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KR-20260065027-A - NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

KR20260065027AKR 20260065027 AKR20260065027 AKR 20260065027AKR-20260065027-A

Abstract

The present application relates to a non-oriented electrical steel sheet with small iron loss variation and a method for manufacturing the same. According to the non-oriented electrical steel sheet and the method for manufacturing the same of the present application, excellent magnetic properties can be obtained, and specifically, low iron loss and low iron loss variation within the coil can be obtained.

Inventors

  • 오규진
  • 강춘구
  • 김민성

Assignees

  • 현대제철 주식회사

Dates

Publication Date
20260508
Application Date
20241031

Claims (13)

  1. In weight percent, Si: 2.8% or more and 3.8% or less, Mn: 0.2% or more and 0.5% or less, Al: 0.5% or more and 1.5% or less, C: greater than 0% and 0.003% or less, S: greater than 0% and 0.002% or less, P: greater than 0% and 0.015% or less, N: greater than 0% and 0.002% or less, Ti: greater than 0% and 0.002% or less, at least one of Sn and Sb totaling 0.01% or more and 0.05% or less, and the remainder comprising Fe and other unavoidable impurities, Non-oriented electrical steel sheet having an average grain size of 85 μm or more and 115 μm or less, and a grain size distribution half-width of 100 μm or less.
  2. In Article 1, Non-oriented electrical steel sheet having an iron loss (W 10/400 ) of 12.5 W/kg or less and an iron loss deviation within the coil of 2.5% or less.
  3. A step of manufacturing a hot-rolled steel sheet by reheating and then hot-rolling a slab comprising, in weight%, Si: 2.8% or more and 3.8% or less, Mn: 0.2% or more and 0.5% or less, Al: 0.5% or more and 1.5% or less, C: greater than 0% and 0.003% or less, S: greater than 0% and 0.002% or less, P: greater than 0% and 0.015% or less, N: greater than 0% and 0.002% or less, Ti: greater than 0% and 0.002% or less, at least one of Sn and Sb in total of 0.01% or more and 0.05% or less, and the remainder being Fe and other unavoidable impurities; A step of heat-treating the above hot-rolled steel sheet after hot rolling; A step of manufacturing a cold-rolled steel sheet by cold-rolling a steel sheet that has been heat-treated after hot rolling; and The above cold-rolled steel sheet includes a step of final heat treatment, and The step of heat treatment after hot rolling above comprises heat treatment for 30 seconds to 120 seconds in an atmosphere with a heat treatment temperature ( T1 ) of 950℃ or higher and 1025℃ or lower and N2 content of 80% or higher and 100% or lower, and cooling at a rate of 20℃/s or higher. A method for manufacturing a non-oriented electrical steel sheet, wherein the final heat treatment step is performed by heat treating for 30 seconds or more and 90 seconds or less in an atmosphere of H₂ 20% or more and a final heat treatment temperature ( T₂ ) of 940℃ or more and 1050℃ or less.
  4. In Paragraph 3, A method for manufacturing a non-oriented electrical steel sheet, wherein the heat treatment temperature ( T1 ) after hot rolling and the final heat treatment temperature ( T2 ) satisfy the following Equation 1. [Equation 1] 1775 ≤ T 1 +(T 2× 0.8) ≤ 1805 (In the above Equation 1, T1 represents the heat treatment temperature after hot rolling (°C), and T2 represents the final heat treatment temperature (°C).)
  5. In Article 3 or Article 4, A method for manufacturing a non-oriented electrical steel sheet having an average grain size of 85 μm or more and 115 μm or less, and a half-width of the grain size distribution of 100 μm or less.
  6. In Article 3 or Article 4, The step of manufacturing the above hot-rolled steel sheet is a method for manufacturing a non-oriented electrical steel sheet in which the reheating temperature is 1000℃ or higher and 1150℃ or lower.
  7. In Article 3 or Article 4, The step of manufacturing the above hot-rolled steel sheet is a method for manufacturing a non-oriented electrical steel sheet in which the hot-rolling finishing temperature is 800°C or higher and 900°C or lower.
  8. In Article 3 or Article 4, The step of manufacturing the above hot-rolled steel sheet is a method for manufacturing a non-oriented electrical steel sheet in which the coiling temperature after hot rolling is 500℃ or higher and 600℃ or lower.
  9. In Article 3 or Article 4, The step of manufacturing the above cold-rolled steel sheet is a method for manufacturing a non-oriented electrical steel sheet, wherein the steel sheet heat-treated after hot rolling is rolled with a reduction rate of 84% or more and 96% or less.
  10. In Article 3 or Article 4, The above final heat treatment step is a method for manufacturing a non-oriented electrical steel sheet, wherein the temperature is raised at a rate of 10℃/s or more.
  11. In Article 3 or Article 4, The above final heat treatment step is a method for manufacturing a non-oriented electrical steel sheet, wherein the cooling is performed at a rate of 10℃/s or higher.
  12. In Article 3 or Article 4, A method for manufacturing a non-oriented electrical steel sheet, wherein the thickness of the hot-rolled steel sheet is 1.6 mm or more and 2.3 mm or less.
  13. In Article 3 or Article 4, A method for manufacturing a non-oriented electrical steel sheet, wherein the thickness of the above cold-rolled steel sheet is 0.1 mm or more and 0.3 mm or less.

