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KR-20260064964-A - Non-oriented electrical steel sheet, motor containing the same, and method of manufacturing the same

KR20260064964AKR 20260064964 AKR20260064964 AKR 20260064964AKR-20260064964-A

Abstract

The present invention provides a non-oriented electrical steel sheet comprising, in weight percent, carbon (C): 0 to 0.005%, silicon (Si): 3.0 to 4.0%, manganese (Mn): 0.1 to 0.5%, aluminum (Al): 0.3 to 1.5%, sulfur (S): 0 to 0.005%, nitrogen (N): 0 to 0.005%, titanium (Ti): 0 to 0.005% or less, and the remainder being iron (Fe) and unavoidable impurities, wherein the non-oriented electrical steel sheet has a surface oxide comprising at least one of Si, Mn and Al on its surface, and the number density of the surface oxide satisfies the following formula 1. [Equation 1] [Unit: pieces/ cm² ] (where a represents the surface oxide number density.)

Inventors

  • 배성민
  • 신경식
  • 강춘구

Assignees

  • 현대제철 주식회사

Dates

Publication Date
20260508
Application Date
20241030

Claims (20)

  1. As a non-oriented electrical steel sheet, In weight percent, it comprises carbon (C): 0 to 0.005%, silicon (Si): 3.0 to 4.0%, manganese (Mn): 0.1 to 0.5%, aluminum (Al): 0.3 to 1.5%, sulfur (S): 0 to 0.005%, nitrogen (N): 0 to 0.005%, titanium (Ti): 0 to 0.005% or less, and the remainder being iron (Fe) and unavoidable impurities, The above non-oriented electrical steel sheet has a surface oxide comprising at least one of Si, Mn, and Al on its surface, and the number density of the surface oxide satisfies the following Equation 1. [Equation 1] [Unit: pieces/ cm² ] (where a represents the surface oxide number density.)
  2. In paragraph 1, A non-oriented electrical steel sheet, wherein when the above non-oriented electrical steel sheet is punched, the non-oriented electrical steel sheet after punching has a burr protruding upward or downward at the end of the corner, and the height of the burr satisfies the following Equation 2. [Equation 2] [Unit: ㎛] (Note: b represents the height of the burr.)
  3. In paragraph 1, A non-oriented electrical steel sheet in which the sum of silicon (Si), manganese (Mn), and aluminum (Al) contained in the above non-oriented electrical steel sheet is 4.0 weight% or more.
  4. In paragraph 1, A non-oriented electrical steel sheet having an iron loss (W 10/400 ) of 13.5 W/kg or less.
  5. In paragraph 1, A non-oriented electrical steel sheet having a magnetic flux density (B 50 ) of 1.65 T or more.
  6. In paragraph 1, A non-oriented electrical steel sheet having a grain size of 80 μm or more and 200 μm or less.
  7. In paragraph 1, A non-oriented electrical steel sheet having a tensile strength (TS) of 550 MPa or more.
  8. As a method for manufacturing non-oriented electrical steel sheets, A hot rolling step for manufacturing a hot-rolled plate by hot rolling a slab comprising, in weight percent, carbon (C): 0 to 0.005%, silicon (Si): 3.0 to 4.0%, manganese (Mn): 0.1 to 0.5%, aluminum (Al): 0.3 to 1.5%, sulfur (S): 0 to 0.005%, nitrogen (N): 0 to 0.005%, titanium (Ti): 0 to 0.005% or less, and the remainder being iron (Fe) and unavoidable impurities; A hot rolling annealing step for manufacturing a hot rolling annealed plate by hot rolling and annealing the above hot rolling plate; A cold rolling step for manufacturing a cold-rolled plate by cold-rolling the above hot-rolled annealed plate; and A cold rolling annealing step for manufacturing a cold rolling annealed plate by cold rolling annealing the above cold rolling plate; Includes, A method for manufacturing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet formed through the above manufacturing steps has a surface oxide comprising at least one of Si, Mn, and Al on its surface, and the number density of the surface oxide satisfies the following Equation 1. [Equation 1] [Unit: pieces/ cm² ] (where a represents the surface oxide number density.)
  9. In paragraph 8, The above cold-rolled annealed plate further includes a stamping step for processing it into a predetermined shape, and A method for manufacturing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet formed through the above stamping step has a burr protruding upward or downward at the end of the corner, and the height of the burr satisfies the following Equation 2. [Equation 2] [Unit: ㎛] (Note: b represents the height of the burr.)
  10. In paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the sum of silicon (Si), manganese (Mn), and aluminum (Al) contained in the above non-oriented electrical steel sheet is 4.0 weight% or more.
  11. In paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the above cold rolling annealing step is performed at a temperature of 900 to 1100 degrees and a time of 30 to 150 seconds.
  12. In paragraph 8, A method for manufacturing non-oriented electrical steel sheets, wherein the above cold rolling annealing step is performed in an atmosphere equipped with hydrogen and the remainder nitrogen.
  13. In paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the iron loss (W 10/400 ) of the above non-oriented electrical steel sheet is 13.5 W/kg or less.
  14. In paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the magnetic flux density (B 50 ) of the above non-oriented electrical steel sheet is 1.65T or higher.
  15. In paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, further comprising a coating step of coating the above-mentioned cold-rolled annealed sheet.
  16. A motor comprising a motor core, wherein the motor core is, A motor comprising a non-oriented electrical steel sheet comprising, in weight percent, carbon (C): 0 to 0.005%, silicon (Si): 3.0 to 4.0%, manganese (Mn): 0.1 to 0.5%, aluminum (Al): 0.3 to 1.5%, sulfur (S): 0 to 0.005%, nitrogen (N): 0 to 0.005%, titanium (Ti): 0 to 0.005% or less, the remainder being iron (Fe) and unavoidable impurities, and having a surface oxide on the surface comprising at least one of Si, Mn and Al, wherein the number density of the surface oxide satisfies the following Equation 1. [Equation 1] [Unit: pieces/ cm² ] (where a represents the surface oxide number density.)
  17. In Paragraph 10, The above-mentioned non-oriented electrical steel sheet has a burr located at the end of a corner and protruding upward or downward, and the height of the burr satisfies the following Equation 2, a motor. [Equation 2] [Unit: ㎛] (Note: b represents the height of the burr.)
  18. In paragraph 1, A motor in which the sum of silicon (Si), manganese (Mn), and aluminum (Al) contained in the above non-oriented electrical steel sheet is 4.0 weight% or more.
  19. In paragraph 1, A motor in which the iron loss (W 10/400 ) of the above non-oriented electrical steel sheet is 13.5 W/kg or less.
  20. In paragraph 1, A motor in which the magnetic flux density (B 50 ) of the above non-oriented electrical steel sheet is 1.65 T or greater.

