolled sheet (hot rolling process), performing self-annealing with heat from a coil wound after hot rolling and furthermore, cooling the coil. As the method for manufacturing the plate, a normal method can be used. [Hot rolling]
[0038] Next, the plate is preferably heated to 1080°C to 1200°C and hot rolled. The heating temperature is preferably set to 1080°C or higher, since the finishing temperature becomes 850°C or higher, and reheating annealing after winding is skipped, as described below. The finishing temperature is preferably set to 1200°C or lower, since the formation of a solid solution and the fine precipitation of an impurity, such as a sulfide, are avoided and iron loss is not increased.
[0039] The finishing temperature is preferably set to 850°C to 1000°C. This is because, as described below, the temperature Petition 870250119774, dated 12 / 26 / 2025, page 21 / 79 / 25, states that the winding temperature is set to 700°C to 800°C to perform self-annealing with heat from a coil, thus bypassing reheat annealing. Furthermore, this is because when the finishing temperature is low, hot workability deteriorates, and there is concern that the accuracy of sheet thickness in the steel sheet width direction may deteriorate. On the other hand, in order to avoid deterioration of stiffness due to thickening of ferrite grain diameters, the finishing temperature is preferably set to 1000°C or lower. [<Enrolamento e autorrecozimento>
[0040] Next, the hot-rolled steel sheet after the end of the finishing rolling is coiled at 700° to 850°. When the hot-rolled steel sheet is coiled from 700° to 850°, it becomes possible to perform self-annealing with the heat accumulated by the coiled coil, and it becomes possible to suppress the development of crystal grains in the {111} orientation, which adversely affect the magnetic characteristics, even when reheat annealing is ignored. In order to improve the magnetic characteristics, particularly the magnetic flux density, it is preferable to further thicken the crystal grain diameters of the hot-rolled steel sheet before cold rolling; However, when hot-rolled steel sheet is annealed at high temperatures, the stiffness deteriorates due to decarburization, and a stiffness-enhancing effect cannot be obtained; therefore, the winding temperature is preferably set to 850°C or lower.
[0041] The self-annealing process in the coil after winding is also called the heat conservation treatment process. The heat conservation treatment process begins when the hot-rolled steel sheet is wound to form the coil and ends when the coil temperature begins to decrease. The point in Petition 870250119774, dated 12 / 26 / 2025, p. 22 / 79 / 25 The time at which the coil is formed is a point in time at which the winding of a single strip of hot-rolled steel sheet into a single turn of a coil is completed. Furthermore, the point in time at which the coil temperature begins to decrease is a point in time at which the cooling rate of the coil changes, i.e., the inflection point of the cooling rate curve. Depending on the heat storage temperature, there are cases where a change in coil temperature is extremely small for a predetermined period of time from the moment the coil winding is completed, and once the predetermined period of time has elapsed, the coil temperature begins to decrease rapidly.
[0042] Furthermore, to thicken the crystal grain diameters of hot-rolled steel sheet before cold rolling, heat can be retained by covering the coil with a heat-retaining cover. In the case of carrying out the heat-retaining treatment process using the heat-retaining cover, the time from the placement of the heat-retaining cover on the coil until its removal is considered as the heat-retaining time. From the point of view of recrystallization of the hot-rolled sheet, the heat-retaining time is preferably one minute or more. On the other hand, when the grains grow excessively, fractures are likely to occur in the pickling process and in a cooling process, and therefore the heat-retaining time is preferably two hours or less.
[0043] The heat retention process by covering the coil with a heat-retaining cover or the self-annealing process with the heat accumulated by the wound coil is also referred to as the heat-retaining treatment process. The temperature of the heat-retaining treatment process is preferably from 720°C to 830°C. When the temperature of the heat-retaining treatment process is set to 720°C or more, the grain diameters before cold rolling increase. Petition 870250119774, dated 12 / 26 / 2025, page 23 / 79 / 25 sufficiently and a high magnetic flux density can be obtained. Furthermore, when the temperature of the heat preservation treatment process is set to 830°C or lower, the effect on an inner oxide layer that is formed on the surface of the steel sheet being suppressed can be obtained. <resfriamento>
[0044] In the present invention, it is important to control the cooling rate so that the concentration of C and the concentration of P at the grain boundaries have the relationship described above.
