1. DX51D material definition and standard
DX51D is a galvanized substrate grade in the European standard (EN 10346). It is a commercial grade cold-rolled low-carbon steel designed for hot-dip galvanizing process. Its core features include:
Low carbon content (C≤0.12%): ensures excellent formability and weldability.
Mechanical properties: yield strength 140-300MPa, tensile strength 270-420MPa, elongation ≥22% (suitable for deep stamping).
Coating adhesion: verified by bending test (0T-3T), the galvanized layer has no peeling.
Related standards:
EN 10346 (EU galvanized steel sheet standard)
ASTM A653 (American standard equivalent grade is CS Type B)
2. Key points of DX51D galvanizing process
DX51D galvanized coil adopts continuous hot dip galvanizing process, and the key control links include:
1. Degreasing and cleaning: remove grease and iron powder on the surface of cold rolled sheet to ensure the bonding strength of the coating.
2. Reduction annealing: heat to 700-800℃ in H₂/N₂ protective atmosphere to eliminate work hardening.
3. Zinc pot immersion: immerse in 460℃ zinc liquid (containing 0.2% aluminum) to form a pure zinc layer (Z) or zinc-iron alloy layer (ZF).
4. Coating control: air knife adjusts the zinc layer thickness (normally 60-275g/m²), and the surface can be treated as ordinary zinc flower, minimum zinc flower or no zinc flower.
Process difficulties:
Aluminum content control: Aluminum in zinc liquid needs to be stable at 0.15-0.25%. Too high will lead to brittle coating, and too low will easily generate thick zinc flowers.
Prevention of surface defects: such as zinc dross and scratches need to be strictly monitored.
3. Performance advantages and application areas
Core advantages:
Corrosion resistance: The zinc coating provides cathodic protection, and there is no red rust in the neutral salt spray test for 500 hours (20μm coating).
Processing adaptability: It can be stamped, bent, and welded (spot welding or MIG welding is recommended).
Economical efficiency: The cost is lower than stainless steel, and the life cycle is cost-effective.
Typical applications:
Construction industry: light steel structure, roof corrugated board, cable tray.
Home appliance manufacturing: washing machine inner drum, air conditioner shell, refrigerator back panel.
Automotive parts: seat frame, fuel tank bracket (non-load-bearing part).
Furniture and decoration: file cabinets, display racks, billboard substrates.
4. Galvanizing layer type and selection recommendations
DX51D can be matched with different coatings to meet the needs:
Pure zinc layer (Z): standard anti-corrosion, suitable for general environment.
Zinc-iron alloy layer (ZF): The coating has higher hardness and wear resistance, but the weldability is slightly worse.
Environmental protection passivation: chromium-free passivation (Cr-free) or oiling treatment, in compliance with the RoHS directive.
Selection reference:
Indoor dry environment: 60-80g/m² coating (such as DX51D+Z60).
Industrial/coastal environment: ≥120g/m² coating (such as DX51D+Z120).
5. Market status and development trend
Demand growth: The global construction and home appliance industries drive the annual demand for DX51D galvanized coils to grow by 3-5%.
Technology upgrade:
High-strength steel substrates (such as DX52D/DX53D) are matched with galvanizing to achieve lightweight.
Digital galvanizing line (AI real-time control of coating thickness).
Environmental regulations: Chromium-free passivation technology gradually replaces traditional hexavalent chromium passivation.
6. Precautions for use and maintenance
Cutting protection: After shearing or drilling, the edge needs to be sprayed with zinc-rich paint to prevent rust.
Storage conditions: Avoid open-air stacking to prevent condensed water from causing white rust (wet storage stain).
Welding process: Reduce current and voltage to reduce the impact of zinc vapor on the strength of the weld.
Summary
DX51D galvanized coil has become one of the basic materials for the manufacturing industry with its balanced performance and cost advantages. Correct selection and processing can maximize its anti-corrosion life, and there is still room for expansion in green manufacturing and high-end applications in the future.