Crown Cap Steel Sheet Dislocation Control for Pressure Resistance
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Solution Overview
Problem
Conventional steel sheets for crown caps fail to provide sufficient pressure resistance when subjected to sheet metal thinning, necessitating the use of expensive soft liners, which hinders cost reduction.
Innovation Solution
Optimizing the chemical composition and production conditions of the steel sheet to control the dislocation structure, ensuring a dense dislocation substructure at half the sheet thickness, thereby enhancing the pressure resistance without the need for a soft liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If sheet metal thinning is performed to reduce cost, then manufacturing cost is reduced, but pressure resistance becomes insufficient
Solution Approach 1:
The invention changes the material parameters by precisely controlling chemical composition (C: 0.006-0.012%, Si: 0.02% or less, Mn: 0.10-0.60%, etc.) and processing parameters (annealing temperature 650-750°C, rolling reduction ratios) to achieve a dislocation substructure with specific density characteristics that provides sufficient pressure resistance in thinned sheets
Solution Approach 2:
The invention creates a composite microstructure consisting of ferrite matrix with controlled dislocation substructure, where the dislocation density distribution (with maximum at 1/4 thickness from surface and minimum at center) provides enhanced mechanical properties that compensate for reduced sheet thickness
2Strength
If a soft liner is used to improve pressure resistance, then pressure resistance is enhanced, but manufacturing cost increases
Solution Approach 1:
The steel sheet itself provides the pressure resistance function through its controlled dislocation substructure, eliminating the need for a soft liner. The material serves its own reinforcement function that would otherwise require an additional component
Solution Approach 2:
The invention extracts the pressure resistance function from the liner component and transfers it to the steel sheet material itself through microstructural control, allowing the crown cap to achieve sufficient pressure resistance with a hard liner and thinned steel sheet
3Loss of substance
If sheet thickness is reduced to 0.20 mm or less for cost reduction, then manufacturing cost is reduced, but formability deteriorates
Solution Approach 1:
The invention optimizes processing parameters including annealing temperature (650-750°C), rolling reduction ratios (first cold rolling: 80-95%, second cold rolling: 5-20%), and chemical composition to create a microstructure that provides both formability and sufficient strength in thinned sheets
Solution Approach 2:
The invention creates local variations in dislocation density throughout the sheet thickness, with higher density near surfaces and lower density at the center, providing different properties at different locations to balance formability and strength
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 optimized steel sheet achieves excellent formability and pressure resistance, allowing for cost reduction by eliminating the need for expensive soft liners, even when the sheet is thinned.
Implementation Method 1
When the sheet thickness of a steel sheet for crown cap is 0.20 mm or less, a crown cap produced from a conventional SR material would have an insufficient pressure resistance. To ensure the pressure resistance, it is conceivable to use a double reduced (DR) steel sheet obtained by performing annealing and subsequent secondary cold rolling, taking advantage of work hardening to compensate for a reduction in strength due to sheet metal thinning
Implementation Method 2
A single reduced (SR) steel sheet is mainly used as a thin steel sheet that serves as a material of a crown cap. Such a SR steel sheet is produced by reducing the thickness of a steel sheet by cold rolling, and subsequently subjecting the steel sheet to annealing and temper rolling
Data Source
Figure 1A~1B
AI summary
A steel sheet for crown cap having excellent formability from which a crown cap having an excellent pressure resistance can be produced without an expensive soft liner even if the steel sheet is subjected to sheet metal thinning, the steel sheet having: a chemical composition containing, in mass%, C: more than 0.006 % and 0.012 % or less, Si: 0.02 % or less, Mn: 0.10 % or more and 0.60 % or less, P: 0.020 % or less, S: 0.020 % or less, Al: 0.01 % or more and 0.07 % or less, and N: 0.0080 % or more and 0.0200 % or less, with the balance being Fe and inevitable impurities; and a percentage of a region of more than 0 % and less than 20 % at a position of 1/2 of a sheet thickness, the region having a dislocation density of 1 × 1014 m-2 or less.