Development of hot dip galvanized sheet production technology

The development process of hot-dip galvanized steel sheet production technology is as follows: the hot-dip galvanized steel sheet production line has developed to high production capacity. Since the 1990s, the hot-dip galvanized steel sheet production line has developed to high production capacity. There are more than 60 sets of hot-dip galvanized steel sheet production lines with a global production capacity of more than 300000 t / A, with a total production capacity of more than 28 million T / A. The specialized production of automobile galvanized sheet and building materials galvanized sheet adopts different types of units. The unit process, single equipment configuration and furnace selection are more reasonable,

 which makes the investment effect obvious and the product cost low. Emphasis on cleaning the surface of the substrate. The galvanizing line for automobile sheet built in recent years basically adopts the process of alkaline electrolytic cleaning and all radiant tube heating furnace of American Steel Union, and even the cleaning section is set before and after the looper device. In order to reduce the investment, the improved Sendzimir process is often used in the building materials type galvanizing line, but the cleaning section is often set in the line to make the substrate surface cleaner and the product quality better. The investment of tower furnace is about 25% ～ 30% higher than that of horizontal furnace. In the past, when the unit production capacity was more than 300000 t / A, tower furnace was often used due to the limitation of furnace length, otherwise horizontal furnace was often used. After the 1990s, the manufacturers pay more attention to the advantages of tower furnace: good air tightness; The number of furnace rollers is small and the service life is long; Low maintenance cost; It is helpful to improve the shape of the plate; Shorten the furnace length, etc. Tower furnace is also used in many galvanizing plants with production capacity of 250000 T / A or less. For example, the 250 kt / a hot-dip galvanizing unit built in December 1990 by solac iron and Steel Company of France; The 250000 T / a hot dip galvanizing unit was built in September 1991 at diedlange steel works in Luxembourg; BHP aluminum and zinc plating unit in California, USA. Tower furnace is also used in several new hot dip galvanizing units in China. Continuously improve the efficiency of the heating furnace, use the heating waste gas to pre heat the hot strip steel to save energy and avoid the deformation of the strip steel; Different cooling sections are set up according to product performance requirements; The hot tension adjusting roll is set to optimize the tension in the furnace; The heating section is equipped with high-precision anti thermal warping roll, and the heating section is added with induction heater; By adopting the heating technologies such as the drum extraction pulse controlled burner and the multi-stage combustion radiant tube, the adjustment range of the burner and the service life of the radiant tube are improved, which is conducive to the uniformity of heating, and can reduce the content of NOx, which is conducive to environmental protection; The roll shape design and surface spraying technology were improved.