[0045] Specifically, when the cooling rate in a temperature range from the winding temperature to 600°C, which is a temperature at which P is likely to segregate at the grain boundaries, is set to fast, P segregation is suppressed, and when the cooling rate in a temperature range from 400°C to 600°C, which are temperatures at which C is likely to segregate at the grain boundaries, is set to slow, C segregation is accelerated. In this case, the deterioration of stiffness due to P grain boundary segregation is suppressed, which makes it possible to avoid fracturing of the steel sheet in subsequent processes. The process of controlling the cooling rate in a temperature range from the winding temperature to 400°C is also called the cooling process.
[0046] The average cooling rate from winding temperature to 600°C is preferably set to 10 to 100°C / min. The average cooling rate from winding temperature to 60°C is more preferably faster than 10°C / min and even more preferably 20°C / min, 30°C / min or 40°C / min.
[0047] The average cooling rate from 400°C to 600°C is preferably as slow as possible to accelerate C segregation at grain boundaries; however, when the average cooling rate is too Petition 870250119774, dated 12 / 26 / 2025, p. 24 / 79 / 25 slow, the self-annealing time becomes long and the grain diameters thicken excessively and therefore degrade the stiffness, and thus the average cooling rate is preferably set to 30 °C / h or faster. When the cooling rate is too fast, C is not sufficiently segregated and therefore the cooling rate is preferably set to 120 °C / h or slower.
[0048] As described, cracks are initiated and the steel sheet fractures at the end portion of the steel sheet, and therefore the cooling rate described above is the cooling rate at the end portion (the side surface of the coil) of the steel sheet. The cooling rate can be controlled by sending air to the coil with a blower and by adjusting the amount or temperature of the air. As the temperature of the end portion of the steel sheet, the temperature of the cross-section of the steel sheet (at a desired location) is measured with a radiation thermometer. The time during which air is sprayed onto the coil with the blower is considered the cooling time. The cooling time is not specifically designated.
[0049] Furthermore, when the cooling rate from 400°C to 600°C is set to 50 to 80 C / h, it is possible to set the ratio CR = Cgb / Cig of the C concentration (Cgb) [% of atoms] present in the grain boundaries of the hot-rolled steel sheet to a non-oriented electrical steel sheet for the C concentration (Cig) [% of atoms] present in the grains to 3.5 or more.
[0050] In detail, the cooling rate is controlled by spraying air onto the coil that has undergone self-annealing (heat conservation treatment process) using, for example, a blower to cool the coil.
[0051] Cooling is most preferably started immediately after removing the lid described above. Alternatively, cooling is Petition 870250119774, dated 12 / 26 / 2025, page 25 / 79 / 25 more preferably initiated before the point in time at which the coil temperature begins to decrease. <Sn e Sb>
[0052] In the case where Sn and Sb are added to the steel plate, since these elements contribute to low iron loss and high magnetic flux density, it is possible to lower the heat retention temperature and, consequently, improve the stiffness. At this point, when the heat retention temperature is set to 850°C or lower, preferably set to 800°C or lower, and more preferably set to 750°C or lower, it is possible to highly satisfy both appropriate stiffness and low iron loss and high magnetic flux density.
[0053] The mechanism by which the addition of Sn and Sb contributes to a decrease in iron loss and an increase in magnetic flux density is considered to be as these elements suppress the growth of {111} oriented grains, which negatively affect the magnetic characteristics.
[0054] When pickling, cold rolling, and final annealing are performed by normal methods on the hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention, which is obtained as described above, it is possible to obtain a non-oriented electrical steel sheet having excellent magnetic characteristics. At this point, since the hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention has excellent rigidity as described above, there are no cases in which cracks are initiated due to bending and non-bending even when pickling is performed by a normal method. As described above, the hot-rolled steel sheet for a non-oriented electrical steel sheet according to the present invention undergoes the hot rolling process, the heat preservation treatment process, and the cooling process. The cooling process can be Petition 870250119774, dated 12 / 26 / 2025, page 26 / 79 / 25 carried out, for example, in the middle of transporting the coil to a pickling device that is used in the pickling process, which is ahead of the cold rolling of the steel sheet, in the manufacturing method of a non-oriented electrical steel sheet.
