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KR-20260065000-A - NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

KR20260065000AKR 20260065000 AKR20260065000 AKR 20260065000AKR-20260065000-A

Abstract

The present application relates to a non-oriented electrical steel sheet 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 can be obtained.

Inventors

  • 최혜정
  • 오규진
  • 고재현

Assignees

  • 현대제철 주식회사

Dates

Publication Date
20260508
Application Date
20241030

Claims (12)

  1. In weight%, Si: 2.8% or more and 3.8% or less, Mn: 0.2% or more and 0.4% or less, Al: greater than 0% 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 0.005% or more and 0.05% or less, and the remainder comprising Fe and other unavoidable impurities, ND//<111> Non-oriented electrical steel sheet having an average magnetic domain width of 3.0 μm or more and 10.0 μm or less.
  2. In Article 1, Non-oriented electrical steel sheet with high-frequency iron loss of 12.5 W/kg or less.
  3. A step of manufacturing a hot-rolled steel sheet by reheating and hot-rolling a slab comprising, in weight%, Si: 2.8% or more and 3.8% or less, Mn: 0.2% or more and 0.4% or less, Al: greater than 0% 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 0.005% 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; A step of finally heat treating the above cold-rolled steel sheet; and It includes a step of performing stress relief heat treatment after punching the final heat-treated steel plate, A method for manufacturing a non-oriented electrical steel sheet, wherein the stress relaxation heat treatment step is such that the temperature (T) is 700°C or higher and 800°C or lower, the holding time (t) is 90 minutes or higher and 150 minutes or lower, the temperature (T) and the holding time (t) satisfy the following Equation 1, and the heating rate is 10.0°C/min or higher and 13.0°C/min or lower. [Equation 1] 150 ≤ (T 0.8 × t)/100 ≤ 230 (In Equation 1 above, T represents the stress relaxation heat treatment temperature (°C), and t represents the stress relaxation heat treatment holding time (minutes).)
  4. In Paragraph 3, ND//<111> Method for manufacturing a non-oriented electrical steel sheet having an average magnetic domain width of 3.0 μm or more and 10.0 μm or less.
  5. 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 1200℃ or lower.
  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 hot-rolling finishing temperature is 800°C or higher and 900°C 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 coiling temperature after hot rolling is 550°C or higher and 650°C or lower.
  8. In Article 3 or Article 4, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of heat treatment after hot rolling is to heat treat for 30 seconds or more and 90 seconds or less in an atmosphere of 80% or more N2 at a temperature of 900℃ or more and 1100℃ or less, and then cool at a rate of 20℃/s or more.
  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 at a rolling rate of 84% or more and 94% or less.
  10. In Article 3 or Article 4, 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 of 950℃ or more and 1100℃ or less.
  11. 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 2.7 mm or less.
  12. 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 0.10 mm or more and 0.27 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 to reduce 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 especially electric vehicles (EVs). In line with the increasing demand for electric vehicles (EVs), the energy conversion efficiency of drive motors for electric vehicles is being improved, and to achieve this, excellent magnetic properties of non-oriented electrical steel sheets, which are used as motor core materials, are required. 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 for them to possess magnetic properties, namely low iron loss and high magnetic flux density. The magnetic properties of electrical steel are influenced by the structure of magnetic domains. A magnetic domain refers to a group of atoms where the magnetic moments of atoms are aligned in one direction. In the absence of an external magnetic field, multiple magnetic domains exist within the electrical steel. When an external magnetic field is applied, the domain walls—the boundaries of the domains—move, causing the entire steel sheet to merge into a single domain. During this magnetization process, the faster the movement of the domain walls, the lower the iron loss and the higher the magnetic flux density. The movement of the domain walls is influenced by the structure of the magnetic domains in the absence of an external magnetic field. Figure 1 is a schematic diagram showing the shape of magnetic domains according to the grain direction. FIG. 2 is a micrograph showing the average domain width of the ND//<111> texture of an electrical steel sheet according to one embodiment of the present application. 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 0.4% or less, Al: greater than 0% 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 0.005% or more and 0.05% or less, and the remainder being Fe and other unavoidable impurities, and the average magnetic domain width of the ND//<111> grains is 3.0 μm or more and 10.0 μm or less. In this specification, the term "ND//<111> texture" refers to a texture in which the <111> plane is parallel to the rolled plane (ND plane) of a non-oriented electrical steel sheet within 5°. FIG. 1 is a schematic diagram showing the shape of magnetic domains according to the grain direction, and among the four types, Type IV represents a schematic diagram of the ND//<111> texture. In addition, in this specification, the term "average magnetic domain width of the ND//<111> texture" refers to the average of the smallest magnetic domain width and the largest magnetic domain width within the grain of the <111> plane. FIG. 2 is a micrograph showing the average magnetic domain width of the ND//<111> texture of an electrical steel sheet according to one embodiment of the present application, and the average of the smallest magnetic domain width and the largest magnetic domain width within the grain (indicated by solid lines) of the present application, i.e., the average magnetic domain width of the ND//<111> texture, is 3.0 μm or more and 10.0 μm or less. By satisfying this range, the average magnetic domain width of the ND//<111> texture of the above-mentioned non-oriented electrical steel sheet can have excellent magnetic properties, specifically, low iron loss. If the average magnetic domain width of the ND//<111> texture of the above-mentioned non-oriented electrical steel sheet is greater than the upper limit of the aforementioned range, eddy current loss increases, and iron loss may increase. In addition, if the average magnetic domain wid