Study On Vacuum Casting Technology Of Cylinder Head Of 3D Printing

In order to meet the requirements of the development of lightweight vehicles,castings developing towards the trend of integration,thinning,precision and toughening.This requires to improve the mold-filling capacity and ensure the intrinsic quality of castings at same time.For this reason,the traditional casting process has been unable to fulfill the requirements of castings production,especially the production process for complicated thin-walled castings.Vacuum casting method is an advanced casting process,it has some certain advantages in the casting of complicated thin-walled aluminum alloy components.The vacuum can increase the mold-filling capacity of the material and reduce the internal defects so that to improve the microstructure of castings.In the increasingly fierce marketable competition,manufacturers must be able to produce their new products,which are able to fulfill the requirements of users,in the possible shortest time with relatively lower cost.The 3D printing technology,which has some advantages such as easy to modify and can be quickly converted into the actual parts,etc.,can be used to replace the traditional mold processing methods.This will shorten the development cycle of new products and reduce costs and risks of improvements.In this thesis,based on the casting mold which produced by 3D printing method,the principle and method of the vacuum casting technology are analyzed and summarized.The vacuum pouring equipment and technology have been developed for the complicated thin-walled samples.The research about vacuum casting is carried out through sample bars with different wall thickness and shape.The effects of different vacuum degree and pouring temperature on the mold-filling capacity,density and microstructure of castings were studied.On this basis,the production attempt of cylinder head was conducted.The research results show the conclusions as following:(1)With increasing vacuum degree,mold-filling capacity and density of castings increased as well.When the vacuum degree reaches-0.04 MPa,the improvement is relatively more obvious.However,it will not improve any more with further continuously increase of vacuum degree,so selection of the vacuum degree from-0.04 MPa to-0.06 MPa is more suitable.(2)Using tensile test bars,the further verification about the advantages of vacuum carried out by looking for the minimum pouring temperature.It can be seen that casting under vacuum conditions,the temperature can be reduced by 30 ~ 50 ?.With decreasing pouring temperature,the microstructure of the alloy is composed of dendrites and rose-like dendrites,which are gradually transform to spherical or granular shape.The grain was relatively refined with the microstructure became more homogeneous and the performance improved.(3)On the basis of the above research,the production attempt of the cylinder head was conducted through the 3D printing technology.It can be seen that vacuum casting improved problems caused by the gravity casting.Furthermore,quality and indicators of the cylinder head are all meet the technical requirements.In this paper,the vacuum casting equipment and process are studied to solve the problem of defects such as common porosity and low mold-filling ability of sand casting.The advantages of vacuum casting are verified as well.The theoretical basis and technical support are provided for the preparation of complicated thin-wall components.The research has important theoretical and practical significance.