Solidification Temperature Field Numerical Simulation of Wear-Resistant Cast Ball Based on the MAGMA (1)
Liang Bing—Li Ye Gen
(Mechanical and Electrical RepairFactory，Jinduicheng Molybdenum Group Co., Ltd, Huaxian714102, Shaanxi, China)
Abstract：The solidification process of the wear-resistant cast baIls made by metal mold was simulated using the software of temperature field numerical simulation. Based on the study of the cast ball solidification process’s temperature distribution law by improving the casting process, the defects such as shrinkage and dispersed shrinkage were eliminated, which guarantee the quality of the cast ball.
Keywords： numerical simulation；temperature field；wear-resistant cast balls；metal mold
There are serious shrinkage porosity and shrinkage cavity in the inner part of low chromium alloy white cast iron wear-resisting cast ball produced by a factory. In the process of ball casting, the parameters of the gating system, such as the location and size of Sprue, have a great influence on the yield and quality of the ball. Because of the casting process’s particularity, casting quality can only be confirmed in the later period. The numerical simulation of the temperature field during casting solidification can predict the temperature distribution of liquid metal during mold filling and solidification and predict the position and shape of the shrinkage cavity in casting; the casting process scheme and parameters can be adjusted according to the simulation results. In this study, Magma simulation software was used to model and simulate the casting ball. The structure and size of the metal mold, the gating and riser, and the sand sleeve were optimized, and the shrinkage porosity and the shrinkage hole were eliminated.
The object of study is a wear-resistant cast ball with a diameter of 120 mm, which adopts a scheme of 12 cast balls with one mould and a sand sleeve heat preservation riser to increase the density of the cast ball and the service life of the die, the structure of the metal mold of the cast ball is shown in Fig. 1. The liquidus temperature of the material is 1150 °c; the solid phase temperature is 1090 °c, the pouring temperature is 1350 °c, and the ambient temperature is 20 °C. The thermophysical properties of the material used in the calculation are shown in Table 1.
2.Original process plan
Initially, the ball casting process is shown in figure 2. After cutting the cast ball, it was found that there were obvious shrinkage porosity and shrinkage hole in the casting ball, and the position was inclined to the side of the riser.
After simulating according to the original process, it was found that in addition to forming a closed loop in the riser area, the isotherms of the actual solid temperature also formed a closed loop in the side of the riser with the ball center deviated from the center, so that porosity or keyhole occurred in the closed-loop, it is necessary to improve the process, will lead to defects in the riser.