Steel Sheet for Cans with Controlled Non-Recrystallized Ferrite
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Solution Overview
Problem
Existing steel sheets for cans lack a balance of high strength, ductility, and formability, particularly for can bodies with neck portions, leading to issues like dents and poor commercial value.
Innovation Solution
A steel sheet with a specific chemical composition and microstructure, including a proportion of non-recrystallized ferrite of 3% or less, and a method involving hot rolling, cold rolling, annealing, and temper rolling processes to achieve an upper yield stress of 550 MPa or more and 620 MPa or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the thickness of steel sheets is reduced to reduce material costs, then material cost is reduced, but the strength of can bodies and can lids decreases
Solution Approach 1:
The invention changes the material parameters by controlling chemical composition (C: 0.005-0.100%, Si: 0.010-0.050%, Mn: 0.10-1.00%, P: 0.007-0.100%, S: 0.0005-0.0090%, Al: 0.001-0.100%, Ti: 0.0050-0.1000%, B: 0.0005-0.0020%, Cr: 0.08% or less) and microstructure (proportion of non-recrystallized ferrite: 3% or less) to achieve high strength (upper yield stress: 550-620 MPa) in ultra-thin steel sheets, resolving the contradiction between reduced material thickness/cost and maintained strength
Solution Approach 2:
The invention creates a composite microstructure consisting of recrystallized ferrite and non-recrystallized ferrite phases with controlled proportions and characteristics. This composite microstructure, combined with specific alloying elements, provides both high strength and adequate ductility in ultra-thin steel sheets, enabling cost reduction through thickness reduction while maintaining structural integrity
2Strength
If the DR method is used to produce high-strength ultra-thin steel sheets, then strength is increased, but total elongation and formability decrease
Solution Approach 1:
The invention changes the material parameters by controlling chemical composition (particularly C: 0.005-0.100% and Ti: 0.0050-0.1000%) and microstructure (proportion of non-recrystallized ferrite: 3% or less) to achieve high strength (upper yield stress: 550-620 MPa) while maintaining adequate total elongation and formability, avoiding the poor ductility associated with conventional DR method steel sheets
Solution Approach 2:
The invention creates local quality differences in the microstructure by controlling the distribution and proportion of non-recrystallized ferrite (3% or less) among the ferrite grains. This local microstructural characteristic provides both high strength and improved formability, resolving the contradiction between strength and total elongation that plagues conventional DR method steel sheets
3Loss of substance
If die neck forming is performed on can mouths to reduce diameter, then material cost is reduced, but dents occur in the neck portion due to local deformation
Solution Approach 1:
The invention changes the material parameters by controlling chemical composition (C: 0.005-0.100%, Mn: 0.10-1.00%, Ti: 0.0050-0.1000%) and microstructure (proportion of non-recrystallized ferrite: 3% or less) to achieve high strength (upper yield stress: 550-620 MPa) and uniform deformability, preventing local deformation and dents during die neck forming while maintaining cost reduction benefits
Solution Approach 2:
The invention applies preliminary action by controlling the microstructure (proportion of non-recrystallized ferrite: 3% or less) and chemical composition before the neck forming process. This preliminary microstructural control ensures uniform deformability and prevents local deformation during subsequent die neck forming, avoiding dents while enabling cost reduction through diameter reduction
4Strength
If secondary cold rolling is performed to increase strength through strain hardening, then strength is increased, but uniform deformability decreases due to uneven strain hardening
Solution Approach 1:
The invention changes the material parameters by controlling chemical composition (C: 0.005-0.100%, Ti: 0.0050-0.1000%, B: 0.0005-0.0020%) and microstructure (proportion of non-recrystallized ferrite: 3% or less) to achieve high strength (upper yield stress: 550-620 MPa) while maintaining uniform deformability. This approach eliminates the need for secondary cold rolling and its associated uneven strain hardening problems
Solution Approach 2:
The invention applies homogeneity by creating a uniform microstructure with controlled proportion of non-recrystallized ferrite (3% or less) distributed among ferrite grains. This homogeneous microstructure, combined with controlled chemical composition, ensures uniform deformability throughout the steel sheet, preventing local deformation and dents during forming operations
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 a steel sheet with high strength and sufficient formability, specifically for can bodies with neck portions, reducing the occurrence of dents and improving commercial value.
Implementation Method 1
annealing, and temper rolling processes to achieve an upper yield stress of 550 MPa or more and 620 MPa or less
Implementation Method 2
cold rolling, annealing, and temper rolling processes
Implementation Method 3
hot rolling, cold rolling, annealing, and temper rolling processes
Implementation Method 4
a microstructure with a proportion of non-recrystallized ferrite of 3% or less
Data Source
AI summary
Provided is a steel sheet for cans with high strength and sufficiently high formability particularly as a material for a can body with a neck portion. The steel sheet for cans of the present disclosure has a chemical composition containing, in mass %, C: 0.010% to 0.130%, Si: 0.04% or less, Mn: 0.10% to 1.00%, P: 0.007% to 0.100%, S: 0.0005% to 0.0090%, Al: 0.001% to 0.100%, N: 0.0050% or less, Ti: 0.0050% to 0.1000%, B: 0.0005% to less than 0.0020%, and Cr: 0.08% or less, where 0.005≤(Ti*/48)/(C/12)≤0.700 is satisfied; and a microstructure with a proportion of non-recrystallized ferrite of 3% or less, wherein an upper yield stress is 550 MPa to 620 MPa.