Cara Membuat Filter Busa Keramik

12 September Cara Membuat Filter Busa Keramik

Posted at 06:13h in Filter Busa Keramik by AdTech 0 Comments

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Adtech akan memberi tahu Anda cara membuat filter busa keramik.
Pembuatan larutan untuk impregnasi busa poliuretan: garam kalium dan asam fosfat dicampur dalam wadah hingga benar-benar netral.
Kemudian ditambahkan bahan pengikat aluminium-kromofosfat, dan selanjutnya, sambil terus diaduk, komponen-komponen terpisah dimasukkan: lelehan, aluminium hidroksida, bahan pengisi, dan limbah filter keramik berbusa yang telah digiling halus.
Proses pengadukan suspensi dilanjutkan selama 30–40 menit hingga tercapai homogenisasi yang sempurna.

Bagaimana Cara Membuat Filter Busa Keramik?

Potongan-potongan berbahan busa poliuretan dengan struktur elastis berpori terbuka direndam dalam larutan keramik yang sudah jadi, lalu sisa larutan tersebut diperas hingga habis.
Produk setengah jadi dikeringkan pada suhu 100–130 °C hingga beratnya konstan, kemudian dibakar pada suhu maksimum 1280–1290 °C.
Filter busa yang telah jadi diuji ketahanannya terhadap filtrasi selama proses pengecoran paduan aluminium.
Komposisi bahan yang diusulkan serta karakteristik fisiko-teknis prototipe diperoleh selama pengujian filter busa.
Solusi yang diusulkan memungkinkan peningkatan kekuatan mekanis dan ketahanan terhadap panas pada filter busa keramik.
Filter busa keramik dari campuran yang diusulkan memiliki keunggulan dibandingkan dengan filter lain berkat tingkat kekuatan mekanis dan ketahanan panas yang lebih tinggi, dan—yang sangat penting—karena tidak adanya retakan pada badan keramik, filter ini memiliki ketahanan patah lentur yang tinggi, yang berdampak positif terhadap kualitas logam yang dibersihkan.
Selain itu, penggunaan limbah yang telah digiling halus dari PCF memungkinkan dilaksanakannya produksi filter busa keramik tanpa menghasilkan limbah.

Filter busa keramik digunakan untuk menghilangkan kotoran pada coran logam.

Filter berbasis PPU menghilangkan kotoran melalui struktur berpori terbuka yang dimilikinya. Jalur aliran logam cair melewati pori-pori tersebut selama proses pengecoran. Pada filter busa keramik, PUF berfungsi sebagai matriks untuk proses katalitik selanjutnya. Busa tersebut dilapisi dengan suspensi keramik dan dikeringkan. Kemudian, bahan baku berbentuk beragam dimasukkan ke dalam tungku, di mana matriks busa poliuretan berpori terbakar habis, meninggalkan kerangka jaring keramik dari filter yang telah jadi. Ukuran pori filter keramik berkisar antara 10 hingga 45 PPI per inci linier.

Struktur jaring pada filter busa keramik memungkinkan penyaringan mendalam, yang secara cermat menghilangkan sejumlah besar kotoran tanpa meninggalkan sisa kotoran

Filter ini mampu menahan tekanan metallostatik yang cukup besar sekaligus tetap menjaga efektivitas penyaringan. Filter busa keramik biasanya digunakan untuk proses peleburan aluminium primer dan sekunder, serta sebagai filter pada tungku peleburan aluminium.

Filter busa keramik memiliki keunggulan-keunggulan berikut ini

1. Penyaringan kotoran logam dan non-logam dari aliran logam cair.
2. Pengurangan oksida selama pembentukan aliran turbulen.
3. Peningkatan aliran logam.
4. Penghilangan inklusi dan berbagai cacat logam.
5. Untuk meningkatkan kualitas pengecoran, filter PPU memiliki sifat mekanis yang baik.
6. Pengurangan limbah dan pekerjaan tambahan dalam proses produksi.
7 Keramik saringan busa tersedia dalam berbagai macam ukuran dan bentuk.
8 Semua filter busa keramik memiliki ciri khas berupa matriks jaring, di mana pori-pori berbentuk bola dengan ukuran dan volume seragam saling terhubung di seluruh volumenya, serta membentuk celah-celah melalui dindingnya. Jalur-jalur berliku pada struktur ini memungkinkan aliran terak cair dan kontaminan lainnya melewatinya sekaligus menahannya. Akibatnya, struktur filter berbasis PPU yang unik ini menunjukkan efisiensi filtrasi logam yang unggul dibandingkan dengan struktur dan filter lain di pasar pengecoran.

