Iron mold sand coating process and common quality problems in original mold casting

1. Original mold design structure

The original mold structure design of t9000-c iron mold sand coated casting cylinder block in 6T series is completely copied from the original resin sand casting mold. After trial production, there are different degrees of casting porosity on the ribs and bosses on the upper surface of the casting. Some casting porosity can be found only after shot blasting, and even subcutaneous casting porosity can be found only after processing, as shown in Figure 1;

2. Preliminary analysis of casting porosity formation

During the initial trial production of this model, almost all products have casting porosity in varying degrees, and 80-90% of the castings in the trial production stage have casting porosity defects. After the casting is shot blasted, the casting porosity are often distributed on the cylinder top of the casting and the upper surface of the water jacket of the upper half of the casting. As shown in the figure above.

In iron mold sand coating process, casting exhaust is the weakness of iron mold, but as long as the exhaust is reasonably arranged, it is completely possible. The casting porosity formation analysis is that the sand core intrudes into the casting due to poor exhaust, which is an invasive casting porosity.

1.1 During pouring, after the casting porosity in the sand core are surrounded by molten iron, a large amount of gas can not be discharged out of the box, but a large air holding phenomenon is formed in the upper half of the mold, which invades the non solidified molten iron and forms casting porosity;

1.2 Too long pouring time and slow flow rate of molten iron are also the reasons for the formation of casting porosity. In general, after the pouring speed exceeds 45s, the proportion of casting porosity formed in castings is very high and there are more locations;

1.3 Molten iron flows in the mold cavity, resulting in suffocation.

3. Iron mold process and original mold design

See Figure 2 for the original exhaust design scheme of the upper half. Disadvantages: there is no exhaust needle at the core head of the water jacket; The number of stomatal needles is small; Whether there are 2 exhaust needles in the middle of the core head, and the exhaust is not smooth; The peripheral core head is not provided with exhaust, so the peripheral core head gas cannot be discharged out of the box.