This paper considers the equipment and technological characteristics of continuous annealing process (CAP) to solve the issue of strip buckling. It analyses the mechanism of hot buckling and transverse compressive stresses from internal and external forces. A basic description of strip buckling is given together with a new concept of a buckling index. The critical buckling condition is presented, and the model of strip buckling index in the CAP is proposed. The distribution of strip buckling index in different sections of the process is analysed quantitatively along with the influence of incoming strip shape, transverse temperature difference, roller profile, friction coefficient, set tension and strip processing speed on the strip hot buckling index in CAP. Results show that with the influence of thermal stress, the transverse compressive stress that affects the middle part of the strip is largest in the heating section, which is also where hot buckling occurs most easily; centripetal force is dominant in the soaking and slow cooling sections, and in these sections buckling occurs at the roller shoulder. In different sections, the strip buckling index distribution differs, whereas the influence of other parameters on buckling index remains similar.
The market demand for high-quality cold-rolled strips has increased along with the rapid development of home appliance manufacturing, aviation and other fields. As the existing research has been largely ignored on the horizontal deflection of work rolls, this paper investigates the characteristics of the equipment and the processes of a slender rolling mill, and then proposes a model for calculating the flattening coefficient between roll gaps at the horizontal deflection of work rolls. A typical product of a 550 mill taken from a steel plant is used as an example, and the factors that affect the flattening coefficient between roll gaps, including the difference between the front and rear tension and the diameter of work rolls, are quantitatively analysed. This paper then proposes a forecasting software that can greatly strengthen the plate-shape controlling ability of rolling mills and improve their product quality, thereby the software deserves to be promoted.
The previous tension setting for the continuous annealing process (CAP) is not comprehensive; that is, it does not synthetically consider the factors of strip deviation, buckling, flatness and width narrowing. To address this issue, this study integrated the mechanical and technological characteristics of a continuous annealing line to present a comprehensive control index that can characterise the stability of a travelling strip. Meanwhile, strip deviation, buckling, strip shape and width narrowing were regarded as constraints in each process section. A comprehensive optimisation technique for the tension setting during CAP was then established, and a related theory was applied during production. In addition, a comprehensive tension setting optimisation software was developed for a cold rolled strip during continuous annealing, and the comprehensive optimisation of the tension parameters in each process section was realised. A practical implementation proves that the developed technique exhibits good application effects and considerable application values.
In the double cold rolling process, the emulsion entering the roll gap during the double cold rolling process has the characteristics of high concentration and small flow rate so that the roll surface oil film thickness will affect roll gap oil film thickness, which in turn affects the rolling friction coefficient. This paper analyzes the formation mechanism and evolution process of the roll surface oil film thickness by considering the equipment and process characteristics of the emulsion direct injection application lubrication system. Then, based on the principle of fluid dynamics, the roll surface oil film thickness model in the double cold rolling process is established, and the prediction of the roll surface oil film thickness during the double cold rolling process is realized. Subsequently, the effects of five factors, such as rolling speed, work roll roughness, maximum contact stress between rolls, emulsion initial dynamic viscosity, and emulsion pressure viscosity coefficient, on the roll surface oil film thickness are quantitatively analyzed, and the corresponding influence laws are given. Finally, the relevant model and software that are applied to the 1220 double cold reduction mill have achieved good results.
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