Steel Sheet for Crown Cap with Optimized Composition
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Solution Overview
Problem
Existing techniques for reducing the thickness of steel sheets for crown caps fail to ensure sufficient strength and formability, leading to pressure resistance issues and non-uniform pleat shapes, which can result in leakage and detachment of the cap.
Innovation Solution
A steel sheet composition with specific elemental content (C: 0.0010% to 0.0050%, Si: 0.10% or less, Mn: 0.05% to 0.50%, P: 0.050% or less, S: 0.050% or less, Al: 0.002% to 0.070%, N: less than 0.0040%, and B: 0.0005% to 0.0020%) and a manufacturing process involving hot rolling, controlled cooling, coiling, primary and secondary cold rolling, and annealing to achieve a yield strength of 500 MPa or more and optimal Lankford values for improved formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the thickness of steel sheet for crown caps is reduced to 0.20 mm or less for cost reduction, then manufacturing cost is reduced, but pressure resistance becomes insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.0010% to less than 0.0050%, Si: 0.003% to 0.100%, Mn: 0.10% to 0.80%, Al: 0.005% to 0.100%, N: 0.0050% to 0.0150%, B: 0.0002% to 0.0050%) and mechanical properties (yield strength: 320 MPa to 500 MPa, total elongation: 15% to 40%) to achieve both reduced thickness and sufficient pressure resistance. This compositional parameter optimization enables the steel sheet to maintain strength while being thinner.
Solution Approach 2:
The patent creates a composite material system by combining multiple alloying elements (C, Si, Mn, Al, N, B) in specific proportions to achieve synergistic effects. The combination of these elements creates a steel sheet with enhanced strength-to-thickness ratio, allowing pressure resistance to be maintained even at reduced thickness levels.
2Strength
If secondary cold rolling reduction is increased to harden the steel sheet for pressure resistance, then strength is improved, but formability deteriorates causing non-uniform pleated shape
Solution Approach 1:
The patent changes the material parameters by optimizing chemical composition (particularly adding B: 0.0002% to 0.0050% and controlling N: 0.0050% to 0.0150%) to achieve a yield strength of 320 MPa to 500 MPa while maintaining total elongation of 15% to 40%. This parameter optimization allows the steel sheet to have sufficient strength without excessive hardening that would compromise formability.
Solution Approach 2:
The patent applies dynamics by controlling the rolling reduction ratio within a specific range (5% to 20%) rather than applying excessive reduction. This dynamic control of the forming process, combined with the optimized material properties, enables the steel sheet to undergo plastic deformation uniformly during crown cap formation, producing uniform pleated shapes while maintaining pressure resistance.
3Strength
If the steel sheet has low formability due to work hardening, then pressure resistance is maintained, but shape failure occurs during crown cap formation
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: chemical composition (C, Si, Mn, Al, N, B contents), mechanical properties (yield strength: 320 MPa to 500 MPa, total elongation: 15% to 40%), and processing parameters (rolling reduction ratio: 5% to 20%). This comprehensive parameter optimization creates a steel sheet that balances strength and formability, enabling successful crown cap formation without shape failure.
Solution Approach 2:
The patent applies partial action by using a moderate rolling reduction ratio (5% to 20%) rather than excessive reduction. This partial hardening approach provides sufficient strength improvement while avoiding over-hardening that would cause shape failure during forming. The controlled, partial application of work hardening achieves the desired balance between strength and formability.
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 steel sheets with enhanced strength and formability, ensuring effective pressure resistance and uniform pleat formation, even at reduced thicknesses, thereby preventing leakage and ensuring the crown cap functions correctly.
Implementation Method 1
an increase in rolling reduction during secondary cold rolling hardens a steel sheet to reduce the formability thereof
Implementation Method 2
a steel plate is thinned by cold rolling, is annealed, and is then temper rolled
Data Source
AI summary
Provided are a steel sheet, having sufficient strength and formability regardless of reduction of thickness, for crown caps; a method for manufacturing the same; and a crown cap. The steel sheet for crown caps has a composition containing C: 0.0010% to less than 0.0050%, Si: 0.10% or less, Mn: 0.05% to less than 0.50%, P: 0.050% or less, S: 0.050% or less, Al: more than 0.002% to less than 0.070%, N: less than 0.0040%, and B: 0.0005% to 0.0020% on a mass basis, the balance being Fe and inevitable impurities, and also has a yield strength of 500 MPa or more in a rolling direction, an average Lankford value (r) of 1.1 or more, and an in-plane anisotropy (Δr) of Lankford value of −0.3 to 0.3.