Study On Simulation And Casting Process Of Complex Parts Based On 3D Printing Sand Mold

At present,traditional manufacture technology is difficult to produce complex parts,while 3D printing sand casting,as a new casting method,is not sensitive to the complexity of parts.Therefore,combining the advantages of 3D printing with the advantages of traditional casting,it can realize the "integrated,short cycle,high precision and high value-added" manufacturing of casting products,and the advantages of fast production response,high efficiency,and low research cost.This technology can also meet the increasing needs of lightweight,green and intelligent equipments,and has broad application prospects in the fields of automotive,ship,aerospace and other industries.This paper focused on the influence of 3D printing sand mold casting process parameters on the microstructure and mechanical properties of casting aluminum alloy;the conformal casting process of one automotive engine cylinder block casting was designed,which also had been simulated and optimized;based on the simulation results and optimization process parameters,the 3D printing sand casting technology was used to quickly produce the engine cylinder block.The main results were as followed:(1)The microstructure and mechanical properties of casting aluminum alloy were affected by the 3D printing process parameters: proper thickness of the sand mold printing layer,moderate pouring temperature,and no preheating of the printed sand mold after drying,which were beneficial to improve the microstructure and mechanical property of the casting.When the thickness of the sand mold printing layer was 0.5 mm,the printing speed was 25 s/layer,with the single-pass printing,the sand mold performance was better and the porosities of the casting were low;the density of the casting was 2.6503 g/cm3.In the casting of 30 mm wall thickness(ZL101A),when casting temperature was 720 ℃,the tensile strength of as-cast sample by 3D printed sand mold was 131 MPa,and the elongation was 2.2 %.The tensile strength after T6 heat treatment was 229 MPa,and the elongation was 0.5 %,which microstructure of the casting was uniform and small without obvious defects.The overall performance was slightly improved in comparison with the traditional sand mold casting.(2)Design the conformal pouring system of one automotive engine cylinder block casting,using simulation software to calculated and optimized.Compared with the traditional pouring system,the conformal pouring system has faster filling efficiency and more reasonable melt flow.Simulation and optimization of the casting process parameters came to these conclusions: the cast iron cylinder liners should place in the lower part,and the built-in heating rod was heated to 400 ℃.The pouring temperature was 730 ℃,and the pouring speed was 3 kg/s.At this time,the solidification quality of engine cylinder block casting was better,and there were no defects in the key areas.The overall filling time only took 10.67 s,and the total volume of defects was only 0.899 cc.The simulation results had proved that the designed casting process was reasonable and can provide some guidance to actual production.(3)Based on the optimized sand mold printing and casting process parameters,the 3D printing sand mold rapid casting process was used to trial-produce an engine cylinder block casting.The actual production cycle only took 3 to 4 days.The inspection results of engine cylinder block casting show that the casting have no obvious defects,the bonding rate of the cylinder liners and the aluminum alloy material were good(average penetration depth 2～3 mm),and the casting quality was high;after the T6 heat treatment of engine cylinder block casting,the microstructure was uniform and small,the tensile strength and elongation was 278 MPa and 2.3%,and the Rockwell hardness value was 97 HB.In a word,the overall performance was good,and met the evaluation standards of related automotive parts.These results show that the 3D printing sand mold rapid casting process was suitable for trial-produce and production of complex castings,with short production cycle and reliable product performance.