薄板冷连轧自激振动的临界轧制速度研究

Research on Critical Rolling Speed of Self-excited Vibration in the Tandem Rolling Process of Thin Strip

轧机是典型的结构与工艺相互耦合的复杂动力学系统,在内源反馈激励作用下驱动能量在某种条件下被转换为结构的振动能量而引起自激振动。轧制速度既是生产效能的直接衡量指标,也是触发轧机振动失稳的关键因素,因此对临界轧制速度的研究对于预测和抑制自激振动的产生具有重要意义。考虑轧制界面的等效弹塑性刚度,建立某薄板轧制六辊轧机的8自由度非对称结构模型,基于平面应变假设运用SLAB理论计算法建立轧制过程模型,通过轧制力计算值和实测值的比较对模型有效性进行验证,并运用TALOR展开得到力能参数的增量模型,从而建立结构-工艺相耦合的动力学模型。通过对模型的LAPLACE变换得到S域特征方程,应用ROUTH稳定性准则得到系统的失稳条件以及产生自激振动的速度阈值,分析工艺参数对其影响规律,并进而提出工艺规程的制订及优化途径。将计算分析结果与生产现场实际情况相结合,对轧制过程升速阶段和匀速运行阶段的典型振动现象及抑制策略进行仿真再现,并从临界轧制速度与自激失稳振动的关系对其进行解释。研究结果表明临界轧制速度是评价轧机振动及轧制稳定性的重要指标,通过连轧机架间的压下规程配比和工艺条件优化可以提高临界轧制速度,从而实现薄板轧机的高速稳定轧制。

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.