Hot-rolled annealed sheet, method for producing same, and method for producing non-oriented electromagnetic steel sheet

Abstract

Provided is a hot-rolled annealing technique for an electromagnetic steel sheet having excellent cold rolling properties. The present invention provides a hot-rolled annealed sheet that has a component composition containing, in terms of mass%, 0.010% or less of C, 1.0-5.0% of Si, 0.05-5.0% of Mn, 0.10% or less of P, 0.010% or less of S, 3.0% or less of Al, 0.0080% or less of N, and 0.0050% or less of O, with the balance being Fe and unavoidable impurities, and in which the ratio Re / Rc of the recrystallized structure between a sheet width center section and an edge section is 0.95 or less. The present invention also provides a method for producing a hot-rolled annealed sheet, in which: a hot-rolled sheet is obtained by subjecting a steel material having the above component composition to hot rolling; the hot-rolled sheet is subjected to hot-rolled sheet annealing; when a sheet width center section of the hot-rolled sheet is heated from the normal temperature to holding temperature and held thereat during the hot-rolled sheet annealing, an edge section of the hot-rolled sheet reaches a maximum temperature, which is lower than the holding temperature, from the normal temperature; and the temperature rising rate Vc of the sheet width center section is increased by 1.0°C / s or more from the temperature rising rate Ve of the edge section.

Description

Hot-rolled annealed sheet, its manufacturing method, and manufacturing method of non-oriented electrical steel sheet

[0001] The present invention relates to a hot-rolled annealed steel sheet, a method for manufacturing the same, and a method for manufacturing a non-oriented electrical steel sheet.

[0002] In recent years, due to concerns about the environment such as global warming, ２ There is a demand for reducing emissions and saving energy. In particular, in the automotive field, development is underway for hybrid electric vehicles (HEVs) that use both engines and motors, electric vehicles (EVs) that are driven solely by electric motors, and fuel cell electric vehicles (FCEVs). To improve motor efficiency, motors used in HEVs, EVs, FCEVs, and the like are generally driven in a high frequency range that is advantageous for high-speed rotation. Non-oriented electrical steel sheets are often used as the iron 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 the high frequency range.

[0003] Conventionally, non-oriented electrical steel sheets have been designed to have low iron loss by increasing resistivity through the addition of alloying elements such as Si and Al, or by reducing eddy current loss through thinning the sheet thickness. However, adding large amounts of alloying elements reduces the ductility and toughness of the steel sheet, resulting in frequent fractures during the cold rolling process.

[0004] As a technique for suppressing fracture of high alloy steel, for example, Patent Document 1 discloses a method for producing a non-oriented electrical steel sheet with high magnetic flux density in which cracking during cold rolling is suppressed by cold rolling a rapidly solidified cast slab at 180°C to 350°C.

[0005] Japanese Patent Application Laid-Open No. 2004-110985

[0006] However, in the technology described in Patent Document 1, although cracking can certainly be suppressed by performing cold rolling in a temperature range of 180 to 350°C, there are problems in that it is difficult to maintain a high temperature of the steel sheet during rolling, and in that there is a high possibility of causing equipment wear, such as seizure of lubricating oil on the rolls.

[0007] In order to solve the above-mentioned problems of the prior art, the present invention aims to provide a hot-rolled annealed steel sheet that is excellent in cold rolling ductility in a subsequent process without causing a deterioration in the magnetic properties of the final product, the non-oriented electrical steel sheet, and to propose an advantageous manufacturing method thereof. Another object is to propose a manufacturing method of a non-oriented electrical steel sheet using the hot-rolled annealed steel sheet. Here, the cold-rolling ductility includes fracture resistance and edge crack resistance.

[0008] After extensive research, the inventors discovered that in most cases, fractures caused by cold rolling originate at the edge of the steel strip. Therefore, they found that increasing the fracture resistance of the edge of the steel strip can significantly suppress fractures and cracks caused by cold rolling, even without increasing the fracture resistance of the entire steel strip. Furthermore, they discovered that a method for increasing the fracture resistance of the edge of the steel strip is to leave a non-recrystallized structure at the edge of the steel strip and differentiate the ratio of recrystallized structure from that of the center of the steel strip. They found that this improves fracture resistance compared to reducing the ratio of recrystallized structure throughout the steel strip, while preventing a deterioration in magnetic properties.

[0009] That is, the hot-rolled annealed steel sheet according to the present invention, which advantageously solves the above-mentioned problems, contains, by 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 element 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. or two types; 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; Group C: one or two types 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; G group: Cu: 0.005% or more and 1.0% or less; H group: 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, 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. and one or two elements selected from the group consisting of Ge: 0.0005% to 0.0300%; and at least one element selected from the group consisting of K, As: 0.001% to 0.020% with the balance being Fe and unavoidable impurities, and the steel sheet is characterized in that the ratio Re / Rc of the recrystallized structure at the steel sheet position Xe 10 mm away from the outermost edge in the width direction to the ratio Rc of the recrystallized structure at the center Xc of the sheet width is 0.95 or less.

[0010] In addition, it is more preferable that the hot-rolled annealed steel sheet according to the present invention further satisfies either one or both of the following: the ratio Rc of the recrystallized structure in the sheet width center portion Xc is 80% or more; and the ratio Re of the recrystallized structure in the steel sheet position Xe is in the range of 5% or more and 95% or less.

