适应变速轧制的精细化轧件温度计算和控制模型

针对因变速轧制和复合冷却带来的卷取温度模型预报精度降低的问题,以热输出辊道上的冷却设备布置信息和辊间冷却换热形式为出发点,采用Crank-Nicolson(C-N)六点格式有限差分方法构建轧件轧后冷却温度计算模型;以前馈为主、反馈为辅,不断进行自学习来对轧件冷却温度进行控制,在精轧出口按照固定时间周期对轧件进行分段采样和前馈设定,在卷取入口按照长度进行分段采样和周期性反馈控制;为使模型适应升速轧制和因终轧温度控制所带来的速度扰动叠加的速度变化,对轧件在冷却区的运动进行精确的位置跟踪,并在冷却区中增设速度补偿区,对设定的冷却规程进行更新以补偿升速带来的冷却不足或降速引起的过冷.新的卷取温度模型以辊间冷却为计算单元,可有效地集成不同的冷却形式,并对变速轧制过程进行有效适应.自现场应用以来,卷取温度设定精度和控制稳定性大幅度提高.

Coiling Temperature Model Applicable to Variable Speed Rolling

To solve the problem that coiling temperature deviation is enlarged under speed up rolling condition or under complex cooling devices, a runout table cooling model was developed based on Crank-Nicolson finite difference method . The layout information such as table roll position, spraying header position, nozzle size and cooling type between table rolls were used in temperature calculation for hot-rolled strip cooling after rolling. Feedforward and feedback loops were implemented in the coiling temperature control ( CTC ) model. Based on scanned data, CTC performed product-to-product adaptations of model parameters to follow changing process conditions. The rolled strip left from finishing mill was virtually divided by a constant time interval into segments with different length. Cooling schedule for each segment was made by CTC model according to the measured finishing temperature, rolling speed and actual thickness. The segment position was precisely tracked when it moved on runout table. A new cooling sub-zone was designated to open or close the valves to compensate the insufficient cooling or to reduce the overcooling for segment located in cooling zone because of the speed variable brought by speed-up rolling and additional speed incremental given by finishing temperature control ( FTC ) . Since the on-site application of the new CTC model, coiling temperature control along the whole strip length has been obviously improved in coiling temperature homogeneity and stability.