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KR-20260064974-A - NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

KR20260064974AKR 20260064974 AKR20260064974 AKR 20260064974AKR-20260064974-A

Abstract

The present application relates to a non-oriented electrical steel sheet and a method for manufacturing the same. According to the present application, a non-oriented electrical steel sheet having excellent magnetic properties as well as high mechanical strength and a method for manufacturing the same can be provided.

Inventors

  • 박준영
  • 곽민석
  • 이동희
  • 강춘구

Assignees

  • 현대제철 주식회사

Dates

Publication Date
20260508
Application Date
20241030

Claims (9)

  1. In weight%, comprising 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, the sum of at least one of Sn and Sb: 0.005% or more and 0.050% 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, and Ti: greater than 0% and 0.002% or less, and comprising the remainder being Fe and other unavoidable impurities, Non-oriented electrical steel sheet satisfying the following general formula 1: [General Formula 1] 1 ≤ a/b ≤ 3 In the above general formula 1, a is the fraction (%) of recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%, and b is the average grain size (μm) of the recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%.
  2. In Article 1, Non-oriented electrical steel sheet in which the fraction of recrystallization formed in the portion from the surface to 20% thickness is 80% or more.
  3. In Article 1, Non-oriented electrical steel sheet having an average grain size of recrystallization formed in the portion from the surface to 20% thickness of 25 μm or more and 100 μm or less.
  4. 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 0.5% or less, Al: 0.5% or more and 1.5% or less, the sum of at least one of Sn and Sb: 0.005% or more and 0.050% 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, and Ti: greater than 0% and 0.002% or less, and the remainder being Fe and other unavoidable impurities; A step of manufacturing a cold-rolled steel sheet by cold-rolling the above hot-rolled steel sheet; and The method includes the step of finally annealing the above cold-rolled steel sheet, A method for manufacturing a non-oriented electrical steel sheet that satisfies the following general formula 1, wherein the final annealed non-oriented electrical steel sheet is: [General Formula 1] 1 ≤ a/b ≤ 3 In the above general formula 1, a is the fraction (%) of recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%, and b is the average grain size (μm) of the recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%.
  5. In Article 4, A method for manufacturing a non-oriented electrical steel sheet in which the fraction of recrystallization formed in the portion from the surface to 20% thickness is 80% or more.
  6. In Article 4, A method for manufacturing a non-oriented electrical steel sheet in which the average grain size of the recrystallization formed in the portion from the surface to 20% thickness is 25 μm or more and 100 μm or less.
  7. In Article 4, A method for manufacturing a non-oriented electrical steel sheet, wherein the final annealing step is performed by finally annealing the cold-rolled steel sheet at a temperature of 700°C or higher and less than 950°C for 10 seconds or more and 90 seconds or less.
  8. In Article 4, A method for manufacturing non-oriented electrical steel sheets in which the above final annealing step is performed under an atmosphere of at least 20% hydrogen and the remainder being nitrogen.
  9. In Article 4, A method for manufacturing a non-oriented electrical steel sheet, further comprising the step of intermediate annealing the hot-rolled steel sheet, which has undergone the step of manufacturing the hot-rolled steel sheet above, at a starting temperature of 750°C or higher and 1000°C or lower for 30 seconds or more and 90 seconds 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. However, in the case of conventional patent document 1, as the motor rotates at high speed due to the high output of electric vehicles (EVs), excellent magnetic properties are satisfied for the rotor material, but high mechanical strength capable of withstanding centrifugal force or stress fluctuations is not satisfied. In particular, high yield strength and fatigue strength to suppress deformation and fatigue failure during motor operation are not satisfied. Therefore, to solve these problems, a non-oriented electrical steel sheet having not only excellent magnetic properties but also high mechanical strength, and a method for manufacturing the same, are required. In the description of numerical ranges in this specification, the notation “X~Y” indicates X or greater and Y or less, unless otherwise specifically stated. Additionally, “greater than or equal to” may be replaced with “greater than,” and “less than or equal to” may be replaced with “less than.” In addition, regarding the numerical ranges described stepwise in this specification, any 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 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, the sum of at least one of Sn and Sb: 0.005% or more and 0.050% 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, and Ti: greater than 0% and 0.002% or less, and the remainder comprises Fe and other unavoidable impurities, satisfying the following general formula 1. [General Formula 1] 1 ≤ a/b ≤ 3 In the above general formula 1, a is the fraction (%) of recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%, and b is the average grain size (μm) of the recrystallization formed in the portion from the surface of the non-oriented electrical steel sheet to a thickness of 20%. A non-oriented electrical steel sheet satisfying the above general formula 1 may be manufactured by including a composition within a specific content range in the present application and controlling the heat treatment temperature, atmosphere, and/or holding time of the final annealing within a specific range in the present application. In this specification, the portion up to 20% thickness from the surface refers to the area measured with respect to the TD plane of the non-oriented electrical steel sheet, and refers to 20% of the upper surface and 20% of the lower surface of the TD plane, totaling 40% of the area. Specifically, the value calculated by the above general formula 1 may be 1.05 or higher and 2.90 or lower, or 1.10 or higher and 2.80 or lower. According to the non-oriented electrical steel sheet of the present application, by including the aforementioned components and satisfying the above general formula 1, it can have excellent magnetic properties as well as high mechanical strength. On the other hand, if the value calculated by the above general formula 1 is below the lower limit of the above range, it may have high iron loss, low yield strength, or low yield strength and low fatigue strength. In addition, if the value calculated by the above general formula 1 exceeds the upper limit of the above range, it may have high iron loss. For example, the above non-oriented electrical steel sheet may have a yield strength of 450 MPa or more, specifically 452 MPa or more or 454 MPa or more. In addition, although the upper limit of the yield strength of the above non-oriented electrical steel sheet is not specifically limited, for example, it may be 1300 MPa or less, specifically 1200 MPa or less or 1100 MPa or less. By satisfying the aforementioned range of yield strength, the above non-oriented electrical steel sheet can suppres