Description

Non-oriented electrical steel sheet and method for manufacturing the same The present application relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Recently, due to policies aimed at reducing CO2 emissions to prevent global warming, conventional internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles such as hybrid electric vehicles (HEVs) and, in particular, electric vehicles (EVs). In line with the increasing demand for EVs, the energy conversion efficiency of drive motors for EVs is being improved, and to this end, excellent magnetic properties are required for non-oriented electrical steel sheets used as motor core materials. Non-oriented electrical steel sheets used as motor core materials play the role of converting electrical energy into mechanical energy in rotating machinery, and for energy saving, it is important to possess magnetic properties—namely, low iron loss and high magnetic flux density. To satisfy these required characteristics, Si content, product thickness, grain size, texture, and precipitates must be appropriately controlled. Increasing Si content and reducing product thickness are effective in reducing iron loss, but they have the disadvantage of lowering magnetic flux density. To compensate for this, controlling grain size, texture, and precipitates during the manufacturing process of non-oriented electrical steel is crucial. Since magnetic properties such as iron loss and magnetic flux density change very sensitively depending on grain size, texture, precipitates, etc., variations in the manufacturing process lead to variations in magnetic properties. Figure 1 is a schematic diagram exemplifying the full width at half maximum of a grain size distribution. Figure 2 is a schematic diagram showing the microstructure when the full width at half maximum of the grain size distribution is less than 100 μm. Figure 3 is a schematic diagram showing the microstructure when the full width at half maximum of the grain size distribution is greater than 100 μm. Embodiments of the present invention will be described in detail below. Furthermore, the scope of the present invention is not limited to the embodiments described below, and may be implemented with arbitrary modifications within the scope that does not deviate from the gist of the present invention. In the numerical ranges described stepwise in this specification, an upper or lower limit value described in any numerical range may be substituted with an upper or lower limit value of another numerical range described stepwise, or may also be substituted with a value shown in the examples. The present application relates to a non-oriented electrical steel sheet, which is a core material used in a motor that converts electrical energy into mechanical energy. The non-oriented electrical steel sheet comprises, in weight percent, Si: 2.8% or more and 3.8% or less, Mn: 0.2% or more and 0.5% or less, Al: 0.5% or more and 1.5% or less, C: greater than 0% and 0.003% or less, S: greater than 0% and 0.002% or less, P: greater than 0% and 0.015% or less, N: greater than 0% and 0.002% or less, Ti: greater than 0% and 0.002% or less, at least one of Sn and Sb in total of 0.01% or more and 0.05% or less, and the remainder being Fe and other unavoidable impurities, and has an average grain size of 85μm or more and 115μm or less, and a half-width of the grain size distribution of 100μm or less. The average grain size of the above-mentioned non-oriented electrical steel sheet can be measured with respect to a plane parallel to the surface of the electrical steel sheet. It can be measured at a thickness ranging from 1/4 to 3/4 of the total thickness of the electrical steel sheet. The average grain size is defined as the average value of the diameters of a virtual circle assumed to have an area equal to the grain area. The average grain size can be measured using an optical microscope. Specifically, the average grain size of the non-oriented electrical steel sheet may be 87 μm or more and 110 μm or less. Iron loss is classified into hysteresis loss and eddy current loss, and iron loss can be reduced by satisfying the aforementioned numerical range for the average grain size of the non-oriented electrical steel sheet. On the other hand, if the average grain size is below the lower limit of the above range, hysteresis loss may increase, and if the average grain size exceeds the upper limit of the above range, eddy current loss may increase. An increase in hysteresis loss and an increase in eddy current loss result in an increase in iron loss, which has an adverse effect on magnetism. Therefore, it is necessary to control the grain size of non-oriented electrical steel sheets so that they have an optimal grain size that achieves low iron loss, and to control the grain size distribution so that it is densely concentrated within the optimal grain size range. The full width at half maximum of t