9. Filter busa keramik memiliki ketahanan panas yang tinggi dan mudah meresap logam cair. Daya tahan yang unggul dari filter berbasis PPU menghilangkan kebutuhan akan saringan logam tambahan.

10 Peningkatan kualitas coran terjadi melalui penyaringan terak yang terbentuk dalam logam cair selama proses pengecoran. Dengan menggunakan filter berbasis PPU, kualitas coran akhir menjadi lebih baik, kemudahan pengolahan logam meningkat, limbah pengecoran berkurang, sekaligus kecepatan produksi lini produksi pun meningkat.

11 Por-pori pada filter busa keramik berfungsi sebagai “penangkap” berbagai kotoran. Struktur filter ini lebih unggul dibandingkan dengan filter keramik standar konvensional. Ketika massa logam besi cair bersentuhan dengan permukaan filter busa keramik, bahan tambahan khusus yang membentuk lapisan filter mulai terurai dan seketika membentuk lapisan fayalite yang terus menerus. Lapisan ini menjadi lunak dan kental pada suhu tinggi, sehingga lapisan fayalite tersebut mampu menahan inklusi berukuran mikron sekalipun saat melewati filter. Filter keramik konvensional tidak mampu menangkap begitu banyak kotoran dari logam cair secara menyeluruh.

Dengan menggunakan filter berbahan busa poliuretan dalam proses produksi, Anda akan memperoleh logam yang lebih bersih, meningkatkan kelancarannya, serta secara umum meningkatkan kualitas hasil pengecoran akhir, yang pada akhirnya akan meningkatkan keuntungan pabrik dan bengkel pengecoran.

1. What is a Ceramic Foam Filter and How Does It Work?

A Filter Busa Keramik (CFF) is a porous, highly refractory ceramic material characterized by a three-dimensional open-cell network (reticulated structure). Designed to withstand extreme temperatures, thermal shock, and molten metal erosion, CFFs are predominantly used in continuous, semi-continuous (DC casting), and shape casting of aluminum alloys.

The Three Filtration Mechanisms

Mechanical Straining (Screening): Large oxide skins and refractory slag particles larger than the filter pore opening are mechanically trapped on the entry face of the filter plate.
Cake Filtration: As trapped particles accumulate at the filter surface, they form a “filter cake.” This layer subsequently acts as a secondary filter medium, capturing particles smaller than the initial pore diameter.
Deep-Bed Adsorption: Microscopic non-metallic inclusions pass into the tortuous 3D network of the reticulated ceramic structure. Due to inertia, thermal convection, and capillary action, these inclusions contact the ceramic strut surfaces and adhere to them via physical adsorption.

Core Benefits for Aluminum Cast Houses

Dross & Inclusion Reduction: Removes non-metallic particles down to a few microns, dramatically lowering rejection rates during X-ray testing.
Laminar Flow Stabilization: Reduces turbulence during mold filling, minimizing secondary oxidation and air entrapment.
Improved Mechanical Properties: Enhances yield strength, fatigue resistance, and surface finish of extruded profiles, aluminum foils, and aerospace-grade sheets.
Machining Tool Longevity: Decreases hard spot density, significantly reducing tool wear during CNC milling and cutting operations.

2. Step-by-Step Ceramic Foam Filter Manufacturing Process

The dominant industrial method for producing high-porosity reticulated ceramic foam filters is the Organic Sponge Impregnation Method (also known as the Schwartzwalder Process). Below is the precise 6-step manufacturing workflow.

Alumina Ceramic Foam Filter manufacturing process including mixing, molding, sintering, inspection and packaging.

Step 1: Polyurethane Sponge Selection and Pre-treatment

Base Material: Flexible, fully reticulated open-cell polyurethane (PU) foam serves as the sacrificial template.
Pore Uniformity: The PU foam must feature uniform pore size distribution, specified in PPI (Pores Per Inch).
Thermal Pre-treatment: The foam template is heat-treated or chemically etched to remove residual cell membranes, ensuring 100% open porosity and optimal slurry adhesion.

Step 2: Ceramic Slurry Preparation & Impregnation

Slurry Formulation: High-purity alumina (Al2O3), silica (SiO2), binder agents (e.g., aluminum phosphate or colloidal silica), rheological additives, and anti-foaming agents are blended in a high-shear mixer.
Viscosity Control: Slurry rheology must exhibit thixotropic behavior—flowing easily under stress while maintaining a stable structure at rest to coat foam struts evenly without clogging pores.
Dipping Process: The pre-cut PU foam matrices are submerged in the ceramic slurry, ensuring complete wet-out of all internal struts.

