Study On Microstructure Evolution And Numerical Simulation Of Hot Deformation Process Of Casting Alloy Steel 40CrNiMo

The main purpose of material processing is "forming" and "modification".To obtain good mechanical properties is the urgent need of modern society.Casting and Forging composite technology as a new processing technology,have overcomed some shortcomings of the traditional single casting or forging process,sush as,long process,low utilization of materials,large industrial cost,which has a good industrial development prospects.Therefore,the microstructure of materials under the conditions of Casting and Forging composite process is an urgent problem.In this paper,40 CrNiMo cast steel as the research object,use the Gleeble-3500 thermal simulation machine,obtaining the flow stress curve of which different locations in the deformation temperatures from 800 ? to 1100?,strain rates from0.0011s-to 101s-,discussing the influence factors of the flow stress behavior,establishing the constitutive equation,dynamic recrystallization model and hot processing map.Simulation the metal mold casting pouring process and the cutting tooth isothermal extrusion process of 40 CrNiMo alloy with ProCast,DEFRORM software respectively,discussing the microstructure evolution rules,and puts forward appropriate cutting teeth hot working parameters.Provide the reference for the research of casting composite process technology.Get the conclusion as follows:(1)With the increase of temperature and decrease of strain rate,the materials stress is reduced,percentages and recrystallization grain size of dynamic recrystallization increases.With above conditions,the dynamic recrystallization behavior of 40 CrNiMo casting steel are more likely to happen.For 40 CrNiMo alloy steel casting bar,if diameter less than or equal to 42 mm of which,initial grain size can not influence on the flow stress.Due to dendritic segregation of the casting materials,microstructure appears banded structure after hot compression.(2)Calculates the growth and nucleation parameters of 40 CrNiMo alloy.For which,the metal mold casting process using a higher pouring temperature,faster casting speed,smaller heat transfer coefficient,the casting shrinkage porosity defect becomes more,and take lower pouring temperature,bigger heat transfer coefficient,stronger chilling ability of cooling medium,the casting microstructure becomes more dense.(3)After the DEFORM software secondary development,simulate 40 CrNiMo cast steel cutter tooth isothermal extrusion process.When the deformation temperatures choosing 950 ?,the strain rate chooseing 11s-,workpiece degree of grain refinement is the best,in the hot processing map above recommended range.