The casting process of crankshaft affects the quality of crankshaft. The casting process parameters include sparing injection temperature, winding injection speed, sand layer thickness of iron mold covered with sand, cooling conditions of iron mold and so on. The effects of pouring temperature and sand layer thickness on the temperature field of nodular cast iron crankshaft will be explored to determine the most appropriate casting process.
At present, the pouring temperature used by ZHY casting is 1420 ° C (cold type). In order to explore the influence of pouring temperature on the temperature field of this type of nodular cast iron crankshaft, change the pouring temperature for simulation calculation, obtain the temperature field at 1450 ° C and 1400 ° C (Fig. 1) and the solidification time at each position of nodular cast iron crankshaft (Fig. 2) respectively, and make comparative analysis.
Observe the temperature field calculated under three pouring temperatures of 1450 ° C, 1420 ° C and 1400 ° C. At 500s, the casting under the pouring condition of 1400 ° C is cooled first, the solidification time at the edge of the crank is only 0.4s, the surface temperature of the crank is basically 900 ° C, the temperature at the central axis is about 1080 ° C, the surface is completely solidified for about 100s, and the slow solidification parts such as hot joints need about 400s to be completely solidified; Under the pouring condition of 1420 ° C, the solidification time of the crank edge is about 40s, the temperature of the crank surface changes from thin to thick from 950 ° C to 1050 ° C, the temperature at the central axis is also higher than the former, the temperature gradient of the casting surface is large, the solidification time gradually increases from outside to inside and from thin to thick, and the complete solidification time of the surface is about 200s, The solidification at the hot spot is slower and the range is larger than that at 1400 ° C; Compared with 1420 ° C, the change trend of temperature field and solidification time under 1450 ° C pouring condition is basically the same, and the temperature difference is small. Only at 500s, the temperature at the hot spot is higher, up to 1150 ° C, which is still in the solidification range.
From the analysis of temperature field, it can be concluded that the process parameters of casting at 1420 ° C are more appropriate. If the temperature is too low, the solidification speed of the edge of the nodular cast iron crankshaft is too fast, the fluidity of the liquid metal is poor, and the feeding can not be carried out in time, resulting in serious casting defects such as shrinkage porosity or insufficient porosity; If the pouring temperature is too high, it can not only cause a waste of energy, but also slow down the solidification speed at the hot joint, so the hot joint can not get better feeding, so it is not suitable.