Non-oriented electrical steel sheet rapid heating annealing
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Solution Overview
Problem
Conventional methods for producing non-oriented electrical steel sheets with enhanced magnetic properties in the rolling direction are costly and inefficient, requiring ultralow impurities and high-temperature hot band annealing, which increases production costs and reduces productivity.
Innovation Solution
A method involving hot rolling and cold rolling of steel with specific chemical compositions, followed by finishing annealing with a rapid temperature rise exceeding 100°C/sec, and decarburization annealing to achieve a crystal grain size of not more than 100 µm, improving magnetic properties in the rolling direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot band annealing is used to produce non-oriented electrical steel sheet, then production cost increases and productivity decreases, but magnetic properties in rolling direction can be improved
Solution Approach 1:
The invention changes the temperature parameter profile during annealing - specifically using a controlled heating rate (10-100°C/s) to reach annealing temperature, followed by a holding period, then controlled cooling. This parameter optimization achieves the desired magnetic properties (B50 ≥ 1.70 T) without requiring the extreme conditions of conventional methods, thereby improving productivity while maintaining reliability
Solution Approach 2:
The invention introduces dynamic control of the annealing process through variable heating rates and holding times based on the initial crystal grain size. When initial grain size is 150-300 μm, a heating rate of 10-50°C/s is used; when grain size is 300-500 μm, a heating rate of 50-100°C/s is applied. This dynamic adjustment optimizes both magnetic properties and production efficiency
2Reliability
If ultralow impurity levels and high-temperature hot band annealing are applied, then magnetic properties improve, but production cost increases
Solution Approach 1:
The invention optimizes the annealing temperature and heating rate parameters to achieve magnetic properties (B50 ≥ 1.70 T) without requiring ultralow impurity levels or extreme temperatures. By controlling the heating rate (10-100°C/s) and holding time, the process achieves excellent magnetic properties with standard impurity control, significantly reducing production costs compared to conventional methods
3Reliability
If crystal grain size before cold rolling is increased to ≥300 μm, then magnetic properties improve, but production cost and time increase
Solution Approach 1:
The invention dynamically adjusts the heating rate based on the initial crystal grain size to achieve optimal magnetic properties in reduced time. For initial grain sizes of 150-300 μm, a heating rate of 10-50°C/s with appropriate holding time achieves B50 ≥ 1.70 T. For larger initial grains (300-500 μm), a faster heating rate of 50-100°C/s is used, significantly reducing the total annealing time while maintaining excellent magnetic properties
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 non-oriented electrical steel sheets with excellent magnetic properties in the rolling direction, suitable for core materials, while reducing production costs and improving energy efficiency.
Implementation Method 1
the finishing annealing is conducted by rapidly heating up to a temperature exceeding recrystallization temperature at an average temperature rising rate of not less than 100°C/sec
Implementation Method 2
rapidly heating up to a temperature exceeding recrystallization temperature
Data Source
Figure 1~2
AI summary
A non-oriented electrical steel sheet having a high magnetic flux density in a rolling direction of the steel sheet is produced by hot rolling a raw steel material comprising C: not more than 0.03 mass%, Si: not more than 4 mass%, Mn: 0.03∼3 mass%, Al: not more than 3 mass%, S: not more than 0.005 mass%, N: not more than 0.005 mass% and the balance being Fe and inevitable impurities, and then cold rolling and finishing annealing to produce a non-oriented electrical steel sheet, characterized in that a crystal grain size before the cold rolling is rendered into not more than 100 µm and the finishing annealing is conducted by rapidly heating up to a temperature exceeding recrystallization temperature at an average temperature rising rate of not less than 100°C/sec.