Hot-rolled annealed sheet and method of manufacturing the same and method of manufacturing non-oriented electrical steel sheet
Patent Information
- Application Number
- KR1020267025497
- Authority / Receiving Office
- KR · KR
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-02-05
- Filing Date
- 2024-10-28
- Publication Date
- 2026-09-09
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Abstract
Description
Technology Field
[0001] The present invention relates to a hot-rolled annealed plate, a method for manufacturing the same, and a method for manufacturing a non-oriented electrical steel plate. Background Technology
[0002] Recently, there has been a demand for reducing CO2 emissions and conserving energy due to environmental concerns such as global warming. In particular, in the automotive sector, the development of hybrid electric vehicles (HEVs) that combine engines and motors, electric vehicles (EVs) driven solely by electric motors, and fuel cell vehicles (FCEVs) is underway. Motors used in the aforementioned HEVs, EVs, and FCEVs are generally operated in high-frequency ranges that are advantageous for high-speed rotation to achieve high motor efficiency. Non-oriented electrical steel sheets are widely used as the core material for these motors. To achieve high motor efficiency, there is a strong demand for these steel sheets to have low iron loss in high-frequency ranges.
[0003] In the past, non-oriented electrical steel sheets have sought to achieve low iron loss by reducing eddy current losses through the addition of alloying elements, such as Si or Al, to increase resistivity or thin the sheet thickness. However, the problem was that the addition of large amounts of alloying elements reduced the ductility and toughness of the steel sheet, leading to frequent fractures during the cold rolling process.
[0004] As for fracture suppression technology for high-alloy steel, for example, Patent Document 1 discloses a method for manufacturing a non-oriented electrical steel sheet with high magnetic flux density that suppresses cracking during cold rolling by cold rolling a rapidly solidified cast billet at 180 to 350°C. Prior art literature
[0005] : Japanese Published Patent Application No. 2004-110985 The problem to be solved
[0006] However, in the technology described in Patent Document 1, although cracking can be effectively suppressed by performing cold rolling in a temperature range of 180 to 350°C, there was a problem in that it is difficult to maintain the steel sheet at a high temperature during rolling, and there is a high possibility of causing equipment wear, such as the lubricating oil sticking to the rolls.
[0007] The present invention aims to solve the aforementioned problems of the prior art by providing a hot-rolled annealed sheet with excellent cold rolling properties in subsequent processes that does not cause a degradation of the magnetic properties of the final product, the non-oriented electrical steel sheet, and by proposing an advantageous manufacturing method thereof. Another objective is to propose a method for manufacturing a non-oriented electrical steel sheet using the hot-rolled annealed sheet. Here, cold rolling properties include fracture resistance and edge crack resistance. means of solving the problem
[0008] The inventors, through careful examination, discovered that in most cases, the fracture initiation point of cold rolling is located at the edge of the steel strip. Therefore, they discovered that fracture or cracking caused by cold rolling can be significantly suppressed by increasing the fracture resistance of the edge of the steel strip without increasing the fracture resistance of the entire steel strip. Furthermore, as a method to increase the fracture resistance of the edge of the steel strip, they discovered that an unrecrystallized structure is left at the edge of the steel strip to create a difference in the ratio of the recrystallized structure compared to the center of the steel strip. By doing so, they found that fracture resistance is improved compared to when the ratio of the recrystallized structure of the entire steel strip is reduced, and that a decrease in magnetic properties can also be prevented.
[0009] That is, the hot-rolled annealed plate related to the present invention, which advantageously solves the above problem, contains, in mass%, C: 0.010% or less, Si: 1.0% or more and 5.0% or less, Mn: 0.05% or more and 5.0% or less, P: 0.10% or less, S: 0.010% or less, Al: 3.0% or less, N: 0.0080% or less, and O: 0.0050% or less, and optionally, one or two types selected from Group A: Sn: 0.001% or more and 0.20% or less, and Sb: 0.001% or more and 0.20% or less; Group B: At least one selected from Ca: 0.0001% or more and 0.10% or less, Mg: 0.0001% or more and 0.10% or less, and REM: 0.0001% or more and 0.10% or less; Group C: One or two selected from B: 0.002% or more and 0.20% or less, and Mo: 0.002% or more and 0.20% or less; Group D: Zn: 0.0005% or more and 0.0050% or less; Group E: Ni: 0.01% or more and 1.0% or less; Group F: Cr: 0.1% or more and 5.0% or less; Group G: Cu: 0.005% or more and 1.0% or less; H Group: at least one selected from Ti: 0.001% or more and 0.010% or less, V: 0.001% or more and 0.050% or less, Nb: 0.001% or more and 0.005% or less, Ta: 0.0001% or more and 0.0020% or less, W: 0.001% or more and 0.050% or less, and Pb: 0.0001% or more and 0.0020% or less; I Group: Co: 0.001% or more and 0.100% or less; J Group: Ga: 0.0005% or more and 0.0300% or less, and Ge: 0.0005% or more and 0.0300% or less; and K Group: As: 0.001% or more and 0.0300% or less.It is characterized by having a composition in which at least one group of elements selected from 0.20% or less is contained, and the remainder consists of Fe and unavoidable impurities, and the ratio of the recrystallization structure Re at steel plate position Xe, 10 mm away in the width direction from the widest edge of the plate, to the ratio Rc of the recrystallization structure at the center of the plate width Xc is Re / Rc, which is 0.95 or less.
[0010] In addition, a hot-rolled annealed plate related to the present invention is more preferably a means of solving the problem if it satisfies either or both of the following: the ratio Rc of the recrystallized structure at the center of the plate width Xc is 80% or more, and the ratio Re of the recrystallized structure at the steel plate position Xe is in the range of 5% or more and 95% or less.
