According to the mass, the cast iron parts of cylinder block can be divided into small cylinder body iron castings with the mass less than 200kg; the small and medium-sized cylinder body iron castings, with the mass distribution of 200-1000kg; and the large-scale cylinder body iron castings, the mass is divided into > 1000kg. On the basis of quality judgment, the following four processes are recommended for cylinder block iron castings: hot side riser and bottom injection open process; top duckbill multi riser, middle injection closed open process; top duckbill multi riser, step closed open process; no riser, ladder semi closed process.
Hot side riser and bottom injection open process is the traditional pouring and riser technology of cylinder block iron castings, which has the advantages of simple structure, convenient production and low process cost. However, the surface of sand mold is easy to sinter, the temperature gradient and residual stress distribution of cylinder block iron castings are not reasonable, and shrinkage porosity and pouring failure are easy to occur. Therefore, this scheme can not be given priority in use, only when other process schemes can not be applied, and can only be applied to small cylinder block iron castings. If it is used for large cylinder block iron castings, it may lead to sand mold surface sintering and is not conducive to the overall feeding of cylinder block iron castings.
The top duckbill multi riser, middle pouring closed open or step closed open pouring process are widely used in small and medium cylinder block iron castings. During the pouring process, the temperature distribution of the casting is uniform and reasonable, and the sand mold is not easy to sinter. In particular, the middle pouring closed open casting process scheme adopts the form of first closing and then opening, taking into account the advantages of closed and open type, and the comprehensive process is the best. In order to reduce the erosion effect of molten metal, the stepped pouring scheme can be used for the cylinder body with large vertical height.
The riser free and ladder semi closed process is mainly used in medium and large cylinder block iron castings. At the height of the gating system, there are not less than two layers of internal runner, which can inject molten iron at different heights. It can improve the temperature gradient distribution of castings and reduce the possibility of casting cracking. However, it is difficult to design and clean the stepped runner, so we should pay attention to it when using it.
The feeding theory and feeding process of cylinder body iron castings were introduced. The problems existing in the design process of feeding riser of cylinder block iron castings were statistically studied. The typical feeding technology of cylinder block iron castings and the use of chill were introduced. Then the typical Pouring Scheme of cylinder block iron castings was statistically studied. In the process of gating system design, the sectional area of gating system and the inner runner were analyzed Finally, the design principles of typical casting process for cylinder block iron castings are summarized.