Continuous hot dip galvanizing process technology
Continuous hot dip galvanizing process has Sendzimir, modified Sendzimir US Steel Union law three kinds. Sendzimir method and improved Sendzimir process is simple, low cost of the product, but due to direct flame heating, although steel rolling oil can burn the surface, but the impact of the strip surface quality, is not conducive to the production of thin gauge products. US Steel Union law set before annealing cleaning section, electrolytic degreasing, the strip surface oil can be completely removed. In addition, the process uses the full reduction furnace radiant tube heating strip, therefore better surface quality galvanized layer. Although the process is relatively complex, low thermal efficiency, but it can produce better surface quality, thinner hot galvanized steel, and can reduce the H2 content in the furnace, improve security, and therefore the new hot dip galvanizing line is mostly US steel Union law.
Modern cold-rolled steel strip continuous hot-dip galvanizing typical process: Feeding → pinch uncoiling, straightening → welding → washing → entry looper → annealing → galvanizing → (alloyed) → cooling → middle Looper → smooth straightening → export after processing looper → Check coiling. Looper can make use of an intermediate mill rollers replacement process section unit to normal operation, this unit is fast, not only to increase production, and a constant line speed craft section will help control the uniformity of the coating thickness. In addition, production of surface roughness demanding galvanized products, the need for frequent replacement of mill work rolls.
Typical process hot-rolled steel strip for continuous galvanizing: hot pickling incoming → welding → washing → entry looper → annealing → straightening flat galvanized → passivation → exit looper → coiling. As can be seen, for hot-rolled substrate characteristics and the use of hot-rolled strip galvanized products, this process has been simplified in the cold-rolled strip steel galvanizing process on the basis that not only saves investment, but also greatly reduces operational costs. Its trend is towards short process, low-power, high-efficiency direction, another online pickling is a direction of development.