Core Point

● High Silica Fiberglass Filter Mesh is an economical pre-filtering core material for small and medium-sized cast steel parts, carbon steel, and stainless steel castings.

● The base material is special high-silicon oxide Fiberglass with a silicon dioxide content of ≥ 96%.

● It is modified through double-strand twisting (sawtooth weaving method) + high-temperature resistant and fire-resistant coating, specifically adapted for high-temperature pouring conditions of 1550~1620℃ molten steel.

● It is used to intercept slag in the molten steel, peeling particles of refractory materials, alumina deoxidation inclusions, and sand debris.

● It is an extremely cost-effective primary purification solution in the cast steel industry.

Basic Material

1. Composition of raw materials 

● The silica content of ordinary fiberglass is only 50-60%.

● High silica fiberglass are produced through phase separation of sodium borosilicate glass, removal of boron and sodium impurities by acid leaching, and high-temperature sintering for shaping.

● Eventually, the purity of silica stabilizes at 96%-98%, forming a dense and high-temperature-resistant silica framework.

● It has inert chemical properties and will not leach out harmful elements into the molten steel, nor will it change the chemical composition of the steel.

2. Key temperature resistance indicators (cast steel core) 

● Fire-resistant coating: Steel water at 1620℃ can be briefly sprayed without causing damage for 10 to 15 seconds, suitable for conventional carbon steel casting. 

● Long-term safe operating temperature: 900 - 1000℃, with instantaneous peak tolerance of 1700℃ (close to the softening point of silica) 

● High-temperature shrinkage rate: At 1000℃, the thermal shrinkage is ≤ 2%. Under high temperatures, the grid does not deform or collapse, ensuring the stability of the filter residue structure.

3. Structural Process 

● It is woven using Leno weaving technique, which is different from plain weave.

● The grid structure will not slip or break off under the high-pressure impact of molten steel; the surface is sprayed with low-gas-emitting refractory phenolic resin.

● After curing, it becomes rigid and does not cause loose edges during cutting.

● The gas emission is much lower than that of ordinary fiberglass nets, and it completely eliminates the defects of air holes in castings.

Principle of Steel Liquid Filtration 

It is divided into two layers of filtering mechanisms, which are suitable for steel casting process: 

1. Physical interception (first layer):

● When the molten steel flows through the filter screen, large lumps of slag, sand clumps, and refractory fragments are directly intercepted by the grid and prevented from entering the cavity.

● Commonly, the mesh aperture of the molten steel filter screen is 1.5mm or 2.0mm.

● For large-scale casting steel, a 2.5mm coarse aperture is used, while for precision small parts, a 1.5mm medium aperture is employed. 

2. Secondary adsorption filtration (second layer):

● High Silica Fiberglass Filter Mesh have a large specific surface area.

● Fine alumina inclusions and oxide scales in the molten steel will adhere to the surface of the fibers.

● As the filter residue accumulates, a dense filter cake naturally forms at the front end of the filter screen, further intercepting micrometer-sized impurities, achieving progressive purification. 

● At the same time, the filter screen can disperse the turbulent flow of molten steel, converting the turbulent jet flow into a stable laminar flow, thereby reducing the secondary oxidation of the molten steel and minimizing the generation of new inclusions at the source.

Unique Advantages 

1. Low emission property: Special refractory carbonization coating, with extremely low smoke emission at high temperatures, perfectly addressing the problems of pores and pinholes in cast steel parts. 

2. Flexible and easy to process: The coil material is supplied as a complete roll. It can be cut into square, circular, or irregular shapes as needed, and is suitable for any sand mold or investment casting gating dimensions. The cutting size is recommended to be 20-30mm larger than the gating section to prevent slag from spilling out from the side during the steel water pouring process. 

3. Resistance to steel liquid erosion: The thickened model has a weight of up to 600g/㎡, and its thickness is three times that of cast iron filter screens. The ability to withstand the impact of high-temperature molten materials has been significantly enhanced, and it will not be broken or torn apart by the steel flow, thus avoiding the occurrence of fiber impurity defects. 

4. Easy demolding: After the casting cools down, the filter screen can be easily broken off by gently tapping at the position. It will not stick to the casting body. The cleaning workload is small and it can also be used as an isolation plate for the riser.

Standard Installation Usage Specifications (Required for Cast Steel) 

Optimal placement positions (sorted by filtering effect)

① Bottom of the pouring cup (preferred): The first barrier for molten steel entering the mold, all the molten steel will pass through the filter, providing the best slag-blocking effect;

② Bottom of the direct pouring channel and the joint of the horizontal pouring channel: Intercept impurities before diversion, protecting each mold cavity;

③ Entrance of the internal pouring channel: Close to the casting, suitable for small and precision steel parts, but prone to clogging and affecting filling.

Applicable Casting Types 

Common carbon steel, alloy steel, martensitic/ferritic stainless steel, cast steel valves, cast steel parts for construction machinery, small cast steel components for locomotives, pre-filtering in lost foam precision casting, and it can also be compatible with high-temperature ductile iron and gray cast iron filters.

Relevant Information

High Silica Fiberglass Filter Mesh VS Zirconia Ceramic Foam Filter (For Cast Steel Filtration)