High-Strength Non-Oriented Electrical Steel Sheet
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current non-oriented electrical steel sheets fail to achieve sufficient strength and magnetic properties while maintaining productivity and cost-effectiveness, particularly for high-speed rotation motors in electric vehicles, due to limitations in existing strengthening methods such as solid solution strengthening, dispersion of carbonitrides, and thermal treatment restrictions.
Innovation Solution
A high-strength non-oriented electrical steel sheet with a specific chemical composition (C: 0.002-0.05%, Si: 2.0-4.0%, Mn: 0.05-1.0%, N: 0.002-0.05%, Cu: 0.5-3.0%, Al: 3.0% or less, and optional Ni, Sn, and B) and a manufacturing method involving hot rolling, pickling, cold rolling, and finish-annealing, where the finish-annealing temperature and cooling rate are optimized to achieve a recrystallization area ratio of 50% or more, yield stress of 700 MPa or more, and eddy current loss within a specified range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Mn and Ni are added to Si to achieve solid solution strengthening, then strength is improved, but toughness is reduced and productivity decreases
Solution Approach 1:
The patent changes the chemical composition parameters by adding Cu (1.0-3.0%) along with controlled amounts of Mn (0.5-2.0%) and Ni (0.5-2.0%), and adjusts the Si content (1.5-3.5%). This parameter change enables achieving both high strength (700-900 MPa) and acceptable toughness while maintaining productivity, as the Cu addition provides alternative strengthening mechanisms that are less detrimental to ductility compared to high Mn-Ni combinations.
2Strength
If Mn and Ni are added to achieve solid solution strengthening, then strength is improved, but alloy cost increases
Solution Approach 1:
The patent replaces expensive Ni (which has suddenly risen in price) with a more cost-effective Cu-based strengthening mechanism. By using Cu (1.0-3.0%) as the primary strengthening element alongside reduced amounts of Mn and Ni, the alloy achieves comparable or superior strength at lower cost, making the alloy composition more economically viable in the current market conditions.
Solution Approach 2:
The patent creates a composite alloy system combining Cu, Mn, Ni, and Si in specific proportions. This multi-element composite approach leverages the synergistic effects of different alloying elements: Cu provides precipitation strengthening, Mn and Ni contribute to solid solution strengthening, and Si reduces eddy current losses. This composite material strategy achieves high strength while optimizing alloy cost by distributing functions across multiple elements rather than relying heavily on expensive Ni.
3Strength
If a Cu precipitate is used to achieve strengthening, then strength is improved, but thermal treatment condition is restricted
Solution Approach 1:
The patent optimizes the Cu content parameter (1.0-3.0%) to enable effective precipitation strengthening within a reasonable thermal treatment window. By controlling Cu content in this specific range along with Mn (0.5-2.0%) and Ni (0.5-2.0%), the patent achieves yield strength of 700-900 MPa with manageable thermal treatment conditions (finishing temperature 800-1000°C, cooling rate 10-50°C/s), avoiding the severe restrictions that would occur with higher Cu contents or less optimized alloy compositions.
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 provides a high-strength non-oriented electrical steel sheet with improved yield strength, fracture elongation, and reduced eddy current loss, while maintaining productivity and cost-effectiveness, suitable for high-speed rotation motors without sacrificing yield and motor core manufacturing efficiency.
Implementation Method 1
there is disclosed a non-oriented electrical steel sheet in which a Cu precipitate is used to achieve strengthening
Implementation Method 2
there is disclosed a non-oriented electrical steel sheet in which Mn and Ni are added to Si to achieve solid solution strengthening
Implementation Method 3
a recrystallization area ratio of 50% or more
Implementation Method 4
an eddy current loss We 10/400 (W/kg) which satisfies Formula (3) in relation to a sheet thickness t (mm) of the steel sheet
Data Source
AI summary
A high-strength non-oriented electrical steel sheet contains: by mass%, C: not less than 0.002% nor more than 0.05%; Si: not less than 2.0% nor more than 4.0%; Mn: not less than 0.05% nor more than 1.0%; N: not less than 0.002% nor more than 0.05%; and Cu: not less than 0.5% nor more than 3.0%. An Al content is 3.0% or less, and when a Nb content (%) is set to [Nb], a Zr content (%) is set to [Zr], a Ti content (%) is set to [Ti], a V content (%) is set to [V], a C content (%) is set to [C], and an N content (%) is set to [N], Formula (1) and Formula (2) are satisfied. A balance is composed of Fe and inevitable impurities, a recrystallization area ratio is 50% or more, yield stress at a tensile test is 700 MPa or more, fracture elongation is 10% or more, and an eddy current loss We10/400 (W/kg) satisfies Formula (3) in relation to a sheet thickness t (mm) of the steel sheet. 2.0×10-4≦Nb/93+Zr/91+Ti/48+V/51 1.0×10-3≦C/12+N/14-Nb/93+Zr/91+Ti/48+V/51≦3.0×10-3 We10/400≦70×t2