Research And Industrial Application Of Rolling With Inter-Pass Cooling Process And Cooling Control Model For Plate Based On Ultra Fast Cooling

Steel plates are the important raw materials for the development of national economy.With the social development,steel fields have made higher requirements for gauge and quality of plate.Due to the improvement of market demand and increasingly fierce competition in the steel industry,problems and difficulties of heavy plate production will be more outstanding.The problems of rolling include long intermediate cooling,low production efficiency and the lack of deformation penetration by the constraint of slab size and rolling capacity.It cannot eliminate internal defects and fine grains and will not benefit quality of products.The difficulties of cooling are to improve precision and stability of current cooling models and solve the weakness of calculated capacity.To solve the above-mentioned problems of plate production,it is based on the national twelfth five-year science and technology support project "Development and application of new generation TMCP equipment and technology for hot rolled strip"(2012BAF04B01)and the fundamental research funds for the central universities "Study of Internal Defects Evolution Mechanism by Temperature Gradient Rolling for Heavy Plate"(L1507020).Starting from the key process parameters of actual control,it researches the variation law of metal plastic deformation in the rolling with inter-pass coolin.Based on the application requirements,industrial control model is developed which realizes precise control of cooling process.The above studies provide important guarantee for industrialization and product development of the rolling with inter-pass cooling and support the national key research and development program "High Strength,Large dimension and easy welding ocean engineering steel and its application"(2016YFB0300601).The main works and achievements are as follows:(1)The theoretical model of non-uniform metal deformation in the rolling with inter-pass cooling process was built.Based on the stress status and hard deformation zone distribution of the internal metal in rolling process,the variation laws of non-uniform metal flow and hard deformation zone were deduced.Furthermore,under the conditions of large temperature gradient through thickness and strong friction on the interface,the variation law of hard deformation zone near plate surface was verified by experiments.(2)The effects of cooling parameters on rolling with inter-pass cooling process were studied systematically by simulation.From aspect of cooling control,some main industrial control parameters:cooling intensity(water flow),water cooling time and air cooling time(reheating)were selected to research effects of above parameters on temperature field,transverse metal flow and strain status.Based on the theoretical research,it firstly made a clear distinction and description between temperature difference and temperature gradient through thickness.It will provide theoretical basis for cooling strategy in industrial rolling process.(3)The effects of rolling parameters on rolling with inter-pass cooling process were studied systematically by simulation.Some key control parameters:rolling temperature,rolling thickness and rolling reduction were selected to research their effects on temperature field,transverse metal flow and plastic strain status in the rolling with inter-pass cooling process.Furthermore,by comparison of small reduction large temperature gradient rolling with large reduction conventional rolling,the equivalent relation between temperature and rolling reduction under the condition of meeting the same deformation penetration was studied.It will provide reference for rolling strategy in industrial applications.(4)Based on the simulation of rolling with inter-pass cooling,the experimental facility of inter-pass cooling was developed.Research experiments include conventional rolling(CVR)and large temperature gradient rolling(LTGR)by single pass,different gradients of LTGR by single pass and different rolling stages of LTGR by multiple passes.It verifies the reliability of simulation results and provide thought and guide for industrial production.(5)The novel online cooling control model was developed.For the strong controllability,high precision and quick response of industrial requirements,it built highly efficient 1.5D model to calculate the temperature field of plate cross-section and provided an effective control method for improving cooling uniformity.Furthermore,self-learning model based on data mining and IA(Intelligence Augmentation)strategies were developed.It has advantages of strong adaptability and low consume to guarantee the industrial application of cooling process.(6)The industrialization of rolling with inter-pass cooling was achieved firstly.The ultra fast cooling system after rolling and inter-pass cooling system was built.The industrial test of heavy plate by rolling with inter-pass cooling has been implemented.It somewhat improves internal equality and increases properties of heavy plate.Based on the new developed models,the cooling control system can effectively improve the precision and stability of temperature control.It has been successfully applied to many domestic plate plants.