Non-oriented electrical steel sheet core loss reduction
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Solution Overview
Problem
Non-oriented electrical steel sheets face challenges in reducing core loss due to the presence of fine Cu sulfide precipitates, which also deteriorate magnetic properties, and existing methods either increase costs or reduce productivity.
Innovation Solution
A non-oriented electrical steel sheet with specific chemical compositions and manufacturing conditions that control the morphology and structure of Cu sulfide, including a hexagonal and cubic structure, to minimize core loss while maintaining magnetic flux density and workability, by optimizing hot rolling and annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fine precipitates are present in the steel sheet to control grain growth during annealing, then grain growth is retarded, but core loss is deteriorated
Solution Approach 1:
The invention converts the harmful effect of Cu sulfide precipitates (which normally deteriorate core loss by inhibiting grain growth) into a beneficial effect by controlling their morphology and distribution. Through specific hot rolling conditions and cooling rates, the Cu sulfide precipitates are transformed from fine harmful particles to coarser, less harmful structures, thereby maintaining grain growth control while improving core loss characteristics.
2Stability of the object's composition
If Cu sulfide precipitates are present in the steel sheet, then grain growth is inhibited, but hysteresis loss is deteriorated
Solution Approach 1:
The invention changes the physical and chemical parameters of Cu sulfide precipitates through controlled hot rolling temperatures, holding times, and cooling rates. By adjusting these parameters, the precipitates transform from fine structures that cause high hysteresis loss to coarser structures with reduced harmful effects, while maintaining their grain-boundary pinning function for stable grain structure.
3Loss of energy
If rapid cooling is performed after final annealing to suppress Cu sulfide precipitation, then core loss is improved, but productivity is reduced due to extended processing time
Solution Approach 1:
The invention performs preliminary control of Cu sulfide precipitate formation during the hot rolling process itself, rather than relying on post-annealing rapid cooling. By controlling the hot rolling temperature, holding time, and cooling rate in advance, the precipitates are formed in a controlled manner that inherently reduces their harmful effects, eliminating the need for extended rapid cooling operations and thereby maintaining productivity.
4Loss of energy
If high purity steel is produced through desulfurization to avoid fine precipitates, then magnetic properties are improved, but cost increases and Cu sulfide formation cannot be completely avoided
Solution Approach 1:
The invention extracts and controls the Cu sulfide precipitate formation process from the bulk steel composition. Instead of attempting to completely eliminate sulfur through costly desulfurization, the method allows Cu sulfide formation but controls it by separating the precipitate formation from the bulk material properties through specific hot rolling and cooling conditions, thereby achieving good magnetic properties without high purification costs.
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 approach effectively makes Cu sulfide harmless, resulting in a steel sheet with improved core loss and maintained magnetic properties without increasing costs or reducing productivity.
Implementation Method 1
fine precipitates are present in a steel sheet, grain growth during annealing is retarded
Implementation Method 2
grain growth during annealing is retarded, and core loss is deteriorated
Implementation Method 3
heating a slab to a temperature of 1000°C or higher and then hot-rolling the slab
Implementation Method 4
I 2θ=46.4 which is a diffraction intensity of Cu sulfide having a hexagonal structure shown at 2θ=46.4°
Data Source
Figure 1~2
AI summary
A non-oriented electrical steel sheet includes chemical compositions including, in terms of mass%: C: 0.0001% to 0.01%; Si: 0.05% to 7.0%; Mn: 0.01% to 3.0%; Al: 0.0020% to 3.0%; S: 0.0001% to 0.1%; P: 0.0010% to 0.15%; N: 0.0010% to 0.01%; Cu: 0.01% to 5.0%; and a remainder including Fe and impurities, in which I2θ=46.4 which is a diffraction intensity of Cu sulfide having a hexagonal structure shown at 2θ=46.4° and I2θ=32.3 which is a diffraction intensity of Cu sulfide having a cubic structure shown at 2θ=32.3°, which are obtained through a X-ray diffraction of an electrolytic extraction residue, satisfy I2θ=46.4/I2θ=32.3 ≤ 0.5.