[0011] Further, a method for producing a hot-rolled annealed sheet according to the present invention, which advantageously solves the above-mentioned problems, is a method for producing any of the above-mentioned hot-rolled annealed sheets, and includes a hot rolling step of hot-rolling a steel material having the above-mentioned composition to obtain a hot-rolled sheet, and a hot-rolled sheet annealing step of annealing the hot-rolled sheet, wherein in the hot-rolled sheet annealing step, a width center portion Xc of the hot-rolled sheet is heated from room temperature to a holding temperature T １ When the hot rolled plate is heated to and held at the holding temperature T １ The maximum temperature T ２ and the temperature rise rate Vc at the sheet width center portion Xc is made 1.0° C. / s or more higher than the temperature rise rate Ve at the steel sheet position Xe.

[0012] In addition, the method for producing a hot-rolled annealed sheet according to the present invention is more preferably achieved by: (a) satisfying at least one of the following (1) to (4) in the hot-rolled sheet annealing step; (b) when subjecting a hot-rolled sheet having a sheet width W in the range of 900 mm to 1100 mm to the hot-rolled sheet annealing step, providing a heat suppression region in a range from 20 mm or more in the sheet width direction from the outermost edge of the sheet width to 0.250 × W or less in the sheet width direction from the outermost edge of the sheet width. １ (2) the holding temperature T １ Holding time t １ (3) the maximum temperature T at the steel plate position Xe is in the range of 2 seconds or more and 120 seconds or less; ２ (4) the maximum temperature T ２ Time t when the temperature is above -50°C ２ is in the range of 5 seconds or more and 20 seconds or less.

[0013] The method for producing a non-oriented electrical steel sheet according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that any of the hot-rolled and annealed sheets described above is cold-rolled to form a cold-rolled sheet, and the cold-rolled sheet is finish-annealed to form a cold-rolled and annealed sheet.

[0014] 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 to reduce breakage even on one side. For example, if edge cracks or breakage occur unevenly on one edge due to the characteristics of the rolling mill, applying this technology to only one side will achieve the effect of reducing breakage.

[0015] According to the present invention, a hot-rolled and annealed steel sheet having excellent cold rolling properties can be provided. Furthermore, the hot-rolled and annealed steel sheet can be used to produce a non-oriented electrical steel sheet having high magnetic flux density, high frequency, and low iron loss.

[0016]

[0033] Hereinafter, embodiments of the present invention will be described together with the reasons for their limitations. [Hot-rolled annealed sheet] <Component composition of steel sheet> A preferred component composition of a hot-rolled annealed sheet according to one embodiment of the present invention will be described. The unit of the content of elements in the component composition is always "mass%", and hereinafter, unless otherwise specified, will be simply represented as "%".

[0017] <Basic Component Composition> C: 0.010% or Less C is a harmful element that causes magnetic aging in the finished non-oriented electrical steel sheet, forming carbides and increasing iron loss. Therefore, if the C content exceeds 0.010%, the adverse effects become particularly pronounced, so the C content in the steel sheet is set to 0.010% or less. Preferably, it is set to 0.004% or less. There is no particular lower limit for the C content, but since steel sheets with excessively reduced C content are very expensive, it is preferable to set it to about 0.0001%.

[0018] Si: 1.0% or more and 5.0% or less Si has the effect of increasing the resistivity of steel and reducing iron loss, and also has the effect of increasing the strength of steel through solid solution strengthening. To achieve these effects, the Si content should be 1.0% or more. On the other hand, if the Si content exceeds 5.0%, the magnetic flux density decreases significantly due to a decrease in the saturation magnetic flux density, so the upper limit is set to 5.0% or less. Therefore, the Si content is set to be in 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%.

[0019] Mn: 0.05% or more and 5.0% or less Like Si, Mn is a useful element for increasing the resistivity and strength of steel. To achieve this effect, the Mn content must be 0.05% or more. On the other hand, a content exceeding 5.0% may promote the precipitation of MnC, deteriorating the magnetic properties. Therefore, the upper limit of the Mn content is set to 5.0%. Therefore, the Mn content is set to the range of 0.05% or more and 5.0% or less. Preferably, it is 0.1% or more and preferably 3.0% or less.

[0020] P: 0.10% or less P is a useful element used to adjust the strength (hardness) of steel. However, if the P content exceeds 0.10%, toughness decreases and cracks tend to occur during processing. Therefore, the upper limit of the P content is set to 0.10%. Although there is no particular lower limit, since steel sheets with excessively reduced P content are very expensive, it is preferable that the P content be 0.001% or more. The P content is preferably 0.08% or less, and more preferably 0.003% or more.

[0021] S: 0.010% or less S is an element that forms fine precipitates and adversely affects iron loss characteristics. In particular, if the S content exceeds 0.010%, the adverse effects become significant. Therefore, the S content is set to 0.010% or less, and more preferably 0.008% or less. Although there is no particular lower limit, since steel sheets with excessively reduced S content are very expensive, it is preferable that the S content be 0.0001% or more. More preferably, it is 0.0003% or more, and even more preferably 0.005% or less.