[0011] In addition, a method for manufacturing a hot-rolled annealed plate related to the present invention, which advantageously solves the above problem, is a method for manufacturing any of the above hot-rolled annealed plates, comprising a hot rolling process for obtaining a hot-rolled plate by performing hot rolling on a steel material having the above composition, and a hot-rolled plate annealing process for performing hot-rolled plate annealing on the hot-rolled plate, wherein in the hot-rolled plate annealing process, when the central part of the plate width Xc of the hot-rolled plate is heated from room temperature to a holding temperature T1 and maintained, the steel plate position Xe, which is 10 mm away in the width direction from the outermost edge of the plate width of the hot-rolled plate, reaches a maximum temperature T2, which is lower than the holding temperature T1 from room temperature, and the heating rate Vc of the central part of the plate width Xc is made greater than the heating rate Ve of the steel plate position Xe by at least 1.0 ℃ / s.
[0012] In addition, the method for manufacturing a hot-rolled annealed plate related to the present invention is,
[0013] (a) In the above hot-rolled plate annealing process, at least one of the following (1) to (4) is satisfied,
[0014] (b) When providing a hot-rolled plate with a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, forming a heat suppression region in the range of 20 mm or more from the edge of the plate width in the plate width direction and in the range of 0.250 × W or less from the edge of the plate width in the plate width direction is a more desirable means of solving the problem.
[0015] (1) Maintaining the holding temperature T1 at the center of the plate width Xc of the hot-rolled plate at 900 ℃ or higher,
[0016] (2) The holding time t1 at the holding temperature T1 at the center of the plate width Xc of the hot-rolled plate is set to a range of 2 s or more and 120 s or less,
[0017] (3) The maximum temperature T2 at the steel plate position Xe is set to a range of 750 ℃ or higher and 1000 ℃ or lower, and
[0018] (4) Satisfying at least one of the following: the time t2 at the maximum temperature T2 - 50 ℃ or higher is in the range of 5 s or more and 20 s or less.
[0019] A method for manufacturing a non-oriented electrical steel sheet related to the present invention, which advantageously solves the above problem, is characterized by cold rolling any of the above hot-rolled annealed sheets to form a cold-rolled sheet, and finishing annealing the cold-rolled sheet to form a cold-rolled annealed sheet.
[0020] In addition, in the present invention, the edge portion refers to both edges in the width direction, but it is not necessary to apply it to both sides, and it is effective for reducing breakage even on one side. For example, in cases where edge cracking or breakage occurs unevenly on one edge due to the properties of the rolling mill, the effect of reducing breakage is obtained by applying this technology only to one side. Effects of the invention
[0021] According to the present invention, a hot-rolled annealed sheet with excellent cold rolling properties can be provided. Furthermore, by using the hot-rolled annealed sheet, it is possible to produce a non-oriented electrical steel sheet with high magnetic flux density and high frequency and low iron loss. Specific details for implementing the invention
[0022] Hereinafter, embodiments of the present invention will be described along with the reasons for their limitation.
[0023] [Hot-rolled annealed plate]
[0024] <Composition of Steel Plate>
[0025] A preferred composition of a hot-rolled annealed plate related to one embodiment of the present invention will be described. The unit of the elemental content in the composition is "mass%", and hereinafter, unless otherwise specifically stated, it will be expressed simply as "%".
[0026] <Basic Ingredient Composition>
[0027] C: 0.010% or less
[0028] C is a harmful element that causes self-aging in non-oriented electrical steel sheets, which are the product plates, forming carbides and increasing iron loss. Therefore, since the adverse effects become significant, particularly when it exceeds 0.010%, the C content in the steel sheet is set to 0.010% or less. Preferably, it is 0.004% or less. In addition, although the lower limit of the C content is not specifically specified, it is desirable to set it to approximately 0.0001%, given that steel sheets with excessively reduced C are very expensive.
[0029] Si: 1.0% or more, 5.0% or less
[0030] Si has the effect of increasing the intrinsic resistance of steel to reduce iron loss, and also has the effect of increasing the strength of steel through solid solution strengthening. To obtain these effects, the Si content should be 1.0% or more. On the other hand, if it exceeds 5.0%, the magnetic flux density decreases significantly along with a decrease in saturation magnetic flux density, so the upper limit was set to 5.0% or less. Accordingly, the Si content is set within the range of 1.0% or more and 5.0% or less. Preferably, it is 1.5% or more, and preferably less than 4.5%. More preferably, it is 2.0% or more, and more preferably less than 4.0%.
[0031] Mn: 0.05% or more, 5.0% or less
[0032] Like Si, Mn is a useful element for increasing the intrinsic resistance and strength of steel. To obtain this effect, it is necessary to contain at least 0.05% Mn. On the other hand, a content exceeding 5.0% may promote the precipitation of MnC, thereby degrading magnetic properties. For this reason, the upper limit of the Mn content was set to 5.0%. Accordingly, the Mn content is set within the range of 0.05% to 5.0%. Preferably, it is 0.1% or more, and preferably 3.0% or less.
[0033] P: 0.10% or less
[0034] P is a useful element used to adjust the strength (hardness) of steel. However, if the P content exceeds 0.10%, toughness decreases, making it prone to cracking during processing. Therefore, the upper limit of the P content is set to 0.10%. In addition, although a lower limit is not specifically specified, it is desirable to have a P content of 0.001% or more, given that steel sheets with excessively reduced P are very expensive. Preferably, it is 0.08% or less, and more preferably 0.003% or more.
[0035] S: 0.010% or less
[0036] S is an element that forms fine precipitates and adversely affects iron loss characteristics. In particular, if it exceeds 0.010%, the adverse effect becomes significant. Therefore, the S content is kept at 0.010% or less. More preferably, it is 0.008% or less. In addition, although a lower limit is not specifically specified, given that steel sheets with excessively reduced S are very expensive, it is desirable to keep the S content at 0.0001% or more. More preferably, it is 0.0003% or more, and even more preferably, 0.005% or less.
[0037] Al: 3.0% or less
[0038] If Al is added in excess, it may promote nitriding on the surface of the steel sheet, thereby degrading magnetic properties. Therefore, the Al content is kept at 3.0% or less. More preferably, it is 2.0% or less. In addition, Al, like Si, is a useful element that increases the intrinsic resistance of steel and has the effect of reducing iron loss. To obtain this effect, it is desirable to add 0.005% or more. More preferably, it is 0.010% or more, and even more preferably, 0.015% or more.
