板带轧制前后滑摩擦自激空间振动机理研究

The rolling mill is the key equipment for the rolling of strip. During the rolling process of thin strip rolling with heavy reduction rate at the low rolling speed, the severe vibrations of the rolling mills made in our country or bought from overseas will occur. The mills have to be operated at a low capacity, and the quality of strip and the yield of steel are badly influenced due to the vibrations. The researchers both in China and abroad have done a lot of research for a long time, however, the vibration mechanism of the mill has not been revealed, and the excitation source and the vibration control method are not clear yet. Based on the previous research, our research group indicates that the roll system with setting of offset distance in multi-roll mill is an unstable roll system. During the rolling process of thin strip with heavy reduction rate, the forward and backward slip zone will appear in the rolling deformation zone. The self-excited vibration will occur with the action of the frictional force in the rolling deformation zone. The cold plate six-high rolling mill is chosen as a research project. The forward and backward slip formation law in the rolling deformation zone, and the accumulating rule of friction work are investigated to determinate the nature of excitation using theoretical analysis, numerical simulation and experimental research. The self-excited vibration frequency generated in the roll gap and the displacement responses of the rolls are obtained. The self-excited vibration model is established, and the spatial vibration analysis can be done to solve the mill’s natural vibration characteristics and response under excitation. The comparison between numerical simulation result and experimental test result is done to verify the validity of the theory. Then the vibration control method of mill is analyzed, and the theory of self-excited vibration that occurs in the roll gap is finally revealed.

轧机是板带材生产的关键设备。在低轧制速度下进行大压下率轧制薄板时，国内外轧机均会出现异常振动现象，使其不得不降低负荷运行，严重影响轧机产量和轧材质量。长期以来，国内外开展了多方面的研究，但仍未能揭示轧机振动的机理，轧机振动的激励源及抑振措施尚不明确。本课题组前期研究过程表明：多辊轧机的偏置辊系是不稳定辊系；以大压下率轧制薄板时，轧制变形区内出现前、后滑动区；在滑动区内摩擦力的作用下，轧机将产生自激振动。本研究以六辊冷轧机为研究对象，以理论解析、数值模拟和实验研究等方法，研究前、后滑区形成规律和摩擦功的积累过程，确定激励性质；获取辊缝自激振动频率和轧辊位移响应；建立轧机空间振动力学模型，求解其固有特性和在辊缝激励下的响应；将模拟结果与轧机振动实验结果对比，验证机理的正确性；研究轧机振动控制方法，揭示轧机辊缝自激振动机理。

板带轧机在低轧制速度下进行大压下率薄板轧制时均会出现异常振动现象。本项目研究以“机构学不静定”的不稳定轧机作为轧机振动研究的突破口，首次提出轧机“空间振动”的概念；为了进行轧机空间振动解析和自激振动机理研究，编程开发了适用于轧机结构特点的空间传递矩阵法；以1580四辊热轧板带轧机为研究对象，建立了轧机空间振动力学模型，利用空间传递矩阵法数值解析轧机系统固有频率和振型，并建立四辊轧机有限元模型仿真分析其振动特性以及不同工艺参数对轧件变形区内各区长度和摩擦功率的影响；开展四辊板带轧机的现场振动测试实验以验证数值解析结果。结果表明：四辊轧机的空间振动特性分析以及振动测试实验充分验证了轧机振动是涉及轧辊水平、垂直、轴向、扭转、交叉和摇摆的空间振动，轧件和摩擦阻尼对轧机系统固有复频率有影响；辊系存在间隙的轧机系统，振动主要表现为垂直和水平的复合振动；消除辊系间隙后的机构学静定轧机，其固有频率普遍高于不静定轧机，且可防止自激振动和辊系的水平及交叉振型并改善垂直和摇摆振型。热连轧机组各道次压下率小于47%时，轧机运行平稳无振动；但压下率达到或者超过52%时，低速轧制的轧机依然能够频繁发生振动且易诱发产生自激振动频率带；随着压下率的增加，轧制变形区内后滑区长度变短，前滑区长度变长，轧件表面速度与轧辊转速的相对速度在轧制变形区出口和入口处分别逐渐变大和变小，轧件和轧辊间的单位摩擦力以及摩擦功率增大。本研究可为产品精度的提高以及轧制设备抑振等方面提供理论意义和现场生产指导。