Dual Phase Magnetic Component Nitrogen Stabilization
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Solution Overview
Problem
Current electric machines for hybrid and electric vehicle traction face a tradeoff between power density, efficiency, and constant power speed range, with traditional methods increasing coercivity and lowering magnetic saturation, necessitating a method to stabilize austenite phases at room temperature without carbides.
Innovation Solution
A dual phase magnetic component is formed with intermixed magnetic and non-magnetic regions, where the non-magnetic region is stabilized by nitrogen rather than carbon, using selective nitriding in a nitrogen-rich atmosphere to maintain high magnetic saturation and reduce coercivity, with carbon concentrations less than 0.05 weight % and nitrogen concentrations greater than 0.4 weight %.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If carbides are used to stabilize austenite regions at room temperature, then the austenite phase can be stabilized, but coercivity increases and magnetic saturation decreases
Solution Approach 1:
The patent changes the chemical composition parameters by substituting carbon with nitrogen to stabilize austenite. Specifically, the steel contains 0.005-0.050 wt% carbon and 0.05-0.50 wt% nitrogen, where nitrogen replaces carbon's role in austenite stabilization while avoiding the formation of carbides that harm magnetic properties
Solution Approach 2:
Nitrogen acts as an intermediary element that performs the function of stabilizing austenite without the harmful side effects of carbon. The nitrogen atoms occupy interstitial sites in the austenite lattice and provide stabilization through electronic interactions, serving as a mediator between the desired phase stability and the need for high magnetic saturation
2Stability of the object's composition
If carbides are present in the magnetic microstructure, then austenite can be stabilized locally, but coercivity increases
Solution Approach 1:
The patent changes the compositional parameters by strictly limiting carbon content to 0.005-0.050 wt% and introducing nitrogen at 0.05-0.50 wt%, thereby preventing carbide formation while maintaining austenite stability through nitrogen's interstitial solid solution strengthening and electronic effects
Solution Approach 2:
The patent converts the potential harm of carbon (which forms harmful carbides) into a benefit by using nitrogen instead. Nitrogen provides the same austenite stabilization function without forming harmful precipitates, effectively turning the search for an alternative stabilizer into a beneficial solution that improves both magnetic and mechanical properties
3Loss of energy
If traditional ferrous-based magnetic steels are used, then magnetic saturation is high, but coercivity is also high due to carbide presence
Solution Approach 1:
The patent creates a composite microstructure consisting of martensite regions (providing high saturation) and nitrogen-stabilized austenite regions (providing low coercivity). This dual-phase composite material combines the advantages of both phases while avoiding the disadvantages of traditional single-phase steels
Solution Approach 2:
The patent applies local quality by creating distinct regions with different phases - martensite in some areas for high saturation and nitrogen-stabilized austenite in other areas for low coercivity. This spatial differentiation of properties allows the material to optimize both magnetic saturation and coercivity simultaneously
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 enhances magnetic utilization, reduces flux losses, and maintains high magnetic saturation while minimizing coercivity, thereby improving the power density and efficiency of electric machines without the drawbacks of carbide presence.
Implementation Method 1
heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900° C., so as to form intermixed first and second regions
Implementation Method 2
heat-treating the component in a nitrogen-rich atmosphere... to form intermixed first and second regions... the second region includes greater than about 0.4 weight % of nitrogen
Implementation Method 3
A range of ferrous based soft magnetic compositions of the rotor lamination may be austenitized by a combination of processes to form regions of low permeability. This phase transformation at selected regions is normally thermally driven
Data Source
AI summary
A magnetic component having intermixed first and second regions, and a method of preparing that magnetic component are disclosed. The first region includes a magnetic phase and the second region includes a non-magnetic phase. The method includes mechanically masking pre-selected sections of a surface portion of the component by using a nitrogen stop-off material and heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900° C. Both the first and second regions are substantially free of carbon, or contain only limited amounts of carbon; and the second region includes greater than about 0.1 weight % of nitrogen.