Laminated Core Surface Alloying With Aluminum Oxide Foil Layers
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Solution Overview
Problem
Existing methods for producing laminated cores of electrical machines are limited in their ability to cost-effectively alloy sheet metal laminations with low aluminum and silicon content to higher levels, while also maintaining the soft magnetic properties and increasing the electrical resistance.
Innovation Solution
The method involves providing foil laminations with a carrier foil made of aluminum, a natural or produced insulator layer, and a foil coating containing an alloy material, an adhesive bonding agent, and aluminum oxide in powder form. These foil laminations are alternately stacked with sheet metal laminations, which are then heat-treated to allow aluminum and alloy material diffusion, forming an alloyed-up region and an insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sheet metal laminations with low aluminum and silicon content are used, then cost is reduced, but electrical resistance is insufficient and efficiency is impaired
Solution Approach 1:
Alloy material is applied to the surface of sheet metal laminations before stacking and heat treatment, pre-positioning the necessary aluminum and silicon content on the surface. This preliminary action enables subsequent diffusion to achieve the desired bulk alloying without requiring expensive high-alloy starting materials.
Solution Approach 2:
The method changes the chemical composition parameters of the sheet metal laminations through controlled diffusion during heat treatment. By adjusting temperature, time, and initial surface coating composition, the aluminum and silicon content is transformed from low bulk concentration to the desired 6.5-10.5% range in the alloyed-up region.
2Loss of energy
If alloy material is added to increase electrical resistance, then efficiency is improved, but soft magnetic properties are impaired
Solution Approach 1:
The alloying is localized to create an alloyed-up region near the surface of the sheet metal laminations, while the core material retains its original low-alloy composition with excellent soft magnetic properties. This spatial differentiation allows the surface to provide high electrical resistance for reduced eddy current losses, while the bulk maintains high permeability and low hysteresis losses.
Solution Approach 2:
The method creates a surface layer that copies the desired high-resistance properties of expensive high-alloy sheets without requiring the entire bulk material to have that composition. The diffusion process replicates the beneficial surface characteristics of high-alloy materials on cost-effective low-alloy substrates.
3Quantity of substance
If high aluminum and silicon content is achieved through conventional coating methods, then electrical resistance is increased, but adhesion and unrolling are impaired
Solution Approach 1:
An adhesive bonding agent is introduced as an intermediary layer between the alloy material powder and the sheet metal lamination surface. This mediator enables proper adhesion of the alloy coating during handling and unrolling, while still allowing subsequent diffusion to achieve the desired aluminum and silicon content in the alloyed-up region.
Solution Approach 2:
The coating is formulated as a composite material system consisting of alloy material powder (aluminum and silicon sources), adhesive bonding agent (for proper adhesion and unrolling), and optional aluminum oxide powder (for insulation). This composite approach combines the beneficial properties of each component: alloying capability, adhesion, and processability.
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 method enables cost-effective alloying of sheet metal laminations to increase the aluminum and silicon content near the surface, thereby enhancing the electrical resistance and maintaining the soft magnetic properties, which improves the efficiency of the electrical machine.
Implementation Method 1
the aluminum diffuses from the carrier foils of the foil laminations with a certain depth into the metal of the respective adjacent sheet metal laminations
Implementation Method 2
the alloy material diffuses from the foil coating of the foil laminations with a certain depth into the metal of the adjacent sheet metal lamination with formation of an alloyed-up region
Implementation Method 3
the aluminum oxide remains from the foil aluminum oxide layer of the foil laminations or from the foil coating of the foil laminations with formation of an insulating layer between the sheet metal laminations
Data Source
AI summary
In a method for producing a laminated core (1) of an electric machine, sheet metal laminations (4, 5), which are based on an iron material, are alloyed by means of heat treatment with an alloy material (16) comprising silicon. Before the heat treatment, aluminum-based foil laminations (6, 7) which comprise foil aluminum oxide layers (8, 9) and are each at least partially coated with the alloy material, are arranged between the sheet metal laminations (4, 5).