The three-dimensional models of casting, sand mold and cold iron are meshed by finite element method. After being imported into procsat, the overlapping surfaces of various components are repaired to make the interfaces in good contact. According to the specification of sand casting of mud pump body, set the material properties of sand casting of each mud pump body and the heat transfer coefficient of each interface, then set the operating parameters and start the analysis of solidification process.
Fig. 1 shows the simulation results of the temperature field at each time during sand casting solidification of the mud pump body (cut off value is set above the solidus temperature). 1 (a) at the end of pouring, it can be seen from the figure that the local temperature of the mud pump body decreases greatly during pouring, and the surface temperature of the stiffener drops below the solidus line under the chilling action of cold iron, and solidification has taken place; 1 (b) is the temperature distribution diagram when 50% of the solidification is completed. At this time, the stiffener has fallen below the solidus line and is completely solidified. The temperature of the end face of the sand mold casting flange of the mud pump body and the bottom of the sand mold casting of the mud pump body has also fallen below the solidus line and partial solidification has occurred, while the temperature of the upper part of the sand mold casting of the mud pump body remains near the liquidus line and there is basically no solidification; 1 (c) is the temperature distribution diagram of mud pump body and pouring riser of sand mold casting when 70% of solidification is completed. The temperature of sand mold casting has basically dropped below the liquidus and is in the state of solid-liquid coexistence. Moreover, it can be seen from the figure that the heat dissipation effect of external sand mold of sand mold casting is better than that of internal sand mold of pump, and the internal temperature of sand mold casting is higher than the external temperature, And the temperature inside the bottom of the sand mold casting is higher than the upper part of the casting, and the sand mold casting does not form a good bottom-up temperature gradient as a whole; 1 (d) is the temperature distribution diagram when 85% of the solidification is completed. At this time, the sand casting body has basically solidified. Although the temperature of the metal in the riser is higher than the liquidus temperature, the solidification has not been completed, the part near the riser neck has basically solidified, the feeding of the riser is basically completed, and the feeding of the riser is not fully utilized.
Figure 2 shows the distribution of solid phase rate of mud pump body and pouring riser of sand casting during solidification (cut off value is set below 70%). 2 (a) is the distribution diagram of solid phase rate when the solidification is completed by 20%. It can be seen that the solid phase rate on the surface of the casting is as high as 70%, and partial solidification has occurred, but the solid phase rate at the main part is less than 10%, which is basically not solidified; When the solidification is 50%, as shown in Figure 2 (b), at this time, the solid phase rate at the stiffener and the flange of the mud pump body is about 100%, which has been completely solidified, while the solid phase rate of the sand mold casting of the mud pump body is distributed in the range of 30% – 70%, which is in partial solidification state. The simulation results are consistent with the results of the temperature field in Figure 1 (b); 2 (c) 70% of the solidification is completed. At this time, the solid rate in most areas of the sand castings of the mud pump body is higher than 70%. Most of the sand castings of the mud pump body have been solidified, but many isolated liquid phase areas have been formed. The area between the upper #2-1 riser and #1 riser and #2-2 riser of the sand castings of the mud pump body has been solidified, but the solid rate in the lower part of the sand castings of the mud pump body is lower than 70%, It has not solidified yet. It can be seen that the span of the three risers is too large, which exceeds the feeding range of the riser, and #2-1 the solid rate near the riser neck is higher than 70%. At this time, the riser has lost the feeding capacity; It can be seen from Fig. 2 (d) that when 85% of the solidification is completed, the solid rate of the sand casting body of the mud pump body is basically higher than 70%, and the sand casting body of the mud pump body has basically completed the solidification, but the solid rate of the area in contact with the inner sprue is still lower than 70%, and the solidification has not been completed.
Figure 3 shows the solidification time distribution of each riser of sand mold casting of mud pump body. It can be seen from the figure that each riser solidifies from the periphery to the center, and the final solidification area is the riser center, but #1, #2-1, #2-4 riser solidifies longer at the bottom riser neck than at the riser root, forming an isolated liquid phase area. The feeding channel is interrupted in advance, and the riser neck solidifies prematurely, Shrinkage porosity and other defects are easy to form in the riser root sand casting. The design of these risers is inappropriate and needs to be improved.
During solidification simulation, thermocouples are set in the sand casting #1 riser of the mud pump body. The position is shown in Figure 4. 1 is the sand casting, 6 is the riser center, and six measuring points are evenly distributed. Fig. 5 shows the cooling curve of each temperature measuring point obtained from the simulation. The analysis of the simulation results shows that the cooling rate of each temperature measuring point is 2 < 3 < 1 < 4 < 5 < 6, and there is no cooling rate gradient towards the center of the riser. The cooling rate of temperature measuring point 1 located in the sand mold casting of the mud pump body is greater than that of temperature measuring points 2 and 3 located in the neck of the riser and less than that of temperature measuring points 4 and 5 located in the center of the riser, During solidification, the riser neck solidifies in advance, resulting in the formation of an isolated liquid phase zone in the sand casting of the mud pump body. Therefore, the cooling rate of temperature measuring point 2 is less than 1, the feeding effect of the riser is poor, #1 the riser design is unreasonable and needs to be improved.
