Research on the Application of Diatomite Fillers in Cast Pipe Release Agents

Characteristics of Diatomite Fillers and the Release Mechanism of Cast Pipes

Diatomite fillers, as a natural inorganic mineral material, demonstrate unique application value in the field of cast pipe release agents. This porous material formed by the deposition of ancient diatom fossils mainly consists of amorphous silica (with a SiO₂ content typically above 85%), featuring appropriate hardness (Mohs hardness 4-5), high porosity (60-90%), large specific surface area (15-60 m²/g), and excellent high-temperature resistance (able to withstand temperatures above 1200°C). These physical and chemical properties of diatomite fillers make them an ideal solid lubricant component for high-performance cast pipe release agents.

During the production of cast pipes, diatomite fillers mainly exert the release function through three mechanisms: Firstly, the micrometer-sized particles of diatomite fillers form a physical isolation layer between the mold and the cast pipe, reducing the direct contact between metal and the mold; Secondly, the porous structure of diatomite fillers can adsorb the organic components in the liquid release agent, achieving controlled release; Thirdly, the layered structure of diatomite fillers generates a sliding effect at high temperatures, reducing the interface friction coefficient. Studies have shown that adding an appropriate amount of diatomite fillers to the release agent can reduce the casting pipe release force by 30-50%, significantly improving production efficiency and the surface quality of the cast pipe.

The Key Role of Diatomite Fillers in Release Agent Formulation

In the design of cast pipe release agent formulations, diatomite fillers are typically used as functional solid lubricants, with the addition ratio controlled within 5-25% according to specific process requirements. Compared with traditional solid lubricants such as graphite and talc, diatomite fillers have more balanced performance: their hardness is moderate, effectively isolating the mold from the cast piece without causing excessive wear on the mold surface; their porous structure can adsorb and release organic release components controllably, prolonging the effective release time; their chemical inertness ensures good compatibility with various release agent substrates.

The application of diatomite fillers in solvent-based release agents is particularly typical. In this type of system, diatomite fillers are surface-modified and uniformly dispersed in organic solvents (such as mineral oil, synthetic esters, etc.) to form a stable suspension. When the release agent is sprayed onto the hot mold surface, the solvent rapidly evaporates, and the diatomite fillers and resin and other film-forming substances together form a high-temperature-resistant isolation film. Experimental data show that a solvent-based release agent containing 15% diatomite fillers can form a uniform isolation layer of 5-10 μm on the mold surface at temperatures ranging from 600 to 800°C, increasing the casting iron pipe release success rate to over 99%.

In water-based release agents, the role of diatomite fillers is more diverse. In addition to the basic lubrication function, diatomite fillers can also improve the rheological properties of the release agent, prevent solid components from settling; enhance the high-temperature stability of the release film; and regulate the drying speed of the release agent. Through special surface treatment technologies (such as silane coupling agent modification), diatomite fillers can maintain good dispersion stability in water phases, avoiding agglomeration and clogging of the spray gun. A water-based release agent containing diatomite fillers developed by a certain enterprise achieved the same release effect as traditional solvent-based products in actual production, while reducing VOC emissions by more than 80%.

The Technical Advantages and Performance Optimization of Diatomite Fillers

Compared with traditional release agent fillers, diatomite fillers demonstrate multiple technical advantages in the application of cast pipe release. From a microscopic structure perspective, diatomite fillers have a unique "interstitial pores" feature - a structure of large pores (1-5 μm) and mesopores (10-50 nm) coexisting, which provides excellent adsorption performance and surface activity. Nitrogen adsorption tests show that high-quality diatomite fillers have a BET specific surface area of 40-60 m²/g and a pore volume of 0.8-1.2 cm³/g, which enables them to effectively carry various release agent active components. From the perspective of thermal stability, the performance of diatomite fillers is outstanding under high temperatures. Thermogravimetric analysis (TGA) shows that diatomite fillers hardly undergo any mass change within 1000°C, which is far superior to many organic demolding components. High-temperature microscopic observation confirms that the demolding film containing diatomite fillers remains intact at 700°C, while the ordinary demolding agent film has significantly cracked at this temperature. This characteristic is particularly important for high-temperature molding processes such as centrifugal casting tubes.

To fully utilize the demolding performance of diatomite fillers, the industry has developed several optimization technologies:

1. Particle size control: By means of classification, diatomite fillers with a D50 of 5-15 μm are obtained, which not only ensures good suspension but also does not affect the spray atomization effect;

2. Surface modification: Using silane coupling agents to treat diatomite fillers improves their compatibility with the organic system, enhancing the strength of the demolding film;

3. Porosity structure optimization: By acid washing or heat treatment, the pore size distribution of diatomite fillers is adjusted to improve their carrying capacity for demolding active components;

4. Composite modification: Combining diatomite fillers with nanomaterials (such as nano-silicon dioxide) further enhances the demolding performance.

