Research On The Forging Process And Microscopic Quality Of Complex Long-axis Forgings

With the development of the automotive industry, the need of the complexlong-axis forgings in automobile, such as connecting rod, crankshaft and front axle,grows rapidly. During manufacture process, such defects as covered fold, not-fullfilling, big grain size, low material utilization and etc. are often found in the massproduced forgings with complicated shape and high quality demands. So a highlyprocess demand is needed. In the present study, the forging process of a typicalcomplex long-axis forging in automobile, connecting rod, is designed. FEM methodis used to simulate and predict the forging process, metal flow and microstructures.The detailed studies are as follows:(1) In consideration of the low material utilization in the forging process of agiven connecting rod, based on the plastic forming theory and roll forging theory,the roll forging process is designed and the optimization process is proposed.(2) Using FEM model, the simulated results in each forging step are comparedto the corresponding real forging stocks in order to verify the accuracy of the FEMmodel.(3) The metal flow, effective stress-strain filed and forming force in theprocess of roll forging, pre-forging, final forging are simulated with FEMsimulation method. The stock of the roll forging is optimized by revised cross-areamethod, the appropriate dimension of blank is defined and the material utilizationis increased.(4) The dynamic recrystallization model of40Cr is inserted to the FEM model.The validity of the this model is examined with the compared results of the meangrain size of the deformed zone after the first roll forging step between simulatedand real experimental stocks. Based on the model, the mean grain size and itstendency of each forging step are predicted.