Research On Titanium Alloy Electromagnetic Induction Heating Auxiliary Incremental Forming Technology

Titanium alloys are widely used in the manufacture of aerospace parts because of their excellent comprehensive properties.The conventional hot forming method of titanium alloy is expensive in equipment,complicated in process,and has a long manufacturing cycle.Sheet metal numerical control incremental forming technology has the characteristics of single piece,small batch,and moldless rapid prototyping,which has a good application prospect in the production of aerospace parts.In order to realize the digital rapid forming of difficult-to-form materials such as titanium alloys at room temperature,this study proposes an electromagnetic induction heating assisted incremental forming technology,taking TC4 titanium alloy as the research object.The detailed investigation has provided useful guidance for the practical application of the subsequent electromagnetic induction heating assisted incremental forming technology.The main research contents and related conclusions are as follows:(1)An electromagnetic induction heating assisted incremental forming system was constructed,and the forming mechanism of sheet metal was explored by a combination of theory and experiment.The results show that the shear deformation of TC4 material in the process of electromagnetic induction heating assisted incremental forming has occurred,and the thickness of the formed part conforms to the cosine law.The 1mm TC4 sheet was subjected to low and medium frequency electromagnetic induction heating.The temperature difference between the two sides of the sheet was not obvious.The metallurgical structure on both sides of the formed part is equiaxed.(2)The electromagnetic simulation software ANSYS Maxwell was used to simulate the magnetic field and eddy current field distribution of induction coils of different structures.The appropriate induction coil structure was selected based on the eddy current field extreme value as a standard.State magnetic-thermal coupling analysis explores the effect of different heating parameters on the temperature field.The results show that the induction coil with inverted T-shaped magnet can effectively gather the magnetic induction lines and obtain better heating effect.The temperature field distribution increases from the center of the induction coil to the edge of the sheet first and then decreases,and the temperature is greatest at the position of the induction coil radius.The temperature of the heating zone on the sheet increases as the induction current increases,the induction distance decreases,and the heating time increases.(3)In this paper,the experimental investigation on the forming performance of TC4 sheet electromagnetic induction heating assisted progressive forming was carried out.The orthogonal experiment was used to explore the influence of each process parameter on the forming temperature.The results showed that the induced distance had the most significant effect on the forming temperature,followed by the induced current.The effect of various process parameters on the forming limit of TC4 sheet was further explored by the control variable method.The results showed that: the appropriate combination of induced current and induced distance,a layer feed of 0.4mm,a large feed speed,and a medium size diameter of the tool head helps to increase the forming limit of the sheet.(4)Experimental investigation on forming quality of TC4 sheet by electromagnetic induction heating incremental forming.The influence of different process parameters on the geometric accuracy and surface accuracy of forming parts was analyzed.The friction mechanism of single-point incremental forming process assisted by electromagnetic induction heating was investigated and shown that the friction state of single-point incremental forming process assisted by electromagnetic induction heating zone was mixed friction.Through the testing of the forming performance of different lubricants,the suitable lubricant for electromagnetic induction heating progressive forming was found.A hemispherical forming tool head was designed to improve the friction state in the forming zone and surface quality of the formed part.The mechanical properties of the formed part were analyzed.The results of the test showed that the hardness of the material generally increased after forming,and decreased with the increase of the induced current,the tensile strength generally decreased,and the microstructure of the formed part was changed slightly.When the induction current is 35 A and the induction distance is 12 mm,a molded part with reliable strength and good forming accuracy can be obtained.