Non-Oriented Electrical Steel Sheet With Surface Nitrogen Control
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Solution Overview
Problem
Existing non-oriented electrical steel sheets face challenges in achieving high magnetic flux density and low iron loss in the high frequency range without adding large amounts of alloying elements like Cr, which decrease saturation magnetic flux density, and without reducing sheet thickness, which affects productivity.
Innovation Solution
Limiting the Co content in the steel to a specific range and subjecting the steel sheet to acidizing to control the nitrogen amount in the surface layer, forming an oxide layer that inhibits nitridation during final annealing, thereby reducing iron loss without affecting magnetic flux density or productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional steelmaking methods are used to produce non-oriented electromagnetic steel sheets, then production cost is reduced, but inclusion particles remain in the steel sheet causing surface defects and reduced quality
Solution Approach 1:
The invention extracts and removes inclusion particles from the steel melt before final solidification by controlling the pouring process. The steel is poured in a specific manner that allows inclusions to be separated and removed, preventing them from becoming embedded in the final product, thus achieving both cost-effectiveness and high surface quality.
Solution Approach 2:
The invention performs preliminary removal of inclusion particles during the pouring process itself, before the steel completely solidifies. By controlling the pouring conditions and timing, inclusions are removed in advance, preventing subsequent surface defects and eliminating the need for expensive post-processing operations.
2Manufacturing precision
If multiple processing steps are added to remove inclusion particles, then surface quality is improved, but production complexity and cost increase
Solution Approach 1:
The invention merges the inclusion removal function with the existing pouring process. By integrating inclusion particle removal into the standard pouring operation through controlled pouring techniques, the system achieves dual functionality without adding separate complex processing steps or equipment.
Solution Approach 2:
The invention enables the steel pouring process to self-remove inclusions through carefully controlled pouring conditions. The process utilizes the natural behavior of the steel flow and solidification to separate and remove inclusions automatically, without requiring external intervention or additional complex processing equipment.
3Productivity
If conventional pouring methods are used, then production speed is maintained, but inclusion particles are embedded in the steel sheet
Solution Approach 1:
The invention performs preliminary removal of inclusion particles during the pouring process itself, before final solidification occurs. By controlling the pouring rate and pattern, inclusions are separated and removed in advance, ensuring both high production speed and effective inclusion removal without requiring post-processing steps.
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 solution enables non-oriented electrical steel sheets with reduced iron loss in the high frequency range without decreasing magnetic flux density or productivity, achieved by adding a small amount of Co and controlling the nitrogen amount in the surface layer through acidizing.
Implementation Method 1
a) preliminary solidification of steel in a pouring basin
Implementation Method 2
inclusion particles are likely to be floating on the steel
Implementation Method 3
the steel is subjected to a rolling process, thereby reducing the thickness of the steel slab
Data Source
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AI summary
Provided is a non-oriented electrical steel sheet with low high-frequency iron loss without addition of a large amount of alloying elements such as Cr, which causes a decrease in magnetic flux density, and without reduction of the sheet thickness, which causes a decrease in productivity. A non-oriented electrical steel sheet comprises a certain chemical composition containing 0.0005 mass% to 0.0050 mass% of Co, wherein at at least one surface of the non-oriented electrical steel sheet, an amount of N existing as AlN in a range from the surface to a depth of 1/20 of a sheet thickness is 0.003 mass% or less, and the surface has an oxide layer containing one or both of Al and Si and having a thickness of 10 nm or more and less than 80 nm.