Structural Predictive Of Continuous-annealing And Cold Rolling For Low-carbon Sheet

Cold rolled low carbon steel sheet is mainly used in automobiles, householdappliances and other industries, the combined cold deformation and annealing processeffect the microstructure and properties of the final products, but its organization regulatedis mainly achieved by annealing after rolling. For cold rolling production process, therolling speed is fast, the sheet after rolling is close to the final product. It is a series ofstructral transformation process when heated to a temperature above Ac1and subsequentcooling, these determine the final organization state of low carbon steel, and alsodetermine mechanical peroperty. So it become the hot issue study for structraltransformation predicting and controlling of cold-rolled sheet during rolling and annealingheating and cooling process.In the paper, taking cold rolling base plate of SPHC as research object, establishedrelated mathematical model and combining with some experiments studied rollingdeformation and organization evolution process for annealing after rolling theexperimental steel, the results can be used as the basis for constituting annealing processand the established model can provide auxiliary process design for annealing.Cold rolled deformation of low carbon steel determines the final product shapeorganization evolution in the heating process after rolling, rolling deformation wassimulated on the four high reversible rolling-mill in the laboratory, combined with theroom-temperature tensile, microhardness testing and microstructure observation,analysised the work-hardening mechanism and its effected on the microstructuralevolution and mechanical properties, established the deformation resistance model andenergy model, provided reliable data and information for structral change and simulationcalculation of the subsequent heating process.Researched on the performance of the cold-rolled low carbon steel after the annealing,after measured the strain hardening performance for three directions of annealed sheet(along the rolling direction, perpendicular to the rolling direction, a direction of45°withthe rolling direction), established the best deformation range of recrystallization annealed for cold-rolled low carbon steel, it improved internal mechanism of recrystallizationannealing producing excellent performance of strip steel.From the principle of phase transformation, calculated the phase interface’sconcentration, driving force of phase change, starting temperature of phase change andother thermodynamic parameters during heating austenitic inverse phase transformationprocess with ultra element model, established models include the bredperiod model phasechange, change amount model, austenitic grain size prediction model, combining resultsof the physical simulation experiment, analysised the influence principle for austenizationwith heating rate, heating temperature and holding time, provided a strong reference forproducing excellent performance of cold rolled low carbon steel.From the essential characteristics of the cold rolled low carbon steel, diffussed theprinciple of structral changes for diffusion and non-expanding-type phase change duringthe cooling process, transformation thermodynamic and kinetics model of proeutectoidferrite and martensitic transformation, analyzed the influence regular for supercooledaustenite transformation with cooling rate, compared with the experimental results andverified the accuracy of calculation model, provided important theoretical basis fororganizations predicting and controlling of producing high strength and high toughnessproducts with cold-rolled low carbon steel using the continuous annealing production ofResearched cold deformation, crystallization annealing after rolling, the austeniticinverse phase transformation and subsequent cooling process, established structraltransformation mathematical model of heating and cooling process with cold rolled lowcarbon steel, it has a certain theoretical reference value and importance for organizationpredicting and controlling process.