Submerged Gate Casting Method And It's Application

Submerged gate casting method means the sprue gate is submerged to a specified distance below the surface of the molten metal in the mold during the filling process.The gate would be moved vertically in synch with the rising of the free surface of the mold liquid by using an automated mechanical system.It could avoid the need for a complex filling system,which is convenient for designing,manufacturing and assembling the mold.Combined with the additive manufacturing technology which could produce complex coated sand mold,it would be suitable to produce complicated castings.It is a digital casting technology,which is highly integrated with the CAD/CAE,the process detection and the control technology.The ladle or mold is moved upwards or downwards by the elevator to ensure that the gate subimerges below the molten metal surface to a specified distance.A submerged gate casting equipment has been designed and manufactured,which included the construction department,the pouring systenm,the calculation software and the controlling system etc.It could be used to do the PIV test in the laboratory or pour the molten metal(such as aluminum alloy and ductile iron)in the laboratory and the foundry plant.Based on the self-developed sbumeged gate casting equipment,the subsequent researches and applications could be carried out.The submerged gate filling processes were investigated through the use of particle image velocimetry(PIV)measurements,numerical simulation and castings production.The results showed that the submerged gate filling can improve the mold filling conditions,which may reduce the occurrence of inclusion defects during casting production.The liquid free surface in the mold rose slowly and smoothly during the filling process,which could reduce the occurrence of oxide film inclusion defects.The flow velocity decreased from the gate to the mold,which may reduce the severity of the liquid impingement that causes sand wash defects.The liquid flow inside the mold,with the exception of the flow path region,was primarily quiescent and the distance from the submerged gate to the free surface was relatively small.Therefore,low density slag in the liquid could be carried to the liquid free surface by the fluid flow and by the slag's buoyancy.The filling capacity and the feeding capacity of the fixed gate pouring(top pouring and bottom pouring)and the submerged gate pouring methods were investigated.By top pouring method,the fluid flow was turbulent during the filling process which would bring turbulent fluidity length results.By bottom pouring method,the free surface of the liquid metal in the mold was smooth from the bottom to the top,but the liquid metal temperature decreased with the rise of the liquid level,which would decrease the filling capacity and the feeding capacity.By submerged gate pouring method,the liquid metal in the mold rose up slowly and smoothly during the filling process,and it had higher temperature in the higher region,which could promote the filling capacity and the feeding capacity for both short freezing range aluminum alloy(ZL102)and long freezing range cast aluminum alloy(ZL203).The solidification characteristic of ductile iron was studied by means of pouring some prototypes in coated sand molds.Results showed that it was very hard to design the feeder exactly,and the unsuitable feeder would cause shrinkage in the casting.Based on the submerged gated casting method,the low temperature molten ductile iron could be poured into the complicated coated sand which was produced by the additive manufacturing technique.The results showed that it had no shrinkage in the complicated casting.The surface appearance,the precision accuracy,the microstructure and mechanical properties all achieved the design requirements.It could be concluded that the complicated ductile iron casing without runner and feeder could be produced by the comprehensively.