INFLUENCE OF CONTROLLED FORGING AND COOLING ON THE MICROSTRUCTURE OF NON-QUENCHED AND TEMPERED 1538MV STEEL FOR CRANKSHAFTS

The effects of forging and the cooling parameters on the microstructure of non-quenched and tempered 1538MV steel were studied using thermal simulation tests. With an increase of the deformation and a decrease of the deformation temperature, the austenite grains were refined, and the volume fraction of ferrite improved. With the increasing of the cooling rate, the austenite grain growth is significantly restrained, and the pearlite lamellar spacing is refined simultaneously. Therefore, the cooling process should be strictly controlled after forging. The cooling rate before the ferrite phase transition should be fast, while that during the phase transition should be slow. This is beneficial to the refinement of the microstructure and the full formation of ferrite, and the abnormal microstructures, such as bainite and martensite, are avoided. The numerical simulations show that the deformation of the finished forging process is very important for the filling of the die cavity and non-overloading of the equipment. The deformation of the finished forging should be reasonable, and the deformation temperature should not be too low. The above research results provide an important basis for the optimization of the forging and the cooling process for non-quenched and tempered 1538MV steel.