Study On Basic Characteristic Of 51CrV4 Spring Steel For Automobile

The research is mainly study of basic characteristic on high-quality 51CrV4 spring flat steel for automobile from actual production line at Fangda Special Steel.Provide technical support for the production and achieve integrated optimization of the entire production process for Fangda Special Steel.The main research contents and conclusions are as follows:The high temperature mechanical properties of 51CrV4 spring steel,was investigated on a Gleeble-3800 thermal simulator.The morphology of the tensile fracture was observed by using scanning electron microscopy between different temperature region.Combination by J-Mat Pro software to research the second phase precipitation condition to analyze the fracture mechanisms.The results show that the 51CrV4 steel has high-temperature brittle zone(1350~1284 ℃),relate to liquid membrane induced by fusing,was melt fracture.low-temperature brittle zone(904~600℃),relate to the precipitation of brittle phase Cr7C3 and Fe3 C as well as Mn/S mass ratio increased,reduced the hot ductility,was typical intergranular fracture.Meanwhile,at single austenite area(1283~905℃)has good plasticity,was typical dimple fracture.The static continuous cooling transformation(CCT)curves were measured using thermal expansion method for 51CrV4 steel.The expansion curves of supercooled austenite during continuous cooling under different cooling rate were determined,simultaneously.With metallographic microhardness method,the effect of different cooling rate on microstructure and performance of 51CrV4 steel was analyzed.The results show that,with the cooling at 0.5 ℃/s,the phases resulted from the cooling transformation are ferrite and pearlite.With the cooling rate at 1 ℃/s,the bainite is obtained.The cooling rate region for getting martensite is between 2 to 30 ℃/s.When cooling rate is up to 12 ℃/s,the product of the cooling transformation is only martensite.Study on the true stress-strain curves determination on 51CrV4 spring steel above different deformation,different strain rate and different deformation temperature.Through single channel experiment and text of thermophysical simulation,analysis influence of deformation,temperature and strain rate on the deformation during hot deformation under stress test conditions.The results show that,with the increasing strain rate,the deformation stress increased at the same experimental temperature.The deformation stress decreased with increasing deformation temperature at the same strain rate.