Grain-Oriented Electrical Steel Sheet Three-Stage Heating Annealing
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Solution Overview
Problem
Existing methods for manufacturing grain-oriented electrical steel sheets do not effectively increase the ratio of Goss-oriented grains, which limits the improvement of magnetic properties, and rely on indirect methods to enhance magnetic flux density by controlling textures during decarburization annealing.
Innovation Solution
A three-stage heating pattern consisting of ultra-rapid heating, rapid heating, and general heating is applied during primary recrystallization annealing to increase the volume fraction of Goss-oriented grains, thereby enhancing the density of crystallographic orientations and improving magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-stage heating is used in primary recrystallization annealing, then the process is simple and easy to control, but the volume fraction of Goss-oriented grains remains low and magnetic properties are not improved
Solution Approach 1:
The heating process is divided into three distinct stages with different heating rates: first-stage rapid heating (100-300°C/sec) to promote nucleation, second-stage moderate heating (10-50°C/sec) for grain growth control, and third-stage slow heating (1-10°C/sec) for texture optimization. This segmentation allows each stage to target specific microstructural evolution goals, significantly increasing the volume fraction of Goss-oriented grains while maintaining controllable process complexity through defined parameter ranges for each stage.
Solution Approach 2:
The invention dynamically changes the heating rate parameter throughout the annealing process, transitioning from high heating rates in the first stage to lower rates in subsequent stages. This parameter change strategy optimizes the balance between nucleation rate and grain growth rate at different temperature ranges, enabling precise control over the development of Goss-oriented textures and achieving superior magnetic properties.
2Reliability
If rapid heating is applied to increase Goss-oriented grains, then magnetic flux density improves, but the heating process becomes more complex and requires precise control
Solution Approach 1:
The heating process employs dynamic adjustment of heating rates based on the progression of recrystallization and texture development. The three-stage approach allows the system to adapt the heating rate to the current microstructural state, starting with rapid heating to stimulate nucleation of Goss-oriented grains, then progressively reducing the rate to control grain growth and prevent excessive complexity in process control while maintaining high magnetic flux density.
3Reliability
If multi-stage heating process is used to maximize Goss orientation, then magnetic properties are significantly improved, but the manufacturing time and process complexity increase
Solution Approach 1:
The three-stage heating process maintains continuous useful action throughout the annealing cycle, with each stage seamlessly transitioning to the next without interruption. The first stage rapidly establishes nucleation sites, the second stage continuously promotes selective grain growth, and the third stage continuously optimizes the texture, ensuring that the beneficial effects of Goss-oriented grain development are maximized throughout the entire process while managing time efficiency through optimized duration of each stage.
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 significantly increases the magnetic flux density and reduces core loss by maximizing the nucleation of Goss-oriented grains, resulting in a grain-oriented electrical steel sheet with improved magnetic properties.
Implementation Method 1
an ultra-rapid heating process for heating the steel sheet at an average heating rate of 300° C./sec or higher, a rapid heating process for heating the steel sheet at a lower average heating rate than the average heating rate of the ultra-rapid heating process, but not lower than 100° C./sec, and a general heating process for heating the steel sheet at a lower average heating rate than the average heating rate of the rapid heating process
Implementation Method 2
subjecting the cold-rolled steel sheet to primary recrystallization annealing
Implementation Method 3
maximizing the nucleation of Goss-oriented grains
Data Source
AI summary
Provided is a method for manufacturing a grain-oriented electrical steel sheet, the method comprising: heating a grain-oriented electrical steel sheet slab; hot-rolling the heated slab; optionally annealing the hot-rolled steel sheet; subjecting the resulting steel sheet to one cold rolling or two or more cold rollings with intermediate annealing therebetween; subjecting the cold-rolled steel sheet to primary recrystallization annealing; and subjecting the annealed steel sheet to secondary recrystallization annealing, wherein the primary recrystallization annealing sequentially comprises an ultra-rapid heating process of heating the steel sheet at an average heating rate of 300° C./sec or higher, a rapid heating process of heating the steel sheet at a lower average heating rate than the average heating rate of the ultra-rapid heating process, but not lower than 100° C./sec, and a general heating process of heating the steel sheet at a lower average heating rate than the average heating rate of the rapid heating process.