[0022] Al: 3.0% or less Excessive addition of Al can promote nitriding of the steel sheet surface and degrade magnetic properties. Therefore, the Al content is set to 3.0% or less, and more preferably 2.0% or less. Similarly to Si, Al is a useful element that has the effect of increasing the resistivity of steel and reducing iron loss. To achieve this effect, it is preferable to add 0.005% or more, more preferably 0.010% or more, and even more preferably 0.015% or more.

[0023] N: 0.0080% or less N is an element that forms fine precipitates and adversely affects iron loss characteristics. In particular, if the N content exceeds 0.0080%, the adverse effects become significant, so the N content is set to 0.0080% or less. Preferably, the N content is set to 0.0030% or less. Although there is no particular lower limit, steel sheets with excessively reduced N content are very expensive, so the N content is preferably set to 0.0005% or more. More preferably, the N content is set to 0.0008% or more.

[0024] O: 0.0050% or less O (oxygen) is an element that forms non-metallic inclusions in molten steel and adversely affects iron loss characteristics. In particular, if the O content exceeds 0.0050%, the adverse effects become significant. Therefore, the O content is set to 0.0050% or less, and preferably 0.0030% or less. Although there is no particular lower limit, since steel sheets with excessively reduced O content are very expensive, the O content is preferably set to 0.0005% or more, and more preferably 0.0008% or more.

[0025] The hot-rolled annealed steel sheet according to this embodiment contains 0.010% or less of C, 1.0% to 5.0% of Si, 0.05% to 5.0% of Mn, 0.10% or less of P, 0.010% or less of S, 3.0% or less of Al, 0.0080% or less of N, and 0.0050% or less of O, with the balance being Fe and unavoidable impurities. Furthermore, depending on the required properties, in addition to the above basic chemical composition, at least one arbitrary element selected from the following groups A to K may be contained.

[0026] Group A: One or two selected from Sn: 0.001% or more and 0.20% or less, and Sb: 0.001% or more and 0.20% or less. Sn: 0.001% or more and 0.20% or less. Sn is an element that is effective in improving magnetic flux density and reducing iron loss by improving texture. To achieve this effect, the Sn content should be 0.001% or more. On the other hand, if the Sn content exceeds 0.20%, the effect saturates and costs increase unnecessarily. Therefore, it is preferable to set the upper limit of the Sn content to 0.20%. Therefore, it is preferable that the Sn content be in the range of 0.001% or more and 0.20% or less.

[0027] Sb: 0.001% or more and 0.20% or less Sb is an element that is effective in improving the texture, thereby increasing the magnetic flux density and reducing iron loss. To obtain this effect, the Sb content should be 0.001% or more. On the other hand, if the Sb content exceeds 0.20%, the effect saturates, resulting in an unnecessary increase in costs. Therefore, it is preferable to set the upper limit of the Sb content to 0.20%. Therefore, it is preferable that the Sb content be in the range of 0.001% or more and 0.20% or less.

[0028] Group B: At least one selected from Ca: 0.0001% to 0.10%, Mg: 0.0001% to 0.10%, and REM: 0.0001% to 0.10%. Ca: 0.0001% to 0.10%. Ca is an element that fixes S as sulfides and contributes to reducing iron loss. To achieve this effect, the Ca content should be 0.0001% or more. On the other hand, if the Ca content exceeds 0.10%, the effect saturates and costs increase unnecessarily. Therefore, it is preferable to set the upper limit of the Ca content to 0.10%. Therefore, it is preferable that the Ca content be in the range of 0.0001% to 0.10%.

[0029] Mg: 0.0001% or more and 0.10% or less Mg is an element that fixes S as sulfides and contributes to reducing iron loss. To obtain this effect, the Mg content should be 0.0001% or more. On the other hand, if the Mg content exceeds 0.10%, the effect saturates and costs increase unnecessarily. Therefore, it is preferable to set the upper limit of the Mg content to 0.10%. Therefore, it is preferable to contain Mg in the range of 0.0001% or more and 0.10% or less.

[0030] REM: 0.0001% or more and 0.10% or less REM (rare earth metal elements) are a group of elements that fix S as sulfides and contribute to reducing iron loss. 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 saturates and costs increase unnecessarily, so the upper limit is set to 0.10%. Therefore, the REM content is preferably in the range of 0.0001% or more and 0.10% or less.

[0031] Group C: B: 0.002% or more and 0.20% or less, and Mo: 0.002% or more and 0.20% or less. B: 0.002% or more and 0.20% or less. B has the effect of forming fine carbides in steel and increasing the strength of the steel sheet. To achieve 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 preferable to set the upper limit of the B content to 0.20%. Therefore, the B content is preferably in the range of 0.002% or more and 0.20% or less.

[0032] Mo: 0.002% or more and 0.20% or less Mo has the effect of forming fine carbides in steel and increasing the strength of the steel sheet. 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 preferable to set the upper limit of the Mo content to 0.20%. Therefore, the Mo content is preferably in the range of 0.01% or more and 0.20% or less.

