Study Of Shell Mold Casting Process On Castings Of The Crankshaft

Shell mould casting process has the advantages such as, good casting surface quality, high dimensional accuracy, small machining allowance, high production efficiency etc. It has been widely used in crankshaft casting production in developed countries. With the development of Chinese auto market and intensive competition, the international major automobile companies push to make the auto parts localization. Many enterprises clearly put forward that the castings of crankshaft must be produced by using shell mould process.TR Company is the largest crankshaft manufacturer in China. The research and application of shell molding process is the inevitable choice during the process of involving international markets, and also it can improve the process control level and shorten the gap with international companies. It will maximize the advantages of shell molding process and improve the economic benefits and core competitiveness through the study of shell mould casting process.In this paper, the reason that caused slag inclusion and surface inclusion in M270 crankshaft castings produced with shell molding process is analyzed systematically by referring foreign and domestic research on the shell mould process and practice, combining the actual production practice in company and using the tools such as brainstorming, fishbone diagram and PFMEA etc.Through series of improving actions, such as improving the purity of charging materials, using scrap steel and carburant, controlling quality of slaging-off, high temperature molten iron holding process, improving nodulizing effect and quality, improving pouring method and pouring temperature, optimizing the design of gating system and using double filtering system to improve the ability of slagging-off of gating system, the rejection rate of slag inclusion was decreased from 4.35% to 0.63%. The weight of gating system for each shell mould decreased 1.2 kg. The process yield increased by 2.2% around. And the cost can be saved 360 thousand RMB every year.Adopting the same melting and control method that solving the casting slag inclusion, using the resin sand with good quality for shell making and zircon power coating to spray the surface of shell molds, adding no rare earth nodularizer and 3-8 magnesium ferrosilicon nodularizer as the scale of 2:1, through above measures, the spheroidizing quality and stability was improved. The surface degradation of casting was controlled under 0.2mm. The rejection rate of poor surface layer was under 10%. And also the metallographic structure of crankshaft casting can completely meet the technical requirement of international famous engine manufacturer.