Study On Splitting And Properties Of Forged Bimetallic Steel Connecting Rod

Fracture splitting processing technology as the most advanced connecting rod manufacturing technology,its quality and performance are critical to the engine.But the requirements of fracture splitting material of connecting rod are very harsh,it is necessary to require the connecting rod to brittle fracture,but also to ensure that the connecting rod has a strong comprehensive mechanical properties.In view of this problem,the bimetallic composite casting technology of connecting rod can break through the limitations of fracture splitting materials in a certain extent,so that high-carbon steel,aluminum and titanium alloy can be used for connecting rod splitting.But in the process of forging is likely to cause the interface fracture,cracking,and the fracture area can not achieve brittle splitting after forging.In order to solve the problem of bimetallic composite casting in forging process,this paper studies the forging process of 25 steel and T10 A composite connecting rod casting.The results show that through the bimetallic forging treatment can make the casting sample structure is dense,the joint surface quality is good,the mechanical performance is improved,the compound crack connection actual production needs.The main work and conclusions of this paper are as follows:(1)First,the steel bimetallic castings were prepared by investment casting.Then,the castings were subjected to forging treatment and heat treatment under different process parameters.Then,the properties of microstructures,interfacial elements and interfacial strength and hardness were studied to study whether the forgings meet the performance requirements of the cracked linkages.Finally,the bimetallic forgings were subjected to cracking and reloading tests.(2)The bonding properties of bimetallic composite casting and forging interface were studied,and the optimum casting and forging process parameters were selected.The results show that when the casting material temperature is suitable and the thickness of the cracked material are within a certain range,the surface of the bimetallic composite casting has no casting defects,and the interface can be fused and bonded to form a diffusion layer with acertain thickness.In a certain forging ratio range,the specimen has a tendency to elliptical deformation,the fracture zone has a certain tension,the bimetallic interface does not fracture,the interface always maintain the metallurgical combination,can meet the requirements of bimetallic forging.(3)The changes of microstructures,interfacial strength and interfacial micro-hardness of the interfacial interface under different forging process parameters were studied.It is concluded that the forging temperature and the forging ratio have a great influence on the cracking of the bimetallic interface.The cooling method has a significant effect on the microstructure,strength and diffusion of the element in the interface area.The quenching and tempering treatment reduces the interface micro-hardness and strength of the area,improve the toughness of the connecting rod and the overall performance,but also to ensure that the fracture splitting material can still brittle fracture.(4)The splitting and reloading tests of bimetallic forgings under different cracking tank parameters were studied.The results show that the sectional shrinkage of the fracture is 1.47%,the fracture surface is flat,no dregs,no steps and other defects,with obvious brittle fracture characteristics;in a certain force to reassemble the sample,the length of the reassembled specimen is increased by 0.23 mm than the original length,less than the 0.5 mm error requirement required for fracture splitting connecting rod,which indicating that the forged sample meets the assembly requirements of fracture splitting connecting rod.The results of the splitting test and the reassembly test also validated the reasonableness of the forging process.