Thermally Formed Combo Bag

Thermally Formed Combo Bag(internally abbreviated as TF diversion bag, thermal forming composite bag, aluminum liquid filtration composite bag).

TF Combo Bag is called for short.

● TF = Thermally Formed, Hot-pressing integrated molding process, different from traditional sewing bags.

● Combo =  Composite multi-chamber integrated structure, simultaneously achieving the combined functions of filtration, stable flow, and diversion.

Core material and technology

1. Base material 

Alkali-free high-twist high-strength E-glass fabric (SiO₂ ≥ 62%), plain weave / gauze weave, regular mesh sizes of 1.5×1.5 / 2.0×2.0 / 2.5×2.5 mm.

2. Surface treatment (core smoke-free process) 

Impregnated with special high-temperature resistant phenolic resin coating, which undergoes high-temperature carbonization and shaping; the finished product is of dark brown/blackish brown color, with a maximum temperature resistance of 1000℃, suitable for aluminum liquid working conditions of 700–760℃.

3. Forming advantages (thermoplastic molding VS sewn bags) 

It is produced by a one-step hot mold pressing process, without loose threads or seamless sewing thread ends. This ensures that thread ends do not mix into the molten aluminum, avoiding inclusions. At high temperatures, its rigidity can be maintained for 90 minutes, without any deformation in size or instability of the cavity structure.

Physical Design

Integrated double-layer composite cavity: 

1. Outer reinforced shell: Thick fiberglass fabric, shaping, installation and fixation. 

2. Inner filter diversion inner compartment: Hollow filter screen, used to intercept alumina and refractory material slag particles. 

3. Optional custom accessories: Flow guide sleeve, bottom flow guide hole, side observation window, reinforcement patch, installation positioning hole.

Core Function (Aluminum Cast VDC/Vertical Semi-Continuous Casting Specialized)

1. Precise flow diversion and stable flow: Disperse the molten aluminum directly into turbulent flow, evenly distribute the melt, and maintain uniform temperature within the mold. 

2. Deep Filtration of Impurities: Capturing impurities such as alumina skins, refractory debris, and recycled aluminum residues, reducing inclusion defects 

3. Reduce casting billet defects: Significantly improve the filling at the bottom of the flat ingot, reduce the tail curl of the casting billet, the scalping amount, and the porosity rate. 

4. Low smoke and environmentally friendly: Carbonized coating, resulting in less smoke and no open flame during casting, improving the working conditions in the workshop. 

5. Compatible with recycled aluminum casting: High capacity for accommodating impurities, resulting in an aluminum liquid recovery rate of over 95%.

Installation operation steps

1. Installation location 

Fixed within the internal part of the flow divider/distribution box attached to the crystallizer, at the final filtering and diversion station before aluminum liquid enters the crystallizer, the closer it is to the liquid surface, the less secondary oxidation occurs.

2. Assembly process

1. Clean the diversion support and the inner wall of the flow channel: Remove the solidified aluminum slag, refractory debris, and the remaining threads of the old diversion bags, and blow away the dust. 

2. Place it smoothly into the TF Combo Bag. The outer reinforced shell is tightly fitted into the bracket slot, and the four corner patches are fully adhered to provide support. 

3. The diversion nozzle should be aligned with the central injection port of the casting machine, and the side windows should face both sides of the mold to ensure that the aluminum liquid flows out evenly and horizontally. 

4. No drain nozzle type: The bottom drainage holes are downward, and the molten aluminum flows out from the shallow layer at the bottom of the bag, avoiding direct impact on the bottom plug. 

5. Gap Sealing: The gap between the support and combo bag is filled with dry refractory fiber strips to prevent the aluminum liquid from short-circuiting and to ensure that it does not enter the crystallizer without filtration. 

6. Post-installation re-inspection: The bag body is not tilted, not compressed or deformed, the filter screen is not torn by the support, and the cavity remains hollow without collapsing.

Change the determination criteria

Stop the machine immediately and replace it if any of the following situations occur:

1. The single casting duration exceeds the rigid limit by 90 minutes. 

2. The filter screen has holes, tears, or areas that have become thinner and are prone to clogging. 

3. During the filling process, there was a large amount of black smoke and flames, indicating that the product was damp and had not been dried properly. 

4. The bag body becomes soft and collapses, the cavity deforms, the aluminum liquid flows unevenly, and the temperature difference between the two sides of the cast billet is large. 

5. In the case of high impurity content in recycled aluminum, the surface of the filter screen is overly covered with oxide slag, resulting in a significant decrease in flow rate. 

6. Corner damage and shell delamination are caused by installation impact.

Service life

1. The high-purity alloy fine mesh type requires a single casting time control of 60-90 minutes; the recycled aluminum coarse mesh type has a single casting time of no more than 60 minutes. 

2. Store properly to prevent moisture and avoid additional re-baking and loss. 

3. Integrated with the same specification guide nozzles, it reduces the impact and wear of the molten aluminum, thereby extending the effective working time. 

4. Comparison with traditional sewing diversion bags: TF hot forming technology eliminates the problem of loose threads, reducing the scrap rate of castings by over 60%, and the machining allowance for milling surfaces is decreased by 30-50%.