关键词: 连续轧制, 临界轧制速度, 稳定性, 自激振动, 轧机

Abstract:

Rolling mills are typically complicated dynamic systems due to the coupling of structure and technique. Under the feedback excitation of inner sources, self-excited vibration is triggered when driving energy is transformed into vibration energy in structures under certain circumstances. The rolling speed is a direct index for measuring productivity, and also a key factor in triggering instability of rolling machines, therefore a research on the critical rolling speed possesses major significance in the forecast and control of self-excited vibration. Taking into consideration the equivalent elastic-plastic stiffness, an 8-DOF structurally asymmetrical model of a certain 6-roller rolling mill for thin strip is set up. A model of rolling process is established based on the plane strain hypothesis and the SLAB theory, and effectively verified by comparing the calculation value and the actual measurement of the rolling force, furthermore the increment model of rolling parameters is attained by TALOR expanded formula, thus a dynamic model with the coupling of structure and technique is presented. The LAPLACE transform is executed to get the characteristic equation in the S-domain, the instability condition of the system and the rolling speed threshold of the self-excited vibration is obtained by the application of ROUTH stability criterion. The influences of technical parameters are analyzed, and then the ways to the optimization of technical schedules are correspondingly proposed. By combing calculation conclusions with the actual producing problems, the typical vibration phenomenon and the vibration suppressing strategies are simulated during the increasing-speed stage and the steady-speed process respectively, and these problems are demonstrated and explained through the relations between the critical rolling speed and instable self-excited vibration. These results show that as a major index for the evaluation of the vibration and stability of rolling mills, the critical rolling speed can be improved through the optimization of the technical conditions and the distribution of the reduction schedules, thus a high-speed stable rolling process is achieved in the tandem rolling mill of thin strip.

Key words: critical rolling speed, self-excited vibration, stability, tandem rolling, roll mill