Non-Oriented Electrical Steel Composition for High-Temperature Fatigue
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Solution Overview
Problem
Existing non-oriented silicon steel materials used in drive motors for electric vehicles lack sufficient high-temperature fatigue performance and yield strength, leading to potential deformation, fracture, or sudden shutdown during high-speed operation.
Innovation Solution
A non-oriented electrical steel sheet with specific chemical compositions and manufacturing processes, including controlled impurity levels and Al2O3 inclusions, to enhance high-temperature fatigue performance and yield strength, ensuring stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional non-oriented silicon steel materials are used, then the material can be processed and manufactured, but the high-temperature fatigue performance and yield strength are insufficient, leading to deformation or fracture during high-speed operation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the steel sheet, including carbon content (0.0015-0.0065%), silicon content (3.05-3.95%), and aluminum content (0.14-1.15%), along with controlled amounts of alloying elements. This compositional parameter optimization enables the material to achieve both high strength and improved high-temperature fatigue performance, resolving the contradiction between manufacturability and operational reliability.
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy system that combines iron with silicon, aluminum, and controlled additions of alloying elements (Mn, Cr, Ni, Mo, Ti, Nb, V). This composite alloy structure synergistically enhances both the yield strength and high-temperature fatigue resistance, ensuring operational stability during high-speed motor operation.
2Reliability
If the steel sheet is designed for high strength and fatigue resistance, then operational safety is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating alloying elements and controlling impurity levels during the initial steelmaking and refining processes. The RH vacuum refining process is used beforehand to remove harmful inclusions and control gas content, while alloying elements are added in advance to achieve the desired compositional range. This preliminary preparation ensures that the final product meets high reliability requirements without requiring complex post-processing operations.
Data Source
AI summary
The present disclosure relates to a non-oriented electrical steel sheet with excellent high-temperature fatigue performance. In addition to Fe and inevitable impurities, the non-oriented electrical steel sheet further comprises the following chemical elements in mass percentage: 0<C≤0.0028%, Si: 3.05-3.95%, Mn: 0.12-0.65%, Al: 0.14-1.15%, Sn: 0.0035-0.25%; and the number of Al2O3 inclusions with a size of 1.5 µm or more in the non-oriented electrical steel sheet is not more than 4.5 counts/mm2. In addition, the present disclosure further relates to a method for manufacturing the non-oriented electrical steel sheet, comprising the following steps: smelting, RH refining, casting, hot rolling, normalizing annealing, cold rolling, final annealing, and application of insulation coating, wherein in the RH refining step: a circulating gas flow rate V1 during decarburization and a circulating gas flow rate V0 at the end of decarburization satisfy the following relationships: V1/V0≥1.12, and V0 ≥ 135 Nm3/h; and after decarbonization, a free oxygen content in molten steel is not more than 225 ppm.