Research On Integrated Control Technology Of Steel Strip Travelling In Continuous Annealing Process

In recent years,with the rapid development of household appliances,automobiles,electronics,construction,shipbuilding,military,aerospace and other industries,the consumption of strip has increased dramatically.Cold rolled steel plate can not be directly used for stamping or other moulding process,which must be annealed to nucleate and recrystallize to reduce the lattice defects for further processing.Continuous annealing unit contains four processes: cleaning,annealing,leveling and finishing.It can produce products with good flatness,uniform performance and high surface cleanliness at lower cost.Due to the rapid heating,high temperature annealing,rapid cooling,overaging treatment technology,the continuous annealing technology has developed rapidly.At the same time,stable strip travelling is the key to ensure the continuous and high speed production of the unit.As the major problems in the field of continuous annealing,strip deviation and buckling has become a bottleneck restricting the further development of the continuous annealing process.Firstly,this paper took into account the equipment and process characteristics of continuous annealing unit.On the basis of analyzed the transverse tension distribution of strip steel in continuous annealing process systematically,the paper studied the influence of strip transverse temperature difference,incoming plate shape,furnace roller type,furnace roller horizontal and vertical direction error on the deformation of steel strip internal element.A set of lateral distribution model of strip internal tension was established,the corresponding calculation method was given,the influence law of each factor on the transverse distribution of the inner tension of strip steel was analyzed quantitatively and the calculation model of the furnace plate shape variation was deduced.Then,taking the asymmetry of transverse distribution of strip tension as the breakthrough point,a strip deviation evaluation system was established and the influence of various factors on the strip deviation was analyzed deeply.At the same time,according to the "strip buckling" defects and changes of setting tension and temperature in different process,combining with the mechanical effect of furnace roller rotation on the strip,the transverse compressive stress model and mechanical conditions of critical instability of strip element were deduced.On the basis of first putting forward the concept of "buckling index",the quantitative prediction technology of strip buckling in continuous annealing process was created to detailedly expound occurrence law of strip buckling in different process.Furthermore,with references to the problems of deflection,buckling and flatness control in continuous annealing process,focusing on the set tension and roller profile,this paper put forward a comprehensive control index for strip stabilized pass for the first time,established a set of tension optimization technology which taking the strip deviation and wrinkling defects as constraint condition and considering the strip shape and narrowing.Besides,the tension compensation technology was developed to solve the decrease of tension caused by surface roughness attenuation.Meanwhile,a new furnace roller profile was designed by the consideration of the advantages and disadvantages of traditional roller profile in the prevention and treatment of the buckling and strip running deviation.Finally,the theoretical and technical achievements of this paper were verified by field tests which showed that the asymmetry of the flatness was the direct cause of strip deviation.Strip deviation has decreased significantly and strip shape has improved after the comprehensive optimization and tension compensation of each process.The relevant technical theory is in line with the actual production,which has strong practicability.