Research On The Mold Material For The Manufacturing Technology Of The Integral Additive Of Mold Shell And Core

The mold material of precision casting is mainly composed of binder,refractory material and some kind of additives.The mold composed of different binders and refractory materials has different strength properties.The manufacturing method of traditional ceramic molds is from wax mold opening to mold roasting,which has many processes and takes a long time.It is difficult to meet the requirements for the rapidity and flexibility of customized small batch castings.Extrusion molding is a ceramic additive manufacturing technology based on water-based ceramic paste extrusion,layered deposition,and three-dimensional molding.Does not require a separate laser energy system.This method has wide applicability,low equipment manufacturing cost,and has good development potential and broad application prospects.Choosing a suitable material system,preparing a paste with good dispersion and uniform composition,and having good sintering performance are key issues in the field of precision casting.Therefore,this article studies the choice of mold material,the design of ceramic slurry formulation,the process parameters and sintering performance of the extruded sample.From the analysis of the influence of refractory materials,binder types and powder-liquid ratio on the mold performance,it can be seen that the bauxite mold has no cracks and no phase transformation during sintering and cooling,and the mold strength is good.The strength of the silica sol mold for the same refractory material is greater than the bending strength of the ethyl silicate hydrolysate and water glass mold.For the Si30 silica sol casting mold made by the same process,its performance is the best.The material system is a combination of bauxite and silica sol,and the powder-liquid ratio is 2.4.It can be seen from the preparation of the paste and the process of extruding the sample that the solid phase volume fraction,dispersant content and pH value will affect the performance of the slurry.For the system,the ball milling time is preferably8 h.The solid phase The volume fraction should reach 38%,and the amount of dispersant added is 0.4wt%.When 3mL of 10% HCl solution is added,the slurry has the best viscosity and the most stable performance.In addition,it was found that the amount of extrusion of each step of the paste and the extrusion speed in three directions will also affect the structure of the extruded sample.When the speed of theX and Y axes is 20 mm / s,the speed of the Z axis is 5 mm / s.,And the extrusion volume of each step is 0.15 mm,the sample can meet the requirements of extrusion molding.From the experiment of the sample under different sintering conditions,it can be seen that when the sintering temperature is 1000 ℃,the bending strength of the mold is 5.06 MPa,the shrinkage in three directions is 1.83%,1.85%,1.69%,and the porosity is 43.6% As the sintering temperature continues to increase,the flexural strength of the sample remains basically the same,but the shrinkage continues to increase and the porosity continues to decrease,which will cause the quality of the shell to decline,so the sintering temperature is preferably 1000 ℃;Keeping the sintering temperature unchanged,the performance of the mold under different holding times was studied.The performance of the mold was the best when holding at 1000 ℃for 4h.At this time,the bending strength of the mold is 5.56 MPa,the shrinkage in three directions is 2.16%,2.18%,2.05%,and the porosity is 40.5%.