Experimental data show that the optimized diatomite fillers can significantly improve the key performance indicators of the demolding agent: the service life of the mold is extended by 30-50%; the surface roughness of the cast pipe is reduced by 20-40%; the consumption of the demolding agent is reduced by 15-25%. These improvements directly reduce the overall cost of pipe production.

Application cases and effect evaluation

In actual pipe production, the demolding agent containing diatomite fillers has achieved significant application results. Taking the centrifugal casting pipe production line of a large-scale pipe manufacturing enterprise as an example, after using the modified diatomite fillers demolding agent, the production process parameters have been comprehensively optimized: the demolding agent spraying pressure has been reduced from 0.6 MPa to 0.4 MPa, and the spraying volume has decreased by 20%; the temperature range allowed for the mold is expanded from 450-550°C to 400-600°C; the demolding success rate has increased from 95% to 99.5%. These improvements have led to an annual cost savings of approximately 750,000 yuan per production line.

In the production of static casting large-diameter ductile iron pipes, the diatomite fillers demolding agent shows unique advantages. Traditional demolding agents cannot meet the dual requirements of demolding performance and surface quality for such castings, while the composite demolding agent containing diatomite fillers forms a uniform high-temperature-resistant isolation layer on the mold surface, ensuring smooth demolding and achieving a surface roughness of Ra ≤ 12.5 μm, reducing the subsequent machining volume. Quality inspection shows that the cast pipes produced using the diatomite fillers demolding agent have a surface defect rate reduced from 3.2% to 0.8%.

From the perspective of performance comparison, the diatomite fillers demolding agent outperforms traditional products in multiple key indicators:

Thermal stability: The stable working temperature of the diatomite fillers demolding agent can reach 800°C, while graphite-based products are usually limited to 600°C;

Demolding effect: Under the same conditions, the demolding force required by the diatomite fillers demolding agent is 30-40% lower than that of the talc-based product;

Pipe quality: The surface inclusion defects of the cast pipes produced using the diatomite fillers demolding agent are reduced by more than 50%;

Economy: Although the unit cost of the diatomite fillers demolding agent is higher, the overall consumption is lower, the mold life is longer, and the overall cost is reduced by 15-20%.

It is particularly noteworthy that the environmental advantages of the diatomite fillers demolding agent. Compared with traditional graphite-based demolding agents, the diatomite fillers demolding agent does not contain harmful substances such as polycyclic aromatic hydrocarbons, and the smoke generation is reduced by more than 60%, which is in line with the requirements of modern casting industry for green development. A certain enterprise has successfully reduced the particulate matter emission concentration in the workshop from 15 mg/m³ to below 5 mg/m³ by fully adopting the diatomite fillers demolding agent.

Industry development trends and outlook

As the casting industry moves towards higher quality and greener directions, the application of diatomite fillers in release agents will exhibit the following trends:

High-performance: Develop diatomite filler release agents specifically for special castings (such as bimetallic composite pipes, high-chromium cast iron pipes, etc.), to meet more stringent process requirements. Through surface nano-modification and composite modification of diatomite fillers, the release agents can adapt to ultra-high temperature environments above 1400°C.

Function integration: Give diatomite filler release agents more additional functions, such as mold protection (by loading corrosion inhibitors on diatomite fillers) and cast pipe surface modification (by carrying alloy elements on diatomite fillers). Studies show that diatomite filler release agents containing specific additives can extend the mold life by 20-30%.

Environmental upgrade: Develop a fully water-based diatomite filler release agent system to completely replace mineral oil solvents. Through fine surface treatment of diatomite fillers, solve the industry problem of insufficient lubrication performance of water-based release agents. An experimental product has achieved a VOC content of <50g/L and a biodegradation rate of >90%.

Intelligent application: Combine Internet of Things technology to develop an intelligent spraying system for diatomite filler release agents. Through real-time monitoring of mold temperature and surface conditions, dynamically adjust the spraying parameters of diatomite filler release agents to achieve precise dosage control. It is expected to save 10-15% of release agent usage.

Market analysis shows that the global annual growth rate of cast pipe production is approximately 3-5%, and the corresponding release agent market size will reach 8-10 billion US dollars by 2025. With the maturity of diatomite filler application technology, its penetration rate in cast pipe release agents is expected to increase from the current approximately 20% to 35-40%. Especially in high-end cast pipes and large-diameter cast pipes, diatomite filler release agents may become the mainstream choice.

From the perspective of the industrial chain, in the future, the production of diatomite fillers will focus more on specialized division of labor: basic filler production will develop towards scale and standardization; the application end will develop specialized modified products for different casting processes. Establishing an application database and performance evaluation standards for diatomite fillers in release agents will also become an important foundation work for industry development.

Overall, diatomite fillers, with their unique performance combination, are reshaping the technical landscape of cast pipe release agents. With the deepening of application research and the improvement of the product system, diatomite fillers are expected to become the core component of a new generation of high-performance release agents, providing key material support for the quality improvement and green transformation of the casting industry. Experts predict that in the next five years, the application of diatomite fillers in release agents will grow at an average annual rate of 8-10%, becoming an important growth point in the non-metallic mineral functional materials market.