Hot Forging Process And Microstructure Of The F40MnVS No-quenched And Tenpered For Truck Front Axle

Non-quenched and tempered steel has been widely used in automobile parts production because it saves quenching and high temperature tempering process,and has a series of advantages,such as saving energy,protecting environment,low production cost and short production cycle.As an important security component of a truck,the front axle bears a complex alternating load in the driving of the vehicle,especially when the downhill brake,the front axle will bear 2/3 of the vehicle load,so the front axle has strict performance requirements.Fatigue performance must be satisfied.Therefore F40MnVS non-quenched and tempered steel needs to explore a suitable production process to meet the fatigue life requirements of the front axle.This paper takes the front axis of a certain model as the research object.The microstructure and properties of the front axle of F40MnVS non-quenched and tempered steel and the front shaft of 40 Cr tempered steel were studied.On this basis,the forming process of the front shaft of F40MnVS non-quenched and tempered steel was determined by combining cooling process experiment with numerical simulation of austenite grain size evolution of the front axle.So that F40MnVS can replace the original 40 Cr to meet the fatigue life requirements of the front axle.The work is as follows:(1)The mechanical properties and microstructure of the front axle F40MnVS forged non-modulated steel and the 40 Cr front axle of the original tempered steel are compared according to the structural characteristics and performance indexes of the front axle of a truck.The results show that F40MnVS tensile strength of the front axis is close to the front axis of 40 Cr,but the yield strength and hardness are lower than that of the front axis of 40 Cr,and the temperature of the front axle is low after thermal correction.(2)By studying the influence of different heating temperature and holding time on austenite growth,the austenite growth model is established.The effect of cooling process on microstructure and properties was found:when cooling directly after forging,the ferrite fraction decreased with the increase of cooling rate,the ferrite grain and pearlite lamellar spacing decreased gradually,and the hardness increased obviously.When the cooling rate is 15?/s,the pearlite layer spacing is distorted.(3)The effect of different heating temperature on austenite grain evolution and die load during forging process is studied.It is found that the difference of austenite grain size at three different heating temperatures will gradually decrease with the continuous deformation of billet.After forging,the gap between grain size becomes very small,grain is refined and grain becomes more uniform.With the increase of heating temperature,the equivalent force and die load of forgings will decrease,and the die life will be improved.Therefore,the heating temperature of the front shaft of the F40MnVS is determined to be 1250?.(4)A trial production of the front axle according to the process parameters of F40MnVS front axle determined by experiment and simulation,the bench test results show that when the heating temperature is 1230-1350?and the cooling rate after forging is 1?/s,the front axle fatigue performance meets the double index requirements of B₅?300000 times and B₁₀?700000 times.The fatigue life of the front axle meets the standard.