Grain-Oriented Electrical Steel Sheet With Laser Stress Domain Refining

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Solution Overview

Problem

Existing grain-oriented electrical steel sheets face challenges in reducing iron loss and noise while maintaining magnetostrictive properties, particularly when subjected to laser irradiation, which requires high energy input and can damage the forsterite film, making it difficult to control film thickness and achieve optimal magnetic domain refining effects.

Innovation Solution

The use of shock waves in conjunction with thermal diffusion during laser irradiation to create a stress distribution that improves iron loss and noise properties, with specific conditions including a picosecond or femtosecond laser, a film thickness ratio of 0.5 or more for forsterite films, and compressive stress in the rolling direction up to 2 μm depth, to prevent film damage and enhance magnetic domain refining.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If high energy laser irradiation is applied to form magnetic domain discontinuous portions, then iron loss reduction is achieved, but the forsterite film is damaged and magnetostrictive property degrades causing noise increase

Engineering Contradiction:

Improveiron lossVSAvoidmagnetostrictive property

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent changes the laser irradiation parameters by using pulsed laser irradiation with specific energy density ranges (0.1-10 J/cm²) and pulse durations (nanosecond to femtosecond range), which allows magnetic domain refining while preventing forsterite film damage and maintaining magnetostrictive properties

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs pulsed laser irradiation instead of continuous irradiation, using periodic pulses with controlled duration and intervals to achieve magnetic domain discontinuous portions without excessive energy accumulation that would damage the forsterite film

Inventive Principle:

Principle #19Periodic action

2Loss of energy

If high energy laser irradiation is used to refine magnetic domains, then iron loss is reduced, but film thickness control becomes difficult and forsterite film is damaged

Engineering Contradiction:

Improveiron lossVSAvoidfilm thickness control

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent optimizes laser irradiation parameters including energy density (0.1-10 J/cm²), pulse duration (nanosecond to femtosecond), and number of pulses to achieve magnetic domain refining while maintaining forsterite film integrity and controllable thickness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies controlled partial energy input through limited pulse numbers and specific energy densities, providing just enough energy to create magnetic domain discontinuous portions without excessive energy that would damage the film

Inventive Principle:

Principle #16Partial or excessive action

3Loss of energy

If electron beam irradiation is used to create magnetic domain discontinuous portions, then low noise and low iron loss are achieved, but extremely large energy input is required due to lower penetrability compared to laser

Engineering Contradiction:

Improveiron lossVSAvoidenergy input

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The patent replaces electron beam irradiation with laser beam irradiation, utilizing the higher penetrability and more efficient energy coupling of laser light to achieve magnetic domain refining with reduced energy input requirements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach results in a grain-oriented electrical steel sheet with reduced iron loss and noise, maintaining effective magnetostriction and preventing forsterite film damage, suitable for transformer applications.

Implementation Method 1

by effectively using shock waves in addition to thermal diffusion which is a conventional magnetic domain refining mechanism

Methodology Applied

Scientific EffectThermal diffusion: Diffusion

Implementation Method 2

by effectively using shock waves in addition to thermal diffusion which is a conventional magnetic domain refining mechanism

Methodology Applied

Scientific EffectShock waves: Shock Wave

Implementation Method 3

compressive stress exists in a rolling direction in a range from a surface of the steel sheet that is the strain-introduced surface to at least 2 μm in a sheet thickness direction

Methodology Applied

Scientific EffectCompressive stress: Compression

Implementation Method 4

forsterite films on both sides of the steel sheet

Methodology Applied

Scientific EffectFilm protection:

Data Source

PatentUS20240011111A1Grain-oriented electrical steel sheet and production method therefor

Publication Date: 2024.01.11 JFE STEEL CORP

AI summary

Provided is a grain-oriented electrical steel sheet comprising a magnetic flux density B8 of 1.92 T or more, wherein a ratio Wa/Wb of a film thickness Wa of a forsterite film on a strain-introduced surface to a film thickness Wb of a forsterite film on a non-strain-introduced surface is 0.5 or more, an average width of a magnetic domain discontinuous portion on the non-strain-introduced surface is 1.00 time or more of an average width of a magnetic domain discontinuous portion on the strain-introduced surface, the average width of the magnetic domain discontinuous portion on the non-strain-introduced surface is 400 μm or less, and compressive stress exists in a rolling direction in a range from a surface of the steel sheet that is the strain-introduced surface to at least 2 μm in a sheet thickness direction.