In order to obtain a high-quality surface, a large number of newly-built galvanizing production lines abroad in the 1990s adopted the American Steel Union method. The American Steel Union method adopts the high-density electrolytic deesterification technology (HCD) to quickly and effectively remove the oil on the surface, and at the same time in the reduction annealing furnace The American Steel Union method replaces the open flame heating in the improved Sendzimir method with a full radiant tube, so the temperature and atmosphere can be strictly controlled to ensure a non-oxidizing atmosphere in the furnace, thereby ensuring the excellent adhesion and surface quality of the coating.
The process layout of the traditional hot-dip galvanizing line is to set up a complete machine. The modern wide-band steel hot-rolling galvanizing line for the production of automotive plates generally has two smoothing machines in the process layout. The first smoothing is to use a four-roll smoothing machine to smooth the surface of the strip to eliminate surface irregularities. Uneven appearance; the second finishing is to choose a two-roll finishing machine to give the strip a certain roughness.
The traditional hot-dip galvanizing lines are all double loopers, arranged at the exit and entrance of the process section. Due to the extremely high requirements for the surface of the automobile plate, when the automobile plate is smoothed, the smooth roll is sometimes replaced with 5-10 rolls. In order to realize the non-stop roll change in the process section and increase the operation rate, some units are in front of the smoothing machine. Adding a looper is a process layout of three loopers in the first line. The storage time of the new looper is generally 120s.
The production capacity and product quality of hot-dip galvanizing lines newly put into production or reforming old hot-dip galvanizing lines in foreign countries have been further improved. Newly built production lines in developed countries can produce hot-dip galvanized steel sheets with a width of 2100mm, and the maximum speed of the line can reach 200m/min. , The alloying speed is 136m/min, and the annual production capacity is 600,000 tons.
