Study On Dynamic Recrystallization Behavior And Sulfide Evolution Of F45MnVS Non-quenched And Tempered Steel

Sulfur-containing non-quenched and tempered steel has the advantages of saving energy,reducing emissions,and avoiding cracking caused by the tempering process.However,it also has the shortcomings of insufficient strength and toughness,so further research work is needed.This article took the F45MnVS non-quenched and tempered as-cast steel produced by Nangang as the research object,and used the Gleeble-3500thermal simulation testing machine to perform a single compression test under different deformation temperatures,strain rates and deformation amounts.Through the above methods,the high temperature plastic deformation behavior,the evolution law of the original austenite grains and sulfide inclusions were studied.The data obtained from the Gleeble simulation machine was plotted as flow stress curves,and established as a constitutive equation of F45MnVS non-quenched and tempered steel.The flow stress curves have similar characteristics under different thermal deformation conditions.With the increase of the amount of strain,the true stress value increases rapidly first,then begins to decline after reaching the peak,and finally falls to a range to remain stable.Besides,the magnitude of peak stress increases with increasing strain rate and decreases with increasing temperature.The constitutive equation was established relying on polynomial regression to obtain the functional relationship between model parametersα,n,Q,A and the dependent variableε.Comparing the calculation results with the experimental results,it was found that the two results are highly consistent,indicating that the model can effectively reflect the flow stress change of F45MnVS non-quenched and tempered steel during hot compression.In order to overcome the deficiency of strength and toughness of F45MnVS non-quenched and tempered steel,the method of refining grain can be used to improve the strength and toughness of the material.In this paper,picric acid was used to place the sample in a water bath for heating corrosion.The effect of deformation temperature,strain rate and deformation amount on the grain size of the treated sample was analyzed by Zeiss microscope,and verified by numerical simulation.The results show that low temperature,high strain rate and large amount of deformation are favorable to obtain smaller austenite grains.The cutting performance of sulfur-containing non-quenched and tempered steel is affected by the morphology,quantity and distribution of sulfide inclusions in the steel.In order to analyze the influence of thermal deformation conditions on sulfide inclusions in the process of thermal compression,the distribution of sulfide was observed by Zeiss microscope,and the number and length width ratio of sulfide were calculated by image analysis software.The results show that the morphology,quantity and distribution of sulfide in F45MnVS non-quenched and tempered steel are relatively good at 1050℃,0.1 s^-1 strain rate and 56%deformation.