Grain-oriented electrical steel sheet and method for manufacturing the same

Abstract

This invention provides a method for manufacturing grain-oriented electrical steel sheets that exhibit good magnetic properties with fewer steps than conventional methods. [Solution] A method for manufacturing grain-oriented electrical steel sheets, using a slab having a specific component composition satisfying 8790 × (5.1 - log[Mn][S]) ≤ 12000 × (2.05 - log[sol.Al][N]), comprising a reheating step under specific conditions; a hot rolling step under specific conditions; a hot-rolled sheet annealing step under specific conditions utilizing rapid heating; a cold rolling step; a magnetic domain refinement step as needed; a primary recrystallization annealing step; a secondary recrystallization annealing step; and a planarization annealing step.

Claims

1. In mass percent, C: 0.005-0.085%, Si: 2.00-4.50%, Mn: 0.03-0.50%, Sol. Al: 0.001% or more and less than 0.025% N: 0.001–0.009% and S: Contains 0.0005 to 0.020%, The Mn, sol. Al, N, and S satisfy the following formula (1), which is expressed using the content of each element in the steel [Mn], [sol. Al], [N], and [S] (unit: mass%), A slab having a composition consisting of Fe and unavoidable impurities in the remainder, A reheating process in which the material is heated to a temperature of 1170°C or higher, A hot rolling process to obtain a hot-rolled sheet by hot-rolling the heated slab so that the completion temperature is 870°C or higher, cooling it for at least 1 second at a cooling rate of 100°C / s or higher within 2 seconds after the completion of the hot rolling, and winding it at a temperature of 600°C or lower, The hot-rolled sheet is subjected to a temperature of 940°C or higher. １ Up to ℃, T １ -50℃ to T １ Heat so that the average heating rate between degrees is 5°C / s or more, T １ A hot-rolled sheet annealing process to obtain a hot-rolled sheet, which involves first cooling so that the first holding time in a temperature range of ±5°C is 10 seconds or less, and then second cooling so that the second holding time in a temperature range of 800°C to 920°C is 20 seconds or more, A cold rolling step is performed to obtain a cold-rolled sheet having a final thickness by cold-rolling the hot-rolled annealed sheet, A primary recrystallization annealing step is performed by heating the cold-rolled sheet to obtain a primary recrystallized sheet. A secondary recrystallization annealing step is performed by heating the primary recrystallized plate to obtain a secondary recrystallized plate. A planarization annealing step is performed by heating the secondary recrystallized plate to obtain a grain-oriented electrical steel sheet. A feature that involves performing Alternatively, a method for manufacturing grain-oriented electrical steel sheets, characterized in that, in addition to the series of steps described above, a magnetic domain refinement step is further performed on at least one side of any of the cold-rolled sheet, the primary recrystallized sheet, the secondary recrystallized sheet, and the grain-oriented electrical steel sheet. 8790×(5.1-log[Mn][S])≦ 12000×(2.05-log[sol.Al][N])...(1)

2. The above component composition is, in mass%, Se: 0.02% or less, Sb: 0.500% or less, Ni: 1.50% or less, Cr: 0.50% or less, Cu: 0.50% or less, P: 0.500% or less, As: 0.050% or less, Sn: 0.50% or less, Bi: 0.500% or less, Mo: 0.100% or less B: 0.0025% or less, Te: 0.0100% or less, Zr: 0.010% or less, Nb: 0.010% or less, V: 0.010% or less and Ta: 0.010% or less A method for manufacturing grain-oriented electrical steel sheets according to claim 1, further comprising one or more elements selected from the group consisting of the following.

3. In the aforementioned hot-rolled sheet annealing process, A method for manufacturing grain-oriented electrical steel sheets according to claim 1, wherein, after the second cooling, a third cooling is performed such that the third holding time in a temperature range of 80°C to 200°C is 30 seconds or more.

4. In the aforementioned hot-rolled sheet annealing process, A method for manufacturing grain-oriented electrical steel sheets according to claim 2, wherein, after the second cooling, a third cooling is performed such that the third holding time in a temperature range of 80°C to 200°C is 30 seconds or more.

5. In the heating process during the hot-rolled sheet annealing process, T １ From temperatures below -50°C １ A method for manufacturing grain-oriented electrical steel sheets according to any one of claims 1 to 4, wherein heating between °C is performed by transverse induction heating.

6. In mass percent, C: 0.085% or less, Si: 2.00-4.50%, Mn: 0.50% or less, Sol. Al: Less than 0.025% N: 0.009% or less and S: Contains 0.020% or less, The composition consists of Fe and unavoidable impurities. When the edge region is defined as the area extending 5 mm inward from each edge in the width direction of the steel plate, and when the grain size in the width direction is defined as a coarse grain, then 30% or more of the area within the edge region is the region where the coarse grain does not overlap. Starting from the aforementioned widthwise edge of the steel plate, the number of edge cracks, each with a length exceeding 3 cm in the widthwise direction, is 0.020 or less per 10 m of longitudinal length of the steel plate, and, Magnetic flux density B ８ However, the grain thickness is 1.920T or more if the steel sheet does not have grooves on both sides, and 1.880T or more if the steel sheet has grooves on at least one side.

7. The above component composition is, in mass%, Se: 0.02% or less, Sb: 0.500% or less, Ni: 1.50% or less, Cr: 0.50% or less, Cu: 0.50% or less, P: 0.500% or less, As: 0.050% or less, Sn: 0.50% or less, Bi: 0.500% or less, Mo: 0.100% or less B: 0.0025% or less, Te: 0.0100% or less, Zr: 0.010% or less, Nb: 0.010% or less, V: 0.010% or less and Ta: 0.010% or less The grain-oriented electrical steel sheet according to claim 6, further containing one or more elements selected from the group consisting of the above.

8. At least one side has a plurality of grooves arranged in a direction transverse to the rolling direction, The grain-oriented electrical steel sheet according to claim 6 or 7, wherein the grooves have a formation pitch in the rolling direction of 30 mm or less, a groove width in the rolling direction of 150 μm or less, and a groove depth of 5 μm or more.

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