Advantages and disadvantages of clay sand, water glass sand and resin sand for sand casting

Various types of sand casting have many advantages. And these advantages are especially obvious in large batch and standard shape castings. However, when sand casting is used to produce castings with small batch, complex shape and high quality (such as cast steel joints and complex impellers), there are still considerable difficulties.

Although clay sand casting has the advantages of low price, simple sand mold manufacturing process, easy reuse of used sand, easy to realize automatic production and so on. However, there are still many problems in the production of cast steel joints and complex impellers by clay sand casting. First, because of the high quality of the casting, the requirement of the strength of the mold is high, and the large mold leads to the difficulty of compaction. Second, the shape of the casting is very complex, and the molding process is difficult. Third, because of small batch production or even single piece production, the mold investment is very high, resulting in increased costs. Therefore, clay sand casting is not suitable for the production of cast steel joints and desulfurization pump impeller.

Water glass sand casting is very suitable for the production of large-scale steel castings. Using water glass as binder is non-toxic and harmless, which can ensure the material of castings and is conducive to obtaining high-quality castings. By using the method of organic grease hardening, the mold has high strength and the hardening process is convenient. Therefore, the cast steel joint produced by Beijing Institute of mechanical and electrical engineering has always been made of sodium silicate sand. However, the biggest difficulty of using water glass sand casting is that the spatial structure of the joint is relatively complex, and there are some problems such as difficult to take out the mold and lower the core when using the traditional wood mold modeling and core making. In addition, the mold making process is relatively difficult, and the cast steel joint is basically a single production, so the wood mold can only be used once, forming a great waste. Generally speaking, there are still many areas worthy of improvement in the production of cast steel joints by water glass sand casting.

Resin sand casting has the advantages of good collapsibility, low wet strength, good fluidity of molding sand, easier molding, convenient recovery of used sand, etc. At present, this kind of impeller is mainly produced by resin sand core molding sand casting technology. The impeller manufacturer studied in this paper is Shijiazhuang industrial pump factory, which adopts the method of resin sand core group. The sand core is divided into five parts, each part is made of wooden core box. Assemble the core in sequence. But at present, the serious defects of this method are: high working intensity, long modeling time, and large positioning error, which directly affect the dynamic balance performance of impeller.

Sand casting is a versatile manufacturing process that employs different types of sand mixtures to create molds for metal casting. Among these, clay sand, water glass sand, and resin sand are commonly used, each with its unique properties, advantages, and disadvantages. Understanding these can help in selecting the most appropriate sand type for specific casting requirements.

Clay Sand (Green Sand)

Advantages:

  • Cost-Effectiveness: Clay sand is relatively inexpensive and readily available, making it a cost-effective option for sand casting.
  • Reusability: The sand can be reused multiple times, reducing waste and further lowering the production costs.
  • Versatility: Suitable for casting a wide range of metals and alloys, making it highly versatile for different casting applications.

Disadvantages:

  • Lower Precision: Clay sand molds may not be as precise as those made from other materials, potentially leading to a lower surface finish and accuracy.
  • Moisture Sensitivity: The presence of moisture can affect the mold’s stability and the quality of the cast, requiring careful moisture control.

Water Glass Sand (Sodium Silicate Sand)

Advantages:

  • High Dimensional Accuracy and Surface Finish: Water glass sand provides molds with higher dimensional accuracy and a smoother surface finish compared to clay sand.
  • Faster Setting Time: The chemical reaction of sodium silicate with CO2 results in a faster setting time, which can improve production efficiency.

Disadvantages:

  • Limited Reusability: The sand mixture is harder to reclaim and reuse than clay sand, leading to higher material costs.
  • Environmental Concerns: The disposal of used water glass sand can be more challenging due to the chemical binders involved.

Resin Sand

Advantages:

  • Superior Strength and Precision: Resin-bonded sand molds exhibit high strength and can produce castings with superior dimensional accuracy and surface finish.
  • Flexibility in Hardening Process: The hardening process of resin sand can be controlled chemically or thermally, offering flexibility in mold and core production.
  • Reduced Defects: The use of resin sand can lead to fewer casting defects, such as gas holes and sand drops, improving the quality of the final product.

Disadvantages:

  • Higher Cost: The resins used in the sand mixture are more expensive than the natural binders in clay sand, increasing the cost of the sand.
  • Environmental Impact: The chemical binders can pose environmental and health risks during handling and disposal, requiring stringent safety measures.
  • Complex Reclamation: Reclaiming and recycling resin sand is more complex and costly due to the presence of chemical binders.

Conclusion

Choosing the right type of sand for sand casting depends on several factors, including the desired accuracy, surface finish, production volume, and cost considerations. While clay sand offers cost-effectiveness and versatility for a wide range of applications, water glass sand and resin sand provide higher precision and better surface finishes at the expense of higher costs and environmental considerations. Understanding the advantages and disadvantages of each sand type allows manufacturers to make informed decisions that best suit their casting needs and production goals.

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