Two-Piece Can Coating and Ironing for Corrosion Resistance
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Solution Overview
Problem
The existing methods for manufacturing two-piece cans by drawing and ironing metal plates result in a reduction of corrosion resistance due to the transformation of the Sn-plated layer from a sea-island shape to a stripe shape, leading to decreased protection against corrosion.
Innovation Solution
A method involving a metal plate with a Sn-plated layer, a Cr-plated layer, and a thermoplastic resin coating, where the plate thickness reduction rate during shaping is controlled to maintain the Sn layer's uniform distribution, and heat treatment is applied to amorphize the coating layer, forming an Fe-Sn alloy for enhanced corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If drawing and ironing process is applied to metal plate with Sn-plated layer, then can body is formed, but the Sn-plated layer transforms from sea-island shape to stripe shape reducing corrosion resistance
Solution Approach 1:
The patent applies heat treatment at specific temperature ranges (500-700°C) to change the physical state of the Sn-plated layer, transforming it from a stripe shape to a uniform distribution. This parameter change (temperature) resolves the contradiction by maintaining corrosion resistance while allowing the drawing and ironing process to form the can body.
Solution Approach 2:
The patent performs heat treatment either before or during the drawing and ironing process to prevent the Sn-plated layer from forming stripes. By applying this preliminary action, the corrosion resistance is preserved before the forming process begins, resolving the contradiction between ease of manufacture and reliability.
2Reliability
If heat treatment is applied to amorphize coating layer, then corrosion resistance is enhanced, but additional process step is required
Solution Approach 1:
The patent combines the heat treatment step with the existing drawing and ironing process by applying heat during the forming operation. This merging of processes achieves the amorphization of the coating layer for enhanced corrosion resistance without adding significant process complexity, as the heating can be integrated into the forming equipment.
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
This approach maintains high corrosion resistance by ensuring the Sn layer remains uniformly distributed and forms an alloy with the base material, effectively preventing corrosion and providing pressure resistance with minimal material usage.
Implementation Method 1
the can body is heated at a temperature equal to or higher than the melting temperature of a resin material for a predetermined time and then rapidly cooled
Implementation Method 2
heat treatment is applied to amorphize the coating layer
Implementation Method 3
forms an Fe-Sn alloy for enhanced corrosion resistance
Data Source
AI summary
A method for manufacturing a two-piece can includes punching a metal plate into a disk shape, the metal plate including a Sn-plated layer of 100 mg/m2 or more and 1500 mg/m2 or less provided on a base material made of steel, a Cr-plated layer of 6 mg/m2 or more and 100 mg/m2 or less provided on the Sn-plated layer, and a coating layer laminated on the Cr-plated layer; and shaping by performing drawing and ironing on the metal plate having the disk shape into a can body having a bottomed cylindrical shape, wherein in the shaping, the drawing and ironing is performed so that ((Tb−Tw)/Tb)×100, which is a plate thickness reduction rate from the metal plate having the disk shape to the can body, is set as 35%≤((Tb−Tw)/Tb)×100(%)≤60%.