Finite Element Anslysis Of Deformation Compatibility Of Mesostructure In Ferrite/Bainite Dual-Phase Steel

With the development of the construction of pipe used for oil and gas transportation,the pipeline has to conquer so many severe geographical environments.In order to guarantee the pipe can make an excellent performance in all kinds of geographical environment and satisfy all of the demand,the mechanical properties of the pipeline steel must be controlled with enough accuracy.Ferrite/bainite dual-phase steel,which has been widely used in domestic pipeline construction,has been proved that its mechanical properties are related to the deformation compatibility of the mesostructure.It has been clarified that the characterize parameters of mesostructure which can affect the deformation compatibility are related to the parameters of TMCP,so study the effect of the characteristic parameters of mesostructure on the deformation compatibility can help to achieve the precise control of the mechanical properties of ferrite/bainite dual-phase steel.The project is focused on the relationship between the characterize parameter of mesostructure and the deformation compatibility of mesostructure.Both RVE model and abstract model has been built to reflect the characterize parameters of the mesostructure;finite element analysis based on real mesostructure has been used to show the distribution of stress and strain in mesostructure and the formation of strain localization band during the macroscopic deformation.The relationship between the mechanical properties of ferrite/bainite dual-phase steel has been built which can be the fundament of the accurate control of the mesostructure and mechanical properties of ferrite/bainite dual phase steel.The volume fraction of bainite will affect the contribution rate of bainite to stress and strain.When the volume fraction of bainite is relatively low,less bainite can get into plastic state.As a result,the difference of the extent of plastic deformation between ferrite and bainite will be expanded,and the strain localization within the mesostructure will be severer.The results of FEA show that the effect of volume fraction of bainite on the deformation compatibility of mesostructure will be different when the volume fraction of bainite locates in different range.The morphology of bainite will affect the plasticity of bainite and ferrite.The banded bainite can promote the efficiency of the transition of stress between ferrite and bainite,the stress localization in and out of bainite will be increased.As a result,the plastic deformation of bainite can be promoted.On the other hand,banded bainite can restrict the room of ferrite,so the plastic deformation of ferrite can be suppressed at the same time.The differences in mechanical properties between bainite and ferrite will decide the time when the strain localization will form.The excessive mechanical properties difference between the two phases will increase the order of the deformation between the two phases and accelerate the formation of the strain localization,both the plasticity and strength of ferrite/bainite dual-phase steel will be suppressed.