[0033] Group D: Zn: 0.0005% or more and 0.0050% or less Zn is an element that is effective in improving the magnetic flux density and reducing iron loss by improving the texture. To obtain this effect, the Zn content should be 0.0005% or more. On the other hand, if the Zn content exceeds 0.0050%, the effect saturates and costs increase unnecessarily. Therefore, it is preferable to set the upper limit of the Zn content to 0.0050%. Therefore, it is preferable to contain the Zn content in the range of 0.0005% or more and 0.0050% or less.

[0034] Group E: Ni: 0.01% or more and 1.0% or less Ni is an element that improves the toughness of steel and can be added as needed. To obtain this effect, the Ni content should be 0.01% or more. However, if the Ni content exceeds 1.0%, the effect saturates, so the upper limit of the Ni content is set to 1.0%. Therefore, the Ni content is preferably in the range of 0.01% or more and 1.0% or less.

[0035] Group F: Cr: 0.1% or more and 5.0% or less Cr has the effect of increasing the resistivity 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 due to a decrease in the saturation magnetic flux density, so the upper limit is set to 5.0%. Therefore, the Cr content is preferably in the range of 0.05% or more and 5.0% or less.

[0036] Group G: Cu: 0.005% or more and 1.0% or less Cu is an element that improves the toughness of steel and can be added as needed. To achieve this effect, the Cu content should be 0.01% or more. However, if the Cu content exceeds 1.0%, the effect saturates, so when Cu is added, the upper limit of the Cu content is set to 1.0%. Therefore, the Cu content is preferably in the range of 0.005% or more and 1.0% or less.

[0037] H group: at least one selected from Ti: 0.001% to 0.010%, V: 0.001% to 0.050%, Nb: 0.001% to 0.005%, Ta: 0.0001% to 0.0020%, W: 0.001% to 0.050%, and Pb: 0.0001% to 0.0020%. Ti is an element that has the effect of increasing the strength of the steel sheet and can be added appropriately. To achieve this effect, the Ti content should be 0.001% or more. However, if the Ti content exceeds 0.010%, fine precipitates will form in the steel sheet, increasing iron loss, so the upper limit of the Ti content is preferably 0.010%.

[0038] V: 0.001% or more and 0.050% or less V is an element that has the effect of increasing the strength of the steel sheet and can be added as needed. To obtain this 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 sheet, increasing iron loss, so it is preferable to set the upper limit of the V content to 0.050%.

[0039] Nb: 0.001% or more and 0.005% or less Nb is an element that has the effect of increasing the strength of steel sheet and can be added as needed. To obtain this 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 sheet, increasing iron loss. Therefore, it is preferable to set the upper limit of the V content to 0.005%.

[0040] Ta: 0.0001% or more and 0.0020% or less Ta is an element that has the effect of increasing the strength of the steel sheet and can be added as needed. To obtain this effect, the Ta content should be 0.0001% or more. However, if the Ta content exceeds 0.0020%, fine precipitates will form in the steel sheet, increasing iron loss, so it is preferable to set the upper limit of the Ta content to 0.0020%.

[0041] W: 0.001% or more and 0.050% or less W is an element that has the effect of increasing the strength of the steel sheet and can be added as needed. To obtain this 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 sheet, increasing iron loss, so it is preferable to set the upper limit of the W content to 0.050%.

[0042] Pb: 0.0001% or more and 0.0020% or less Pb is an element that has the effect of increasing the strength of the steel sheet and can be added as needed. To obtain this 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 sheet, increasing iron loss. Therefore, it is preferable to set the upper limit of the Pb content to 0.0020%.

[0043] Group I: Co: 0.001% or more and 0.100% or less Co is an element that has the effect of increasing the magnetic flux density of the steel sheet and can be added as needed. To achieve this effect, the Co content should be 0.001% or more. However, since a large amount of Co increases the alloy cost, it is preferable to set the upper limit of the Co content to 0.100%.

[0044] J group: one or two elements selected from Ga: 0.0005% to 0.0300% and Ge: 0.0005% to 0.0300% Ga: 0.0005% to 0.0300% Ga is an element that has the effect of improving the texture of the steel sheet and increasing the magnetic flux density, and can be added as needed. To achieve this effect, the Ga content should be 0.0005% or more. However, adding a large amount of Ga saturates the effect and increases the alloy cost, so it is preferable to set the upper limit of the Ga content to 0.0300%.

[0045] Ge: 0.0005% or more and 0.0300% or less Ge is an element that has the effect of improving the texture of the steel sheet and increasing the magnetic flux density, and can be added as needed. To obtain such effects, the Ge content should be 0.0005% or more. However, if a large amount of Ge is added, the effect saturates and the alloy cost increases, so it is preferable to set the upper limit of the Ge content to 0.0300%.

[0046] K group: As: 0.001% or more and 0.020% or less 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 preferable to set the upper limit of the As content to 0.020%.

[0047] Of the above optional elements, a content below the preferred range in which they effectively act is permissible as an unavoidable impurity since it does not affect the cold rolling properties or the magnetic properties of the electrical steel sheet product.

[0048] <Microstructure of Steel Sheet> Next, the microstructure of the hot-rolled annealed sheet according to this embodiment will be described. Here, recrystallization refers to the generation and growth of crystal grains with extremely low dislocation density by holding the material at high temperature. The recrystallized structure and the non-recrystallized structure can be distinguished by observation with an optical microscope.