[0039] N: 0.0080% or less
[0040] N is an element that forms fine precipitates and has an adverse effect on iron loss characteristics. In particular, since the adverse effect becomes significant when it exceeds 0.0080%, it is kept below 0.0080%. Preferably, it is below 0.0030%. In addition, although a lower limit is not specifically specified, given that steel sheets with excessively reduced N are very expensive, it is desirable to keep the N content at 0.0005% or higher. More preferably, it is above 0.0008%.
[0041] O : 0.0050% or less
[0042] Oxygen (O) is an element that forms non-metallic inclusions in molten steel and has an adverse effect on iron loss characteristics. In particular, if it exceeds 0.0050%, the adverse effect becomes significant. Therefore, the O content is kept at 0.0050% or less. Preferably, it is 0.0030% or less. In addition, although a lower limit is not specifically specified, given that steel sheets with excessively reduced O content are very expensive, it is desirable to keep the O content at 0.0005% or more. More preferably, it is 0.0008% or more.
[0043] The hot-rolled annealed plate related to the present embodiment comprises: C: 0.010% or less, Si: 1.0% or more and 5.0% or less, Mn: 0.05% or more and 5.0% or less, P: 0.10% or less, and S: 0.010% or less.
[0044] It contains Al: 3.0% or less, N: 0.0080% or less, and O: 0.0050% or less, and the remainder contains Fe and unavoidable impurities. In addition, depending on the required characteristics, in addition to the above basic component composition, it may contain at least one element selected from Group A to Group K below.
[0045] Group A: Sn: 0.001% or more and 0.20% or less, and Sb: 0.001% or more and 0.20% or less, one or two types selected from
[0046] Sn: 0.001% or more, 0.20% or less
[0047] Sn is an element effective for improving magnetic flux density and reducing iron loss through the improvement of the texture. To obtain such effects, the Sn content should be 0.001% or more. On the other hand, if the Sn content exceeds 0.20%, the effect becomes saturated, leading to an unnecessary increase in costs. Therefore, it is desirable to set the upper limit of the Sn content to 0.20%. Accordingly, it is desirable for the Sn content to be in the range of 0.001% or more and 0.20% or less.
[0048] Sb: 0.001% or more, 0.20% or less
[0049] Sb is an element effective in improving magnetic flux density and reducing iron loss through the improvement of the texture. To obtain such effects, the Sb content should be 0.001% or more. On the other hand, if the Sb content exceeds 0.20%, the effect becomes saturated, leading to an unnecessary increase in costs. Therefore, it is desirable to set the upper limit of the Sb content to 0.20%. Accordingly, it is desirable for the Sb content to be in the range of 0.001% or more and 0.20% or less.
[0050] Group B: At least one type selected from Ca: 0.0001% or more and 0.10% or less, Mg: 0.0001% or more and 0.10% or less, and REM: 0.0001% or more and 0.10% or less.
[0051] Ca: 0.0001% or more, 0.10% or less
[0052] Ca is an element that contributes to reducing iron loss by fixing S as a sulfide. To obtain this effect, the Ca content should be 0.0001% or more. On the other hand, if the Ca content exceeds 0.10%, the effect becomes saturated, leading to an unnecessary increase in costs. Therefore, it is desirable to set the upper limit of the Ca content to 0.10%. Accordingly, it is desirable for the Ca content to be in the range of 0.0001% or more and 0.10% or less.
[0053] Mg: 0.0001% or more, 0.10% or less
[0054] Mg is an element that contributes to iron loss reduction by fixing S as a sulfide. To obtain this effect, the Mg content should be 0.0001% or more. On the other hand, if Mg exceeds 0.10%, the effect becomes saturated, leading to an unnecessary increase in costs. Therefore, it is desirable to set the upper limit of the Mg content to 0.10%. Accordingly, it is desirable to contain Mg in the range of 0.0001% or more and 0.10% or less.
[0055] REM: 0.0001% or more, 0.10% or less
[0056] REM (rare earth metal elements) is a group of elements that contribute to iron loss reduction by fixing S as sulfides. To obtain this effect, the REM content should be 0.0001% or more. On the other hand, if the REM content exceeds 0.10%, the effect becomes saturated and causes an unnecessary increase in costs, so the upper limit is set to 0.10%. Therefore, it is desirable that the REM content be in the range of 0.0001% or more and 0.10% or less.
[0057] Group C: B: 0.002% or more and 0.20% or less, and Mo: 0.002% or more and 0.20% or less, one or two types selected from
[0058] B: 0.002% or more, 0.20% or less
[0059] B has the effect of increasing the strength of the steel plate by forming fine carbides in the steel. To obtain this effect, the B content should be 0.002% or more. On the other hand, if the B content exceeds 0.20%, excessive carbides are formed, and iron loss increases. Therefore, it is desirable to set the upper limit of the B content to 0.20%. Accordingly, it is desirable for the B content to be in the range of 0.002% or more and 0.20% or less.
[0060] Mo: 0.002% or more, 0.20% or less
[0061] Mo has the effect of increasing the strength of steel sheets by forming fine carbides in the steel. To obtain this effect, the Mo content should be 0.01% or more. On the other hand, if the Mo content exceeds 0.20%, excessive carbides are formed, and iron loss increases. Therefore, it is desirable to set the upper limit of the Mo content to 0.20%. Accordingly, it is desirable for the Mo content to be in the range of 0.01% or more and 0.20% or less.
[0062] Group D: Zn: 0.0005% or more, 0.0050% or less
[0063] Zn is an element effective for improving magnetic flux density and reducing iron loss through the improvement of the texture. To obtain such effects, the Zn content should be 0.0005% or more. On the other hand, if the Zn content exceeds 0.0050%, the effect becomes saturated, leading to an unnecessary increase in costs. Therefore, it is desirable to set the upper limit of the Zn content to 0.0050%. Accordingly, it is desirable to contain Zn in the range of 0.0005% or more and 0.0050% or less.
