As the original sand mold casting process adopts the bottom pouring process, as shown in Figure 1, through comparative analysis, it is found that the sand mold casting belongs to the thin-walled part with complex cavity, which is difficult to process. It adopts three box modeling and has poor molten iron filling capacity, which is easy to produce shrinkage defects at the inner half shaft. During the solidification process of the axle housing, due to the temperature difference in the cavity, There is an isolated liquid phase area at the position of the axle shaft oil seal seat in the sand casting axle housing, which makes it impossible to solidify at the same time at this position, resulting in shrinkage defects. In addition, the original pouring temperature of the axle housing is required to be 1550 ℃, the original pouring time is 25s, and the axle housing shall be unpacked below 200 ℃.
As can be seen from Fig. 1, the red part is the sand casting gating system and riser feeding system, and the green part is the chill solidification chilling system. The sand casting process adopts bottom pouring. The main disadvantages are that it is difficult to pour and fill, resulting in local shrinkage defects.
As shown in Figure 2, the product belongs to a complex box thin-walled part. For cast steel products, it is difficult to control defects, which brings great pressure in subsequent processing, inspection and sealing inspection. The one-time inspection qualified rate is less than 30%. Sand casting defects are mainly distributed in the inner half shaft depression.
Through the analysis of the original design structure and technology of sand casting axle housing, it is clear that the pouring and analysis surface of axle housing adopts horizontal type, the pouring temperature is determined as 1580 ℃, the dimensional tolerance of sand casting axle housing adopts ct12 grade, and the linear shrinkage of sand casting axle housing is 2%. For the inner cavity size of the core head, the length of the left core head in the horizontal direction is 50mm, the length of the right core head is 50mm, and the inclination of the left and right core heads is 3 °; The length of the upper core head in the vertical direction is 50mm and the length of the lower core head is 30mm; The inclination of the lower core head is 1 °, and the inclination of the upper core head is 4 °.