Through the production verification of product k141 and the implementation of lack of vision countermeasures, it can be seen that combined with the filling capacity of liquid metal, the solidification mode of steel castings and the shrinkage of steel castings, it is difficult to design a perfect sand casting process under the guidance of sand casting process manual. Sand casting products are complex and diverse, with different sizes and shapes. Theoretical knowledge and reference books can only provide one design idea, which can not be targeted, and can not ensure that sand casting workers can design perfect sand casting process for each product.
According to defect analysis and countermeasure verification, the following suggestions for improvement of design method can be obtained in eliminating shrinkage cavity and porosity defects of steel castings through sand casting process design:
(1) When designing the riser, the module method is used to calculate the riser module. The module magnification mentioned in the process manual cannot be rigidly observed. The module of the top riser can be enlarged to 1.15-1.25 times that of the steel casting, and the module of the side riser can be enlarged to 1.2-1.3 times that of the steel casting.
(2) When the top riser is set as the heating riser, the riser base shall be set, and the height of the riser base shall be set as 10mm-30mm. The height of the riser base shall be gradually increased according to the increase of the heating riser module. At the same time, the riser base should not stick to the standard circle, but should be adjusted according to the different structure of steel castings. The key is to form a mode of decreasing modulus between the riser, riser base and steel castings in the feeding range. Only in this way can we ensure that the riser can have enough liquid metal and enough feeding channels to feed the steel castings.
(3) The heating riser or concealed riser shall be used as the side riser, and attention shall be paid to the selection of riser neck size and shape. Standard riser neck can be used for steel castings with standard shape. When the corresponding part of riser neck is a part with complex structure, the size and shape of riser neck shall be adjusted appropriately according to the structure of steel castings. It is necessary not only to ensure the mode of decreasing modulus between the side riser, riser neck and steel castings, but also to flexibly adjust the size and shape of riser neck.
(4) When designing thin-walled steel castings, special attention should be paid to feeding and chilling at the corner. Priority should be given to setting risers and subsidies to ensure good feeding effect. When it is difficult to design risers, cold iron can be set to quench.
| Number | Project | Attention |
| 1 | Riser modulus magnification | The modulus of side riser is enlarged by 1.2-1.3 times, and that of top riser is enlarged by 1.15-1.25 times. |
| 2 | Heating riser | The riser base is set with a height of 10-30mm, and the shape can be set arbitrarily according to the needs. |
| 3 | Riser neck | The side riser and riser neck are set according to the product structure and cannot be limited to the regular shape. |
| 4 | Thin wall structure | Risers and subsidies are preferentially set for feeding, and cold iron auxiliary chilling can be set |
The table is a summary of the matters needing attention in the actual design of sand mold casting process.