Invasive porosity casting defects of bucket teeth castings

Take the bucket tooth sleeve of loader as an example (as shown in Figure 1). The single blank mass of gear sleeve casting is about 6kg, which is produced with Liugong brand mt1450. The process adopts the stacked series casting method of vertical casting (as shown in Figure 2), and 10 pieces can be produced in one string.

During the initial trial production, the crane was used to lift the 1 t leaky ladle for manual pouring. During pouring, the ladle was easy to shake and it was difficult to align with the gate cup. Due to the large pressure head and fast speed, the steel liquid flowing out at the moment of contacting the side wall of the gate cup formed a curl, resulting in air entrainment (mechanism diagram is shown in Figure 3), the sprue was not filled, and these gases were difficult to be discharged in time, resulting in air holes in the casting (shown in Figure 4), Such pores are large in volume and generally 5 ~ 10 mm in diameter.

Preventive measures:

a) Increase the sprue basin, adopt 1 t subcontracting pouring, follow the principle of “slow fast slow”, keep the sprue basin full of liquid steel, so as to ensure that the sprue is always full, and the liquid metal flows smoothly without air entrainment during mold filling. The pouring speed shall be reasonably controlled, and the pouring time shall be controlled at 18 s / string.

b) When designing the process, reasonably arrange the exhaust position of shell mold and sand core, so as to smoothly discharge the gas involved in the pouring process.