[0049] <<The ratio Re / Rc of the recrystallized structure ratio Re at the widthwise center Xc to the widthwise edge Xe 10 mm away from the widthwise edge is 0.95 or less.>> According to the inventors' studies, by providing a difference in the recrystallized structure ratio between the widthwise center Xc and the widthwise edge Xe, fractures and edge cracks during the cold rolling process were significantly suppressed compared to simply reducing the recrystallized structure ratio of the entire hot-rolled and annealed sheet. The inventors believe the reason for this is as follows: Generally, the work-hardening rate for plastic deformation decreases as the recrystallized structure ratio decreases. It is presumed that the work-hardening rate at the widthwise edge Xc is smaller than that at the widthwise center Xc, resulting in stress acting to reduce tension at the widthwise edge Xe during rolling. This significantly suppresses the initiation of cracks at the edge Xc, thereby reducing fractures and edge cracks. That is, by setting the ratio Re / Rc of the recrystallized structure at the position Xe 10 mm away from the edge in the width direction to the ratio Rc of the recrystallized structure at the width center Xc of the hot-rolled annealed sheet to be 0.95 or less, a hot-rolled annealed sheet can be obtained in which breakage and edge cracking during cold rolling are sufficiently suppressed. It is preferably 0.8 or less, more preferably 0.7 or less. There is no particular need to set a lower limit, but it is usually 0.05 or more in hot-rolled annealed sheets manufactured using the method described below.

[0050] <<The ratio Rc of recrystallized structure in the width center portion Xc is 80% or more>> The hot-rolled annealed sheet of this embodiment controls the ratio Rc of recrystallized structure in the width center portion to the ratio Re of recrystallized structure at the steel sheet position Xe on the width edge side, and the effects of the present invention are not limited by the value of the ratio of recrystallized structure in the width center portion itself. On the other hand, there is a suitable range for the ratio of recrystallized structure in the width center portion, and the effects of the present invention are even more pronounced when it is within that range. When the ratio of recrystallized structure in the width center portion Xc is 80% or more, the magnetic properties of the final product are less likely to deteriorate. For the above reasons, it is more preferable that the ratio Rc of recrystallized structure in the width center portion Xc is 80% or more.

[0051] <<The ratio Re of recrystallized structure at position Xe on the width edge side is in the range of 5% to 95%>> In the hot-rolled annealed steel sheet of this embodiment, the ratio Rc of the recrystallized structure at the width center of the steel sheet and the ratio Re of the recrystallized structure at position Xe on the width edge side of the steel sheet are controlled, and the effects of the present invention are not limited by the value of the ratio of recrystallized structure at position Xe on the steel sheet itself. However, there is a preferred range for the ratio of recrystallized structure at position Xe on the width edge side of the steel sheet, and the effects of the present invention are more pronounced when the ratio is within that range. In the hot-rolled annealed steel sheet of this embodiment, when the ratio Re of recrystallized structure at position Xe on the width edge side of the steel sheet is 5% or more, the width edge portion does not become excessively hard, and the generation of fracture initiation points is suppressed. On the other hand, when the ratio Re of recrystallized structure at position Xe on the width edge side of the steel sheet is 95% or less, the fracture suppression effect achieved by controlling the ratio Re / Rc is more likely to be significantly exhibited. For these reasons, it is preferable that the ratio Re of recrystallized structure at position Xe on the width edge side of the steel sheet be in the range of 5% to 95%.

[0052] [Manufacturing conditions for hot-rolled annealed sheet] Next, a manufacturing method for the hot-rolled annealed sheet according to this embodiment will be described. Briefly, this method involves sequentially hot-rolling and hot-rolled annealing a steel material having the above-described chemical composition to obtain the hot-rolled annealed sheet according to this embodiment. In this embodiment, as long as the chemical composition and hot-rolled annealing conditions are within the ranges specified in the claims, any commonly known method may be used.

[0053] <Steel Material> The steel material is not particularly limited as long as it is a steel material having the above-mentioned composition. The method for producing the steel material and the method for adjusting the composition are not particularly limited, and known methods for producing the steel material using a converter or an electric furnace, a vacuum degassing device, or other devices and methods can be used. From the viewpoint of productivity and the like, it is preferable to produce a slab (steel material) by continuous casting after the production. On the other hand, a slab or thin slab may also be produced by known casting methods such as ingot making-blooming rolling or thin slab continuous casting.

[0054] <Hot rolling step> The hot rolling step is a step of hot rolling a steel material having the above-mentioned composition to obtain a hot-rolled sheet. The hot rolling step is not particularly limited as long as it is a step of heating a steel material having the above-mentioned composition and hot rolling it to obtain a hot-rolled sheet of a predetermined size, and a conventional hot rolling step can be applied.

[0055] Examples of commonly used hot rolling processes include the following hot rolling process. For example, a steel material is heated to a temperature in the range of 1000°C to 1200°C. The heated steel material is hot rolled at a finish rolling outlet temperature in the range of 800°C to 950°C. After hot rolling is completed, the steel material is subjected to appropriate post-rolling cooling, for example, cooling in 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. The steel material is then coiled at a coiling temperature in the range of 400°C to 700°C to form a hot-rolled sheet of predetermined dimensions and shape.