[0064] Group E: Ni: 0.01% or more and 1.0% or less
[0065] Ni is an element that improves the toughness of steel and can be added appropriately. To obtain such an effect, the Ni content should be 0.01% or more. However, since the effect becomes saturated when the Ni content exceeds 1.0%, the upper limit of the Ni content was set to 1.0%. Therefore, it is desirable for the Ni content to be in the range of 0.01% or more and 1.0% or less.
[0066] Group F: Cr: 0.1% or more and 5.0% or less
[0067] Cr has the effect of increasing the intrinsic resistance of steel and reducing iron loss. To obtain this effect, the Cr content should be 0.05% or more. On the other hand, if the Cr content exceeds 5.0%, the magnetic flux density decreases significantly along with a decrease in saturation magnetic flux density, so the upper limit was set to 5.0%. Therefore, it is desirable for the Cr content to be in the range of 0.05% or more and 5.0% or less.
[0068] Group G: Cu: 0.005% or more, 1.0% or less
[0069] Cu is an element that improves the toughness of steel and can be added appropriately. To obtain such an effect, the Cu content should be 0.01% or more. However, since the effect becomes saturated when the Cu content exceeds 1.0%, the upper limit of the Cu content when adding Cu is set to 1.0%. Therefore, it is desirable to contain Cu in the range of 0.005% or more and 1.0% or less.
[0070] H group: at least one type selected from Ti: 0.001% or more and 0.010% or less, V: 0.001% or more and 0.050% or less, Nb: 0.001% or more and 0.005% or less, Ta: 0.0001% or more and 0.0020% or less, W: 0.001% or more and 0.050% or less, and Pb: 0.0001% or more and 0.0020% or less.
[0071] Ti is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the Ti content should be 0.001% or more. However, if the Ti content exceeds 0.010%, fine precipitates are formed in the steel sheet, increasing iron loss, so it is desirable to set the upper limit of the Ti content to 0.010%.
[0072] V: 0.001% or more, 0.050% or less
[0073] V is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the V content should be 0.001% or more. However, if the V content exceeds 0.050%, fine precipitates will form in the steel sheets and increase iron loss, so it is desirable to set the upper limit of the V content to 0.050%.
[0074] Nb: 0.001% or more, 0.005% or less
[0075] Nb is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the Nb content should be 0.001% or more. However, if the Nb content exceeds 0.005%, fine precipitates will form in the steel sheets and increase iron loss, so it is desirable to set the upper limit of the V content to 0.005%.
[0076] Ta: 0.0001% or more, 0.0020% or less
[0077] Ta is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the Ta content should be 0.0001% or more. However, if the Ta content exceeds 0.0020%, fine precipitates are formed in the steel sheets, increasing iron loss, so it is desirable to set the upper limit of the Ta content to 0.0020%.
[0078] W: 0.001% or more, 0.050% or less
[0079] W is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the W content should be 0.001% or more. However, if the W content exceeds 0.050%, fine precipitates will form in the steel sheets and increase iron loss, so it is desirable to set the upper limit of the W content to 0.050%.
[0080] Pb: 0.0001% or more, 0.0020% or less
[0081] Pb is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain such an effect, the Pb content should be 0.0001% or more. However, if the Pb content exceeds 0.0020%, fine precipitates will form in the steel sheets and increase iron loss, so it is desirable to set the upper limit of the Pb content to 0.0020%.
[0082] Group I : Co : 0.001% or more 0.100% or less
[0083] Co is an element that has the effect of increasing the magnetic flux density of steel sheets and can be added appropriately. To obtain such an effect, the Co content should be 0.001% or more. However, since increasing the amount of Co increases the alloy cost, it is desirable to set the upper limit of the Co content to 0.100%.
[0084] Group J: One or two types selected from Ga: 0.0005% or more and 0.0300% or less, and Ge: 0.0005% or more and 0.0300% or less.
[0085] Ga: 0.0005% or more, 0.0300% or less
[0086] Ga is an element that improves the texture of steel sheets and increases magnetic flux density, and can be added appropriately. To obtain such an effect, the Ga content should be 0.0005% or more. However, since adding a large amount of Ga saturates the effect and increases alloy costs, it is desirable to set the upper limit of the Ga content to 0.0300%.
[0087] Ge: 0.0005% or more, 0.0300% or less
[0088] Ge is an element that improves the texture of steel sheets and increases magnetic flux density, and can be added appropriately. To obtain such an effect, the Ge content should be 0.0005% or more. However, since adding a large amount of Ge saturates the effect and increases alloy costs, it is desirable to set the upper limit of the Ge content to 0.0300%.
[0089] Group K : As : 0.001% or more 0.020% or less
[0090] As is an element that has the effect of increasing the strength of steel sheets and can be added appropriately. To obtain this effect, the As content should be 0.001% or more. However, if the As content exceeds 0.020%, the risk of fracture during cold rolling increases. Therefore, it is desirable to set the upper limit of the As content to 0.020%.
[0091] Among the above optional elements, amounts below the desirable range for effective function are permitted as unavoidable impurities, as they do not affect cold rolling properties or the magnetic properties of electrical steel sheet products.
[0092] <Microstructure of Steel Plate>
[0093] Next, the microstructure of the hot-rolled annealed plate related to the present embodiment will be described. Here, recrystallization refers to the generation and growth of crystal grains with significantly low dislocation density by maintaining the material at a high temperature. Recrystallized and unrecrystallized structures can be distinguished by observation using an optical microscope.
