Cold-Rolled Packaging Steel Composition for Thin Deep-Drawn Cans
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Solution Overview
Problem
Current cold-rolled steel sheets for packaging face challenges in achieving high biaxial strength and deformation capability at minimal thickness, as high total cold reductions lead to earing tendencies and material defects, limiting the production of thin, stable packaging without compromising strength.
Innovation Solution
A cold-rolled steel sheet with a specific composition and nitrogen content, processed through single or double cold rolling and recrystallization annealing, is developed to achieve high biaxial strength and multiaxial deformation capacity, characterized by a biaxial stress/strain curve using the hydraulic cupping test, ensuring stability during deep drawing and ironing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If total cold reduction is increased to achieve thinner final thickness, then packaging weight is reduced, but earing tendency deteriorates and material defects occur
Solution Approach 1:
The invention changes the chemical composition parameters of the steel sheet, specifically controlling carbon content at 0.001-0.06% and nitrogen content at 0.002-0.12%, to optimize the material's deformation behavior. This allows achieving total cold reductions of 85% or more while maintaining acceptable earing tendency and avoiding material defects that would otherwise occur at such high reduction levels.
Solution Approach 2:
The invention creates a composite microstructure through controlled alloying and heat treatment processes. The specific composition ranges and processing conditions produce a refined grain structure that combines high strength with improved deformability, enabling the material to withstand the stresses of high total cold reduction without developing excessive earing or defects.
2Strength
If carbon and nitrogen content are increased to achieve higher strength, then packaging stability is improved, but total cold reduction optimum decreases
Solution Approach 1:
The invention optimizes the balance between strength and manufacturability by precisely controlling carbon content at 0.001-0.06% and nitrogen content at 0.002-0.12%. This parameter optimization achieves sufficient biaxial strength for packaging stability while maintaining a high total cold reduction optimum, allowing cold reductions of 85% or more without excessive earing.
Solution Approach 2:
The invention applies different composition requirements to different performance needs: lower carbon content (0.001-0.06%) to maintain deformability and high total cold reduction optimum, while controlled nitrogen content (0.002-0.12%) provides sufficient strength. This localized optimization of composition elements resolves the contradiction between strength and manufacturability.
3Weight of moving object
If hot strip thickness is reduced to achieve lower final thickness, then packaging weight is reduced, but material defects increase
Solution Approach 1:
The invention performs preliminary optimization of the steel composition before the cold rolling process. By controlling carbon at 0.001-0.06% and nitrogen at 0.002-0.12% in the hot strip, the material is pre-conditioned to withstand high total cold reductions of 85% or more without developing defects, enabling the use of thinner hot strips for weight reduction.
Solution Approach 2:
The invention changes the material parameters (chemical composition) to enable the use of thinner hot strips. The optimized composition allows achieving final thicknesses of less than 0.6 mm through high total cold reduction while maintaining material integrity and avoiding defects that would occur with conventional 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 enables the production of packaging with high biaxial strength and multiaxial deformation capacity, allowing for significant thinning without material failure, while maintaining strength and reducing package weight, as demonstrated by the biaxial stress/strain curve analysis.
Implementation Method 1
Single-reduced steel sheets (SR) are recrystallization annealed after cold rolling to restore deformability
Implementation Method 2
the hot-rolled steel sheet (hot strip) is cold rolled singly or doubly for thickness reduction
Implementation Method 3
packaging sheet metal products are exposed to strong deformations during the production of packaging, for example, in deep drawing or ironing methods
Implementation Method 4
A method for the characterization of packaging sheet metal products according to the invention is further disclosed
Data Source
AI summary
A packaging sheet metal product from a cold-rolled steel sheet with a thickness of less than 0.6 mm has a specified composition. The packaging sheet metal product during biaxial deformation in a bulge test has a lower yield strength (SbeL) of more than 300 MPa and a corresponding elongation at break (Ab) of more than 10% and in the plastic region between the Lüders elongation (Abe) and an upper (plastic) elongation limit of εmax=0.5·Ab·(SbeL/Sbm) has a biaxial stress/strain diagram σB(ε) that can be represented by a function εB=b·εn, with: σB is the true biaxial stress in MPa; ε is the amount of true elongation in the thickness direction in %; Sbm is the absolute strength; b is a proportionality factor; and n is a strain-hardening exponent. A strengthening of the packaging sheet product in the thickness direction is characterized by a strain-hardening exponent of n≥0.353-5.1·SbeL/104 MPa.