Research And Application Of High Intensity Uniformity Cooling Technology After Rolling For Hot Rolled Strip

In order to realize the high intensity uniformity cooling after rolling for hot rolled strip,the key technology and core problem were researched for the ultra-fast cooling equipment and process development after rolling for hot rolled strip,and the relevant structure equipment and process technology were designed and developed.The research object is the impingement jet heat transfer process after hot rolling under the ultra-fast cooling,the background of the study is "the development and application of the equipment and process technology of the NG-TMCP for hot rolled strip" subject under the "Green production technology and application demonstration of steel industry" for "12th Five-Year Plan" Nation Key Technology R&D Program.The favorable effect also was obtained in practical application.The chief original work and results of the present paper are as follow:(1)Base on the turbulent flow characteristic of the impinging jet process for the high intensity cooling after rolling for hot rolled strip,the related basic control equation and discrete method were expounded,the theoretical principle and applicable scope of the impinging jet turbulent model were analyzed.At the same time,combining with characteristic of the main process and parameters under the condition,the velocity distribution law and turbulent structure characteristic and the applicable scope of the plan and circle impinging jet of the different turbulent models were obtained by using the method of numerical simulation,and provided a theoretical reference for improving the calculation precision of turbulent flow of the high intensity cooling.(2)Combining with the base structure features and related parameters of the high intensity cooling for hot rolled strip,the influence law of the flow characteristic of the ultra-fast cooling nozzle internal and exit were researched by the finite element analysis software.The changing law of the pressure and flow velocity of the nozzle internal was obtained under the different process environment and structure parameters.The structure optimization parameters of the nozzles were obtained by contrastive analyzing the change of the exit flow velocity and the internal pressure.(3)According to the heat transfer character of the single slot and circular jet impingement for the high intensity cooling after rolling for hot rolled strip,the chief influence factor of the strip heat transfer surface were researched under the submerged and non-submerged condition.The optimization design parameters of the cooling process for the hot rolling strip were obtained by analyzing the variation feature of the strip surface heat transfer coefficient and the change law of the average heat transfer coefficient.(4)Combining with the heat transfer feature of multiple jet impingement for the high intensity cooling process after rolling for hot rolled strip,the influence law of the different spacing from the nozzle to the strip,the spacing from nozzle to nozzle centerline,the temperature of cooling water and the velocity of the jet inlet to the intensity of the strip surface were investigated for the twin slot and circular jet impingement under the non-submerged condition.The functional relationship between the average Nusselt number and the systematic parameters was obtained by analyzing the local Nusselt number,average Nusselt number and the peak value of the strip surface.It provides the technical support for the further optimize layout of the equipment of the ultra-fast cooling after rolling for hot rolled strip.(5)Tacking the jet impingement cooling of the strip up and bottom surface for the high intensity cooling process as the research object,the flow velocity and pressure variation feature of the strip up and bottom surface were investigated under the different jet velocity of fluid inlet,jet angel,the ratio of the top and bottom surface spacing,and the width of the fluid inlet.Base on the heat transfer symmetry,the variation feature of the strip up and bottom surface local Nusselt number and the change law of the average Nusselt number were researched,and the function relationship between process parameters and the discrepancy of the average Nusselt number or the coordinate values of stagnation point were obtained.It provides the theoretical support for improving the cooling uniformity of the strip thickness direction.(6)The cooling rate of the low alloy plain carbon steel,pipe line steel and dual phase steel,the strip shape after ultra-fast cooling and the microstructure uniformity in the length or thickness direction of the strip were analyzed.The development of the ultra-fast cooling technology for the hot rolled strip better met the requirement of the production and satisfied the requirement of high intensity and uniformity cooling.The work of the thesis was aimed at the development of high intensity and uniformity cooling technology and practical application after rolling for hot rolling strip.The present results have strong practical significance for further optimization of the ultra-fast cooling equipment and of the hot rolling strip improving of the high intensity uniformity cooling technology after rolling for hot rolling strip.The related technology and achievement has been successfully used in Shougang Qian An Steel,Shougang Jing Tang Steel,and Baotou steel,and achieved significant benefit.