Description

Non-oriented electrical steel sheet, motor containing the same, and method of manufacturing the same The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Due to policies to reduce carbon dioxide emissions aimed at preventing global warming, existing internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles (such as hybrid and electric vehicles). In line with the increasing demand for electric vehicles (EVs), the energy conversion efficiency of EV motors is being improved, and to achieve this, excellent magnetic properties of the motor core materials are required. Generally, electrical steel sheets are classified into oriented and non-oriented types; oriented steel is used in stationary components such as transformers. On the other hand, non-oriented electrical steel, which possesses uniform magnetic properties in all directions regardless of the rolling direction, is utilized in automotive drive motors that perform rotational motion. Therefore, non-oriented electrical steel requires a low deviation in magnetic properties between the rolling direction and other directions at a certain angle relative to the rolling direction. In other words, non-oriented electrical steel must have low magnetic anisotropy. High magnetic anisotropy hinders motor rotation and can lead to reduced energy efficiency. Since electric vehicles must generate high torque during low speeds or acceleration and rotate at high speeds during constant speed and high-speed driving, non-oriented electrical steel sheets used as core materials for motors must simultaneously satisfy high magnetic flux density and low iron loss, as well as high mechanical strength capable of withstanding centrifugal force or stress fluctuations. In particular, non-oriented electrical steel sheets with low high-frequency iron loss are required to improve motor efficiency during high-speed driving, where energy loss is high. Magnetic flux density refers to the number of magnetic field lines induced in a material under a specific magnetic field, and Tesla [T] is used as the unit of magnetic flux density. Generally, the B 50 value, which is the magnetic flux density induced under a magnetic field of 5,000 A/m, is evaluated. This magnetic flux density can vary depending on the chemical composition, grain size, and texture. Iron loss refers to the energy loss that occurs during the magnetization process of electrical steel sheets, and the unit of iron loss is W/kg. Iron loss can be classified into hysteresis loss, which is caused by the magnetization phenomenon itself, and eddy current loss, which is caused by eddy currents generated during magnetization. Therefore, methods such as reducing the sheet thickness or increasing the resistivity are being studied to reduce iron loss in non-oriented electrical steel sheets. When the content of alloying elements with high resistivity, such as Si, Mn, and Al, is increased to increase resistivity, the magnetic flux density decreases and brittleness increases, which may lead to a decrease in cold rolling performance. Consequently, a problem arises in that it becomes difficult to thin the steel sheet. In addition, the added elements combine with elements such as C, S, N, and Ti to form precipitates, and these precipitates hinder the movement of magnetic domains when a magnetic field is applied, resulting in inferior magnetic properties. FIGS. 1 and FIGS. 2 are flowcharts schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a non-oriented electrical steel sheet according to one embodiment of the present invention. Figure 4 is a drawing showing an image of surface oxide of a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 5 is a drawing showing the end of a non-oriented electrical steel sheet according to one embodiment of the present invention. The present invention will be described in detail below. However, in describing the present invention, if it is determined that a detailed description of related known technologies or configurations may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component. In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise. In the following embodiments, when various components such as layers, films, regions, and plates are described as being "on" another component, this includes not only cases where they are "directly on" another component, but also cases where another component is interposed between them. In the drawings, the size of components may be