Ultra-thin Crown Cap Steel Sheet Yield Strength and Formability
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Solution Overview
Problem
Current steel sheets for crown caps face challenges in achieving both sufficient strength and formability, especially when reduced in gauge, leading to issues with sealing performance and pleat evenness.
Innovation Solution
Optimizing the composition and controlling yield strength and Lankford values within specific ranges, combined with a production process involving hot-rolling, coiling, pickling, first and second cold-rolling, and annealing, to produce a steel sheet with a yield strength of 500 MPa or more and an average Lankford value of 1.3 or more, while maintaining a thickness of less than 0.20 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of crown cap steel sheets is reduced to less than 0.20 mm for cost reduction, then material cost decreases, but strength becomes insufficient leading to poor sealing performance
Solution Approach 1:
The invention changes the chemical composition parameters of the steel sheet, specifically controlling C content at 0.003-0.010%, Si at 0.05% or less, Mn at 0.05-0.30%, P at 0.030% or less, S at 0.020% or less, and Al at 0.005-0.0100%, to achieve both reduced thickness and sufficient strength for sealing performance
Solution Approach 2:
The invention creates a composite microstructure consisting of ferrite and martensite phases through controlled composition and heat treatment, where the martensite provides strength for sealing while the ferrite ensures formability, enabling ultra-thin gauge steel sheets to maintain both strength and formability
2Quantity of substance
If the thickness of crown cap steel sheets is reduced to less than 0.20 mm, then material cost decreases, but formability deteriorates leading to poor pleat evenness
Solution Approach 1:
The invention optimizes composition parameters (C: 0.003-0.010%, Si: 0.05% or less, Mn: 0.05-0.30%, P: 0.030% or less, S: 0.020% or less, Al: 0.005-0.0100%) and applies controlled cooling to achieve a dual-phase microstructure that ensures uniform plastic deformation and even pleat formation in ultra-thin steel sheets
Solution Approach 2:
The invention creates local microstructural quality control by distributing ferrite and martensite phases throughout the steel sheet, with ferrite providing ductility for formability and martensite providing strength, ensuring uniform local deformation behavior during crown cap forming
3Strength
If low-carbon steel is used for DR steel sheets to ensure strength, then strength increases, but formability deteriorates causing sealing failure
Solution Approach 1:
The invention creates a composite microstructure of ferrite and martensite phases, where martensite provides the necessary strength and ferrite provides the necessary formability, avoiding the need to choose between low-carbon steel (good formability, poor strength) or high-carbon steel (good strength, poor formability)
Solution Approach 2:
The invention changes the microstructural state through controlled composition (C: 0.003-0.010%, Mn: 0.05-0.30%, Al: 0.005-0.0100%) and heat treatment parameters to achieve a dual-phase structure that simultaneously provides high strength and good 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 resulting steel sheet exhibits both high strength and good formability, enabling effective sealing and pressure resistance even when reduced in gauge, with improved pleat evenness and pressure resistance.
Implementation Method 1
a hot-rolling step of rough-rolling a slab having the composition according to claim 1 and finish-rolling the rough-rolled slab at a finish-rolling temperature of 850°C or higher
Implementation Method 2
a first cold-rolling step of cold-rolling the hot-rolled sheet after the pickling step, an annealing step of annealing the cold-rolled sheet, which is obtained in the first cold-rolling step
Implementation Method 3
an annealing step of annealing the cold-rolled sheet, which is obtained in the first cold-rolling step, at 650°C or higher and 790°C or lower
Data Source
AI summary
Provided is a steel sheet for crown cap that, even when reduced in gauge, has sufficient strength and formability suitable for forming crown caps, and a method for producing the steel sheet for crown cap. The steel sheet for crown cap has a composition including, in terms of % by mass, C: 0.002% or more and 0.010% or less, Si: 0.05% or less, Mn: 0.05% or more and 0.30% or less, P: 0.030% or less, S: 0.020% or less, Al: less than 0.0100%, N: 0.0050% or less, and the balance being Fe and unavoidable impurities. The C content is more than 0.003% when the Al content is 0.005% or more. The yield strength in the rolling direction is 500 MPa or more. The average Lankford value described below is 1.3 or more.