US-12620513-B2 - Oriented electrical steel sheet and method for manufacturing same

US12620513B2US 12620513 B2US12620513 B2US 12620513B2US-12620513-B2

Abstract

A manufacturing method of a grain-oriented electrical steel sheet according to an embodiment of the present invention includes producing a cold-rolled plate; forming a groove in the cold-rolled plate; performing primary recrystallization annealing to the cold-rolled plate; and applying an annealing separator to the primary-recrystallized cold-rolled plate and performing secondary recrystallization annealing, wherein a weight ratio of SiO 2 /Fe x SiO y of the surface layer part of the cold-rolled plate is 0.3 to 3 after the primary recrystallization annealing of the cold-rolled plate. (Here, x is an integer from 1 to 2, and y is an integer from 2 to 4.)

Inventors

Jong-Tae Park
Oh-Yeoul Kwon
Woo-Sin Kim

Assignees

POSCO

Dates

Publication Date: 20260505
Application Date: 20191218
Priority Date: 20181219

Claims (4)

1 . A grain-oriented electrical steel sheet comprising: a groove positioned in a surface of an electrical steel sheet surface; a metal oxide layer positioned on the groove; and a discontinuously distributed metal oxide-based island positioned below the groove, the discontinuously distributed metal oxide-based island comprising a plurality of islands, wherein the density of the plurality of islands positioned below the groove is 3 to 15 per groove, and wherein the density of the plurality of islands positioned under the groove is 0.5 islands/μm 2 or less, wherein at least one of the plurality of islands overlaps the groove in a thickness direction of the electrical steel sheet.
2 . The grain-oriented electrical steel sheet of claim 1 , wherein: among the plurality of islands positioned under the groove, the number of islands with sphericity of 0.6 to 1.0 is 60% or more.
3 . The grain-oriented electrical steel sheet of claim 1 , wherein: the groove includes 2 to 10 grooves intermittently formed in a direction perpendicular to a rolled direction.
4 . The grain-oriented electrical steel sheet of claim 1 , wherein: the length direction of the groove and a rolled direction of the steel sheet form an angle of 75 to 88°.

Description

CROSS-REFERENCE OF RELATED APPLICATIONS This application is the U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/KR2019/018025, filed on Dec. 18, 2019, which in turn claims the benefit of Korean Application No. 10-2018-0165644, filed on Dec. 19, 2018, the entire disclosures of which applications are incorporated by reference herein. TECHNICAL FIELD The present disclosure relates to a grain-oriented electrical steel sheet and a manufacturing method thereof. More specifically, it relates to a grain-oriented electrical steel sheet in which magnetism is improved by controlling a weight ratio of SiO2/FexSiOy to properly form an island after primary recrystallization annealing, and a manufacturing method thereof. BACKGROUND ART Since a grain-oriented electrical steel sheet is used as an iron core material of an electrical device such as a transformer, in order to improve energy conversion efficiency thereof by reducing power loss of the electrical device, it is necessary to provide a steel sheet having excellent iron loss of the iron core material and a high occupying ratio when being stacked and spiral-wound. The grain-oriented electrical steel sheet refers to a functional material having a texture (referred to as a “GOSS texture”) of which a secondary-recrystallized grain is oriented with an azimuth {110}<001> in a rolling direction through a hot rolling process, a cold rolling process, and an annealing process. As a method for lowering the iron loss of the grain-oriented electrical steel sheet, a magnetic domain refining method is known. In other words, it is to reduce the size of a large magnetic domain of the grain-oriented electrical steel sheet by scratching or applying an energy impact to the magnetic domain. In this case, when the magnetic domain is magnetized and the direction thereof is changed, energy consumption may be reduced compared to when the size of the magnetic domain is large. As the magnetic domain refining method, there are permanent magnetic domain refining, in which magnetic characteristics are improved even after a heat treatment, and the effect is maintained, and a temporary domain refining, which is not. The permanent magnetic domain refining method, which shows the effect of improving the iron loss even after a stress relief heat treatment above the heat treatment temperature at which the recovery occurs, may be divided into an etching method, a roll method, and a laser method. Since it is difficult to control a groove shape because the grooves are formed on the surface of the steel sheet by a selective electrochemical reaction in a solution, it is difficult to uniformly secure the iron loss characteristics of the final product in the width direction. In addition, an acid solution used as a solvent has a disadvantage that it is not environmentally friendly. The method of refining the permanent magnetic domain using a roll is a technology of magnetic domain miniaturization partially generating recrystallized particles under the groove by forming and then annealing a groove having a constant width and depth on the surface of the plate by processing a protrusion shape on the roll to be pressed by the roll or the plate. The roll method is disadvantageous in stability in machine processing, reliability to obtain stable iron loss depending on the thickness, and process complexity, and deterioration of the iron loss and the magnetic flux density characteristics immediately after the groove formation (before the stress relaxation annealing). The permanent magnetic domain miniaturizing method by the laser uses a method of irradiating a high power laser to the surface part of the electrical steel plate and forming a groove accompanying fusion of a supporting part by the laser irradiation. However, with this permanent magnetic domain refinement method, it is also difficult to refine the magnetic domain to the minimum size. In the case of the temporary domain refinement, the laser is not irradiated with higher intensity than a certain level because research is being performed in a direction of not applying the coating once more after applying the laser in the coated state. This is because it is difficult to properly exert the tension effect due to the damage of the coating if the laser is applied over a certain level. In the case of the permanent magnetic domain refining, the groove is dug to widen the free charge area that may receive static magnetism, so the deepest groove depth is required. Of course, side effects such as a deterioration of the magnetic flux density also occur due to the deeper groove depth. Therefore, in order to reduce the deterioration of the magnetic flux density, it is managed with an appropriate groove depth. DISCLOSURE An embodiment of the present invention provides a grain-oriented electrical steel sheet and a manufacturing method thereof. In detail, an embodiment of the present invention is to provide a grain-oriented electrical st