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Fiberglass mesh is not a mere ordinary glass product; rather, it is a high-performance composite material treated through specialized processes.
1. Substrate:
Primarily composed of woven medium-alkali or alkali-free fiberglass fabrics. The diameter of the individual filaments typically ranges from 5 to 24 μm, endowing the material with exceptionally high tensile strength.
2. Coating:
The surface undergoes an immersion coating treatment using polymer anti-emulsion agents-such as acrylate copolymers-and is further fortified with additives like zirconium oxide and titanium oxide to form a protective film. This treatment imparts outstanding alkali resistance to the material, with an alkali-resistance retention rate exceeding 85%.
3. Structure:
Formed through the interlacing of warp and weft threads to create various mesh aperture sizes (e.g., 4 mm × 4 mm, 5 mm × 5 mm). This structural configuration serves a dual purpose: it ensures the material's flexibility while simultaneously enabling the effective dispersion of stress.
During the casting process, molten metals (such as iron, steel, and aluminum) are highly prone to entraining slag inclusions, sand inclusions, and gas pores. Fiberglass filter screens address these issues through the following mechanisms:
Leveraging its core characteristics-namely "high strength, light weight, corrosion resistance, and electrical insulation"-fiberglass mesh has emerged as a critical foundational material in fields such as architectural crack prevention, industrial filtration, and aerospace protection. Its most outstanding attributes are its exceptionally high tensile strength (exceeding that of ordinary steel by more than two times) and its superior chemical stability, enabling it to maintain structural integrity even in extreme environments characterized by strong acids, strong alkalis, and high temperatures.
1. Mechanical Properties:High Strength, High Modulus, and the "Soft Reinforcement" Effect
The mechanical properties of fiberglass mesh far surpass those of traditional building materials, serving as the foundation for its role as a "reinforcing skeleton" in engineering applications.
1) Ultra-High Tensile Strength:
The tensile strength of fiberglass can reach between 1,000 and 4,000 MPa-two to three times that of ordinary carbon steel, and a staggering 20 to 50 times that of ordinary glass products. This immense strength enables it to effectively withstand the massive stresses generated by wall settlement and wind pressure impacts.
2) High Elastic Modulus:
Its elastic modulus is approximately one-third to one-sixth that of steel; while lower than that of steel, it remains significantly higher than that of organic fibers. This implies minimal deformation under load, allowing it to effectively limit crack propagation within the matrix material (such as mortar or resin).
3) The "Soft Reinforcement" Effect:
In building thermal insulation systems, the mesh fabric utilizes its high tensile strength-acting along both the warp and weft directions-to uniformly disperse localized stresses across the entire wall surface. This prevents the cracking of plaster mortar or the detachment of the insulation layer, issues often triggered by thermal expansion and contraction.
2. Chemical Stability:Acid, Alkali, and Corrosion Resistance
As an inorganic, non-metallic material, fiberglass mesh demonstrates exceptional stability in chemically corrosive environments, making it the preferred choice for chemical filtration and construction projects situated in harsh conditions.
3. Thermal Properties: High-Temperature Resistance and Dimensional Stability
The thermal properties of fiberglass mesh enable it to perform effectively in extreme operating conditions, such as high-temperature flue gas filtration and fire barrier zones.
1) High-Temperature Resistance:
Standard alkali-free fiberglass can operate continuously within a temperature range of 260°C to 300°C, with short-term resistance reaching over 500°C. High-silica fiberglass can withstand even more extreme temperatures exceeding 1000°C. This makes it a core material for filter media in high-temperature baghouse dust collectors.
2) Low Coefficient of Thermal Expansion:
It possesses an extremely low linear coefficient of thermal expansion (approximately 4.8 × 10-6/°C). Consequently, dimensional changes upon heating are minimal, preventing structural damage caused by thermal stress during rapid temperature fluctuations
3) Non-Combustibility:
Classified as a Class A non-combustible material, it does not burn or emit toxic fumes when exposed to fire. It effectively inhibits the spread of flames, making it an ideal material for use in architectural fire barrier zones.
4. Electrical and Physical Properties: Electrical Insulation and Lightweight Nature
1) Excellent Electrical Insulation:
Alkali-free fiberglass exhibits exceptionally high volume resistivity and dielectric strength, coupled with a low dielectric constant. This makes it an ideal substrate for the manufacture of printed circuit boards (PCBs), radomes, and high-voltage insulation materials.
2) Lightweight and High-Strength:
With a density of only 2.5 to 2.7 g/cm³, it is three to four times lighter than steel; however, it possesses an exceptionally high specific strength (strength-to-density ratio). This attribute facilitates a reduction in structural dead weight, thereby lowering transportation and construction costs.
3) Electromagnetic Transparency:
It is transparent to electromagnetic waves and is frequently utilized in the fabrication of antenna radomes, where it protects internal equipment without interfering with signal transmission.
Compared to other filtration materials (such as foam ceramics or straight-channel ceramics), fiberglass mesh offers distinct advantages:
1. Cost-effectiveness:
It is inexpensive-costing only a fraction of ceramic filters-making it suitable for large-scale production.
2. Convenience:
It is extremely thin (approximately 0.35 mm to 0.5 mm), requiring no dedicated space reservation during mold assembly; it does not alter the dimensions of the casting and offers flexible application.
3. Chemical Inertness:
It does not alter the chemical composition of the metal and exhibits low gas evolution, thereby preventing the introduction of new defects.
In actual production systems, the correct installation method directly determines the effectiveness of the filtration process. Based on the principles of foundry technology, the following are the key operational points:
1. Installation Position:
1) Optimal Position:
At the junction of the runner and the ingate, or at the bottom of the sprue in the area adjacent to the ingate. The closer the filter is positioned to the casting cavity, the better the filtration effect; however, care must be taken to prevent erosion.
2) Alternative Positions:
Beneath the pouring cup, or on the parting surface of the runner. The results are even more effective when used in conjunction with a slag trap.
2. Size Design:
1) Area Ratio:
The effective working area of the filter screen should be 4 to 6 times the choke area (constricting cross-section) of the gating system to ensure that the metal filling speed remains unaffected.
2) Runner Widening:
The cross-sectional area of the runner at the location where the filter screen is placed must be increased to 2 to 3.5 times its original size to compensate for the flow resistance caused by the filter screen.
3. Fixing Method:
1) The filter screen can be cut into any desired shape (square, circular) and laid directly onto the parting surface or the joint surface of the sand cores.
2) For green sand casting, ensure a contact width of 1-2 cm along the edges of the screen; for dry sand casting, refractory clay strips must be pressed around the screen to prevent the molten metal from washing it away.
