1.Why are galvanized coils suitable for making decorative edge strips?
Excellent Flexibility and Processability:
The substrate of galvanized coils is cold-rolled low-carbon steel, which inherently possesses excellent ductility.
After hot-dip galvanizing, the zinc layer forms a metallurgical bond with the steel substrate. As long as the zinc layer's adhesion and plasticity are sufficiently good (as in normally produced commercial coils), it can withstand forming operations such as edge rolling, bending, and stamping without large-scale zinc layer peeling or cracking.
Strong Corrosion Resistance:
Decorative strips are commonly used indoors and outdoors, especially in outdoor environments (such as building exterior wall trims, roof edges, etc.) where they are exposed to sun and rain.
The zinc layer first acts as a sacrificial anode, protecting the underlying steel substrate from corrosion. Even with minor surface scratches, this protective effect remains. This ensures the decorative strip's long service life and resistance to rust.
High cost-effectiveness:
Compared to other corrosion-resistant metals such as stainless steel and aluminum alloys, galvanized coils are less expensive, offering a highly competitive price-performance ratio.
2.When using galvanized coils to make decorative strips, how should the zinc layer thickness be selected?
Principle: The more complex the forming process (the smaller the curling radius), the better the zinc coating adhesion and plasticity should be selected. Generally, the thinner the zinc coating, the better the formability.
Recommendation: For general curling operations, a medium zinc coating thickness is sufficient, such as Z60-Z100 (i.e., double-sided zinc coating weight 60-100g/m²). Excessively thick zinc coatings (such as Z180 and above) increase the risk of micro-cracks during severe bending, but usually do not affect their corrosion resistance.
3.What are the requirements for substrate material and mechanical properties?
The type of steel used for the decorative strip needs to be selected based on the stress it will be subjected to. For purely decorative, non-stressed rolled edge strips, the most common DX51D (generally used) or DC01 (cold-rolled low-carbon steel) is sufficient. If a certain level of strength and support is required, a higher strength steel grade can be considered.
4.What are the requirements for surface treatment?
Spangle-free/small spangle: This is the preferred choice because of its uniform surface, making it particularly suitable for subsequent spraying and resulting in a smooth and aesthetically pleasing paint film.
Smooth surface: Galvanized coils that have undergone smoothing treatment have a smoother surface, eliminated yield plateaus, improved formability, and are less prone to developing Lüders bands (strain lines), making them ideal for producing high-quality decorative strips.
5.What are the requirements for subsequent processing and connection?
Cutting: Laser cutting and CNC punching and shearing can both achieve good cut results.
Welding: Zinc vapor is generated during welding of the galvanized layer, which affects weld quality and worker health. Special processes (such as MIG welding with adjusted parameters) and good ventilation are required. Decorative strips are usually connected mechanically (clamps, riveting, adhesive) and welding is less common.