[0055] In the present invention, the stiffness of the hot-rolled sheet means the stiffness of the steel sheet for a non-oriented electrical steel sheet before the pickling process that has undergone the cooling process after the self-annealing described above. [Examples]
[0056] Examples of the present invention will be described below, but the conditions in the examples are examples of conditions adopted to confirm the feasibility and effect of the present invention, and the present invention is not limited to these examples. The present invention is capable of adopting a variety of conditions within the scope of the essence of the present invention, provided that the objective of the present invention is achieved. <Exemplo 1>
[0057] The steels having the components shown in Table 1 were melted and hot-rolled, thus producing hot-rolled sheets having a sheet thickness of 2.0 mm. After that, under the conditions shown in Table 2, the hot-rolled sheets were wound into coils, the heat was retained, and the coils were cooled, thus producing hot-rolled steel sheets for a non-oriented electrical steel sheet.
[0058] Cooling was performed by spraying air onto the end portions. As well as the cooling rates, the cooling rates at the end positions of the steel plates were measured using a radiation thermometer.
[0059] A manufacturing method sign B0 is a reference example in which hot-rolled steel sheet has been rolled, cooled and Petition 870250119774, dated 12 / 26 / 2025, page 27 / 79 / 25 after annealing in an atmosphere with 100% nitrogen. The measurement results of C and P concentrations at the grain boundaries in the end portions of hot-rolled steel sheets produced for a non-oriented electrical steel sheet and the transition temperatures in a Charpy test performed to evaluate stiffness are shown in Table 3.
[0060] The concentrations of C and P at grain boundaries were measured by cutting Charpy test pieces from the end portions in the sheet width direction of steel sheets, making notches on the lateral surface sides of the steel sheet, performing the Charpy test in an atmosphere of -50°C or lower, and analyzing the intergranular fractured surfaces by Auger electron spectroscopy (AES).
[0061] The fractured surface transition temperatures were measured by performing a Charpy test according to JIS Z 2242. In the present examples, in a case where the fractured surface transition temperature was below 0°C, the stiffness was determined to be favorable.
[0062] Next, the hot-rolled steel sheets produced for a non-oriented electrical steel sheet were pickled by immersion in hydrochloric acid (85°C, 7.5% by mass) for 30 seconds, then cold-rolled to a thickness of 0.5 mm at a rolling reduction of 75% and finally annealed at 1050°C for 30 seconds, thus obtaining non-oriented electrical steel sheets.
