In order to reduce the process cost, the mold filling process and casting cooling process were studied respectively. The Nodular Cast Iron Flywheel Casting and nodular cast iron crankshaft casting are analyzed and verified by experiments. Study the optimization of iron mold sand coated casting process by numerical simulation, and predict the possible defects such as shrinkage porosity, shrinkage cavity and slag inclusion before tooling manufacturing. In this paper, the German casting numerical simulation software MAGMAsoft is used to simulate and analyze the iron mold sand coated casting process. Combined with theoretical data and experimental verification, the conclusions are as follows:
(1) Shrinkage cavity and shrinkage porosity defects are generally formed in the thick part of the final solidification of the casting. Due to the lack of sufficient liquid iron supply from the outside, the shrinkage and expansion at the same point are separated in time. From a macro point of view, the basic cause of shrinkage cavity in the casting is that after the internal sprue is frozen, the volume of liquid shrinkage and solidification shrinkage in the casting shell is greater than the volume of casting shape reduced by solid shrinkage of the shell.
(2) General rules of gating system design for iron mold sand coated casting: for the iron mold sand coated casting process with one mold and multiple parts, the runner design is not only related to the structure of the casting itself, but also considers the layout of the casting in the iron mold; Generally, slag collecting bags or serrated protrusions are set at the outlet of the inner gate (for slag retaining): for crankshaft castings, the inner gate mostly adopts narrow and high arch section, which can make the gating system play the feeding role of the riser after the mold filling; The distribution of the inner gate should be set in combination with the structural characteristics of the casting: according to the filling flow information provided by the numerical simulation, the flow rate and filling state can be effectively controlled by changing the gate ratio.
(3) The iron mold sand coated casting of Flywheel Casting adopts the balanced solidification theory and the riser free process, which makes good use of the self feeding effect of the casting in the solidification process, solves the problem of shrinkage cavity and porosity, and improves the process yield of Flywheel Casting. In the production of iron mold sand coated casting of Flywheel Casting, the reasonable layout of sprue in gating system is helpful to improve the distribution of temperature field. The shape, size and distribution of hot spot of flywheel casting are simulated and calculated by magmasofi software, which can provide an intuitive and reliable basis for the process design of iron mold sand coated casting.
(4) In the process design of iron mold sand coated casting of Flywheel Casting, we should not only consider the reasonable distribution of temperature field, but also pay great attention to the rationality of molten iron flow field. In this way, it can be ensured that in the process of pouring and filling, in the process of rapid filling, the flow of molten iron will not produce eddy current as much as possible, and the rapid and stable filling: after the molten iron is filled with the mold, the molten iron in the mold will be calm, reduce or eliminate the eddy current as soon as possible, so that the pouring system can well feed the molten iron in the mold.
(5) The pouring experiment verifies the accuracy of the simulation results, and the gating system design schemes B and C are feasible; Experiments show that the temperature field and flow field distribution during mold filling can be adjusted by changing the number of internal gates and opening direction, so that the liquid metal can fill the mold smoothly, form a temperature field distribution conducive to balanced solidification, and finally obtain a dense and good casting.
(6) The cooling process of nodular iron crankshaft was studied. The cooling curves of nodular cast iron crankshaft castings at different unpacking times were measured by experiments. The best unpacking time is 10 ~ 15min. With the continuous improvement of the production line, the continuous improvement of the degree of automation and the acceleration of the production beat, the unpacking time will become easy to control. In this way, it will be possible to stably produce as cast qt800.3 crankshaft without adding alloy elements.