Non-Oriented Electrical Steel Sheet with Controlled Recrystallization
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Solution Overview
Problem
Existing non-oriented electrical steel sheets face a challenge in balancing hot-rolled sheet toughness with magnetic characteristics, as the addition of segregating elements often degrades toughness and leads to fractures during pickling, making it difficult to achieve both low iron loss and high magnetic flux densities.
Innovation Solution
Control the soaking temperature and time during hot-band annealing, and adjust the cooling rate in the width direction to achieve a specific recrystallization rate, resulting in a steel sheet with improved toughness and magnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If segregating elements are added to improve magnetic characteristics, then magnetic flux density and iron loss are improved, but toughness is degraded and fractures occur during pickling
Solution Approach 1:
The patent changes the chemical composition parameters by strictly limiting segregating elements (P≤0.09%, S≤0.005%, B≤0.0060%) and optimizing beneficial elements (Si: 1.9-3.5%, Al: 0.10-3.0%, Mn: 0.10-2.0%) to achieve both improved magnetic characteristics and maintained toughness, resolving the contradiction between magnetic performance and mechanical strength
Solution Approach 2:
The patent creates a composite chemical composition system that combines multiple elements in specific proportions (C: 0.0040% or less, Si: 1.9-3.5%, Al: 0.10-3.0%, Mn: 0.10-2.0%, P: 0.09% or less, S: 0.005% or less, N: 0.0040% or less, B: 0.0060% or less) to achieve synergistic effects that simultaneously improve magnetic characteristics and maintain toughness, avoiding the need to add segregating elements
2Reliability
If soaking temperature and time during hot-band annealing are increased to improve recrystallization, then magnetic characteristics are improved, but sheet toughness is degraded
Solution Approach 1:
The patent optimizes the hot-band annealing parameters by controlling soaking temperature to 850-950°C and soaking time to 10-120 seconds, achieving sufficient recrystallization for good magnetic characteristics while preventing excessive grain growth that would degrade sheet toughness, thus resolving the contradiction between magnetic performance and mechanical strength
Solution Approach 2:
The patent applies partial recrystallization rather than complete recrystallization during hot-band annealing, achieving the necessary magnetic characteristics through controlled partial transformation of the microstructure while preserving enough original structure to maintain sheet toughness, avoiding the excessive action that would cause brittleness
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 steel sheet achieves both high hot-rolled sheet toughness and magnetic characteristics, enabling stable production of non-oriented electrical steel sheets with low iron loss and high magnetic flux density, suitable for iron core materials in electrical equipment.
Implementation Method 1
when the soaking temperature and time during hot-band annealing are controlled to be within specific ranges
Implementation Method 2
a recrystallization rate of a structure of a sheet thickness-direction cross section at each position 10 mm apart toward a sheet width center from each of both end portions in a sheet width direction is less than 50%
Implementation Method 3
the cooling rate is changed in the width direction
Data Source
AI summary
What is provided is a steel sheet for a non-oriented electrical steel sheet containing, in mass %, C: 0.0040% or less, Si: 1.9% or more and 3.5% or less, Al: 0.10% or more and 3.0% or less, Mn: 0.10% or more and 2.0% or less, P: 0.09% or less, S: 0.005% or less, N: 0.0040% or less, B: 0.0060% or less, and the remainder comprising Fe and impurities, in which the recrystallization rate of the structure of a sheet thickness-direction cross section at each position 10 mm apart toward the sheet width center from each of both end portions in the sheet width direction is less than 50%, and, when the sheet width is represented by W, the recrystallization rate of the structure of a sheet thickness-direction cross section at the position of ¼W from each of both end portions in the sheet width direction is 50% or more.