1.What is the thermal conductivity of pure zinc?
Numerical range: At room temperature (20°C - 25°C), the thermal conductivity of high-purity zinc is typically between 110 and 120 W/(m·K). A widely cited engineering reference value is 116 W/(m·K).
Comparative references:
Carbon steel: approx. 50 W/(m·K)
Aluminum: approx. 237 W/(m·K)
Copper: approx. 400 W/(m·K)
Air: approx. 0.026 W/(m·K)
2.What is the actual thermal conductivity of galvanized coils?
Substrate: Typically low-carbon steel with a thermal conductivity of approximately 50 W/(m·K).
Coating: Zinc layer with a thermal conductivity of approximately 116 W/(m·K).
3.What are the key factors in the overall thermal conductivity of the entire galvanized coil?
The zinc layer is very thin: the thickness of the galvanized layer is typically between a few micrometers and tens of micrometers (for example, Z60 indicates a zinc layer with a total weight of 60 g/m² on both sides, approximately 4.2 μm thick per side), while the thickness of the steel substrate is from a fraction of a millimeter to a few millimeters.
Thermal resistance is series: heat must pass through the zinc layer and then the steel layer sequentially as it passes through the galvanized sheet. Because the steel substrate is much thicker, its thermal resistance dominates.
4.What are the influencing factors?
Temperature: Thermal conductivity changes with temperature. Generally, the thermal conductivity of a metal decreases slightly with increasing temperature.
Zinc-Iron Alloy Layer: During hot-dip galvanizing, a brittle zinc-iron alloy layer forms between the zinc layer and the steel substrate. The chemical composition and crystal structure of this alloy differ from pure zinc, resulting in slight differences in its thermal conductivity, but these are usually considered in the overall design.
Zinc Flower Morphology: Different surface morphologies, such as common zinc flowers and those without zinc flowers, have little impact on macroscopic thermal conductivity.
5.What is the overall effective thermal conductivity of galvanized coil?
In engineering applications and heat transfer calculations, for simplicity, the value for the steel substrate is usually approximated, approximately 50 W/(m·K). This approach is conservative and practical.