Grain-Oriented Electrical Steel Heating Profile
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Solution Overview
Problem
Conventional methods for producing grain-oriented electrical steel sheets with low iron loss require high heating rates, which necessitate large and expensive heating installations and can lead to deteriorated sheet quality due to sharp temperature changes, while achieving similar effects at lower heating rates is challenging.
Innovation Solution
A method involving primary recrystallization annealing with a heating rate of 40-200°C/s between 550°C and 700°C, combined with a slower heating rate of ≤10°C/s within the 250°C to 550°C range to refine secondary recrystallized grains, promoting {110} orientation and reducing {222} recrystallization, thereby improving iron loss properties without the need for extreme heating rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a high heating rate (not less than 80°C/s) is applied during primary recrystallization annealing to refine secondary recrystallized grains and improve iron loss, then the iron loss property is improved, but large and expensive heating installations are required and input of large energy is required in a short time
Solution Approach 1:
The patent applies parameter changes by precisely controlling the heating rate as a function of temperature. The heating rate is set to 10-100°C/s in the 200-550°C range and 30-200°C/s in the 550-700°C range, rather than using a uniformly high heating rate throughout. This temperature-dependent parameter control achieves grain refinement and improved iron loss while reducing overall energy input requirements compared to conventional high heating rate methods.
2Manufacturing precision
If a high heating rate (not less than 80°C/s) is applied during primary recrystallization annealing to refine secondary recrystallized grains, then the grain orientation is improved, but the form of the steel sheet is deteriorated and sheet threading performance is lowered
Solution Approach 1:
The patent employs parameter changes by implementing a temperature-dependent heating rate profile. By setting the heating rate to 10-100°C/s below 550°C and 30-200°C/s above 550°C, the process achieves adequate grain orientation improvement while avoiding excessive thermal stress that would deteriorate sheet form and threading performance. This staged heating approach balances microstructural control with macrostructural integrity.
3Use of energy by stationary object
If a heating rate of not more than 15°C/s is applied in the temperature range of not more than 500°C, then energy consumption is reduced, but rapid heating is not effectively commenced below 550°C to suppress γ-fiber growth
Solution Approach 1:
The patent resolves this contradiction through parameter changes by defining different heating rate ranges for different temperature zones. The heating rate is set to 10-100°C/s in the 200-550°C range (moderate heating) and 30-200°C/s in the 550-700°C range (rapid heating). This staged approach ensures that rapid heating is effectively commenced below 550°C to suppress γ-fiber growth while maintaining energy efficiency, as the higher heating rate is applied only in the critical 550-700°C range where it is most needed for grain refinement.
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 allows for the stable production of grain-oriented electrical steel sheets with low iron loss, matching the refining effect of higher heating rates while using more energy-efficient and less stressful heating processes, maintaining sheet quality and performance.
Implementation Method 1
performing primary recrystallization annealing by heating a cold rolled steel sheet to a temperature of 550°C to 750°C
Implementation Method 2
improve primary recrystallization texture and refine secondary recrystallized grains
Data Source
Figure 1~2
Figure 3
AI summary
In a method of producing a grain-oriented electrical steel sheet by hot rolling a steel slab having a chemical composition comprising C: 0.001∼0.10 mass%, Si: 1.0∼5.0 mass%, Mn: 0.01∼0.5 mass%, S and/or Se: 0.005∼0.040 mass%, sol. Al: 0.003∼0.050 mass% and N: 0.0010∼0.020 mass%, subjecting to single cold rolling or two or more cold rollings including an intermediate annealing therebetween to a final thickness, performing primary recrystallization annealing, and thereafter applying an annealing separator to perform final annealing, a temperature range of 550°C to 700°C in a heating process of the primary recrystallization annealing is rapidly heated at an average heating rate of 40∼200°C/s, while any temperature zone of from 250°C to 550°C is kept at a heating rate of not more than 10°C/s for 1∼10 seconds, whereby the refining of secondary recrystallized grains is attained and grain-oriented electrical steel sheets are stably obtained with a low iron loss.