Research On The Key Technologies Of Coating Weight Control On Baosteel1730CGL

For a long time, air knife parameters which influence the coating weight of the strip on the hot-dip galvanizing line have been adjusted according to the data from downstream coating gauge and experiences of operators. Various state enterprises try their best to break these limitations of traditional operational method, in order to achieve precision control on the continuous galvanizing line. The key technologies of coating weight control and process rules will be used in the hot load test of1730CGL, which is a new project in the cold rolling plant of BAOSTEEL.First, the theory and principle of air knife have been studied. Then, on the basis of the analytic equation of coating weight proposed by Mr. Ellen, which presents the conclusion and recommendations, the numerical simulation on air impinging jet have been researched by using the software Fluent. The mean pressure and shear stress distribution have been calculated through numerical simulation. Combined with the product data, the model parameter have been optimized and corrected.The model has been developed to predict the zinc coating weight. The calculated results show good agreement with product data, with the relative error is-9.275-7.12%. The model has been developed as the functions of jet pressure, impingement distance, and slot gap and strip velocity.To solve the problem of variant of jet pressure and impingement distance, the length of incipient stage during impinging jet has been studied, and the critical values of the length of incipient stage on the diverse slot gap have been determined. The value of impingement distance should be less than the length of incipient stage on the definite slot gap. The critical value of the length of incipient stage on the1.3mm slot gap is7.47-9.04mm.A pre-set table of air knife parameters has been proposed for service, in order to control the coating weight accurately. A process specification, including the admission data of jet pressure, flutter distance and strip velocity, has been suggested.