High Silicon Electrical Steel via Coating Diffusion
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Solution Overview
Problem
The production of electrical laminated cores with high silicon content is restricted due to the brittleness of silicon-rich strips, which limits their formability and increases core losses, while existing methods for increasing silicon content are complex and costly.
Innovation Solution
A method involving hot-rolling of electrical steel strips, coating with an aluminum and/or silicon-rich alloy, and subsequent heat treatment to diffuse these elements into the steel, allowing for increased silicon content and reduced core losses without compromising ductility, using edgewise rollers for forming the core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the silicon content of electrical steel is increased to reduce remagnetization losses, then the electrical resistance increases and losses decrease, but the material becomes brittle and loses formability
Solution Approach 1:
The patent divides the electrical steel product into two distinct parts: a base steel with low silicon content (0.5-3.0 wt.%) that provides good formability, and a surface coating with high silicon content (5-95 wt.%) that provides low remagnetization losses. This segmentation allows each part to optimize its function independently without the trade-off present in homogeneous high-silicon steel.
Solution Approach 2:
The patent creates a composite material structure consisting of a metallic coating layer containing 5-95 wt.% silicon applied to a base electrical steel strip. This composite structure combines the benefits of high-silicon steel (high electrical resistance, low losses) with the advantages of low-silicon steel (good ductility, formability), resolving the contradiction between energy loss reduction and ease of manufacture.
2Loss of energy
If gas deposition and heat treatment are used to increase silicon content to 7 wt.%, then electrical resistance increases to 0.8 μΩm, but the process becomes more complex and expensive
Solution Approach 1:
The patent applies the silicon-rich coating to the electrical steel strip after the strip has been formed into its final shape. This preliminary action of coating the formed core allows the use of simple coating techniques without requiring complex equipment, while the subsequent heat treatment diffuses silicon into the steel to achieve the desired electrical properties.
Solution Approach 2:
The patent uses a metallic coating layer as an intermediary medium to transfer silicon to the electrical steel. This coating layer, containing 5-95 wt.% silicon, serves as a reservoir that releases silicon during heat treatment, achieving high silicon content in the steel through a simpler process than direct gas deposition.
3Productivity
If edge rolling is used to manufacture electrical steel stacks, then production is more cost-effective than stamping and stacking, but high-silicon strips cannot be used due to brittleness
Solution Approach 1:
The patent segments the electrical steel into a low-silicon base material (providing ductility for edge rolling) and a high-silicon surface coating (providing low losses). This allows the base material to be processed by edge rolling while the coating provides the desired electrical properties, combining the advantages of both approaches.
Solution Approach 2:
The patent employs a composite material with a low-silicon ductile base steel and a high-silicon coating layer, enabling the use of edge rolling manufacturing while achieving the low remagnetization losses characteristic of high-silicon steel. The composite structure resolves the contradiction between manufacturing efficiency and material ductility.
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
Enables the production of electrical laminated cores with high silicon content, reducing core losses and maintaining ductility, thus improving manufacturability and performance.
Implementation Method 1
During heat treatment, the coating diffuses into the electrical steel, increasing its aluminum and/or silicon content
Data Source
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Figure 3~4
AI summary
The invention relates to a method for producing an electrical steel stack (71). This method comprises producing a starting electrical steel stack (40) from an electrical steel strip by means of edge rolling, coating layers (510, 520, 530) of the starting electrical steel stack with a coating (61, 62) containing at least 20 wt.% aluminum and/or silicon, and heat-treating the coated starting electrical steel stack (50) to obtain the electrical steel stack (71). If the heat treatment is carried out until a homogeneous distribution of silicon is achieved in the electrical steel stack (71), an electrical steel stack (71) with a silicon content of at least 6.5 wt.% can be obtained. If the heat treatment is carried out until at least a gradient of silicon content is present in the electrical steel stack, an electrical steel stack with a silicon content of more than 4 wt.% and less than 6.5 wt.% can be obtained.