| Required workpiece is obtained by hot die forging in the condition that material is put into the pre-heated die model(the temperature is about 200～350℃) after it's temperature(the temperature is about 1000～1200℃) is heated higher than the re-crystal temperature, and huge plastic deformation is produced by powerful pressure and velocity of a hot forging machine. In forging process, the mechanic loading and thermal loading between die and workpiece will lead to the invalidation of dies. The common invalidation types include crack, wear, deforming, erode, fatigue in the condition of hot or mechanic loading etc, the most possible invalidation regions are the place where suffer higher load and where no better lubricating and dispelling heat.Along with the development of modern industry, hot die forging has been playing an important role in manufacturing. The inactivation and lifespan of hot-forging dies is still difficult to be studied because of uncompleted analysis in quantity and quality on many factors. In this thesis, the analysis of hot open-die forging process for cylinder was done by finite element method (FEM), the up die's temperature field was obtained, and the influence of temperature on lifespan of hot-working die was studied.In this thesis, the failure modes and mechanism is analyzed based on the experimentation research, manufacture experience and investigation. Furthermore, we summarized the status quo and deficiencies in hot forging die's lifespan research worldwide, and summarized the research status quo of spray technique and lubricating technique in forging industry. The basic theory of numerical simulation and temperature field simulation was expounded. Moreover, the characteristic of MSC.SuperForge was introduced.By using the professional software MSC.SuperForge, the hot forging process is simulated by considering the difference of initial temperature and heater exchange among up die, workpiece, lower die and environment. The working process was analyzed in dynamic method. Satisfying results which are consistent with the practice was obtained. After simulation, the temperature fields at any time in the forging process were obtained. The mutative rules were summarized, and the influence of temperature to the die's lifespan was analyzed then. We find out that the temperature field plays an important role in shortening the life of forging die, and the main influence is taken place in the surface of die. Further more, systemic simulation on the temperature of surface layer was carried out. By change techno-parameter, the effects of the frictional coefficient, the velocity of forging machine, the original temperature of workpiece, and the original temperature of dies were investigated. The mathematical expressions were given out by curve fitting with the simulation results base on the polynomial least square method in Matlab to find out the rules. The results of the research here can provide reference to prolong the life of hot forging die and optimize the structure of surface of die.By summing up the manufacture experience, theory analyzing in this thesis and numerical simulation, designed a spraying system to spurt cooling fluid and water lubricant onto the surface of dies to cool and lubricate the surface of dies.In this thesis, systemic numerical simulation on hot forging process is carried out. The theory is preciseness. And we draw a fulfilled conclusion. This work can turn traditional way of empirical analysis into effective way of qualitative analysis. The spraying cooling and lubricating system is safe and dependable, it is useful and is proved to be helpful to prolong the life of dies and improve the quality of workpiece.
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