According to the optimized process design, the production process control scheme and on-site construction scheme of sand casting shall be prepared, the production process shall be tracked to ensure that the pouring system is consistent with the process requirements, and the process validation shall be done well.
1. Modeling and box closing control
(1) Modeling control
Qualified molding sand and core sand shall be used as required to ensure that the 24h tensile strength of molding sand and core sand is not less than 0.8 MPa. Sand filling in layers shall be adopted during molding and core making. The thickness of each layer shall be controlled at about 200 mm, fully compacted with wooden rods, etc., and the parts that are difficult to reach by sand mold shall be compacted by hand. After the sand core is trimmed and cleaned, it shall be placed for more than 4 hours. The flow coating method shall be used to apply the alcohol based coating. The sand mold shall be applied with the alcohol based coating 4 hours after the mold is lifted to ensure that the thickness of the coating is about 1 mm. The parts prone to sand sticking shall be appropriately thickened.
(2) Box closing control
The box shall be inspected before the box is closed to ensure that the parting surface and the air outlet core head clay bar are fully compacted and the air outlet holes such as the cover box are unobstructed. After the box is closed, the sprue cup shall be placed correctly to align the sprue cup with the cover box sprue, and to prevent sundries from entering the gating system and the mold cavity.
2. Melting and pouring plan
(1) Melting scheme
The chemical composition shall be determined according to the material and structure of the sand casting, as shown in the table, to ensure that the performance of the sand casting meets the design requirements.
| C | Si | Mn | P | S | Cr |
| 3.0-3.2 | 1.7-2.0 | 0.8-1.1 | ≤ 0.07 | 0.06-0.09 | ≤ 0.20 |
(2) Pouring plan
Two ladle pouring shall be adopted, and the temperature of two ladle molten iron shall be consistent as far as possible, and the temperature difference shall not exceed 20 ℃.
The discharging temperature is more than 1450 ℃, and the pouring temperature is controlled at 1320~1340 ℃. In order to reduce the inoculation recession, Longyi high-efficiency composite inoculant is used.