Non-oriented Electrical Steel Sheets with Controlled Alloy Composition
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Solution Overview
Problem
Existing non-oriented electrical steel sheets face challenges in reducing iron loss and increasing magnetic flux density, particularly due to the limitations of conventional hot-rolled sheet annealing processes which increase costs and are difficult to apply universally, leading to suboptimal magnetic properties.
Innovation Solution
A non-oriented electrical steel sheet composition with controlled alloy elements (C, Si, Mn, Al, and impurities) and a hot rolling process that minimizes deformation energy by rolling in the austenite+ferrite two-phase region, omitting hot-rolled sheet annealing, and subsequent cold rolling and final annealing to achieve improved magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot-rolled sheet annealing is performed to homogenize texture and improve magnetic properties, then magnetic flux density increases and iron loss decreases, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The invention extracts and eliminates the hot-rolled sheet annealing process from the manufacturing sequence. By developing a hot rolling method that directly produces the desired texture and grain structure without requiring subsequent annealing, the patent removes this costly and time-consuming intermediate step while maintaining magnetic property requirements.
Solution Approach 2:
The invention changes the hot rolling parameters (temperature range, reduction ratio, deformation rate) to achieve texture homogenization and grain coarsening directly during the hot rolling process itself, rather than requiring a separate annealing step. Specifically, rolling is performed in the austenite-to-ferrite transformation region with controlled parameters that produce the desired microstructure.
2Loss of energy
If hot-rolled sheet annealing is performed to improve magnetic properties, then iron loss decreases and energy efficiency improves, but manufacturing cost increases
Solution Approach 1:
The invention extracts and eliminates the hot-rolled sheet annealing process from the manufacturing sequence. By developing a hot rolling method that directly produces the desired texture and grain structure without requiring subsequent annealing, the patent removes this costly and time-consuming intermediate step while maintaining magnetic property requirements.
Solution Approach 2:
The invention replaces the expensive and time-consuming annealing process with a simpler, more economical hot rolling procedure that achieves the same microstructural outcomes directly, effectively substituting a complex thermal process with a more efficient mechanical-thermal combined process.
3Ease of manufacture
If conventional hot rolling conditions are used, then manufacturing process is simple, but magnetic properties are insufficient due to fine grain size and unfavorable texture
Solution Approach 1:
The invention changes the hot rolling parameters (temperature range, reduction ratio, deformation rate) to achieve texture homogenization and grain coarsening directly during the hot rolling process itself, rather than requiring a separate annealing step. Specifically, rolling is performed in the austenite-to-ferrite transformation region with controlled parameters that produce the desired microstructure.
Solution Approach 2:
The invention utilizes the phase transition from austenite to ferrite during hot rolling to control grain growth and texture development. By performing rolling within the transformation temperature region and controlling the cooling rate, the process leverages phase transformation to achieve the desired microstructure that provides excellent magnetic properties.
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 results in a steel sheet with reduced iron loss and increased magnetic flux density, allowing for the production of high-quality electrical steel without the need for hot-rolled sheet annealing, thereby improving productivity and reducing costs.
Implementation Method 1
deformation resistance caused by the transformation from austenite to ferrite will be lowered so that rolling will be stabilized
Implementation Method 2
the rolling reduction ratio is limited to 40% or less at a temperature range from an austenite-to-ferrite transformation start temperature +20°C to an austenite-to-ferrite transformation end temperature −20°C
Data Source
AI summary
The present invention relates to technology for manufacturing electrical steel sheets having excellent magnetic properties through the control of a hot-rolled texture using the phase transformation of steel. More particularly, it relates to a non-oriented electrical steel sheet that has reduced iron loss and increased magnetic flux density by controlling alloy component elements and optimizing hot-rolling conditions, even though hot-rolled sheet annealing is not carried out, as well as a manufacturing method thereof. More specifically, the invention provides a non-oriented electrical steel sheet which has excellent magnetic properties while hot-rolled sheet annealing can be omitted, the steel sheet being comprised of 0.005 wt % or less of C, 1.0-3.0 w % of Si, 0.1-2.0 wt % of Mn, 0.1 wt % or less of P, 0.1-1.5 wt % of Al, and a remainder of Fe and other inevitable impurities, in which the relationship between the elements Mn and Al satisfies an equation of −0.2<m(=Mn−Al)<1.0, and a slab for the steel sheet, when reheated, has a two-phase region of austenite+ferrite at a temperature ranging from ArI to 1250° C.