Offline Simulation And Data Analysis Of Laminar Cooling System For Hot Strip Mill

As a main cooling mode of controlled cooling after hot strip rolling,laminar cooling has a direct impact on the microstructure and phisical properties of the hot strip.This thesis takes a domestic laminar cooling line as the research object,establishes cooling model,and develops the off-line simulation software.Simulation analysis on the main influencing factors of cooling temperature during laminar cooling of strip steel are carried out and it has a practical significance for the designing of cooling technology of the hot rolled strip.The main work of this thesis is as follows:(1)One-dimensional finite difference temperature model along the thickness direction of strip is established and the boundary conditions,initial conditions and thermal physical parameters of the model are studied.Based on the basic theory of heat transfer,the heat transfer model is established for the strip surface.The modes of it include the jet impingement zone,the film boiling zone,the air cooling zone.(2)An off-line simulation program for laminar cooling is developed,which consists of self-learning function based on set parameters of historical strip production,predicting function of cooling curve of strip in cooling zone,pre-setting function of number of open valves in cooling header and real-time dynamic setting function of the strip header after the mill exit.The visual interface of the simulation program is programed by MFC to realize the function of inputting the cooling parameters and displaying the simulation results.The difference between the simulated temperature and the measured temperatrue at entry of coiler is within ±15 ℃.The accuracy and reliability of the simulation system meet the site requarement.(3)Based on the off-line simulation system of laminar cooling for hot-rolled strip,the main influencing factors of coiling temperature,such as strip thickness,temperature after rolling and ratio of opening valve of single header,are simulated and analyzed separately.The influence of each variable factor on coiling temperature is obtained: with the increase of rolling thickness of strip,the proportion of water-cooled section in cooling zone increases and the cooling capacity increases;The variation trend of cooling capacity decreases and the coiling temperature of strip increases with the increase of rolling thickness of strip.With the increase of the ratio of single manifold to open valve,when the ratio of single manifold to open valve is in the range of 25%-75%,the ratio of single manifold to open valve is proportional to the cooling capacity of cooling section.Above 75%,the increase of cooling capacity of cooling section is not obvious.Therefore,when the strip steel is thicker,changing the ratio of single manifold to open valve will have a great influence on coiling temperature.With the increase of the final rolling temperature,the cooling capacity of the main cold section will increase with the increase of the final rolling temperature of the strip until the cooling section is fully opened.