Research On Stable Traveling Of Strip And Coupling Model Between Heat Transfer And Phase Transformation In Hot-Dip Galvanizing Line

A continuous galvanizing production line (CGPL) is the developing tendency of strip galvanizing technology, which composed of many processing procedures, including strip cleaning, annealing, galvanizing and post-treatment. The strips produced by CGPL can attain annealing without felting defaults, and finally get a good surface. But the most serious problem that exists in CGPL is how to realize the stable strip traveling with a high speed and correctly predict heat transfer and phase transformation in the cooling process. With the demand of cold rolling and hot zincification strips increasing, it is necessary to make a basic, then deeper research on this problem.In production, Air-cushion devices are widely used for non-contact support during transfer process of strip steel in heat treatment or plastic, paper and other webs. Aerodynamic characteristics are key parameters of pressure-pad air bars, also theoretical basis for their structure design and selection of related equipment. To get more practical data, a set of equipment for experiment is built on the basis of others' research. Besides, the flow features of the air-cushion (uniformity, amplitude, pressure coefficient) are numerically and theoretically investigated in this paper based on FLUENT, CFD software. The effect of structural parameters ,including flotation height, slot width, etc. and operating parameters , such as total pressure of the air jet, ejection velocity and other conditions of newly developed air-cushion are mainly analyzed. Results show that the cushion pressure increases with the increasing of the width of the air jet, gage pressure and with the decreasing of the flotation height, but the distance between the two slot nozzles has no significant effect on it .The result of this paper provides reference basis for practical applications of air cushion devices in the production locale of hot galvanized strip.Slit injection cooling belongs to jet impingement, which is an effective manner of enhanced heat transfer, has the highest heat transfer coefficient. Thus it is more and more important and gets further research. In this paper, the fluid flow and heat transfer of slit injection cooling with mixed gas(50%H2+50%N2)was studied, through the establishment of fluid-structure interaction model based on FLUENT. Also the numerical simulations is used to simulate the distribution of convective heat transfer coefficient at the stagnation point and local area effected by exit velocity, nozzle-to- surface spacing and other parameters. The result shows that latent heat of phase transformation has limited impact on the temperature distribution, and surface heat transfer coefficient varies little in different region of strip, and it's reasonable to introduce the average heat transfer coefficient to describe gas jet cooling process. The result of this paper provides reference basis for design of annealing technology for cold rolled strip.Those research conclusions provide believable rule for design and choosing of air cushion and annealing procedures, the application of which can effectively solve the serious problem in production line, and will enhance the production efficiency.