Hot-dip galvanizing, also known as hot-dip zinc coating or hot-dip zinc plating, is an effective metal corrosion prevention method mainly used on metal structural facilities in various industries. It involves immersing derusted steel components into molten zinc at approximately 500°C, allowing a zinc layer to adhere to the surface of the steel components, thereby achieving corrosion prevention. The hot-dip galvanizing process flow includes: finished product pickling - water washing - adding assistant plating solution - drying - hanging for plating - cooling - passivation - cleaning - polishing - completion of hot-dip galvanizing. Hot-dip galvanizing has evolved from older hot-dip methods and has been used in industries since France applied it in 1836, with a history spanning over 170 years. In the past three decades, along with the rapid development of cold-rolled steel strips, the hot-dip galvanizing industry has undergone significant expansion.
For hot-dip galvanizing of steel pipes, a gear-disk full immersion semi-automatic galvanizing method is adopted, utilizing mechanical principles of insertion, pressing, spiraling, extraction, and lifting to complete the hot-dip galvanizing process.
Process parameter control: The temperature of the zinc solution should be controlled between 440-460°C; the immersion time should be controlled between 30-60 seconds; aluminum addition (aluminum content in the zinc solution surface: 0.01-0.02%).
The zinc ingots used should comply with the national standard Zn0-3.
Regular maintenance and control are essential to ensure the reliability of the insertion, pressing spiral, extraction, and lifting devices. Lubrication of the cylinders should be enhanced, and the height and angle of the galvanized pipe distributor should be adjusted to optimize equipment performance.
The placement of proximity switches must be accurate; thermocouple wires and meters should be of a unified model; otherwise, temperature errors may be significant. The protective sleeve of the thermocouple should be frequently inspected and replaced.
Operators at the control panel should manually adjust the speed based on the operation of the equipment and hand gestures to prevent pipe jamming.
Tools used by furnace operators should be preheated before use to prevent zinc splashing and injury; regularly check for steel pipes falling into the pot and remove them promptly; adjust the equipment in a timely manner to prevent pipe jamming and ensure equipment safety.
When adding zinc to the zinc pot, the zinc ingots should be preheated. Adding zinc in bundles is strictly prohibited; add no more than five ingots each time. Slowly slide the zinc ingots longitudinally against the wall of the zinc pot to avoid damaging the pot and splashing zinc, which can cause injury. Iron-based materials are strictly prohibited from falling into the zinc solution to prevent the generation of a large amount of zinc slag.
When melting zinc, heat should be applied slowly, avoiding rapid heating, which can damage the galvanizing pot and result in the emission of substantial zinc vapor. Inhaling excessive amounts of this harmful gas can lead to "metal fume fever." During the zinc melting process, once the zinc reaches a high temperature, never use your hands to stir the zinc blocks to avoid burns; use appropriate tools instead.
Regularly remove zinc ash from the surface of the zinc solution. When scraping, gently scrape the surface of the zinc solution with a scraping board without stirring too vigorously to avoid raising zinc ash. The scraping board should not touch the steel pipes during immersion or extraction to prevent accidents or equipment damage.
Zinc blocks, zinc fragments, zinc brought out during galvanizing, and zinc flowing out of steel pipes on the furnace floor should be recovered and returned to the pot promptly to reduce heat loss from the zinc pot.
When adding aluminum ingots to the surface of the zinc solution, ensure even distribution of aluminum by moving the ingots back and forth several times.
To facilitate slag removal and zinc extraction, 20 tons of lead should be placed inside the zinc pot.
Preheat the slag removal machine before use. Store zinc slag in different sizes. The temperature for slag removal should be controlled above 455°C. Use special tools when operating the slag grabbing machine, and stand with feet in a "T" position, one meter away from the zinc pot.
The hot-dip galvanizing process requires precision. Therefore, during hot-dip galvanizing production, it is essential to maximize work efficiency. In other words, a higher number of pieces or tonnage per unit time results in lower costs, and vice versa.
