For the convenience of research, the pouring system is classified into top pouring, bottom pouring and step pouring according to the position of molten iron in the mold cavity.
For large iron castings, the top pouring type is mainly the deluge gate. The pouring method has the following characteristics:
(1) The molten iron has a great impact on the bottom of the mold and has a lot of contact with the air, which is easy to cause casting defects such as porosity, cold beans, oxide inclusions, etc.
(2) The solidification mode of casting is from bottom to top, which improves the feeding capacity of riser.
(3) . the spatter is large during pouring, which requires high side wall strength of the mold
(4) Quick filling and convenient operation.
Based on the above characteristics, the system is mainly used for cylinder castings with high casting height and some cylinder castings. In the actual production process, in order to reduce the impact of molten iron on the bottom, refractory bricks are often placed in the right gate position, with good effect.
For the bottom pouring type, it is usually the reverse deluge gate, which has the following characteristics:
(1) The molten iron has less impact on the mold and will not cause splashing.
(2) , the molten iron rises slowly from the bottom to the top, the cavity is easy to vent, and the molten iron is not easy to oxidize; however, the rising direction is just opposite to the feeding direction of the riser, which reduces the feeding capacity of the riser.
(3) The temperature distribution of the casting is even, and the metallographic structure is even
It can be seen from the above characteristics that the system is mainly used for the cylinder castings with high surface requirements and small height and large bed castings.
The stage gating system has the following characteristics:
(1) . the hot metal filling is stable, and the cavity gas is easy to discharge.
(2) The temperature of molten iron in the upper part is higher than that in the lower part, which improves the feeding capacity of riser.
(3) Reduce local overheating near the inner gate.
(4) , complicated modeling and difficult design.
Therefore, the stepped gating system is often used in large castings with complex structure and large height.
In the actual production, the appropriate gating system is often selected according to the shape and quality requirements of castings. However, for the shrinkable parts, Yulin type and step pouring system are often used.