Dual Phase Magnetic Component Selective Nitriding
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Solution Overview
Problem
Current electric machines for hybrid and electric vehicle traction/propulsion applications face a tradeoff between power density, efficiency, and rotor mechanical strength, with traditional methods increasing coercivity and reducing magnetic saturation due to the presence of carbides in magnetic microstructures.
Innovation Solution
A dual-phase magnetic component is formed with intermixed magnetic and non-magnetic regions using selective nitriding, where nitrogen diffuses into unmasked areas to stabilize austenite phases, reducing coercivity and maintaining magnetic properties in masked areas through the use of a metal coating as a nitrogen stop-off material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If carbides are present in the magnetic microstructure to stabilize austenite regions, then the austenite phase is stabilized at room temperature, but coercivity increases and magnetic saturation decreases
Solution Approach 1:
The patent extracts and removes carbides from the magnetic microstructure by using a controlled nitriding process that stabilizes austenite through nitrogen diffusion rather than carbide formation. This eliminates the harmful effect of carbides on magnetic properties while maintaining austenite stability.
Solution Approach 2:
The patent changes the stabilizing mechanism from carbide-based to nitrogen-based by controlling the nitriding process parameters (temperature, time, nitrogen potential). This parameter change allows austenite stabilization without the formation of carbides, thereby maintaining low coercivity and high magnetic saturation.
2Power
If rotor speed is increased to increase power density, then power density increases, but rotor mechanical strength becomes limiting
Solution Approach 1:
The patent applies local quality by creating regions with different magnetic properties (magnetic and non-magnetic regions) within the rotor lamination. This allows optimization of magnetic flux distribution to increase power density without requiring proportional increases in overall rotor strength, as the structural integrity is maintained while magnetic utilization is enhanced.
Solution Approach 2:
The patent creates a composite magnetic material with dual-phase microstructure (magnetic and non-magnetic regions) that combines the benefits of high magnetic utilization with maintained mechanical strength. The non-magnetic regions provide flux pathways while the magnetic regions provide flux conduction, optimizing power density without compromising rotor strength.
3Power
If machine size is increased to increase power output, then power output increases, but mass and cost increase
Solution Approach 1:
The patent changes the magnetic material parameters by creating a dual-phase microstructure with optimized nitrogen content and distribution. This allows higher magnetic utilization factor, enabling smaller machine size for the same power output, thereby reducing mass while maintaining power output.
4Loss of energy
If magnetic utilization is increased by creating dual phase magnetic material, then flux losses are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating alloying elements (Al, Ti, V, Nb, Ta) during the initial material formulation stage that facilitate controlled nitrogen diffusion and austenite stabilization. This preliminary preparation simplifies the subsequent nitriding process and ensures consistent dual-phase microstructure formation, reducing overall manufacturing complexity.
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 enhances magnetic saturation and reduces coercivity, improving the power density and efficiency of electric machines while maintaining mechanical strength by stabilizing austenite phases without the negative effects of carbides, thus addressing the tradeoff between power density and rotor strength.
Implementation Method 1
the initial component may be heated to a treatment temperature in the presence of nitrogen gas such that nitrogen diffuses into the unmasked area of the initial component to transform the magnetic ferrous composition to a non-magnetic austenite composition
Implementation Method 2
nitrogen diffuses into the unmasked area of the initial component
Implementation Method 3
the use of a metal coating as a nitrogen stop-off material
Data Source
AI summary
A dual phase magnetic component, along with methods of its formation, is provided. The dual phase magnetic component may include an intermixed first region and second region formed from a single material, with the first region having a magnetic area and a diffused metal therein, and with the second region having a non-magnetic area. The second region generally has greater than 0.1 weight % of nitrogen.