[0063] In addition, the magnetic characteristics of the obtained non-oriented electrical steel sheets were measured in accordance with JIS C 2556.
[0064] 55 mm x 55 mm samples were collected from non-oriented electrical steel sheets, W15 / 50s (iron losses at the moment of magnetization of the steel sheets for a magnetic flux density of 1.5 T at 50 Hz) were measured with a single-sheet tester (SST), and the iron losses were evaluated. The magnetic flux densities were Petition 870250119774, dated 12 / 26 / 2025, page 28 / 79 / 25 evaluated using B50s, which are magnetic flux densities at a magnetic field strength of 5000 A / m. The measurement results are all shown in Table 3. Petition 870250119774, dated 12 / 26 / 2025, page 29 / 79 / 25 [Table 1] N° of chemical components (% mass) (or residual Fe and impurezas) C Si Mn PS Al NB Sn Sb Cu REM Ca Mg A1 0.0011 3.21 0.21 0.05 0.003 1.18 0.0012 0.0013 - - - - - - Exemplo Inventivo A2 0.0049 2.92 0.25 0.01 0.002 1.51 0.0023 0.0021 - - - - - - A3 0.0013 1.91 0.16 0.02 0.004 2.83 0.0021 0.0035 - - - - - - A4 0.0024 3.48 0.23 0.01 0.005 0.83 0.0016 0.0024 - - - - - - A5 0.0035 3.12 0.06 0.04 0.002 1.39 0.0013 0.0042 - - - - - - A6 0.0024 2.56 1.95 0.02 0.003 0.84 0.0026 0.0027 - - - - - - A7 0.0026 1.94 0.56 0.09 0.002 2.52 0.0023 0.0031 - - - - - - A8 0.0021 2.41 0.78 0.03 0.005 1.80 0.0021 0.0042 - - - - - - A9 0.0015 3.43 1.41 0.05 0.002 0.12 0.0031 0.0033 - - - - - - A10 0.0042 1.92 0.06 0.09 0.003 2.88 0.0024 0.0051 - - - - - - A11 0.0013 2.38 1.52 0.03 0.002 1.35 0.0039 0.0024 - - - - - - A12 0.0032 2.87 0.28 0.04 0.003 1.56 0.0021 0.0058 - - - - - - A13 0.0045 2.95 0.37 0.03 0.001 1.40 0.0023 0.0023 - - - - - - A14 0.0036 3.11 0.26 0.05 0.003 1.27 0.0014 0,0034 - - - - - - A15 0.0021 3.21 0.23 0.01 0.002 1.17 0.0032 0.0023 - - - - 0.0010 - A16 0.0023 3.14 0.25 0.01 0.001 1.24 0.0015 0.0023 - - - - - 0.0020 A17 0.0012 3.02 0.33 0.04 0.002 1.34 0.0023 0.0021 - - 0.34 - - - A18 0.0013 2.95 0.66 0.02 0.001 1.21 0.0016 0.0034 - - - 0.0009 - - A19 0.0012 3.02 0.15 0.02 0.002 1.46 0.0017 0.0021 0.43 - - - - - A20 0.0015 2.56 0.23 0.03 0.001 1.97 0.0016 0.0025 - 0.41 - - - - A21 0.0018 2.68 0.25 0.02 0.002 1.81 0.0023 0.0032 0.04 - 0.05 - - - a1 0.0002 3.24 0.06 0.02 0.002 1.24 0.0013 0.0032 - - - - - - Exemplo Comparative o a2 0.0081 2.97 0.24 0.04 0.003 1.46 0.0024 0.0054 - - - - - - a3 0.0034 1.82 0.07 0.02 0.002 3.00 0.0031 0.0023 - - - - - - a4 0.0021 4.13 0.07 0.06 0.003 0.13 0.0025 0.0031 - - - - - - a5 0.0028 2.65 0.02 0.02 0.004 2.00 0.0025 0.0051 - - - - - - a6 0.0032 1.99 3.44 0.06 0.004 0.56 0.0031 0.0021 - - - - - - a7 0.0013 2.37 1.35 0.21 0.002 1.47 0.0034 0.0034 - 0.03 - - - - a8 0.0023 2.65 1.25 0.04 0.009 1.19 0.0032 0.0032 0,04 - - - - - a9 0.0016 2.88 0.45 0.07 0.003 0.08 0.0021 0.0021 - - 0.22 - - - a10 0.0036 1.92 0.06 0.01 0.002 3.59 0.0011 0.0044 - 0.13 0.26 - - - a11 0.0028 3.16 0.75 0.01 0.003 0.89 0.0081 