Research status of sand casting simulation in China

Sand casting belongs to metal liquid forming technology. In actual production, sand casting engineers often formulate processes according to previous experience, and lack scientific and rigorous judgment on flow field, temperature field and defect location and size. However, sand casting defects often exist in the body, which is difficult to find by naked eye and existing detection means, This is the root cause of quality hidden dangers and quality accidents in many production units.

In recent years, with the large-scale application of computer numerical simulation technology, sand casting simulation technology has also been carried out on a large scale in sand casting production enterprises. Through three-dimensional modeling, database analysis, visualization technology and other means, various materials and processes are systematically simulated in the stage of metal filling mold cavity, metal solidification The change of flow field and temperature field in the cooling stage of metal, and finally complete the prediction of defect location in advance. Sand casting simulation technology can complete the pouring process simulation as a whole, so as to reduce the trial production cycle and defects, improve the metal utilization rate and reduce the production cost. The main research contents of sand mold casting simulation are as follows:

(1) According to the hydrodynamics theory of metal, the fluidity of metal in liquid stamping process is analyzed, and the distribution diagram of flow field is obtained. It is conducive to the simulation of the whole gating system, so as to avoid the occurrence of sand mold casting defects such as sand flushing, insufficient pouring, air voiding and so on.

(2) Simulation and analysis of temperature field: it analyzes the heat transfer process of sand casting by using the relevant theoretical knowledge of heat transfer, and obtains the temperature field distribution of sand casting in the solidification process, so as to predict the location and size of sand casting defects such as shrinkage porosity and shrinkage cavity of axle housing.

(3) Coupling simulation of flow and heat transfer: Based on the basic principles of hydrodynamics and heat transfer, the heat transfer process is calculated on the basis of simulating the filling process of axle housing, which can predict sand casting defects such as air wrapping, cold shut and insufficient pouring. In addition, the temperature field distribution after sand mold filling can be obtained, which provides initial conditions for the subsequent solidification process simulation.

(4) Microstructure simulation: it is divided into macro, micro and mesoscopic microstructure simulation. The mathematical model is used to calculate the dendrite growth rate, microstructure transformation process and nucleation number, so as to predict the microstructure and properties of sand casting bridge shell.

(5) Stress field simulation: Based on the basic principles of mechanics, analyze the stress field distribution of the axle housing during the forming process, so as to predict sand casting defects such as hot crack, cold crack and deformation.