[0094] 《The ratio of the ratio of the recrystallized structure Re at Xe, located 10 mm away in the width direction from the furthest edge of the plate, to the ratio Rc of the recrystallized structure Xc at the center of the plate width: Re / Rc is 0.95 or less》
[0095] According to the inventors' review, by setting a difference in the ratio of the recrystallized structure between the center of the plate width and the edge of the plate width, fracture or edge cracking during the cold rolling process was suppressed significantly more than simply lowering the ratio of the recrystallized structure of the entire hot-rolled annealed plate. The inventors believe the reason for this is as follows. Generally, the work hardening rate for plastic deformation decreases along with a decrease in the ratio of the recrystallized structure. It is presumed that because the work hardening rate of the edge of the plate width is smaller than that of the center of the plate width, a stress that reduces the tension of the edge of the plate width was applied during rolling. As a result, it is believed that the occurrence of crack initiation points at the edge of the steel plate was significantly suppressed, thereby reducing fracture or edge cracking. That is, by making the ratio Re / Rc of the recrystallized structure at a position Xe 10 mm away from the widest edge of the plate in the width direction relative to the ratio Rc of the recrystallized structure at the center of the plate width Xc of the hot-rolled annealed plate 0.95 or less, it is possible to produce a hot-rolled annealed plate that sufficiently suppresses fracture or edge cracking during cold rolling. Preferably, it is 0.8 or less, and more preferably 0.7 or less. Although there is no need to specifically limit the lower limit, it is typically 0.05 or more for a hot-rolled annealed plate manufactured using the method described below.
[0096] The ratio Rc of the recrystallized structure in the central Xc of the plate width is 80% or more.
[0097] The hot-rolled annealed plate of the present embodiment controls the ratio of the recrystallized structure ratio Rc in the central part of the plate width to the ratio Re of the recrystallized structure at steel plate position Xe on the edge side of the plate width, and the effect of the present invention is not limited by the value of the ratio of the recrystallized structure in the central part of the plate width itself. Meanwhile, there exists a preferred range for the ratio of the recrystallized structure in the central part of the plate width, and the effect of the present invention becomes even more pronounced when it is within that range. When the ratio of the recrystallized structure at Xc in the central part of the plate width is 80% or more, it is difficult for the magnetic properties of the final product to deteriorate. As described above, it is more preferable that the ratio Rc of the recrystallized structure at Xc in the central part of the plate width is 80% or more.
[0098] The ratio Re of the recrystallized structure at position Xe on the edge side of the plate width is in the range of 5% or more and 95% or less.
[0099] The hot-rolled annealed plate of the present embodiment controls the ratio of the recrystallized structure Rc at the center of the plate width and the ratio of the recrystallized structure Re at position Xe on the plate width edge side, and the effect of the present invention is not limited by the value of the ratio of the recrystallized structure at position Xe on the plate width itself. On the other hand, there exists a preferred range for the ratio of the recrystallized structure at position Xe on the plate width, and the effect of the present invention becomes even more pronounced when it is within that range. In the hot-rolled annealed plate of the present embodiment, if the ratio of the recrystallized structure Re at position Xe on the plate width edge side is 5% or more, the plate width edge side does not become excessively hard, and the formation of fracture initiation points is suppressed. On the other hand, if the ratio of the recrystallized structure Re at position Xe on the plate width edge side is 95% or less, the fracture suppression effect resulting from controlling the above-mentioned ratio Re / Rc is likely to be significantly exhibited. In the above, it is desirable that the ratio Re of the recrystallized structure at position Xe on the edge side of the plate width be in the range of 5% or more and 95% or less.
[0100] [Manufacturing Conditions for Hot-Rolled Annealed Plates]
[0101] Next, a method for manufacturing a hot-rolled annealed plate related to the present embodiment will be described.
[0102] In summary, the method involves sequentially performing hot rolling and hot-rolled plate annealing on a steel material having the above compositional properties to obtain a hot-rolled annealed plate related to the present embodiment described above. In the present embodiment, as long as the above compositional properties and the hot-rolled plate annealing conditions are within the scope specified in the patent claims, any other method may be a commonly known method.
[0103] <River Material>
[0104] The steel material is not particularly limited as long as it is a steel material having the above-mentioned composition.
[0105] The method of melting the steel material and the method of adjusting its composition are not particularly limited, and known melting methods using a converter or electric furnace, vacuum degassing device, and other devices and methods may be employed. Due to issues such as productivity, it is preferable to make the material into a slab (steel material) by a continuous casting method after melting. On the other hand, the material may be made into a slab or a thin slab by known casting methods such as ingot-blowing rolling or thin slab continuous casting.
[0106] <Hot Rolling Process>
[0107] The hot rolling process is a process of obtaining a hot-rolled plate by performing hot rolling on a steel material having the above composition. The hot rolling process is not particularly limited, and any commercially available hot rolling process may be applied, as long as it is a process in which a steel material having the above composition is heated and hot-rolled to obtain a hot-rolled plate of a predetermined size.
[0108] As an example of a commercial hot rolling process, the following hot rolling process may be exemplified. For example, a steel material is heated to a temperature in the range of 1000°C to 1200°C. Hot rolling is performed on the heated steel material at a finish rolling exit temperature in the range of 800°C to 950°C. After the hot rolling is completed, appropriate post-rolling cooling is performed, for example, at a temperature range of 450°C to 950°C at an average cooling rate in the range of 20°C / s to 100°C / s. Then, the material is coiled at a coiling temperature in the range of 400°C to 700°C to form a hot-rolled plate of a predetermined size and shape.
[0109] <Hot Rolled Plate Annealing Process>
[0110] The hot-rolled plate annealing process is a process of annealing a hot-rolled plate by heating the hot-rolled plate and maintaining it at a high temperature. More specifically, when the central part Xc of the plate width of the hot-rolled plate is heated and maintained to an appropriate holding temperature T1 required for the recrystallization of the hot-rolled plate, the steel plate position Xe, located 10 mm away in the width direction from the outermost edge of the plate width of the hot-rolled plate, reaches a maximum temperature T2, which is lower than the holding temperature T1 from room temperature. Furthermore, it is a hot-rolled plate annealing process in which the heating rate Vc of the central part Xc of the plate width is at least 1.0 ℃ / s greater than the heating rate Ve of the steel plate position Xe. Also, preferably, the holding temperature T1 is 900 ℃ or higher. Preferably, the holding time t1 at the holding temperature T1 is in the range of 2 s or more and 120 s or less. Preferably, the maximum temperature T2 at the steel plate position Xe is in the range of 750 ℃ or more and 1000 ℃ or less. Preferably, the time t2 at the maximum temperature T2 of the steel plate position Xe is 50°C or higher is set to a range of 5 s or more and 20 s or less. Preferably, in providing a hot-rolled plate with a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, the hot-rolled plate annealing process forms a heating inhibition zone in a range of 20 mm or more in the plate width direction from the widest edge of the plate width to a range of 0.250 × W or less in the plate width direction from the widest edge of the plate width.
