Investigations On Mathematical Models And Process Control System In Tandem Cold Rolling For Strips

Under the background of tandem cold rolling line which was designed to produce stainless/carbon steel,aiming at the existing key issues which contains mathematical models,process control system and surface thermal scratch defects of strip steels,as well as the production of high-precision fine blanked steels with limited thickness,the systematic theoretical research was carried out,and then a good practical application effect was obtained.Based on the original work,the following main conclusions are drawn:(1)In the laboratory,the lubrication experimental research on the effects of roll surface roughness on setting up of process parameters and control of strip surface quality was carried out.Then,based on experiment and theoretical analytical method,important and key mathematical models on deformation resisitance,friction coefficient,roll surface roughness,strip surface roughness,temperature in the deformation region,oil film thickness in the deformation region,and viscosity of emulsion were successfully established,which can lay a theoretical foundation for achieving applications of these mathematical models for practical production,and also for enriching and improving process control system of tandem cold rolling.(2)In view of specific control and technological requirement of tandem cold rolling process,the process control system for tandem cold rolling was investigated and developed.The structure frame and process functions for process control system have been designed,of which main functional modules,consisting of model setup calculation,coil tracking,communication,data processing and management,HMI and logging,were provided.Meanwhile,a multi-objective optimization model of rolling schedule was developed and presented.Based on the Nelder-Mead simplex algorithm(NMS),the optimization method of rolling schedule for tandem cold rolling was provided.With the characteristics of steadily operating,and high precision of setup calculation,the process control system can completely satisfy the requirement of automatic control for tandem cold rolling at high rolling pacing.(3)The lubrication experimental research was carried out,and the effects of technological parameters on thermal scratch defects were analysized and studied,which contain the reduction,the concentration and temperature of emulsion,as well as the roll surface roughness during the cold rolling process.Then the mechanism of thermal scratch defects was explored and the distribution regularity of oil film thickness in the deformation region during cold rolling was studied and analyzed.Also the mathematical model of high-precision oil film thickness during the cold rolling was established.According to the principle of statistics and statistical rules during the research of thermal scratch defects,the mathematical model of critical oil film thickness in deformation region for thermal scratch was built,through fitting and regression analytical method,and then based on the temperature comparison and thickness comparison method,the criterion for deciding thermal scratch defects was put forward,which offered a core technology solution for prediction and control of thermal scratch defects.(4)A software on the control and prediction of thermal scratch was developed on the basis of the joint application of Microsoft Visual Studio 2008,Oracle lOg and MFC,which was embedded into the process control system successfully and then applied in production practice for cold rolling.The high-precision prediction of surface thermal scratch defects was implemented online.In addition,the thermal scratch defects were prevented and controlled perfectly by adjusting parameters which contain rolling speed distribution,reduction distribution,the concentration and temperature of emulsion,roughness,etc.Ultimately,the function for mathematical model of thermal scratch defects was realised.(5)Based on the lubrication experimental research,the process technology of rolling for fine blanked steels with limited thickness in 1750mm cold tandem rolling mills was developed,and then under conditions of different tension,rolling speed,lubrication state and reduction,the rolling characteristics of fine blanked steels with limited thickness was also studied,to provide the technical schedule for tandem cold rolling of fine blanked strip steels.Meanwhile,the capacity of coiling for carrousel coiler was effectively enhanced and improved,which made a breakthrough for the technical bottleneck of coiling.In the guarantee of dimensional accuracy of fine blanked steel and on the basis of reasonable distribution of deformation,the influences of annealing process on the micro structure and mechanical properties of experimental steel were discussed,and then the effective heat treatment schedule was established,which provide technology guidance and theoretical basis of improving the mechanical properties and structure of fine blanked steel products.