Grain-Oriented Electrical Steel Sheet Annealing for Wrinkle Suppression
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Solution Overview
Problem
Grain-oriented electrical steel sheets with protrusions and recesses on the surface, generated during rapid temperature increase in primary recrystallization annealing, lead to voids when stacked, reducing the stacking factor and degrading transformer performance, and existing methods fail to sufficiently suppress fine protrusions and recesses.
Innovation Solution
A method for manufacturing grain-oriented electrical steel sheets involving a rapid temperature increase process with an average velocity of 400 °C/s or more in the temperature range of 550°C to 700°C, controlling the steel sheet tensile force, and optimizing the T/L ratio to minimize wrinkles and improve surface shape, thereby reducing iron loss without magnetic domain refinement treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rapid temperature increase is applied in primary recrystallization annealing to improve magnetic characteristics, then Goss orientation crystal grains increase, but protrusions and recesses (wrinkles) are generated on the surface
Solution Approach 1:
The patent applies parameter changes by precisely controlling the temperature increase velocity (400-1000 °C/s) and the T/L ratio (0.05-0.5 °C/mm) during primary recrystallization annealing. By adjusting these parameters within specific ranges, the patent achieves both improved magnetic characteristics through increased Goss orientation grains and suppressed surface wrinkles, resolving the technical contradiction between magnetic performance and surface quality.
2Reliability
If higher temperature increase velocity is used to further improve magnetic characteristics, then Goss orientation grains increase more, but surface wrinkles become more severe
Solution Approach 1:
The patent resolves this contradiction by introducing a coupled control of two parameters: temperature increase velocity (400-1000 °C/s) and T/L ratio (0.05-0.5 °C/mm). The specific combination of these parameters creates optimal conditions where rapid heating promotes Goss orientation grain formation while the controlled T/L ratio prevents excessive thermal gradients that cause wrinkles, achieving both improved magnetic characteristics and acceptable surface quality.
3Shape
If conventional temperature increase methods are used to avoid surface wrinkles, then surface shape is maintained, but magnetic characteristics are insufficient
Solution Approach 1:
The patent overcomes this limitation by implementing rapid temperature increase (400-1000 °C/s) within a specifically controlled T/L ratio range (0.05-0.5 °C/mm). This parameter control enables the steel sheet to undergo rapid heating that promotes Goss orientation grain formation for improved magnetic characteristics, while the constrained T/L ratio prevents thermal gradients from becoming large enough to cause severe surface wrinkles, thus achieving both goals simultaneously.
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 results in a grain-oriented electrical steel sheet with a favorable surface shape and decreased iron loss, enhancing the stacking factor and performance of transformer core materials.
Implementation Method 1
when the temperature of a steel sheet is rapidly increased in a temperature increase process for primary recrystallization annealing carried out ahead of secondary recrystallization, it is possible to increase crystal grains in a Goss orientation
Implementation Method 2
Crystal orientations in a grain-oriented electrical steel sheet can be controlled using a catastrophic grain growth phenomenon called secondary recrystallization
Data Source
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AI summary
A method for manufacturing a grain-oriented electrical steel sheet including a step of hot-rolling a slab containing a predetermined component composition with a remainder including Fe and an impurity to obtain a hot-rolled steel sheet, a step of, after carrying out hot-rolled steel sheet annealing on the hot-rolled steel sheet, carrying out cold rolling to obtain a cold-rolled steel sheet, a step of carrying out primary recrystallization annealing including a rapid temperature increase at an average temperature increase velocity V of 400 °C/s or more and imparting of a steel sheet tensile force S on the cold-rolled steel sheet, and a step of applying an annealing separating agent to a surface of the cold-rolled steel sheet after the primary recrystallization annealing and then carrying out flattening annealing.