[0056] <Hot-rolled sheet annealing step> The hot-rolled sheet annealing step is a step of annealing the hot-rolled sheet by heating the hot-rolled sheet and holding it at a high temperature. More specifically, the widthwise center portion Xc of the hot-rolled sheet is annealed at an appropriate holding temperature T １ When the hot rolled plate is heated to and held at this temperature, the steel plate position Xe, which is 10 mm away from the outermost edge of the hot rolled plate in the width direction, changes from room temperature to the holding temperature T １ The maximum temperature T ２ In this hot-rolled sheet annealing step, the temperature rise rate Vc at the sheet width center portion Xc is made 1.0°C / s or more higher than the temperature rise rate Ve at the steel sheet position Xe. １ Preferably, the holding temperature T １ Holding time t １ Preferably, the maximum temperature T ２ is set to a range of 750°C or more and 1000°C or less. Preferably, the maximum temperature T ２ Time t when the temperature is above -50°C ２Preferably, when a hot-rolled sheet having a sheet width W in the range of 900 mm to 1100 mm is subjected to the hot-rolled sheet annealing step, a heat suppression region is provided in a range from 20 mm or more in the sheet width direction from the outermost edge of the sheet width to 0.250 × W or less in the sheet width direction from the outermost edge of the sheet width.

[0057] After the hot-rolled sheet annealing step, a pickling step is usually performed. The pickling step is not particularly limited as long as it is a step that can pickle the pickled steel sheet to an extent that cold rolling can be performed, and a conventional pickling step using, for example, hydrochloric acid or sulfuric acid can be applied. This pickling step may be performed continuously in the same line as the hot-rolled sheet annealing step, or may be performed in a separate line. The hot-rolled sheet annealed in the present invention includes both a state that has not been pickled (black skin) and a state that has been pickled (white skin).

[0058] <<The temperature increase rate Vc at the sheet width center Xc is made 1.0°C / s or more higher than the temperature increase rate Ve at the steel sheet position Xe>> In the hot-rolled sheet annealing process, the sheet width center Xc is heated from room temperature to the holding temperature T １ The temperature rise rate when heating to the maximum temperature T is set to Vc. ２ The heating rate until the temperature reaches 1.0°C / s is defined as Ve. The heating rate is limited to Vc - Ve ≥ 1.0°C / s. If Vc - Ve < 1.0°C / s, the difference in the ratio of recrystallized structure at the center and edge portions of the sheet width becomes small, and the ratio Re / Rc of the ratio Rc of recrystallized structure at the center and the ratio Re of recrystallized structure at the edge portions of the sheet width cannot be set to 0.95 or less. Preferably, Vc - Ve ≥ 3°C / s, and more preferably, Vc - Ve ≥ 5°C / s.

[0059] 《Holding temperature T of plate width center part Xc １ In the hot-rolled sheet annealing process, the holding temperature T １ It is preferable that T is 900°C or higher. １ By setting the temperature to 900°C or higher, the ratio Rc of the recrystallized structure at the sheet width center Xc can be set to 80% or higher. １If the holding temperature T of the width center Xc is higher than 1100°C, the width edge portion of the sheet may be heated by heat conduction, and the ratio of the recrystallized structure at the width edge portion of the sheet may become excessively high. １ It is preferable to control the temperature to 900°C or higher and 1100°C or lower.

[0060] 《Holding temperature T of plate width center part Xc １ Holding time t １ In the hot-rolled sheet annealing process, the holding temperature T １ Holding time t １ It is preferable that t is 2 seconds or more and 120 seconds or less. １ When the holding time t is 120 seconds or less, the ratio Re / Rc of the recrystallized structure at the width center portion to the width edge portion can be set to 0.95 or less, which improves the cold rolling property, and is therefore preferable. １ By setting the lower limit of the temperature T at the center Xc of the sheet width to 2 seconds, recrystallization and grain growth due to the hot-rolled sheet annealing are sufficient, and the magnetic properties are improved. １ Holding time t １ is preferably set to 2 seconds or more and 120 seconds or less.

[0061] <<Maximum temperature T at steel plate position Xe>> ２ In the hot-rolled sheet annealing process, the maximum temperature T at a steel sheet position Xe 10 mm away from the outermost edge of the hot-rolled sheet in the width direction is set to a range of 750 ° C. or more and 1000 ° C. or less. ２ The maximum temperature T ２ When the maximum temperature T ２ When the maximum temperature T ２ The maximum temperature T at the steel plate position Xe is preferably 750°C or higher and 1000°C or lower. ２ is the holding temperature T at the center of the plate width Xc １ If not, the ratio Re of the recrystallized structure at the steel sheet position Xe will be higher than the ratio Rc of the recrystallized structure at the sheet width center portion Xc.

[0062] <<Maximum temperature T at steel plate position Xe>> ２ Time t when the temperature is above -50°C ２ In the hot-rolled sheet annealing process, the maximum temperature T ２ Time t when the temperature is above -50°C ２ It is preferable that t is in the range of 5 seconds or more and 20 seconds or less. ２ is the maximum temperature T ２ The time it takes to heat up to the maximum temperature T ２ The total time is the time from the start of heating to the end of cooling. ２ When the time is 5 seconds or more, the steel plate position Xe reaches the maximum temperature T ２ After the temperature reaches t, sufficient time is ensured until the material is cooled, so that recrystallization proceeds appropriately and the ratio Re of the recrystallized structure can be made 5% or more. ２ When the time is 20 seconds or less, recrystallization proceeds moderately, and the ratio Re of the recrystallized structure can be set to 95% or less.

