At present, the production of nodular cast iron crankshaft mainly adopts iron mold sand coating casting. The filling, solidification and cooling process of castings can be completed under ideal conditions by reasonably matching the weight of iron mold, the wall thickness of iron mold and the thickness of sand coating. It can realize the stable production of as cast nodular cast iron crankshaft, avoid the deformation of crankshaft caused by heat treatment process, and simplify the production process. The iron mold sand coated casting process has fast crystallization and cooling speed, which makes the grain of the casting refined, so the mechanical properties and service properties have also been significantly improved. In addition, due to the good rigidity of iron mold, it can effectively change the graphitization expansion direction of nodular iron during solidification, which is conducive to obtain compact castings and realize riser free casting process; At the same time, due to the good rigidity of the iron mold and the difficult deformation of the mold cavity, the accuracy of the casting is greatly improved.
Shell mold iron filled shot casting is similar to iron mold sand coated casting, which can meet the stable production requirements of various high-grade crankshafts. At present, the shell mold manufacturing process is still developing, and the sand shooting process and shell making process are constantly improved. For example, some European countries use laser sintering to manufacture shell mold. Its principle is to use the characteristics of uniform laser heating and flexible use to produce castings with complex structure.
The above two processes are of great significance to realize the stable production of high-strength nodular cast iron crankshaft. It can also be organically combined with alloying to improve the comprehensive mechanical properties of crankshaft. The boxing time and cooling mode after boxing can also further improve the pearlite content in the crankshaft matrix, refine the pearlite sheet spacing, and then improve the performance of castings, but strict process control is required in production.