Sand mold casting process design of large bearing pedestal

The material of the bearing seat is ZG310-570, and the production nature is mass production.

1. Sand casting process scheme

The sand casting belongs to large thick wall parts. According to the production program, the process scheme of sand casting is adopted for production. The upper and lower molds are made of fake boxes, and the sand is filled mechanically and manually. The sand mold is made of phenolic modified furan resin self hardening sand; Alcohol based coating is adopted; The parting agent is manually coated with silver graphite powder for demoulding.

2. Sand casting process design

2. 1 Determination of parting surface

According to the structural characteristics of the bearing pedestal, three box curved surface parting is adopted. The parting scheme is upper, middle and lower three box shape, as shown in Figure 1. The lower parting surface is a curved surface, which is modeled with a false box, that is, first make a template and put it on the upper mold, and then fill sand to make the lower mold. In this way, due to the support and positioning of the false box at the bottom of the upper mold, the dimensional accuracy of the lower mold is guaranteed, at the same time, the production efficiency is improved, and then turn the box to make the upper mold; The upper parting surface is plane.

2. 2. Design of pouring and caving system

In the process design of sand casting, the gating system is selected as an open stepped gating system, which is poured with the bottom ladle. According to the material of sand casting, it is determined that the gate cup is made of refractory bricks, and the gating systems are connected with ceramic pipes. The size of each element in the gating system of the sand mold casting is calculated by the flow blocking section design method, and the diameter of each unit refractory ceramic tube in the gating system is determined according to the calculated data.

It is set to use riser feeding and cooperate with cold iron to strengthen sequential solidification. The general open riser is selected as the riser. According to the solidification shrinkage rate of sand cast steel, the dimensions of 1, 2, 3 and 4 risers are preliminarily determined as follows: the diameter of 1 and 3 risers is 323 mm and the height is 485 mm. The diameter of 2 riser and 4 riser is 336 mm and the height is 485 mm. The placement position of pouring system is shown in Figure 2, and the placement position of cold iron is shown in Figure 3.

Shrinkage rib, also known as cutting rib, is designed to prevent hot cracking of sand casting. It is mainly used in the production of sand casting steel. Specific reference [4] design, thickness t = (1 / 3 ~ 1 / 4) δ= 65 mm( δ Is the thickness of the auxiliary wall of sand mold casting), the bevel length L = (8 ~ 12) t = 520 mm, and the interval d = (15 ~ 20) t = 975 mm. From the minimum interval of 975 mm, it can be concluded that only one cutting rib can be set and arranged symmetrically, as shown in Fig. 4, which is the position diagram of shrinkage rib.

2. 3 Sand core design

From the three-dimensional diagram of the sand mold casting, it can be seen that the middle inner cavity of the sand mold casting needs to be cast. A cylindrical sand core can be designed, and the core head is square; There are four inner cavities to be cast on the two-week fixed seat. The shape is made according to the inner cavity of sand mold casting. There are air holes in the middle of the sand core. Fig. 5 is a three-dimensional view of the sand core.

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