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.