Steel Sheet for Cans with Nb-Ti Grain Refinement
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Solution Overview
Problem
Existing methods for producing steel sheets for cans face challenges in achieving high formability, low working heat, and preventing surface roughness and film exfoliation, while also increasing production costs and requiring specialized equipment.
Innovation Solution
A steel sheet composition of 0.0016 to 0.01% C, 0.05% to 0.60% Mn, 0.02% or less P, 0.02% or less S, 0.01 to 0.10% Al, and 0.020 to 0.080% Nb, with controlled Nb-based precipitates and ferrite grain diameter, is used to create a laminated steel sheet with a chromium metal plating film and organic resin coating, optimizing pinning effects and surface properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 0.4 to 1.0% by mass of Mn is added to achieve refinement of crystal grains, then grain refinement is improved, but working heat of steel sheet during can making increases
Solution Approach 1:
The patent changes the chemical composition parameters by reducing Mn content to 0.05% or less and adding Ti (0.01-0.05% by mass) instead. This parameter substitution achieves grain refinement through TiC precipitation while avoiding the solid-solution hardening effect of Mn that generates excessive working heat during can making.
Solution Approach 2:
The patent uses ultra-low carbon steel (0.001-0.005% C) as a base material, which is a low-cost, readily available material. By combining this with minimal Mn addition and Ti addition, the patent achieves the desired grain refinement without the need for expensive alloying elements or complex processing, thereby controlling working heat while maintaining productivity.
2Manufacturing precision
If Nb is added and crystal grain diameter is reduced to 6 μm or less to prevent surface roughness, then surface properties are improved, but production cost increases and specialized equipment is required
Solution Approach 1:
The patent extracts Nb from the alloy composition entirely, replacing its grain refinement function with Ti instead. This eliminates the need for Nb-based precipitates and associated complex hot-rolling control, simplifying the manufacturing process and reducing production costs while achieving the same grain refinement effect through TiC precipitation.
Solution Approach 2:
The patent uses conventional, inexpensive ultra-low carbon steel with minimal Mn and Ti additions as the base material. This approach avoids the need for expensive Nb alloying and specialized equipment, making the process economically viable and suitable for existing production lines while still achieving excellent surface properties through controlled grain refinement.
3Manufacturing precision
If water cooling is started within a short time after the end of finish rolling to achieve grain refinement, then crystal grain diameter is reduced, but equipment modification and operational complexity increase
Solution Approach 1:
The patent uses a simple, conventional water cooling system that can be implemented without modifying existing rolling equipment. By controlling the timing of water cooling to start within a short time after finish rolling, the patent achieves grain refinement using standard equipment and operational procedures, avoiding the need for complex device modifications or specialized control systems.
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 results in a steel sheet with excellent surface properties after drawing and ironing, suppressing surface roughness and film exfoliation, and maintaining compression strength, while being producible using existing equipment, thus enhancing industrial feasibility.
Implementation Method 1
the amount of Nb-based precipitates is 20 to 500 ppm by mass, the average grain diameter of Nb-based precipitates is 10 to 100 nm, and the average crystal grain diameter of ferrite is 6 to 10 μm
Implementation Method 2
0.05% to 0.60% by mass of Mn, which is a typical solid-solution hardening element
Implementation Method 3
ultra-low-carbon steel containing about 0.001 to 0.005% by mass of C
Data Source
AI summary
A component composition contains, by % by mass, 0.0016 to 0.01% of C, 0.05 to 0.60% of Mn, and 0.020 to 0.080% of Nb so that the C and Nb contents satisfy the expression, 0.4 ≤ (Nb/C) × (12/93) ≤ 2.5. In addition, the amount of Nb-based precipitates is 20 to 500 ppm by mass, the average grain diameter of the Nb-based precipitates is 10 to 100 nm, and the average crystal grain diameter of ferrite is 6 to 10 µm. Nb is added to ultra-low-carbon steel used as a base, and the amount and grain diameter of the Nb-based precipitates are controlled to optimize the pinning effect. Grain refinement of ferrite is achieved by specifying the Mn amount, thereby achieving softening and excellent resistance to surface roughness of steel. Therefore, it is possible to provide a steel sheet for cans with excellent surface properties which causes little surface roughness and no film exfoliation after drawing and ironing, and also provide a method for producing the steel sheet.