Direct hanging sand method
No matter what kind of iron mold it is, when hanging sand, first brush a layer of adhesive paint on the inner surface of the iron mold (see Table 1). Then place the center hole model and use molding sand to compact the sand layer layer by layer. The compactness should be above 90 degrees. Then take out the center hole model and bake it at a low temperature of 100° to 250°C for about 2 hours. After cooling down slightly, apply paint on the surface of the sand coating (the paint is ordinary sand casting), and then dry it thoroughly before use. If cracks occur during the drying process, apply paste to the mold, then apply paint and dry until dry. This process is suitable for single piece and small batch production.

Process features:
1. Iron mold sand-coated casting has the characteristics of sand casting, that is, it has a rigid sand mold shell, which makes the sand mold overall high strength and non-deformation. It has wide adaptability, easy demoulding of castings, reliable positioning and high precision.
2. Iron mold sand-coated casting has the characteristics of coated sand shell mold casting, which is convenient in shaping and
 
It is fast. No matter what kind of casting sand mold, the molding can be completed within two or three minutes. The density of the molding sand and the surface hardness of the casting mold are ensured by the equipment and are always consistent, and there is no need to apply any paint. Not only obtains smooth castings, but also improves the shape and dimensional accuracy of the castings.
3． Iron mold sand-coated casting also has the characteristics of metal mold casting. The iron mold has an obvious cold shock effect during the crystallization process of the metal liquid, which can refine the grain size of the casting, thereby improving the overall strength of the casting. At the same time, due to The existence of sand tires avoids the shortcomings of metal mold casting. Castings will not produce white spots. For iron castings, various materials can be produced in the as-cast state without heat treatment.
4． The casting mold composed of an iron mold and a thin sand tire has high stiffness, small deformation and fast cooling after locking. The resulting casting has high dimensional accuracy, small machining allowance and dense structure. It is especially suitable for the production of ductile iron. In the production of ductile iron The graphitization expansion of ductile iron can be used to self-feed the castings - achieving less and no riser casting of ductile iron to obtain high-quality castings; because the iron mold cools quickly, it is suitable for the production of high-grade pearlite matrix discs, Rod and shaft castings are particularly beneficial.
5. Generally speaking, the hardness of castings produced by iron mold sand coating is about 20 HB units higher than that of castings produced by ordinary casting methods.
6. The waste heat of the iron mold after casting is used to solidify the coated sand produced by recycling, which not only reduces the electricity consumption, but also the casting process presents a closed cycle production state, and the production area is very small (for example, one ton of iron is smelted in one hour) When using (steel) water, a molding pouring area of two to three hundred square meters is enough), no sand treatment equipment is needed, the investment is small, and the results are quick.
7. Due to the chilling of the iron mold, the molding sand will not be over-burned. Not only can the molding sand be reused, but also the phase change of the molding sand (quartz sand) occurs due to the roasting during the pouring process, and the thermal expansion coefficient of the sand is reduced from 15 to 5. Therefore, the old sand generated during the production process can also be recycled and reused, which is in line with the development of circular economy.
  The iron type after being packed together
8. Iron mold sand-coated casting is particularly suitable for the production of medium and small castings in large batches. If the number of changes is small, the overall scrap rate can be reduced to about 3%.
9. The service life of the sand-coated iron mold can reach more than 10,000 times, but due to long-term repeated thermal expansion and contraction and the influence of the casting environment, additional maintenance is required.
Application scope
Any process method has its own uniqueness and limitations, and iron mold sand coating is no exception. During the production of iron mold sand coating, the sand mold is thermally cured using the hot core box method, which requires a certain temperature and time, which affects the production efficiency of iron mold sand coating and is not suitable for the production of large-volume products; the shape of the iron mold sand coating The machine can be said to be a hot core box core shooting machine, so it is not suitable for the production of large and complex parts.