The thermophysical parameters of glass quartz sand mold used in actual sand mold casting production were tested by means of experiments, and the correctness of the parameters was verified by numerical simulation. The solidification and cooling process of large cast steel frame produced by sand casting is numerically simulated and analyzed. The main conclusions and results are as follows:
1) The three-dimensional heat transfer mathematical model of sand mold casting solidification process is established, the heat transfer boundary conditions in sand mold casting process are analyzed, and the temperature and stress fields in sand mold casting solidification process are solved by finite element method; The applicability of the test method of thermophysical parameters is analyzed.
2) The appropriate test method of thermophysical parameters is selected, the test device for testing the thermophysical parameters of sand mold is designed, the temperature field of sand mold in the process of heat transfer is tested, and the distribution of sand mold temperature field which can be used for calculation and simulation is obtained. Based on the basic mathematical model of one-dimensional heat transfer, the specific heat and thermal conductivity of sand mold are calculated by using the measured reverse method. The obtained data can be used in numerical simulation to form a database of thermophysical parameters for simulation.
3) The interface mode between ProCAST software and preprocessing software is analyzed, and the best interface mode is obtained. The interface heat transfer coefficient of sand mold heat transfer process is inversely calculated by using the reverse module. Through the numerical simulation of sand mold temperature field, it is proved that the thermophysical parameters and interface heat transfer coefficient obtained by the measured reverse method are reliable.
4) Analyze the sand casting process of the frame, establish the three-dimensional finite element model of numerical simulation of sodium silicate sand casting process of large cast steel frame, and carry out the pretreatment of numerical simulation, so as to provide reliable data for the numerical simulation of temperature field. The distribution of temperature field in the frame solidification process is analyzed. The results show that the frame solidification starts from the protruding place on the outside and the edges and corners of the column. The feeding channel in the solidification process is cut off about 8 hours after pouring. It is less likely that shrinkage cavity and porosity defects appear in the frame sand casting process.
5) The stress field distribution of sand mold casting frame during solidification and cooling is simulated and analyzed. The hot crack trend of sand mold casting frame at the root of large and small risers and transition fillets is small. After using the hot crack potential analysis, it is found that the possibility of hot crack is small during solidification; The residual stress at the root of the large riser in the cooling process of the sand casting frame is the largest, which must be properly handled in the process of handling and cutting; The maximum deformation in the length direction of the sand mold casting frame appears in the right end beam, the width direction appears in the middle of the column, and the deformation in the height direction is relatively uniform.
By measuring the temperature field of sand mold, the formation of one-dimensional heat conduction process of casting sand mold is the most difficult to ensure. Although the method of thermal insulation material is used to avoid heat dissipation in other directions in the test process, the error in the test process is inevitable due to the limitations of test equipment and test materials.
The filling process in the actual sand mold casting production is not considered in the numerical simulation process, and there are still some differences between the analysis of temperature field and the actual sand mold casting production. If in the later numerical simulation analysis of sand casting process, combined with the simulation of sand casting filling process, the simulation process can be closer to the actual production, and the simulation results have more guiding significance.