Non-oriented silicon steel deoxidation and normalizing for magnetic permeability
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Solution Overview
Problem
Current methods for producing non-oriented silicon steel with high magnetic permeability and low iron loss at a working magnetic flux density of 1.0–1.5 T are inadequate to meet the miniaturization and energy-saving requirements of electronic devices, as they fail to effectively control inclusions and grain morphology.
Innovation Solution
The method involves proper deoxidation control in RH refining and high-temperature treatment for a short time during normalizing, reducing oxide inclusions and improving grain morphology, which is achieved by adjusting the input amount of deoxidizer and normalizing temperature and time, resulting in a non-oriented silicon steel with enhanced magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional steel making and heat treatment methods are used, then production process is simple, but magnetic permeability is insufficient and iron loss is high
Solution Approach 1:
The patent applies preliminary action by performing deoxidation control during RH refining before subsequent processing steps. By adding deoxidizers (Al, Si, Ca) and controlling oxygen content to ≤50 ppm in the molten steel before casting, the patent prevents inclusion formation early in the process, which subsequently improves magnetic permeability without requiring complex post-processing steps.
Solution Approach 2:
The patent applies parameter changes by modifying the normalizing heat treatment parameters: heating to Ac3+30-50℃ (higher than conventional), holding for 5-15 minutes (shorter than conventional), and controlling cooling rate. These parameter changes optimize grain structure and magnetic properties, achieving high magnetic permeability (μ10+μ15≥8000) and low iron loss while maintaining a relatively simple production process.
2Loss of energy
If deoxidation control and high-temperature short-time treatment are applied, then magnetic permeability increases and iron loss decreases, but production process complexity increases
Solution Approach 1:
The patent performs deoxidation control as a preliminary action during RH refining, adding deoxidizers before casting. This preliminary deoxidation prevents oxide inclusion formation, which would otherwise increase iron loss. By addressing the root cause early in the process rather than requiring complex post-processing removal methods, the patent reduces iron loss while maintaining process simplicity.
Solution Approach 2:
The patent modifies normalizing treatment parameters (higher temperature Ac3+30-50℃, shorter time 5-15 min) to optimize grain structure and reduce eddy current losses. These parameter changes directly reduce iron loss by improving magnetic domain structure and reducing hysteresis losses, achieving energy efficiency without requiring additional complex equipment or processes.
3Reliability
If conventional normalizing treatment is used, then processing time is longer, but grain morphology and magnetic properties are insufficient
Solution Approach 1:
The patent applies parameter changes by heating to Ac3+30-50℃ (higher than conventional normalizing temperature) and holding for only 5-15 minutes. The higher temperature accelerates austenite formation and uniformity, while the short holding time is sufficient to achieve homogeneous grain structure. This parameter optimization produces favorable grain morphology for high magnetic permeability while significantly reducing treatment time compared to conventional slower normalizing processes.
Solution Approach 2:
The patent creates a composite microstructure through controlled deoxidation (adding Al, Si, Ca) that forms specific inclusion types acting as nucleation sites for grain growth. This composite approach—combining chemical composition control with thermal processing—achieves superior grain morphology and magnetic properties in less time than conventional single-parameter normalizing treatments.
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 significantly increases magnetic permeability and reduces iron loss, enabling non-oriented silicon steel to achieve a motor efficiency of 90% or more when used in electronic devices, thus meeting the requirements for miniaturization and energy conservation.
Implementation Method 1
a decarbonization and deoxidation treatment is proceed in said RH refining, wherein the input amount of the deoxidizer Y satisfies the following formula: Y=K×m×([O]−50)
Implementation Method 2
in said normalizing step c), the hot-rolled steel strip after hot rolling is heated to a temperature of phase transformation point temperature Ac1 or above and 1,100° C. or below and is held for a time period t of 10 ̃90 s
Data Source
AI summary
An unoriented silicon steel having high magnetic conductivity and low iron loss at a working magnetic density of 1.0-1.5 T and method for manufacturing same. By proper deoxidation control in a RH refining and high-temperature treatment for a short time in a normalizing step, the method can reduce the amount of inclusions in the silicon steel and improve grain shape, so as to improve the magnetic conductivity and iron loss of the unoriented silicon steel at a magnetic density of 1.0-1.5 T.