Research On Shell Mold Casting Process Optimization Of Nodular Cast Iron In Screw Pump

Screw pump is a new type of pump.It has the advantages of compact structure,small size,high reliability,long service life,strong transportation capacity,etc.It has been rapidly developed and widely used at home and abroad.Due to the late development of Chinese screw pump industry and foreign technology monopolies,currently Chinese screw pump products mainly rely on imports,which are expensive and have long supply cycles.They are far from meeting domestic demand.Therefore,the development of our own screw pump products is of vital importance to the development of the screw pump industry.The castings in the screw pump are mostly thin-walled,with uneven wall thickness and complicated structure,and it is easy to form thermal joints in thick-walled parts,which will cause shrinkage porosity defects.The casting materials in screw pumps are mostly ductile iron.Due to its pasty solidification characteristics and the graphite expansion phenomenon during solidification,nodular cast iron is very poor in shrinkage and has a strong tendency to shrink.Therefore,the rejection rate of screw pump castings is very high.Castings in screw pumps have high requirements for surface quality and dimensional accuracy.They are produced by shell casting.This article takes the typical thin-walled ductile iron gearbox and pump body in a screw pump as an example,and uses ProCAST casting simulation software to study its shell casting process.The specific research content and research results are as follows:(1)Establish three dimensional solid model of the site process scheme,use ProCAST software to observe the filling and solidification process,analyze the cause of the high casting rejection rate,and confirm the accuracy of the ProCAST simulation results by comparing with the actual casting defect position.(2)Optimize the shell mold casting scheme of gear box and design the sand mold casting scheme of gear box;obtain the best shell mold casting scheme by optimizing the inner runner diameter and the gating system height;optimize the cold iron setting to obtain the best sand mold casting scheme;both solutions can completely eliminate the shrinkage porosity defects in the casting.(3)Compare the best shell mold casting scheme of the gear box with the best sand mold casting scheme,and consider factors such as process yield and process difficulty to determine the final production scheme as the shell casting scheme.The on-site trial casting of the shell casting scheme was carried out at a pouring temperature of 1430? and a pouring time of 11 s.The obtained casting was of good quality and had no shrinkage porosity defects,indicating that the shell casting scheme was designed reasonably.(4)Design the shell casting method of the pump body.By coating chromite sand on the outside of the shell core,changing the type and position of the riser,the shrinkage porosity defects can be transferred to the inside of the riser,so as to eliminate the internal defects of the casting.On-site trial casting of the best process scheme of the pump body,it can obtain a casting with a complete profile,and after testing,the quality of the casting is good,which indicates that the shell casting scheme of the pump body is reasonable.