Operating Procedures for Sand Molding
Operating procedures for sand molding, a common method used in metal casting to create molds for casting various metal objects, involve a series of steps. These steps are designed to ensure the proper creation of the mold and its subsequent use in the casting process. Here are the general operating procedures for sand molding:
1. The molder shall make the sand mold and sand core according to the casting process drawing.
2. Be familiar with and understand the process drawing, correctly receive the model, core box, pouring riser, etc. according to the process requirements, and check whether they are complete.
3. The sand box shall be set reasonably according to the size of the mold, the size of the pouring riser and the cutting amount during oxygen cutting.
4. During molding, the part close to the surface of the mold, that is, the part to be in direct contact with the liquid metal, shall use the surface sand with good performance, its thickness shall be 30 ~ 50mm, and the mold shall be well covered. The molding sand near the gate and riser also needs the surface sand, and the other parts shall use the back sand with poor performance. The surface sand and back sand shall be loose before adding.
5. During sanding, the sand layer between the punch and the mold shall not be too thin, and shall be kept at 20 ~ 30mm. The sand filling of each layer shall not exceed 100mm. The hardness of the whole sand mold shall be reasonably distributed. The molding sand near the box edge shall be stronger than that near the mold, the lower part of the sand mold shall be stronger than the upper part, and the lower sand mold shall be stronger than that of the upper sand mold.
6. If there are concave parts or parts that are not easy to be compacted on the mold, the molding sand of this part shall be compacted by hand or head before sanding.
7. In order to prevent fire escape when pouring molten steel, the edge of the wooden formwork shall keep a certain distance from the inner side of the sand box, which is usually determined by the size of the sand box. See the following table:
8. The parting surface shall be flat, and there shall be no large drape joint, so as to avoid the casting being pulled and cracked by the drape joint during shrinkage and fire running during pouring.
9. The pores for CO2 blowing must be evenly arranged to ensure the reasonable distribution of sand mold hardness. In order to obtain high strength of sand mold, the CO2 blowing time cannot be too long, generally 20 ~ 60 seconds / hole.
10. In order to discharge the gas smoothly when molten steel is poured into the mold cavity, the exhaust must be unblocked. The exhaust hole and exhaust riser shall be inserted during modeling. The vent hole shall not be inserted into the mold cavity to prevent the liquid metal from entering the vent hole and blocking during pouring.
11. In order to prevent being washed away by liquid metal, the sharp part of the cavity (including the gate) must be rounded. If there are places marked with rounded corners on the drawing, it shall be rounded enough according to the dimensions in the drawing.
12. Some weak surfaces on the sand mold, convex places at the corners and near the gate sometimes need to be strengthened by inserting iron nails to prevent the sand mold in these places from falling off during pouring.
4.13 during mold repair, the damaged part shall be carefully repaired with surface sand, and the repaired part shall be firm, accurate, smooth and flat to avoid sand inclusion in the casting caused by the impact of molten steel.
14. In strict accordance with the process requirements, correctly open the gate and riser, and pay attention to their size and quantity. Type of gating system, proportional relationship of section, height of ingate position, etc.
15. According to the process requirements, if the mud core needs to be added with core bone, it must be added with core bone, and if it needs to be coated, it must be coated. The paint must be brushed evenly, smooth and dried.
16. Properly mark the company according to the specified requirements, so as to facilitate the traceability of workpieces in the future.
17. When positioning with the inner box pin, the inner box pin must be vertically driven into the sand mold, and the depth of driving into the lower box shall ensure the smooth development of box fastening.
18. After the sand mold and mud core are made, carefully measure the dimensions of the mold cavity and mud core.
19. Cleaning and Finishing:- Remove any excess material, gates, runners, and risers from the casting.
- Perform any necessary finishing operations such as grinding, machining, or surface treatment to achieve the desired final product.
20. Inspection:- Inspect the casting for defects and dimensional accuracy.
21. Reclamation:- Sand can often be reclaimed and reused in future mold-making processes.
22. Repeat:- Repeat the process for additional castings if needed.
These steps provide a general overview of sand molding procedures. The specific details and variations may depend on factors such as the complexity of the part being cast and the type of metal being used. Proper training and safety measures are essential when working with molten metals and sand molding equipment.
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