Non-oriented electrical steel sheet for motor cores
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Solution Overview
Problem
Conventional methods for producing non-oriented electrical steel sheets for motor cores face challenges in achieving high strength for rotor cores and excellent magnetic properties with low iron loss for stator cores from the same raw material, while also being cost-effective and efficient in production.
Innovation Solution
A non-oriented electrical steel sheet is produced with controlled Si, Al, and Mn content ranges, and a stress relief annealing cooling rate not exceeding 10°C/min, allowing for the simultaneous manufacture of high-strength rotor cores and low-iron-loss stator cores from the same raw material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional methods are used to produce non-oriented electrical steel sheets, then production cost is reduced, but it is difficult to achieve both high strength for rotor cores and excellent magnetic properties with low iron loss for stator cores from the same raw material
Solution Approach 1:
The invention changes the chemical composition parameters of the steel sheet by precisely controlling the content ranges of Si (2.0-4.0%), Al (0.01-2.0%), and Mn (0.05-2.0%), while limiting impurity elements. This parameter optimization enables the same steel sheet material to achieve both high strength (yield strength ≥400 MPa) and excellent magnetic properties (low iron loss W10/400 ≤25 W/kg) after stress relief annealing, eliminating the need for different materials for rotor and stator cores.
2Loss of energy
If stress relief annealing is applied to improve magnetic properties, then iron loss is reduced, but production cost increases due to additional processes like Ni addition or skin pass rolling
Solution Approach 1:
The invention optimizes the chemical composition parameters, particularly Si content (2.0-4.0%) and Al content (0.01-2.0%), which inherently reduce iron loss through solid solution strengthening and magnetic property improvement. This parameter optimization reduces the need for additional expensive processes like Ni addition or skin pass rolling, making stress relief annealing more cost-effective while achieving low iron loss (W10/400 ≤25 W/kg).
Solution Approach 2:
The invention uses inexpensive alloying elements (Si, Al, Mn) within optimized ranges to achieve the desired magnetic properties and strength, replacing more expensive solutions like Ni addition or complex surface treatment processes. This approach provides a cost-effective method to reduce iron loss without requiring additional manufacturing steps.
3Loss of energy
If impurity elements are decreased to very low level to promote crystal grain growth, then magnetic properties are improved, but production cost increases
Solution Approach 1:
The invention optimizes the balance between impurity element control and alloying element content. By setting specific ranges for Si (2.0-4.0%), Al (0.01-2.0%), and Mn (0.05-2.0%), and limiting impurities (Ti≤0.005%, S≤0.005%, N≤0.005%, V≤0.005%, Nb≤0.005%, Zr≤0.005%, As≤0.005%), the invention achieves good magnetic properties without requiring extremely low impurity levels. This balanced parameter approach promotes crystal grain growth and reduces iron loss while maintaining cost-effectiveness in production.
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 enables the production of motor cores with improved mechanical and magnetic properties, enhancing productivity by meeting the distinct requirements of rotor and stator cores while reducing production costs and iron loss.
Implementation Method 1
a stress relief annealing cooling rate not exceeding 10°C/min
Implementation Method 2
stress relief annealing
Data Source
Figure 1~2
AI summary
There are provided a method for producing a non-oriented electrical steel sheet, a method for manufacturing a motor core from such a steel sheet, and a motor core. In the production of a non-oriented electrical steel sheet by subjecting a steel slab containing given amounts of C, Si, Mn, P, S, Al, N, Ti, Nb and V, provided that Si, Al and Mn satisfy Si - 2Al - Mn ≥ 0, to hot rolling, cold rolling, finish annealing and stress relief annealing, conditions of the finish annealing and stress relief annealing are adjusted such that a yield stress after the finish annealing is not less than 400 MPa and iron loss W10/400 (W/kg) after the stress relief annealing in relation to a sheet thickness t (mm) satisfies W10/400 ≤ 10 + 25t and magnetostriction λο-p (bake)after the stress relief annealing is not more than 5.0 x 10-6 and a ratio (λο-p (bake) / λο-p (green)) of magnetostriction λο-p (bake) after the stress relief annealing to magnetostriction λο-p (green) before the stress relief annealing is less than 0.8, whereby a high-strength rotor core and a stator core having excellent magnetic properties after stress relief annealing can be obtained from the same steel material.