[0063] <Providing a Heat Suppression Zone in a Range of 20 mm or More from the Edge of the Sheet Width in the Sheet Width Direction> In the hot-rolled sheet annealing process, the following methods can be used to provide a heat suppression zone that intentionally changes the temperature in the sheet width direction: (a) preventing overheating by weakening burner heating only at the edge, (b) preventing overheating by applying an edge cover, (c) applying a temperature rise prevention material that has low emissivity and can suppress radiant heating, and (d) preventing temperature rise by removing black scale only at the edge, thereby reducing emissivity. Any method that can intentionally impart temperature change is acceptable and does not limit the scope of the invention. It is preferable to provide a heat suppression zone in a range of 20 mm or more from the edge of the sheet width in the sheet width direction. If the heat suppression zone is in a range of 20 mm or more from the edge of the sheet width, the temperature of the steel sheet at position Xe, 10 mm from the edge, is less likely to rise due to thermal conduction through the steel sheet. Therefore, the heating rate Vc at the widthwise center Xc can be made 1.0°C / s or more higher than the heating rate Ve at the steel sheet position Xe. Regarding the upper limit of the heating suppression region, when a hot-rolled sheet having a width W in the range of 900 mm to 1100 mm is subjected to the hot-rolled sheet annealing process, it is preferable to provide the heating suppression region in a range from the outermost width edge to 0.250 × W or less in the width direction. This range ensures a sufficient proportion of recrystallized structures throughout the steel sheet, thereby suppressing deterioration of magnetic properties. Therefore, the heating suppression region is preferably set to a range of 20 mm or more in the widthwise direction from the outermost width edge. Preferably, when a hot-rolled sheet having a width W in the range of 900 mm to 1100 mm is subjected to the hot-rolled sheet annealing process, the heating suppression region is set to a range from the outermost width edge to 0.250 × W or less in the width direction.

[0064] <Pickling process> The pickling process is a process of pickling the hot-rolled annealed sheet after the hot-rolled sheet annealing process. The pickling process is not particularly limited as long as it is a process that can pickle the steel sheet after pickling to an extent that cold rolling can be performed, and a conventional pickling process using, for example, hydrochloric acid or sulfuric acid can be applied. When the hot-rolled sheet annealing process is performed, this pickling process may be performed continuously in the same line as the hot-rolled sheet annealing process, or may be performed in a separate line.

[0065] <Cold Rolling Step> The cold rolling step is a step of cold rolling the hot-rolled annealed sheet (pickled sheet) that has been subjected to the pickling. In the cold rolling step, the hot-rolled annealed sheet that has been subjected to the pickling is cold-rolled to obtain a cold-rolled sheet. There are no particular limitations on the cold rolling step as long as it is a step that obtains a cold-rolled sheet of predetermined dimensions by cold rolling, and any conventional cold rolling step can be applied.

[0066] An example of a commonly used cold rolling process is a cold rolling process in which a pickled sheet is rolled using a five-stand tandem mill under conditions of a total reduction of 80% or more but less than 95% to form a cold-rolled sheet of a predetermined size and shape. The number of stands may be four or less, or six or more.

[0067] <Finish annealing step> The finish annealing step is a step in which the cold-rolled sheet that has been subjected to the cold rolling step is annealed to obtain a cold-rolled annealed sheet. The finish annealing step is not particularly limited as long as it is a step in which the cold-rolled sheet is heated, held, and cooled to obtain a cold-rolled annealed sheet, and a conventional annealing step can be applied. Note that an insulating coating may be applied to the surface after the finish annealing step. The method and type of insulating coating are not particularly limited, and a conventional insulating coating step can be applied.

[0068] An example of a commonly used annealing step is a finish annealing step in which a cold-rolled sheet is heated to a temperature of 800° C. to 1200° C. in a non-oxidizing atmosphere, held at that temperature for 5 to 60 seconds, and then cooled.

[0069] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0070] <Production of Hot-Rolled Annealed Sheet> Molten steel having the chemical composition shown in Table 1 was produced by a commonly known method and continuously cast into a slab (steel material) having a thickness of 230 mm. The obtained slab was hot-rolled to obtain a hot-rolled sheet having a thickness of 2.0 mm. The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing and pickling under the conditions shown in Tables 2-1 and 2-2 to obtain a hot-rolled annealed sheet (pickled sheet).

[0071] <Production of Cold-Rolled Sheet> The hot-rolled annealed sheet (pickled sheet) was then cold-rolled at room temperature using a tandem mill to a sheet thickness of 0.25 mm to obtain a cold-rolled sheet.

[0072] <Production of Cold-Rolled Annealed Sheet> The cold-rolled sheet was then subjected to finish annealing by a known method in which it was held at 1000°C for 10 seconds in a non-oxidizing atmosphere, and then coated by a known method to obtain a cold-rolled annealed sheet (non-oriented electrical steel sheet).