0.0025 0.22 0.34 - - - - a12 0.0043 2.67 0.58 0.02 0.001 1.61 0.0034 0.0088 0.37 0.24 0.25 - - -, Petition 870250119774, dated 12 / 26 / 2025, p. 30 / 79 / 25 [Table 2] Manufacturing Method Signal Hot Rolling Process Hot Strip Annealing Process Heat Preservation Treatment Process Average Cooling Rate Plate Heating Temperature Finishing Temperature Coil Winding Temperature Annealing Temperature Heat Preservation Temperature Heat Preservation Time Winding Temperature at 600°C 600°C at 400°C (°C) (°C) (°C) (°C) (°C) (min) (°C / min) (°C / hr) B0 1160 870 650 920 - - - - B1 1082 890 760 - 750 65 50 58 B2 1195 882 790 - 780 63 60 67 B3 1123 852 819 - 790 28 90 76 B4 1187 998 778 - 760 48 30 38 B5 1165 920 768 - 740 2 30 56 B6 1189 870 813 - 800 118 40 84 B7 1154 890 780 - 760 28 70 35 B8 1176 928 797 - 780 47 60 118 B9 1143 932 780 - 750 114 30 50 B10 1128 890 782 - 740 39 50 112 b1 970 904 778 - 790 45 30 45 b2 1423 936 739 - 780 109 90 79 b3 1165 801 728 - 750 46 30 86 b4 1187 1180 716 - 740 29 40 98 b5 1165 890 729 - 760 0,5 50 55 b6 1165 920 726 - 730 200 20 102 b7 1181 930 709 - 720 114 30 12 b8 1174 890 729 - 740 93 70 198 b9 1165 890 780 - 740 65 110 80 b10 1156 920 770 - 800 70 5 90 b11 1176 900 760 - 680 70 30 80 b12 1156 880 780 - 900 65 20 90 b13 1156 890 770 - 720 45 30 20, [Table 3] Signal Steel No. Manufacturing Method No. TR=C / P Hot-rolled sheet stiffness Magnetic flux density Iron loss Charpy transition temperature B50 W15 / 50 (°C) (T) (W / kg) C0 A1 B0 1.2 28 C1 A1 B1 4.2 -4 1.68 2.51 C2 A2 B2 4.5 -3 1.68 2.56 C3 A3 B3 5.3 -4 1.71 2.54 C4 A4 B4 5.6 -10 1.68 2.58 C5 A5 B5 4.2 -10 1.68 2.55 C6 A6 B6 3.7 -6 1.68 2.57 C7 A7 B7 5.5 -8 1.65 2.55 C8 A8 B8 3.7 -2 1.65 2.54 C9 A9 B9 3.5 -7 1.66 2.54 C10 A10 B10 4.8 -9 1.67 2.59 C11 A11 B1 4.2 -10 1.67 2.54 C12 A12 B2 5.1 -11 1.69 2.52 C13 A13 B7 5.6 -9 1.71 2.51 C14 A14 B8 6.3 -8 1.72 2.52 Petition 870250119774, dated 12 / 26 / 2025, page 31 / 79 / 25 c1 a1 b1 2.8 13 1.61 2.63 c2 a2 b2 2.7 14 1.61 2.68 c3 a3 b3 1.3 13 1.58 2.65 c4 a4 b4 1.5 15 1.58 2.64 c5 a5 b5 1.6 17 1.59 2.67 c6 a6 b6 1.5 9 1.55 2.66 c7 a7 b7 1.4 8 1.54 2.65 c8 a8 b8 1.3 7 1.55 2.64 c9 a9 b1 1.8 9 1.54 2.65 c10 a10 b2 1.8 9 1.57 2.69 c11 a11 b3 2.1 8 1.56 2.69 c12 a12 b4 2.1 15 1.59 2.64 c13 A1 b5 2.8 9 1.62 2.62 c14 A2 b6 2.9 8 1.59 2.63 c15 A3 b7 2.7 7 1.59 2.64 c16 A4 b8 2.8 9 1.58 2.63 c17 A4 b9 2.5 5 1.56 2.62 c18 A5 b10 2.4 6 1.58 2.67 c19 A6 b11 2.4 7 1.57 2.64 c20 A7 b12 2.6 2 1.56 2.66 c21 A8 b13 2.1 8 1.59 2.67 c22 a1 B1 1.2 5 1.56 2.63 c23 a2 B2 1.6 3 1.57 2.64 c24 a3 B3 1.2 4 1.58 2.63 c25 a4 B4 2.5 6 1.58 2.64 c26 a5 B5 1.2 7 1.58 2.64 <Exemplo 2>
[0065] Hot-rolled steel sheets for a non-oriented electrical steel sheet were produced in the same manner using steels shown in Table 1 and manufacturing methods shown in Table 2, and then non-oriented electrical steel sheets were obtained.
