Research On Hot Deformation Behavior And Microstructure-Properties Of As-cast Ring Pieces During Casting-Rolling Forming Process

With the development of centrifugal casting technology as well as hot rolling forging technology, casting-rolling forming process as a kind of energy efficiency, environmental protection and high efficiency new process have been proposed,the refining discipline of cast microstructure and heat treatment process of casting workpieces have been requested meanwhile.This paper has obtained the thermalphysical property parameters of as-cast 42CrMo steel by Jmatpro simulation software and established the material model. Then the flow stress constitutive model, the dynamic recrystallization model and static recrystallization model of as-cast 42CrMo steel were calculated by experimental datas according to single pass and two-pass thermal compression experiment on Gleeble-1500D thermal simulation machine. These models are implemented into the Deform-3D software, the temperature field,stress field and microstructure distribution of as-cast 42CrMo steel during hot deformation process were also simulated. Besides, pre-heat treatment process of as-cast 42CrMo steel was studied then normalizing parmeters and tempering parmeters were established and the experiments were carried out. Finally, the relative performance parmeters tests have been carried out,which has meet the property requirements. Major research findings and conclusions are as follows:(1) By using JmatPro software, the thermalphysical property parameters of as-cast 42CrMo steel were precisely simulated and the material model IS established.(2) The single-pass and two-pass compressed experiments is carried out on the Gleeble-1500D thermal simulation machine,the discipline that influncence various strain rates and temperatures on the flow stress of as-cast 42CrMo steel during hot deformation process has been investigated. Besieds, the flow stress constitutive model,dynamic recrystallization models and static recrystallization models were evaluated by linear regression and other math analysis methods combined with the experimental data.(3) The best hot deformation process parameters of as-cast 42CrMo steel was obtained by analysizing single pass deformed samples'microstructure. The result shows that: On the condition of 1050℃, 5s-1 and deformation degree 0.6, the grain size is further refined from initial 246μm to 28μm on average and the refing effect is the most obvious.(4) The pre-heat treatment process of as-cast 42CrMo steel was established as follow: heat to 880℃hold for 9h then air-cooled to 250℃, reheat to 600℃with the speed of 60℃/h then hold for 8h, furnace -cooled to 350℃then cool in air. The mechanical property tests of as-cast 42CrMo steel specimen after normalizing and tempering treatment have been carried out. The parameters measured are as follows: hardness 257～269HB,tensile strengthσb 870Mpa,yield strengthσs 685Mpa or so, reduction of areaψ45% or so,elongationδs 13% or so and impact energy Akv 28J or so, which has meet the process requirements before rolling.