Non-Oriented Electrical Steel Sheet With Annealing-Free Hot Rolling
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Solution Overview
Problem
The existing manufacturing process for non-oriented electrical steel sheets requires hot-rolled sheet annealing, which increases production costs and can deteriorate the cold-rolling property by coarsening crystal grains, while also challenging the optimization of magnetic properties.
Innovation Solution
A method for manufacturing a non-oriented electrical steel sheet that omits the hot-rolled sheet annealing process, involving heating a slab, hot-rolling it, cold-rolling without annealing, and finally annealing the cold-rolled sheet, while controlling the alloy composition and process conditions to improve magnetism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot-rolled sheet annealing is performed to improve texture and magnetic properties, then magnetic flux density is improved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent removes the hot-rolled sheet annealing process from the manufacturing sequence, extracting this unnecessary step while maintaining magnetic properties through optimized cold-rolling and final annealing parameters
Solution Approach 2:
The patent performs preliminary texture optimization during the cold-rolling process by controlling reduction ratios and intermediate annealing conditions, preparing the material in advance for final annealing to achieve desired magnetic properties without requiring separate hot-rolled annealing
2Reliability
If hot-rolled sheet annealing is performed to improve texture, then magnetic properties are improved, but crystal grains are coarsened and cold-rolling property deteriorates
Solution Approach 1:
The patent performs preliminary grain refinement during cold-rolling by controlling reduction ratios and intermediate annealing, preparing the material in advance for final annealing to achieve desired magnetic properties without grain coarsening
Solution Approach 2:
The patent changes the temperature and time parameters of the final annealing process to achieve grain growth and magnetic property optimization simultaneously, avoiding the grain coarsening issue associated with hot-rolled annealing
3Loss of energy
If addition amounts of Si, Al, and Mn are increased to reduce iron loss, then specific resistance increases and eddy current loss decreases, but magnetic flux density deteriorates
Solution Approach 1:
The patent optimizes the compositional parameters of Si, Al, and Mn within specific ranges (Si: 2.0-3.5%, Al: 0.01-0.10%, Mn: 0.50-2.00%) to achieve the right balance between specific resistance and magnetic flux density
Solution Approach 2:
The patent creates a composite alloy system combining Si, Al, and Mn in optimized proportions, where each element contributes to reducing iron loss through different mechanisms while maintaining overall magnetic performance
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 reduces manufacturing costs, maintains excellent magnetic properties, and eliminates the need for stress relief annealing, thereby improving the overall efficiency and productivity of the steel sheet production.
Implementation Method 1
heating a slab... to a temperature sufficient to transform to an austenite single phase
Implementation Method 2
cold-rolling the hot-rolled sheet without annealing the hot-rolled sheet
Implementation Method 3
final-annealing the cold-rolled sheet... after final-annealing, a volume fraction of grains in which an angle formed by a {111} surface and a rolling surface is 15° or less is 27% or more
Data Source
AI summary
A non-oriented electrical steel sheet according to an embodiment of the present invention includes, in wt %, C at 0.005% or less (excluding 0%), Si at 0.5 to 2.4%, Mn at 0.4 to 1.0%, S at 0.005% or less (excluding 0%), Al at 0.01% or less (excluding 0%), N at 0.005% or less (excluding 0%), Ti at 0.005% or less (excluding 0%), Cu at 0.001 to 0.02%, and the balance of Fe and inevitable impurities, and satisfies Formula 1 below, wherein a volume fraction of grains in which an angle formed by a {111} surface and a rolling surface of the steel sheet is 15° or less is 27% or more.[Mn]/([Si]+150×[Al])≤0.35 [Formula 1](In Formula 1, [Mn], [Si], and [Al] are contents (wt %) of Mn, Si, and Al, respectively.)