Electrogalvanized Sheet Processing for Low-Waviness Vehicle Panels
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Solution Overview
Problem
Zinc-based metal coatings on metal sheets used for vehicle body parts exhibit waviness that leads to an 'orange peel' appearance, which can only be mitigated by increasing paint thickness, resulting in suboptimal surface quality.
Innovation Solution
A method involving cold rolling with work cylinders of reduced roughness, followed by recrystallization annealing, skin-passing, and electrodeposition of the zinc-based coating, which reduces the waviness of the metal coating's surface, allowing for thinner paint films or improved appearance quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cold rolling with standard roughness work cylinders is used, then manufacturing process is simpler and productivity is higher, but the waviness of the metal coating surface increases causing orange peel appearance
Solution Approach 1:
The invention applies preliminary action by performing skin-pass rolling with specially prepared smooth work cylinders before electrodeposition to pre-condition the substrate surface. This preliminary smoothing action reduces the waviness that would otherwise be amplified during subsequent coating and forming operations, thereby achieving low surface waviness without requiring complex downstream processes.
Solution Approach 2:
The invention changes the parameter of work cylinder roughness from conventional values to Ra≤0.4μm for the skin-pass operation. This parameter change in the rolling process directly controls the surface waviness of the metal coating, enabling the achievement of Wa0.8≤0.5μm after deformation without compromising manufacturing efficiency.
2Manufacturing precision
If paint film thickness is increased to mask waviness, then surface appearance quality improves, but material consumption increases and manufacturing cost rises
Solution Approach 1:
By performing skin-pass rolling with smooth work cylinders before electrodeposition, the invention preliminarily smooths the substrate surface to minimize waviness generation. This preliminary action ensures that the metal coating surface has low waviness (Wa0.8≤0.5μm) after deformation, allowing thin paint films to achieve excellent appearance quality without requiring thick paint layers for masking.
3Manufacturing precision
If work cylinders with reduced roughness are used in cold rolling, then surface waviness is reduced, but device complexity and manufacturing complexity increase
Solution Approach 1:
The invention applies local quality by using smooth work cylinders (Ra≤0.4μm) specifically for the skin-pass rolling operation, while other rolling operations can use conventional cylinders. This localized application of high precision only where needed (in the final surface conditioning pass) achieves low waviness without requiring all rolling equipment to be complex high-precision devices.
Solution Approach 2:
The invention uses consumable or replaceable smooth work cylinders for skin-pass rolling that can be relatively simple in construction (e.g., ground cylinders or EDT-treated cylinders). These cylinders serve their purpose in the skin-pass operation and can be replaced when worn, avoiding the need for permanently complex, high-maintenance precision rolling equipment throughout the entire line.
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 method effectively reduces the waviness of the metal coating's surface, enabling thinner paint films or enhanced appearance quality while maintaining corrosion protection, thus addressing the 'orange peel' issue and improving manufacturing efficiency.
Implementation Method 1
cold rolling the substrate, during which step at least the last cold rolling pass is done with work cylinders whose work surface have a roughness Ra2.5 of less than or equal to 3.6 μm
Implementation Method 2
recrystallization annealing of the cold rolled substrate
Implementation Method 3
deposition of the metal coating, on at least one face of the annealed substrate, by electrodeposition to form the metal sheet
Data Source
AI summary
A method for manufacturing parts is provided. The method includes cold rolling a substrate with work cylinders whose work surface has a roughness Ra2.5 of less than or equal to 3.6 μm, depositing the metal coating on at least one face of the annealed substrate by electrodeposition to form the metal sheet and deforming the cut metal sheet to form the parts. The outer surface of the metal coating has a waviness Wa0.8 of less than or equal to 0.5 μm after the deformation step. A part and vehicle are also provided.