| In order to solve problems encountered in manufacturing forging die usingtraditional method, especially large hydraulic press forging die, such as: difficult tomake hammer forging using die, poor forging penetration efficiency, low hardness afterheat treatment, high frequency showing flaws after heat treatment, high manufacturingcost, massive waste discarded if die failed, and etc.. This paper for the first timeannounced a method, adopting casting steel as a basal body and on a pouring (casting)die cavity, using Bimetal Gradient Layer (BGL)-connecting strength and hardnessgradient-to make forging die, This means pouring (casting) basal body using specialcasting steel (JXZG) as the material of forging die; at the same time, the basic form ofdie cavity is poured out. Then, connecting BGL (the first layer, welding material JXHC1,is strength and hardness gradient transiting layer; the second layer, welding materialJXHC2, is high strength and hardness layer) to make large forging hydraulic pressforging die.This paper studies on forging die and primarily focuses on the requirement anddemand encountered in real production, On the basis of thoroughly researched forgingproperty and process performance, a research is made on material connection betweenbody layer and transition layer, connecting method and strength between two layers, andtransformation pattern of microstructure and property along thickness direction, Then,analyze transformation pattern of material structure property during welding and forging,which obtains rational thickness range of material for transition layer and surface layer.Furthermore, this paper studies stress field distribution and safety on bearing ofconnection area and casting steel basal body. Establish a model that reasonably matcheswith connection layer thickness, acquire a reasonable thickness range for connectionmaterial in different bearing cavity area under sufficient bearing capacity. Thus, makesure the final cavity size for casting steel basal body.The forging die isstudied with this method. The result shows that the tensile yieldstrength of JXZG、JXHC1and JXHC2is respectively520MPa、893MPa and1349MPa.BGL and casting steel basal body have formed stable metallurgical bonding, andthe bonding strength is strong:the strength could reach707MPa; the connection strengthbetween surface layer material and transition layer material could reach1132MPa.Performance and gradient gradually changes in the entire BGL of casting steel basal body. Apply finite element simulation software to simulate welding research on thesurface of casting steel basal body.The minimum welding layer thickness is15mm forcasting steel basal body under this process condition.The study utilizes element finite stimulation software to numerically simulateforging forming process on a50MN hydraulic press using forging die. According to thepattern of temperature field and stress distribution, combine with properties of castingsteel basal body (JXZG), transition layer-welding layer (JXHC1) and surfacelayer-welding layer (JXHC2), the distribution of allowed strength and safety parameterof material from different forging die locations are obtained. Then, the pre-forging dieof beam for a large aircraft lifting compartment, casting steel basal body of final forgingdie, structure model of transition layer and surface layer are designed using method ofBGL on casting steel basal body. The produced forging parts have passed dimension andperformance inspections.The forging die is intact after forging. The trial production hasprovedmanufacturing forging die using this method is rational and practical.Compared with the forging die with5CrNiMo,life time of die is increased;manufacturing cost of die is decreased20～30%. Precision and performance havecompletely reached requirements when using such forging dies; the main failures arefatigue wear on surface of die cavity; collapse, flaw or crack is not visited. The trialproduction has proved manufacturing forging die using this method is rational andpractical. |
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