STUDY OF SOLIDIFICATION THERMAL PARAMETERS OF 430 FERRITE STAINLESS STEEL BASED ON 3D－CAFE METHOD

The dendrite tip growth kinetic coefficients and Gauss distribution parameters for3D-CAFE simulation are determined according to the main compositions of 430 ferrite stainless steel and the macrostrueture forming under the experimental condition of slow cooling.Based on the repeated computation with different heat transfer coefficients,the heat transfer coefficient under slow condition is determined when the solidification structure by above simulation computation is basically the same as the experimental one under slow cooling.The temperature fields and flow fields of 430ferrite stainless steel during the solidification process under the conditions of slow cooling,air cooling and water cooling were analyzed by use of 3D-CAFE method,respectively.The results show that the temperature field of solidification process under slow cooling condition is the most uniform and the solid-liquid region is the widest,followed by air cooling condition,while the temperature fieldunder water cooling is quite non-uniform and the solid-liquid region is the narrowest.The maximum solidification rates are 2.3 mm/s with slow cooling,3.0 mm/s with air cooling and 3.3 mm/s with water cooling,respectively,which are obtained in the center of the castings.The maximum flow rate is obtained in the center of casting with the value of 8.9 mm/s under slow cooling condition,and the maximum flow rate is 9.8 mm/s near the side wall under air cooling condition,while the maximum flow rate is 4.6 mm/s at the position with the 3/5 distance from the side wall under water cooling condition.The solidification structure of casting is composed of almost all equiaxed grains under slow cooling condition,and only a few equiaxed grains exist in the centre of casting under air cooling condition,while the solidification structure of casting consists of coarse columnar grains under water cooling condition.