[0111] In addition, a standard pickling process is performed after the hot-rolled plate annealing process. The pickling process is not particularly limited as long as it is a process capable of pickling the steel plate to a degree that allows for cold rolling after pickling; for example, a commercial pickling process using hydrochloric acid or sulfuric acid may be applied. This pickling process may be performed continuously within the same line as the hot-rolled plate annealing process or on a different line. The hot-rolled plate annealed in the present invention includes both a state in which pickling has not been performed (black scale) and a state in which pickling has been performed (white scale).
[0112] The heating rate Vc at the center of the plate width Xc is made at least 1.0 ℃ / s greater than the heating rate Ve at the steel plate position Xe.
[0113] In the hot-rolled sheet annealing process, the heating rate when heating the center of the sheet width Xc from room temperature to a holding temperature T1 is set as Vc. Also, the heating rate when steel sheet position Xe, located 10 mm away in the width direction from the widest edge of the sheet, reaches the maximum temperature T2 from room temperature is set as Ve. Furthermore, it is limited to Vc - Ve ≥ 1.0 ℃ / s. If Vc - Ve < 1.0 ℃ / s, the difference in the ratio of the recrystallized structure between the center of the sheet width and the edge of the sheet width becomes small, so the ratio of the recrystallized structure Rc of the center of the sheet width to the ratio Re of the recrystallized structure Re of the edge of the sheet width, Re / Rc, cannot be made 0.95 or less. Preferably, Vc - Ve ≥ 3 ℃ / s, and more preferably, Vc - Ve ≥ 5 ℃ / s.
[0114] Maintaining temperature T1 of the center of the plate width Xc at 900 ℃ or higher
[0115] In the hot-rolled sheet annealing process, it is preferable to set the holding temperature T1 at the center of the sheet width Xc to 900°C or higher. By setting T1 to 900°C or higher, the ratio Rc of the recrystallized structure at the center of the sheet width Xc can be set to 80% or higher. Additionally, although no specific upper limit is specified, if T1 is higher than 1100°C, the edge of the sheet width is heated by heat conduction, and there is a risk that the ratio of the recrystallized structure at the edge of the sheet width will become excessively high. Therefore, it is preferable to control the holding temperature T1 at the center of the sheet width Xc to be between 900°C and 1100°C.
[0116] The holding time t1 at the holding temperature T1 of the center part Xc of the plate width is set to be between 2 s and 120 s.
[0117] In the hot-rolled sheet annealing process, it is preferable to set the holding time t1 at the holding temperature T1 at the center of the sheet width Xc to be 2 s or more and 120 s or less. If t1 is 120 s or less, the ratio of the recrystallization structure between the center of the sheet width and the edge of the sheet width, Re / Rc, can be set to 0.95 or less, which improves cold rolling performance and is therefore desirable. In addition, by setting the lower limit of the holding time t1 to 2 s, sufficient recrystallization and grain growth by hot-rolled sheet annealing are achieved, resulting in good magnetic properties. Accordingly, it is preferable to set the holding time t1 at the holding temperature T1 at the center of the sheet width Xc to be 2 s or more and 120 s or less.
[0118] The maximum temperature T2 at steel plate location Xe shall be in the range of 750 ℃ or higher and 1000 ℃ or lower.
[0119] In the hot-rolled sheet annealing process, it is desirable that the maximum temperature T2 at a steel sheet position Xe, located 10 mm away in the width direction from the widest edge of the hot-rolled sheet, be 750°C or higher and 1000°C or lower. If the maximum temperature T2 is 750°C or higher, recrystallization at steel sheet position Xe is sufficient, satisfying the requirement that the ratio Re of the recrystallized structure is 5% or higher. On the other hand, if the maximum reached temperature T2 is 1000°C or lower, the requirement that the ratio Re of the recrystallized structure is 95% or lower is satisfied. Therefore, it is desirable that the maximum reached temperature T2 at steel sheet position Xe be 750°C or higher and 1000°C or lower. The maximum reached temperature T2 at steel sheet position Xe needs to be lower than the holding temperature T1 at the center of the sheet width Xc. Otherwise, the ratio Re of the recrystallized structure at steel sheet position Xe will become higher than the ratio Rc of the recrystallized structure at the center of the sheet width Xc.
[0120] The time t2 during which the maximum temperature T2 of the steel plate position Xe is 50 ℃ or higher shall be in the range of 5 s or more and 20 s or less.
[0121] In the hot-rolled sheet annealing process, it is desirable to set the time t2, during which the maximum temperature T2 of the steel sheet position Xe is 50°C or higher, to a range of 5 s or more and 20 s or less. Additionally, t2 is the sum of the time for heating to the maximum temperature T2 and the time for cooling from the maximum temperature T2. If t2 is 5 s or more, sufficient time can be secured from the time the steel sheet position Xe reaches the maximum temperature T2 until it cools down, allowing recrystallization to proceed appropriately and enabling the ratio of the recrystallized structure Re to be 5% or more. If t2 is 20 s or less, recrystallization proceeds appropriately, allowing the ratio of the recrystallized structure Re to be 95% or less.
[0122] A heating inhibition zone is formed in a range of 20 mm or more in the direction of the plate width from the outermost edge of the plate width.
