TF Combo Bag Fiberglass Filter Bag for Molten Aluminum

Material Construction and How the Bag Is Built

The bag is thermo-formed from high-purity E-grade alkali-free fiberglass cloth, coated with a high-temperature refractory treatment that stiffens the fabric while keeping it chemically inert to molten aluminum. The yarn diameter is about 0.45 mm and the fabric weight is about 350 g/m² — heavy enough to resist the scouring of a continuous aluminum stream, light enough to flex into the launder without breaking.

TF Combo Bag is a double-walled box, not a single sock:

● Inner bag receives the incoming aluminum from the launder or trough.

● Outer bag surrounds the inner bag and forms the rigid outer wall that sits against the launder or filter box.

● Aluminum is poured into the inner bag, rises to the top edge, and overflows outward through the fiberglass filter wall into the outer bag.

● The filtered metal then exits through a bottom opening that is sized to control metal head and flow rate into the mold or filter box.

This overflow design means the metal does not punch straight through a single filter plane. It has to pass sideways through the fiberglass wall, which gives a longer contact path, captures more oxide, and calms the stream before it reaches the casting.

Specifications:

Why a Combo Bag Instead of a Flat Mesh Piece?

Flat fiberglass mesh pieces are placed across the sprue base or runner and do an excellent job at the mold. But aluminum foundries also need filtration where the metal is transferred between process steps: from ladle to holding furnace, along the launder, into the distribution box ahead of the mold, or into a DC casting trough. A flat mesh piece cannot sit in those open troughs, and a ceramic foam filter plate is too rigid and heavy for many launder configurations.

The TF Combo Bag is made for those trough and distribution points. It sits in the open trough, receives the metal, filters it, calms it, and meters it out — all in one disposable bag. Foundries running aluminum wheels, pistons, battery housings, and DC-cast extrusion billets use it as the first filtration step before a sprue mesh or ceramic foam plate downstream.

How It Works — Three Jobs in One Bag

1. Filtration (overflow through the wall). As aluminum overflows from the inner bag through the fiberglass wall, oxide skin, dross agglomerates, flux residues, and non-metallic inclusions are trapped on the inner surface of the filter wall. The growing oxide layer on the wall helps capture finer particles as the pour proceeds.

2. Flow straightening. The long, sideways flow path through the cloth removes turbulence and vorticity. The metal exits the bottom opening calmly, so air entrainment and fresh oxide-film folding are suppressed.

3. Flow distribution. The box shape and bottom opening spread the metal evenly across the mold or filter box cross-section, instead of letting the stream surge down one side or vortex in the center.

The bag is a single-pour consumable: it is placed dry, used once, and removed with the dross after the pour.

Typical Applications

1. Process points

● Launder-to-holding-furnace transfer

● Holding furnace trough and distribution box

● Ladle-to-mold launder filtration

● DC casting trough and filter box

● Gravity casting, permanent mold, and low-pressure casting launders

2. Common castings and products

● Aluminum wheels and automotive aluminum parts

● Pistons and engine components

● New-energy battery housings and structural parts

● DC-cast extrusion billets and rolling ingots

● Aluminum ingots, bars, and profiles

3. Compatible casting alloys

● Pure aluminum and commercial purity grades

● Al–Si: A356.0/A356.2, 356.0, 319.0, A413.0, 443.0

● Al–Si–Cu: 380.0/A380, 383.0, ADC10, ADC12

● Al–Mg: 514.0, 520.0

Quality Benefits for Foundries

● Cleaner metal at the launder: oxide skin and dross removed before the metal reaches the mold or downstream filter

● Fewer pinholes, porosity, and blisters, because the carbonized cloth adds almost no extra gas

● Calmer filling: straightened flow reduces air entrainment, turbulence, and secondary oxide formation

● Even distribution: no surging or vortex in the launder, so metal temperature and flow rate stay uniform across the mold

● Rugged under metal load: thermo-formed coating holds the box shape; rated to about 25 kg per cm² of filter wall

● Fast changeover: one bag per pour, lifted out with the dross when the cycle ends

● No harmful reaction with aluminum alloy; no phosphate or binder leaching into the melt

How to Choose the Right Bag?

Bag size by throughput.

Frequently Asked Questions

1. What does "TF" stand for?

Thermo-formed. The fiberglass cloth is heated and shaped into a rigid double-walled box, so it holds its shape in the launder instead of flopping like a loose cloth sock.

2. How is this different from a flat fiberglass mesh piece?

A flat mesh piece sits across the sprue or runner at the mold. The TF Combo Bag sits in the open launder, trough, or distribution box. It filters, straightens, and distributes the metal in one step and handles a larger volume of dross than a flat piece.

3. How is this different from a ceramic foam filter?

A ceramic foam plate is rigid and sits in a filter box for depth filtration. The TF Combo Bag is a flexible cloth bag placed in the launder or trough; it is a lower-cost primary filtration step for transfer points, often used upstream of a ceramic foam plate.

4. What temperature range is it rated for?

700–900 °C continuous, matched to the 680–780 °C range of aluminum pouring. It is not rated for iron, steel, or copper.

5. Do I need to preheat the bag?

No. The thermo-formed bag is placed dry; preheating is not required for aluminum pouring.

6. Can it be used for iron or steel?

No. This is an aluminum-grade product. For iron, copper, or steel filtration, use high-silica fiberglass mesh or ceramic foam filters.