Can Steel Sheet Composition for High-Strength Curl Formability
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Solution Overview
Problem
Conventional steel sheets for cans face challenges in achieving a balance between high strength, ductility, and working accuracy, particularly for complex-shaped can lids, due to issues with local deformation and uniform deformability, which affects the hermeticity and shape accuracy of curl portions.
Innovation Solution
A steel sheet with a specific chemical composition and processing method, including hot rolling, coiling, cooling, primary and secondary cold rolling, and annealing, to achieve an upper yield strength of 550 MPa or more, with controlled cementite content and Ti-based carbide precipitation, ensuring high strength and reduced local deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the thickness of steel sheet is reduced to lower material costs, then material cost is reduced, but the strength of can body or can lid decreases
Solution Approach 1:
The invention changes the material parameters by controlling chemical composition (C: 0.010-0.130%, Si: 0.04% or less, Mn: 0.10-1.00%, Ti: 0.0050-0.1000%, etc.) and microstructure (cementite proportion in ferrite grains ≤10%, upper yield strength ≥550 MPa) to achieve high strength in ultra-thin steel sheets, resolving the contradiction between thickness reduction and strength maintenance
Solution Approach 2:
The invention creates a composite microstructure consisting of ferrite grains with controlled cementite distribution and Ti-based carbide precipitates, combining the ductility of ferrite with the strength contribution from cementite and Ti-carbides to achieve both thinness and high strength
2Strength
If DR method is used to produce high-strength and ultra-thin steel sheet, then strength is improved, but total elongation and workability deteriorate
Solution Approach 1:
The invention changes the strengthening mechanism from strain hardening through cold rolling to precipitation strengthening by Ti-based carbides and controlled cementite distribution, achieving high strength (≥550 MPa) while maintaining good ductility and workability suitable for complex-shaped can lids
Solution Approach 2:
The invention creates local quality differences by controlling the distribution of cementite and Ti-based carbides within ferrite grains, ensuring uniform deformability while maintaining high strength, which prevents local deformation and wrinkling during forming operations
3Strength
If secondary cold rolling is performed to strengthen steel sheet, then strength is improved, but uniform deformability deteriorates due to non-uniform strain hardening
Solution Approach 1:
The invention changes the strengthening approach from mechanical strain hardening through secondary cold rolling to metallurgical precipitation strengthening through controlled Ti-based carbide formation and cementite distribution, achieving uniform strength without compromising deformability or shape accuracy
Solution Approach 2:
The invention replaces the mechanical strengthening system (secondary cold rolling) with a metallurgical strengthening system (precipitation hardening through Ti-based carbides and controlled cementite distribution), eliminating the non-uniform strain hardening problem while maintaining high strength
4Strength
If high-strength steel sheet is used for can lid with complex shape, then strength is improved, but working accuracy deteriorates due to local deformation and wrinkling
Solution Approach 1:
The invention optimizes the microstructural parameters (cementite proportion ≤10%, upper yield strength ≥550 MPa, controlled Ti content 0.0050-0.1000%) to achieve a balance between strength and uniform deformability, preventing local deformation and wrinkling during curling operations while maintaining high strength for can lid applications
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 results in a steel sheet with high strength and improved working accuracy for can lids, preventing wrinkling and ensuring high uniform deformability, thus enhancing the production of can lids with precise shape and hermetic sealing.
Implementation Method 1
Ti-based carbide precipitation
Implementation Method 2
annealing
Data Source
AI summary
Provided is a steel sheet for cans. A steel sheet for cans comprises: a chemical composition containing, in mass %, C: 0.010% or more and 0.130% or less, Si: 0.04% or less, Mn: 0.10% or more and 1.00% or less, P: 0.007% or more and 0.100% or less, S: 0.0005% or more and 0.0090% or less, Al: 0.001% or more and 0.100% or less, N: 0.0050% or less, Ti: 0.0050% or more and 0.1000% or less, and Cr: 0.08% or less, and satisfying a relationship 0.005≤(Ti*/48)/(C/12)≤0.700 where Ti*=Ti−1.5S, with a balance consisting of Fe and inevitable impurities; a microstructure in which a proportion of cementite in ferrite grains is 10% or less; and an upper yield strength of 550 MPa or more.