[0123] In the annealing process of a hot-rolled sheet, the following methods may be exemplified for forming a heat suppression zone that intentionally imparts a temperature change in the sheet width direction: (a) prevention of overheating by weakening burner heating only at the edge portion; (b) prevention of heating by covering the edge; (c) application of a temperature rise prevention material capable of suppressing radiative heating with low emissivity; and (d) prevention of temperature rise by reducing emissivity by removing black scale only at the edge portion. Any method capable of imparting an intentional temperature change may be used, and this does not limit the scope of the invention. It is preferable to form a heat suppression zone in a range of 20 mm or more in the sheet width direction from the outermost edge portion of the sheet width. If the heat suppression zone is in a range of 20 mm or more from the outermost edge portion of the sheet width, it becomes difficult for the temperature at position Xe of the steel sheet, 10 mm from the outermost edge, to rise due to heat conduction in the steel sheet. Therefore, the heating rate Vc at the center of the plate width Xc can be made at least 1.0 °C / s greater than the heating rate Ve at the steel plate position Xe. Meanwhile, regarding the upper limit of the heating suppression region, when providing a hot-rolled plate with a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, it is preferable to form a heating suppression region in the range from the widest edge of the plate width to 0.250 × W or less in the plate width direction. In this range, the proportion of the recrystallization structure throughout the steel plate becomes sufficient, thereby suppressing the deterioration of magnetic properties. Accordingly, preferably, the heating suppression region is set to a range of 20 mm or more in the plate width direction from the widest edge of the plate width. Preferably, when providing a hot-rolled plate with a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, the heating suppression region is set to a range from the widest edge of the plate width to 0.250 × W or less in the plate width direction.
[0124] <Pickling Process>
[0125] The pickling process is a process of pickling the hot-rolled annealed plate after the above-mentioned hot-rolled plate annealing process. The pickling process is not particularly limited as long as it is a process capable of pickling the steel plate to a degree that allows for cold rolling after pickling, and commercially available pickling processes using, for example, hydrochloric acid or sulfuric acid may be applied. When the above-mentioned hot-rolled plate annealing process is performed, this pickling process may be performed continuously within the same line as the hot-rolled plate annealing process or on a different line.
[0126] <Cold Rolling Process>
[0127] The cold rolling process is a process of performing cold rolling on the hot-rolled annealed plate (pickled plate) that has undergone the above-mentioned pickling. In the cold rolling process, a cold-rolled plate is obtained by performing cold rolling on the hot-rolled annealed plate that has undergone the above-mentioned pickling. Any commercial cold rolling process can be applied as long as it is a process in which a cold-rolled plate of a predetermined size is obtained by performing cold rolling, without being particularly limited.
[0128] As a commercial cold rolling process, for example, a cold rolling process in which a pickled plate is rolled under conditions of a total reduction ratio of 80% or more and less than 95% using a 5-stand tandem mill to form a cold rolled plate of a predetermined size and shape can be provided. The number of stands may be 4 stands or less, or 6 stands or more.
[0129] <Final Annealing Process>
[0130] The finishing annealing process is a process of obtaining a cold-rolled annealed plate by performing annealing on a cold-rolled plate that has undergone a cold rolling process. The finishing annealing process is not particularly limited as long as it is a process in which the cold-rolled plate is heated, held, and cooled to obtain a cold-rolled annealed plate, and any commercially available annealing process may be applied. Additionally, an insulating coating may be applied to the surface after the finishing annealing process. The method and type of insulating coating are not particularly limited, and any commercially available insulating coating process may be applied.
[0131] As an example of a commercial annealing process, a finishing annealing process can be exemplified by heating a cold-rolled sheet to a temperature of 800°C or higher and 1200°C or lower under a non-oxidizing atmosphere, holding it for 5 to 60 seconds, and then cooling it.
[0132] Examples
[0133] The present invention will be specifically explained below with reference to examples. However, the present invention is not limited to these.
[0134] <Manufacture of Hot-Rolled Annealed Sheets>
[0135] Molten steel having the compositional composition shown in Table 1 was melted by a commonly known method and continuously cast to form a slab (steel material) with a thickness of 230 mm. By hot rolling the obtained slab, a hot-rolled plate with a thickness of 2.0 mm was obtained. The obtained hot-rolled plate was subjected to hot-rolled annealing and pickling under the conditions shown in Tables 2-1 and 2-2 to obtain a hot-rolled annealed plate (pickled plate).
[0136] <Manufacture of Cold-Rolled Sheets>
[0137] A hot-rolled annealed plate (pickled plate) was subsequently cold-rolled to a thickness of 0.25 mm using a tandem mill at room temperature to obtain a cold-rolled plate.
[0138] <Manufacture of Cold-Rolled Annealed Sheets>
[0139] A cold-rolled plate was then subjected to finishing annealing by a known method of holding at 1000°C for 10 seconds in a non-oxidizing atmosphere, and then subjected to coating by a known method to obtain a cold-rolled annealed plate (non-oriented electrical steel plate).
[0140] [Table 1]
[0141]
[0142] [Table 2-1]
[0143]
[0144] [Table 2-2]
[0145]
[0146] <Evaluation>
[0147] ≪Tissue Observation≫
[0148] For the obtained hot-rolled annealed plate, specimens for microstructure observation were taken from the center of the plate width and from a position 10 mm from the edge of the plate width. Subsequently, the taken specimens were embedded in resin with the cross-section in the plate thickness direction as the observation surface, and observed with an optical microscope to measure the ratio of recrystallized microstructure.
[0149] ≪Rollability Evaluation≫
[0150] For the obtained cold-rolled sheet, the number of edge cracks per 1000 m length was investigated. Edge cracks with a crack length of 2 mm or more were counted as the number N. It was stated that the cold rolling performance was good when the number of edge cracks per 1000 m length of the cold-rolled sheet was 2.0 or less.
[0151] ≪Self-Assessment≫
[0152] From the obtained cold-rolled annealed plate, a magnetic measurement test specimen with a width of 30 mm and a length of 280 mm was taken with the longitudinal direction oriented as the rolling direction and the rolling direction perpendicular to the rolling direction, and the magnetic flux density B50 and iron loss W of the cold-rolled annealed plate were measured by the Epstein method in accordance with JIS C2550-1:2011. 10 / 400 was measured. The magnetic flux density was evaluated as good when B50 ≥ 1.55 T, and W after annealing 10 / 400 The iron loss characteristics were evaluated as good when ≤ 14.0 W / kg.