[0066] Regarding the hot-rolled steel sheets obtained for a non-oriented electrical steel sheet, in addition to the measurement results of Example 1, the ratios between the C concentration at the grain boundary and the intragranular C concentration were measured. Regarding the non-oriented electrical steel sheets, the magnetic characteristics were measured in the same way as in Example 1. The results are shown in Table 4. [Table 4] Petition 870250119774, dated 12 / 26 / 2025, page 32 / 79 / 25 Signal Steel No. Manufacturing Method No. TR=C / P CR=Cgb / Cig Hot-rolled sheet stiffness Magnetic flux density Iron loss Charpy transition temperature B50 W15 / 50 (°C) (T) (W / kg) D1 A1 B4 4.2 3.2 -4 1.68 2.51 Comparative Example D2 A2 B6 4.5 3.1 -3 1.68 2.56 Comparative Example D3 A13 B9 5.6 5.2 -19 1.71 2.51 Inventive Example D4 A14 B2 6.3 6.1 -18 1.72 2.52 Inventive Example D5 a1 b1 2.8 3.1 13 1.61 2.63 Comparative Example D6 A2 b6 2.9 3.2 8 1.59 2.63 Comparative Example D7 a1 B1 1.2 3.1 5 1.56 2.63 Comparative Example
[0067] It was possible to confirm that when the CR = Cgb / Cig ratio of the concentration of C Cgb [% of atoms] present at the grain boundaries to the concentration of C Cig [% of atoms] present in the grains was set at 3.5 or more, superior characteristics were obtained. Although not explicitly shown in Table 3, the CRs were 3.5 or more at C1, C2, C3, C5, C9, C11 and C12.
[0068] It was possible to confirm that the use of hot-rolled steel sheet for a non-oriented electrical steel sheet of the present invention allows obtaining a non-oriented electrical steel sheet having characteristics as excellent as the non-oriented electrical steel sheets for which a conventional hot-rolled steel sheet was used for a non-oriented electrical steel sheet that underwent hot band annealing without causing fracture of the steel sheet during pickling. [Industrial applicability]
[0069] According to the present invention, it is possible to provide a hot-rolled steel sheet for a non-oriented electrical steel sheet having sufficient stiffness of hot-rolled sheet, even in the case of ignoring annealing in a hot rolling process, and satisfying both low iron loss and high magnetic flux density. Petition 870250119774, dated 12 / 26 / 2025, page 33 / 79 / 25 when a non-oriented electrical steel sheet is produced. Therefore, it is possible to stably produce and provide a non-oriented electrical steel sheet having low iron loss and high magnetic flux density without causing fracture, and thus the present invention is able to sufficiently meet an urgent demand for mass production in the field of electrical equipment for which non-oriented electrical steel sheet is used as ferrous core material and has an extremely high industrial value.< / resfriamento>
Claims
1. Hot-rolled steel sheet for a non-oriented electrical steel sheet, characterized in that it comprises, in % by mass: C: 0.0010% to 0.0050%; Si: 1.90% to 3.50%; Al: 0.10% to 3.00%; Mn: 0.05% to 2.00%; P: 0.10% or less; S: 0.005% or less; N: 0.0040% or less; B: 0.0060% or less; Sn: 0% to 0.50%; Sb: 0% to 0.50%; Cu: 0% to 0.50%; REM: 0% to 0.0400%; Ca: 0% to 0.0400%; Mg: 0% to 0.0400%, and a remainder consisting of Fe and impurities, wherein, in an end portion in the width direction of hot-rolled steel sheet for a non-oriented electrical steel sheet, a concentration of C [% atom] at a crystal grain boundary is 3.0 or more times a concentration of P [% atom], and the concentration of C [% atom] at the crystal grain boundary of hot-rolled steel sheet for a non-oriented electrical steel sheet is 3.5 or more times a concentration of C at a crystal grain.
2. Hot-rolled steel sheet for a non-oriented electrical steel sheet according to claim 1, characterized in that it comprises, in % by mass, one or two or more of: Petition 870250119774, dated 12 / 26 / 2025, page 35 / 79 2 / 2 Sn: 0.01% or more and 0.50% or less; Sb: 0.01% or more and 0.50% or less; Cu: 0.01% or more and 0.50% or less; REM: 0.0005% or more and 0.0400% or less; Ca: 0.0005% or more and 0.0400% or less; and Mg: 0.0005% or more and 0.0400% or less.