Application of water glass sand in the foundry industry

As an essential sand material in the foundry industry, water glass sand has played an important role in the production of castings since its advent. It is a foundry sand with specific properties formed by mixing water glass (aqueous solution of sodium silicate) as a binder with sand in a particular proportion. This article will discuss the application of water glass sand in the foundry industry in detail, from its historical background, raw material preparation, process flow, performance characteristics, application fields, common problems and solutions.

1. Historical background and development

Casting technology has been an essential part of the development of human civilization since ancient times, and sand casting is the mainstream technology. From early ceramic mold casting to modern sand casting, casting materials have evolved from natural sand and clay to various organic and inorganic binders. As a kind of inorganic binder, water glass sand has been popular in the world since the early 1950s and has become an essential innovation in the foundry industry. However, with the rise of resin-bonded sand, water-glass sand was once challenged. However, in recent years, due to the increase in environmental awareness and the rise in resin prices, water glass sand has once again attracted attention and has been given new life in continuous improvement.

2. Raw material preparation and ratio

The preparation of water glass sand first requires the preparation of raw materials such as water glass, sand and possible catalysts. The quality of water glass directly affects the strength and hardening speed of the sand mold, so its modulus, density and other indicators need to be strictly tested. The sand material is generally made of quartz sand, and its particle size distribution needs to be carefully selected according to the size and complexity of the casting. The addition of catalysts can accelerate the hardening process of water glass and improve the strength of the sand mold.

In terms of ratio, the amount of water glass needs to be precisely controlled. Too much will cause the sand mold to agglomerate and harden too quickly, affecting the demolding and surface quality of the casting; too little will not fully activate the surface of the sand particles and reduce the strength of the sand mold. Therefore, a reasonable ratio is the key to the preparation of water glass sand.

3. Process flow

The casting process of water glass sand mainly includes raw material preparation, sand material mixing, model making, sand mold preparation, pouring and solidification, post-processing and other steps.

Raw material preparation: As mentioned above, prepare raw materials such as water glass, sand and catalyst.

Sand mixing: Mix water glass and sand in a specific ratio and add an appropriate amount of catalyst. This process needs to ensure uniform mixing to avoid poor local hardening.

Model making: Make an accurate model according to the product design requirements and perform surface treatment to ensure the quality of the sand mold. The model material needs to be resistant to high temperatures, manageable to de-mold and reusable.

Sand mold preparation: Fill the water glass sand mixture around the model and solidify it through vibration, compaction and other processes. This process requires controlling the compactness and uniformity of the sand mold.

Pouring and solidification: Pour the molten metal into the sand mold and demold it after it solidifies. The pouring temperature needs to be strictly controlled to ensure that the molten metal has good fluidity and wettability.

Post-processing: Perform post-processing processes such as grinding and polishing on the casting to ensure that the product quality meets the requirements. This process needs to avoid damage to the surface of the casting.

4. Performance characteristics

Water glass sand has a series of critical performance characteristics, making it an essential material in the foundry industry.

Good fluidity: Water glass sand has good fluidity and is easy to fill complex cavities.

Good disintegration: The sand mold is easy to disintegrate after pouring, which is convenient for demolding and cleaning castings.

Fast hardening speed: The hardening process of water glass can be accelerated by adding catalysts or adopting specific hardening processes.

High strength: Reasonable ratios and process parameters can ensure that the sand mold has high strength and meets the production needs of castings.

Good environmental protection: Water glass sand is non-toxic, harmless, and has no odor, which meets environmental protection requirements.

5. Application fields

Water glass sand has a wide range of applications in the foundry industry, including but not limited to the following aspects:

Steel casting production: Water glass sand is one of the commonly used sand mold materials in steel casting production. Its high strength and good disintegration help ensure the dimensional accuracy and surface quality of castings.

Cast iron and non-ferrous alloy casting production: Water glass sand is also suitable for the production of cast iron and non-ferrous alloy castings. By adjusting the ratio and process parameters, the production needs of castings of different materials can be met.

Complex casting production: Water glass sand has good fluidity and filling properties and is suitable for filling and molding complex cavities. This is of great significance for the production of castings with complex structures.

Environmentally friendly casting: With the increase in environmental awareness, more and more foundry companies have begun to use ecologically friendly sand materials such as water glass sand. This helps to reduce pollution emissions during the casting process and improve the environmental image of the company.

6. Common problems and solutions

Although water glass sand has a wide range of application prospects in the casting industry, there are still some common problems in the actual application process. The following are some common problems and their solutions:

Poor demolding: Due to the low strength of water glass sand or improper surface treatment of the model, the surface of the casting may be damaged during demolding. Solutions include increasing the strength of the sand mold, optimizing the surface treatment process of the model, and using a suitable demolding agent.

Porosity defects: Water glass sand is easy to absorb air. If the air cannot be discharged entirely during the pouring process, it will cause porosity defects. Solutions include adjusting the pouring temperature and speed, optimizing the sand mold exhaust system, and using vacuum pouring technology.

Difficulty in regenerating old sand: In the traditional water glass sand process, the large amount of water glass added makes it challenging to regenerate old sand. In recent years, this problem has been effectively solved by improving the process and developing new regeneration equipment. However, it is still necessary to continue to study and improve the old sand regeneration technology to improve resource utilization and reduce production costs.

7. Future development trends

With the continuous advancement of casting technology and increasingly stringent environmental protection requirements, the application prospects of water glass sand in the casting industry will be broader. Future development trends may include the following aspects:

Research and development of environmentally friendly water glass sand: In order to meet environmental protection requirements, more non-toxic, harmless and degradable water glass sand products will be developed.

Application of intelligent preparation technology: By introducing intelligent preparation technology, the automation and precision preparation of water glass sand can be realized, and production efficiency and product quality can be improved.

Improvement of old sand regeneration technology: Continue to study and improve old sand regeneration technology, improve resource utilization and reduce production costs.

Development of multifunctional water glass sand: Develop water glass sand products with unique properties such as high-temperature resistance, wear resistance, corrosion resistance, etc., in response to the needs of specific application fields.

In summary, water glass sand has broad application prospects and essential application value in the foundry industry. Through continuous improvement and perfection of preparation technology, solving everyday problems and developing new products and technologies, water glass sand will play a more critical role in the foundry industry in the future.