[0073]

[0074]

[0075]

[0076] <Evaluation> <Structural Observation> Test specimens for structural observation were taken from the center of the sheet width and from a position 10 mm from the outermost edge of the sheet width of the obtained hot-rolled annealed sheet. The test specimens were then embedded in resin with the cross section in the sheet thickness direction as the observation surface, and observed with an optical microscope to measure the proportion of recrystallized structure.

[0077] <<Evaluation of Rollability>> The number of edge cracks per 1000 m of the obtained cold-rolled sheet was investigated. Edge cracks with a crack length of 2 mm or more were counted as the number N. When the number of edge cracks per 1000 m of the cold-rolled sheet was 2.0 or less, the cold-rollability was considered to be good.

[0078] <Magnetic Property Evaluation> A test piece for magnetic measurement, 30 mm wide and 280 mm long, with the length direction being the rolling direction and the direction perpendicular to the rolling direction, was taken from the obtained cold-rolled annealed sheet, and the magnetic flux density B50 and iron loss W of the cold-rolled annealed sheet were measured by the Epstein method in accordance with JIS C2550-1:2011. １０／４００ When B50≧1.55T, the magnetic flux density was evaluated as good, and after annealing, W １０ / ４００ When the wattage was ≦14.0 W / kg, the core loss characteristics were evaluated as good.

[0079] In the evaluation column, for cold rolling property, those that broke during rolling and those that had more than 2.0 edge cracks per 1000 m of cold rolled sheet length were marked "bad." In addition, those that had a composition outside the range of the present invention and had a magnetic flux density B50 of less than 1.55 T or an iron loss W １０／４００ Of the remaining, those with a magnetic flux density B50 of 1.55 T or more and an iron loss W１０ / ４００ The value of 14.0 W / kg or less was designated as "excellent", and the rest was designated as "good".

[0080]

[0081]

[0082] From the results of Tables 3-1 and 3-2, it can be seen that all of the hot-rolled annealed sheets according to the present invention have excellent cold rolling properties, and further, the cold-rolled annealed sheets obtained by cold-rolling and annealing the hot-rolled annealed sheets according to the present invention also have excellent magnetic properties.

Claims

1. Containing, by 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 further containing: Group A: one or two 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: 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: 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; E Group: Ni: 0.01% or more and 1.0% or less; F Group: Cr: 0.1% or more and 5.0% or less; G Group: Cu: 0.005% or more and 1.0% or less; H Group I: 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; Group J: Co: 0.001% or more and 0.100% or less; and at least one element selected from the 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 0.020% or less, with the balance consisting of Fe and unavoidable impurities, wherein a ratio Re / Rc of the recrystallized structure at a steel sheet position Xe 10 mm away from an outermost edge portion in the sheet width direction to a ratio Rc of the recrystallized structure at a sheet width center portion Xc is 0.95 or less.

2. The hot-rolled annealed sheet according to claim 1, further satisfying either or both of the following: a ratio Rc of recrystallized structure in the sheet width center portion Xc is 80% or more; and a ratio Re of recrystallized structure in the steel sheet position Xe is in the range of 5% or more and 95% or less.

3. A method for producing a hot-rolled annealed sheet according to claim 1 or 2, comprising: a hot rolling step of hot-rolling a steel material having the above-mentioned chemical composition to obtain a hot-rolled sheet; and a hot-rolled sheet annealing step of annealing the hot-rolled sheet, wherein in the hot-rolled sheet annealing step, a widthwise center portion Xc of the hot-rolled sheet is heated from room temperature to a holding temperature T １ When the hot rolled plate is heated to and held at the holding temperature T １ The maximum temperature T ２ and the temperature rise rate Vc at the sheet width center portion Xc is made 1.0°C / s or more higher than the temperature rise rate Ve at the steel sheet position Xe.

4. The method for producing a hot-rolled annealed sheet according to claim 3, wherein the hot-rolled sheet annealing step satisfies at least one of the following conditions (1) to (4): (1) The holding temperature T １ (2) the holding temperature T １ Holding time t １ (3) the maximum temperature T ２ (4) the maximum temperature T ２ Time t when the temperature is above -50°C ２ The time should be in the range of 5 seconds or more and 20 seconds or less.

5. A method for manufacturing a hot-rolled annealed sheet according to claim 3, wherein when a hot-rolled sheet having a sheet width W in the range of 900 mm to 1100 mm is subjected to the hot-rolled sheet annealing process, a heat suppression region is provided in a range from 20 mm or more in the sheet width direction from the outermost edge of the sheet width to 0.250 × W or less in the sheet width direction from the outermost edge of the sheet width.

6. A method for producing a hot-rolled annealed sheet according to claim 4, wherein when a hot-rolled sheet having a sheet width W in the range of 900 mm to 1100 mm is subjected to the hot-rolled sheet annealing process, a heat suppression region is provided in a range from 20 mm or more in the sheet width direction from the outermost edge of the sheet width to 0.250 × W or less in the sheet width direction from the outermost edge of the sheet width.

7. A method for producing a non-oriented electrical steel sheet, comprising cold rolling the hot-rolled annealed sheet according to claim 1 or 2 to obtain a cold-rolled sheet, and then finish-annealing the cold-rolled sheet to obtain a cold-rolled annealed sheet.

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