Microstructure And Property Evolution Of Carbon Steel During Warm Plastic Deformation

Surface oxidation of rolled metal, burnout of alloying elements and difficulty tocontrol bring by hot rolling could be mitigated by using warm rolling to producecarbon steel. Warm rolling is also used to generate superior organization. Theorganization and its dynamic evolution during warm rolling are both different from hotrolling. Flow stress is increased and deformation behavior could be different, and thatis expressed in macro which would affect rolling process. Microstructure evolutionand mechanical properties of carbon steel during warm plastic deformation wasresearched represented by45-steel and65Mn-steel. Diversification of deformationresistance was considered and the rolling force of carbon steel during warm rollingwas calculated. Variation of temperature and rolling force of carbon steel during warmrolling was analyzed and provide the theory basis for the making of warm rollingprocesses and the configuration of mill. The high quality carbon steel that used in theresearch is widely used in basic machinery and equipment manufacturing. Warmrolling make the full use of warn rolling spheroidization organization produced duringmachining. The improvement of product quality promoted the quality of entiremechanical products.Warm rolling process of45-steel and65Mn-steel was simulated on Gleeble-3500which is also used for preparation of warm rolling organization with differentproduction process. The warm rolling organization of steel for experiment wasanalyzed. Mechanism of ferrite recrystallization and dissolving spheroidization ofcementite was investigated. Influence of initial organization and process conditions onspheroidization and recrystallization. Mechanical property of warm rolling was testedand relationship between warm rolling organization and process variables wasdemonstrated and then the control principle of warm rolling process was determined.The results show that: the yield strength, tensile strength and elongation of materialwere improved with different degrees comparing with quenched and temperedproducts in GB/T699-1999. So mechanical property of warm rolling organizationexceed that of quenched and tempered products. Products better than quenched and tempered steel could be produced directly without quenched and tempered using warmrolling.Rheological behavior of medium high carbon steel during warm rolling wasresearched by the unidirectional warm compression experiment and materialmicroscopic mechanism during rheological process was observed and analyzedcombining with stress-strain curve and microstructure. The difference of hot rollingand warm rolling was compared and analyzed. Curve characteristic value and Zparameter and deformation activation energy was calculated. Influence of deformationcrafts on deformation process was also obtained. Mathematical model whose accuracyis consistent with requirements for warm processing equation and deformationresistance was build.Model apply to warm rolling of medium high carbon steel in which rolling forceis calculated in subparagraph was build based on the Kalman-Cailicove solutionconsidering the flow stress distribution and elastic deformation of roll system duringwarm rolling. Warm rolling process of carbon steel was simulated byANSYS/LS-DYNA finite element software for explicit nonlinear dynamic analysis.Theoretical calculations was compared with FEM so that deviation of theoreticalrolling force calculation could be analyzed. The reason for deviation was explained bycomparing and analysis of distribution of rolling force.Questions that may be involved in high quality carbon steel using warm rollingwas comprehensively analyzed. The result show that high quality carbon steel isapplicable in wide range of material. The product could be used in producing strip, barand so on. The warm rolling carbon steel was conducive to implement of continuousannealing online. Multiple product that needed by machining could be producedcombining with different heat treatment. It is realistic and feasible to produce highquality carbon steel using warm rolling.