Research On Design Method Of Pouring Riser For Investment Casting Based On Proportional Solidification

Since the development of the portional solidification technology in the 1970s,it had been used less in the investment casting.The process yield of the series of three pass stainless steel castings which were produced by investment casting in a company at Shijiazhuang was 20%~30%,and there were shrinkage in some casting.In the paper,the pouring risers of the series of investment castings were improved by proportional solidification technology,and the improved process was simulated by ProCAST to improve the process yield and eliminatie the shrinkage,and the general method was found to design the pouring risers of three pass castings.In the process of simulation using Pro CAST,the accuracy for the heat transfer coefficient of theinterface between the casting and the mold shell directly affects the correctness of the simulation results.In this paper,taking the production result as the simulation target,the heat transfer coefficient of theinterface was determined to be 500~700 W/(m~2·?)by inverse verification method,which layed the foundation for the simulation and optimization of the later process plan.The four castings'process were improved based on portional solidification technology with the single-factor method to control the variable of the modulus ratio and riser deviation factor,and the improved process was simulation analyzed,and finally the relationship between modulus ratio and riser deviation factor when the diffient hot spots were fed by risers:When the ratio of the center distance and the sum of the diameters of two hot spots is not less than 3,the two hot spots are required to feed with two risers respectively,and the max of riser deviation factor is proportional to modulus ratio;The max of riser deviation factor increase with the decrease of hot spot when the modulus ratio is identical,and the riser deviation factor decreases when there is small hot spot;The hot spot can be well fed when the modulus ratio in 0.8~1.0.it is suggested that the riser deviation factor should be less than 1.6 for safe.When the ratio of the center distance and the sum of the diameters of two hot spots is less than 3,the two spots can be well fed with one riser when the modulus ratio is 1 to the larger riser;When the size of two hot spots are same or similar,the riser is placed in the middle of the two heats;When the size of two hot spots are diffient,the riser is placed near the larger hot spot,and the location of the riser is in the max of riser deviation factor for two hot spots respectively.