Grain-Oriented Electrical Steel Nitriding for Flux Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods struggle to maintain a consistent and high temperature gradient throughout an industrial-scale coil during the manufacturing of grain-oriented electrical steel sheets, leading to regions with insufficient magnetic flux density improvement.
Innovation Solution
A method involving a hot rolling step, decarburization annealing, nitriding treatment, and final annealing with controlled nitrogen content and temperature gradient to enhance magnetic flux density, even under small temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a temperature gradient of 2°C/cm or more is applied during final annealing to improve magnetic flux density, then magnetic flux density is improved, but it is difficult to maintain such a high temperature gradient throughout an industrial-scale coil
Solution Approach 1:
The invention changes the parameter of nitrogen content from its conventional level to 210 ppm or more, which fundamentally alters the mechanism of secondary recrystallization. This parameter change allows the process to proceed effectively with a much lower temperature gradient (0.5°C/cm or more), resolving the contradiction between achieving high magnetic flux density and maintaining temperature gradient control in industrial-scale coils.
2Manufacturing precision
If conventional methods are used to apply temperature gradient, then some regions achieve sufficient magnetic flux density improvement, but low-temperature gradient regions (about 0.5°C/cm) fail to improve magnetic flux density sufficiently
Solution Approach 1:
By increasing the nitrogen content to 210 ppm or more, the invention changes the recrystallization behavior of the steel. This parameter change makes the secondary recrystallization process insensitive to temperature gradient variations, allowing uniform magnetic flux density improvement across the entire coil even in regions where the temperature gradient is as low as 0.5°C/cm.
3Ease of manufacture
If the temperature gradient is reduced to facilitate industrial-scale production, then ease of manufacture is improved, but magnetic flux density improvement becomes insufficient
Solution Approach 1:
The invention introduces a fundamental parameter change by specifying nitrogen content of 210 ppm or more, which decouples the relationship between temperature gradient magnitude and magnetic flux density improvement. This allows industrial-scale production with reduced temperature gradients (0.5°C/cm or more) while maintaining high magnetic flux density, thus resolving the contradiction between ease of manufacture and manufacturing precision.
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
The method stabilizes magnetic flux density across the coil by increasing nitrogen content to 210 ppm, allowing for effective grain orientation and improved magnetic properties even with a temperature gradient as low as 0.5 °C/cm.
Implementation Method 1
a nitriding treatment step of increasing a nitrogen amount in the steel sheet
Implementation Method 2
a final annealing step of final-annealing the steel sheet coiled into a coil shape
Implementation Method 3
the crystal orientation control is achieved using a catastrophic grain growth phenomenon called secondary recrystallization
Data Source
AI summary
The method of manufacturing a grain-oriented electrical steel sheet includes: a hot rolling step; a hot-rolled sheet annealing step performed as necessary; a cold rolling step; a decarburization annealing step; an annealing separator applying step; a nitriding treatment step; and a final annealing step, wherein the final annealing step has a temperature raising process and a soaking process, and a temperature gradient of 0.5 °C/cm or more is generated in a boundary region between a primary recrystallization region and a secondary recrystallization region at least in one period from the start of secondary recrystallization to completion of the secondary recrystallization in the temperature raising process; and the nitriding treatment step is performed by annealing in an atmosphere containing a gas having nitriding ability at least in one stage of: during the decarburization annealing step; between the decarburization annealing step and the final annealing step; and during the temperature raising process in the final annealing step and before the start of the secondary recrystallization, so that the nitrogen amount in the steel sheet is 210 ppm or more based on mass after the nitriding treatment step.