冷连轧升降速过程板形控制工艺润滑制度优化

Optimization of lubrication system for flatness control process in cold tandem rolling

冷连轧机组在带钢升降速过程中,轧制速度会出现频繁的、较大程度的波动,轧制变形区的摩擦因数也会随之发生较大的波动,引起轧制压力来回波动,从而造成升降速阶段的板形相较平稳阶段的板形而言呈现出大幅度变差的问题。工艺制度优化对于摩擦因数引起的板形问题非常有效,因此,首先分析了不同乳化液浓度、初始温度和流量下的带钢在升降速过程中板形的变化过程。针对升降速阶段板形缺陷,采用分段离散法将带钢分别沿横向和纵向分成若干条元,提出升降速过程中板形横向目标函数和纵向目标函数,进而构造出升降速过程中板形动态变化目标函数,实现对轧制过程中板形波动在横向和纵向上的综合控制。由于乳化液浓度和初始温度在轧制过程中无法改变,所以结合板形目标函数,以带钢不发生打滑和热划伤、各机架轧制力不超过限定轧制力为约束条件,提出乳化液浓度和初始温度优化设定函数;乳化液流量优化针对频繁变化的局部浪形缺陷能够起到有效控制,因此乳化液流量一般随轧制速度呈非线性变化,以出口板形波动最小为控制函数,以不发生打滑和热划伤、各机架乳化液总量不超限为约束条件,提出乳化液流量跟随速度优化函数。最后将优化模型应用于国内某钢厂冷连轧机组,根据优化前后轧制力分布、带钢板形云图可知现场应用效果良好。

In the process of strip speed rise and fall of tandem cold rolling mill,the rolling speed will fluctuate frequently and greatly,and the friction coefficient in the rolling deformation zone will fluctuate greatly,causing the rolling pressure to fluctuate back and forth,resulting in the problem that the shape in the speed rise and fall stage is significantly worse than that in the stable stage.The optimization of process system is very effective for the shape problem caused by friction coefficient.Therefore,firstly,this paper analyzes the shape change process of strip steel in the process of speed increase and decrease under different emulsion concentration,initial temperature and flow rate.In view of the shape defects in the speed up and down stage,the strip steel is divided into several strip elements along the transverse and longitudinal directions by using the piecewise discrete method,the transverse and longitudinal objective functions of the shape in the speed up and down process are proposed,and then the dynamic change objective function of the shape in the speed up and down process is constructed to realize the comprehensive control of the shape fluctuation in the transverse and longitudinal directions in the rolling process.Since the emulsion concentration and initial temperature cannot be changed in the rolling process,combined with the shape objective function,the optimal setting function of emulsion concentration and initial temperature is proposed under the constraints that the strip does not slip and heat scratch and the rolling force of each stand does not exceed the limited rolling force;The emulsion flow optimization can effectively control the frequently changing local wave shape defects.Therefore,the emulsion flow generally changes nonlinearly with the rolling speed.Taking the minimum fluctuation of outlet plate shape as the control function,and taking no slip and thermal scratch and the total amount of emulsion in each frame as the constraint conditions,the emulsion flow following speed optimization function is proposed.Finally,the optimization model is applied to the tandem cold rolling mill of a domestic steel plant.According to the rolling force distribution before and after optimization and the cloud diagram of strip shape,it can be seen that the field application effect is good.