[0153] In the evaluation section, regarding cold rolling performance, fractures occurring during rolling and the number of edge cracks exceeding 2.0 per 1,000 m length of the cold-rolled sheet were indicated as "defective." Additionally, the composition is outside the scope of the present invention, and regardless of the hot-rolled sheet annealing conditions, a magnetic flux density B50 of less than 1.55 T, or an iron loss W 10 / 400 Those exceeding 14.0 W / kg were evaluated as "defective." Among the remainder, those with a magnetic flux density B50 of 1.55 T or higher, and iron loss W 10 / 400 Those with a value of 14.0 W / kg or less were labeled as "Excellent," and the rest were labeled as "Good."
[0154] [Table 3-1]
[0155]
[0156] [Table 3-2]
[0157]
[0158] From the results of Tables 3-1 and 3-2, it can be seen that the hot-rolled annealed plate according to the present invention has excellent cold rolling properties, and also that the cold-rolled annealed plate obtained by cold rolling and annealing the hot-rolled annealed plate according to the present invention has excellent magnetic properties.
Claims
Claim 1 In mass%, it contains C: 0.010% or less, Si: 1.0% or more and 5.0% or less, Mn: 0.05% or more and 5.0% or less, P: 0.10% or less, S: 0.010% or less, Al: 3.0% or less, N: 0.0080% or less, and O: 0.0050% or less, and additionally optionally, Group A: one or two types selected from Sn: 0.001% or more and 0.20% or less, and Sb: 0.001% or more and 0.20% or less; Group B: Ca: 0.0001% or more and 0.10% or less, Mg: 0.0001% or more and 0.10% or less, and REM: 0.0001% or more and 0.10% or less. At least one type selected from among; Group C: B: 0.002% or more and 0.20% or less, and Mo: 0.002% or more and 0.20% or less, one or two types selected from; Group D: Zn: 0.0005% or more and 0.0050% or less; Group E: Ni: 0.01% or more and 1.0% or less; Group F: Cr: 0.1% or more and 5.0% or less; Group G: Cu: 0.005% or more and 1.0% or less; H group: at least one selected from Ti: 0.001% or more and 0.010% or less, V: 0.001% or more and 0.050% or less, Nb: 0.001% or more and 0.005% or less, Ta: 0.0001% or more and 0.0020% or less, W: 0.001% or more and 0.050% or less, and Pb: 0.0001% or more and 0.0020% or less; I group: Co: 0.001% or more and 0.100% or less; J group: Ga: 0.0005% or more and 0.0300% or less, and Ge: 0.0005% or more and 0.0300% or less; and K group: As: 0.001% or more and 0.0300% or less.A hot-rolled annealed plate having a composition in which at least one group of elements selected from 0.20% or less is present, and the remainder consists of Fe and unavoidable impurities, and the ratio Re / Rc of the ratio of the recrystallized structure Re at a steel plate position Xe, 10 mm away in the width direction from the widest edge of the plate, to the ratio Rc of the recrystallized structure at the center of the plate width Xc is 0.95 or less. Claim 2 A hot-rolled annealed plate according to claim 1, additionally satisfying either or both of the following: the ratio Rc of the recrystallized structure at the center of the plate width Xc is 80% or more, and the ratio Re of the recrystallized structure at the steel plate position Xe is in the range of 5% or more and 95% or less. Claim 3 A method for manufacturing a hot-rolled annealed plate according to claim 1 or 2, comprising a hot rolling process for obtaining a hot-rolled plate by performing hot rolling on a steel material having the above compositional composition, and a hot-rolled plate annealing process for performing hot-rolled plate annealing on the hot-rolled plate, wherein in the hot-rolled plate annealing process, when the central part Xc of the plate width of the hot-rolled plate is heated from room temperature to a holding temperature T1 and maintained, the steel plate position Xe, located 10 mm away in the width direction from the outermost edge of the plate width of the hot-rolled plate, reaches a maximum temperature T2, which is lower than the holding temperature T1, from room temperature, and the heating rate Vc of the central part Xc of the plate width is made greater than the heating rate Ve of the steel plate position Xe by at least 1.0 ℃ / s. Claim 4 In claim 3, a method for manufacturing a hot-rolled annealed plate, wherein the hot-rolled plate annealing process satisfies at least one of the following (1) to (4): (1) setting the holding temperature T1 at the center of the plate width Xc of the hot-rolled plate to 900 ℃ or higher; (2) setting the holding time t1 at the holding temperature T1 at the center of the plate width Xc of the hot-rolled plate to a range of 2 s or more and 120 s or less; (3) setting the maximum temperature T2 at the steel plate position Xe to a range of 750 ℃ or more and 1000 ℃ or less; and (4) setting the time t2 at the maximum temperature T2 - 50 ℃ or higher to a range of 5 s or more and 20 s or less. Claim 5 A method for manufacturing a hot-rolled annealed plate according to claim 3, wherein, in providing a hot-rolled plate having a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, a heating inhibition region is formed in a range of 20 mm or more in the plate width direction from the widest edge of the plate width to a range of 0.250 × W or less in the plate width direction from the widest edge of the plate width. Claim 6 A method for manufacturing a hot-rolled annealed plate according to claim 4, wherein, in providing a hot-rolled plate having a plate width W in the range of 900 mm or more and 1100 mm or less to the hot-rolled plate annealing process, a heating inhibition region is formed in a range of 20 mm or more in the plate width direction from the widest edge of the plate width to a range of 0.250 × W or less in the plate width direction from the widest edge of the plate width. Claim 7 A method for manufacturing a non-oriented electrical steel sheet, wherein a hot-rolled annealed sheet described in claim 1 or 2 is cold-rolled to form a cold-rolled sheet, and said cold-rolled sheet is finished annealed to form a cold-rolled annealed sheet.