Research Of Shot Peening And Nitriding Surface Strengthing Process On Hot Forging

In addition to enough high strength and toughness， forging die also requires goodwear resistant performance. Based on the research of failure forms of5CrNiMo steelcrank shaft forging die in a factory， it have been found that the main cause of themould rejection is die wear. Therefore it is needed to improve the wearability of mouldto improve mould life. Nitriding and shot peening surface treatment are two commonmethods which got very extensive application because of its low cost and simpleoperation. This paper mainly focuses on the research how to improve the wearresistance of the die through these two methodsIn this study， we first studied the effect of shot peening on5CrNiMo steel.Numerical simulation of shot peening process was used to analyses the effect of processparameters on the distribution of residual stress on surface. According to the shotpeening parameters optimized by the simulation analysis， combined with the actualshot peening equipment， the relative reasonable blasting parameters were selected.These parameters were used to experimental study and actual production. A great dealof experimental research work was conducted to study the property of surfacestrengthening layer， and the results were verified through actual production.The author， in combination with actual production experiences， selected thecatalyst of multi-gas-element and rare earth in tufftride， to analyzes the effect ofnitriding on the wearability of mould. The paper compares and analyses the propertyand microstructure of surface strengthening layer of these two technologies. Throughexperimental study of specimen and tracking the production of experimental die， it hasbeen finally confirmed， the catalyst of multi-component thermochemical in tufftridehas better surface hardening effect and is more appropriate for this5CrNiMo steel crankshaft forging die.In order to further improve the effect of these process，specimen and experimentaldie were surface strengthened with combination of shot penning and multi-componentthermochemical in tufftride treatment。 The paper compares and analyses theimprovement of surface strengthening layer property， and finished cost calculation，finally the optimum process was proposed.This paper analyzed the hardening effect and their associated costs of theseprocesses，and ultimately determined the catalyst of multi-component thermochemical in tufftride has better surface hardening effect than the others， and can save moreproduction cost. So this kind of surface hardening process is more appropriate for this5CrNiMo steel crank shaft forging die，and should be widely applied to production.