The Mechanism And Methods To Alleviate Thermal Stress Of Hot Forging Die

The working condition of hot forging die is very bad, its service life is very lowgenerally. The cost of the pieces and the economic efficiency of the manufactory wereaffected directly. The impact forging holds the dominant position in the forgingprofession. There is a bigger disparity between average service life of hot forging dieof our country and the international advanced level. Therefore, how to enhance theservice life of hot forging die and how to reduce cost of the pieces are the questionsof hot forging profession awaiting to be solved urgently.The hot forging die simultaneously withstands the periodic thermal load and themechanical load, which causes thermal stress and mechanical stress separately. Thethermal load is the main reason which causes damage of hot forging die. Therefore,this means the important social economic significance to study the mechanism andthe methods to alleviate thermal stress of hot forging die and providesthermodynamics basis theroy on material design and the manufacture craft for the hotforging die which has long service life.The following topics were studieded in this dissertation. These topics include:the temperature distribution and heat transfer characteristic of hot forging die; thepeak temperature of mold cavity surface layer; temperature difference peak betweencavity surface layer and near surface layer; theory expression on peak thermal stressof hot forging die. The methods to alleviate thermal stress of hot forging dieaccording to influential parameters of the formula about thermal stress, and thesimulation using the DEFORM-2D program were analysed. The preliminary theoryinstruction and the manufacture methods for making the hot forging die which haslong service life were proposed in this dissertation.The methods to alleviate the thermal stress of hot forging die proposed in thisdissertation are as followings: reduceing temperature difference value between themold cavity surface layer and the near surface layer; selecting the better hot forgingdie material; developing new function material; improving craft parameters.The concepts of the gradient function hot forging die and the polymetallic hotforging die was proposed on the foundation of bimetallic hot forging die. The polymetallic hot forging die which could be realized easier in production practice andits structure and manufacture method were introduced. New idea about selectionmatreials, the material component designning, the structural designning and the.manufacture method of hot forging die was introduced.