Step 3: Mechanical Rolling and Excess Slurry Removal

Squeezing Action: The impregnated foam passes through precision-calibrated roller presses to squeeze out excess slurry.
Web Thickness Retention: Controlled clearance settings on the rollers maintain optimal ceramic strut coating thickness while preserving open passage channels.

Step 4: Controlled Drying Phase

Moisture Evaporation: The coated foam blocks undergo drying in continuous tunnel dryers or microwave drying systems operating between 100°C and 150°C.
Crack Prevention: Humidity and temperature profiles are carefully regulated to prevent shrinkage cracks, warpage, or structural deformation.

Step 5: High-Temperature Sintering

Polyurethane Burn-out: As temperature reaches 300°C to 600°C in the sintering kiln, the internal polyurethane foam template burns out completely without leaving toxic carbon residue.
Ceramic Bonding: The kiln ramps up to sintering temperatures between 1100°C and 1500°C (depending on binder and alumina purity). Thermal sintering fuses ceramic grains together, developing high mechanical strength and thermal shock resistance.

Step 6: Edge Gasket Application & Quality Inspection

Thermal Expansion Gasket: Expandable ceramic fiber or refractory gasket strips are fitted around the edges of the filter plate to ensure a tight seal inside the filter box, preventing molten metal bypass.
Dimensional & Visual QC: Each filter plate undergoes dimensional tolerance verification, pore density checks, and structural integrity testing.

3. Key Technical Specifications & Material Comparison

Selecting the correct ceramic material matrix is crucial to withstand thermal stress and chemical reaction with specific molten alloys.

Property / Parameter	Alumina (Al2O3) Ceramic Filter	Silicon Carbide (SiC) Filter	Zirconia (ZrO2) Ceramic Filter
Primary Alloy Application	Aluminum, Al-Mg Alloys, Zinc	Cast Iron, Ductile Iron, Copper Alloys	Carbon Steel, Stainless Steel, Superalloys
Max Operating Temp	Up to 1150°C (2102°F)	Up to 1500°C (2732°F)	Up to 1700°C (3092°F)
Porosity Rate	80% – 90%	80% – 85%	75% – 85%
Flexural Strength	≥ 0,8 MPa	≥ 1,5 MPa	≥ 2.0 MPa
Ketahanan terhadap Guncangan Termal	Luar biasa	Superior	Outstanding
Ketidakreaktifan Kimia	Highly Resistant to Molten Al	Highly Resistant to Slag	High Resistance to Corrosion

Standard Physical Specifications (Alumina CFF for Aluminum)

Chemical Composition: Al2O3 ≥ 85%, SiO2 ≤ 10%
Kepadatan Volume: 0.40 – 0.55 g/cm³
Cold Compressive Strength: ≥ 0.5 MPa
Thermal Expansion Coefficient: 7.5 × 10⁻⁶ /K

4. How to Choose the Right PPI for Aluminum Casting

Pores Per Inch (PPI) defines the pore density of a ceramic foam filter. Selecting the appropriate PPI depends on your casting method, alloy cleanliness requirements, and molten metal flow rate goals.

Ceramic foam filter PPI selection guide showing 10–60 PPI pore size, filtration efficiency and aluminum casting applications

PPI Selection Matrix

10 PPI to 20 PPI (Coarse Filtration)

Primary Uses: Primary aluminum remelt, foundry ingot production, scrap recycling, and gravity casting.
Key Characteristics: High volumetric flow rate, high dirt-holding capacity, low initial priming head requirement.
Target Inclusions: Removes large dross particles, furnace lining flakes, and coarse oxide skins.

30 PPI to 40 PPI (Medium-Fine Filtration)

Primary Uses: Direct Chill (DC) casting of extrusions, aluminum billets, rolling slabs, and automotive component foundries.
Key Characteristics: Balanced performance offering efficient micro-inclusion removal alongside stable flow velocity.
Target Inclusions: Traps intermediate non-metallic inclusions down to 30 microns.

50 PPI to 60 PPI (Ultra-Fine / Precision Filtration)

Primary Uses: High-precision aluminum foil stock, aerospace alloys, lithographic sheet production, and ultra-thin wire drawing.
Key Characteristics: High filtration efficiency with tight pore channels. Requires preheating and higher molten metal priming head pressure.
Target Inclusions: Captures micro-inclusions down to 5–10 microns.

5. Application Scenarios & Filter Box Installation Best Practices

Correct installation and preheating of ceramic foam filters in casting operations are critical to preventing molten metal bypass, thermal shock breakage, and cold folds.

Step-by-Step Installation Guidelines

Inspect Filter Box & Seating: Clean the filter bowl or launder box thoroughly. Remove residual aluminum, oxide scale, or damaged lining refractory.
Apply Expansible Gasket: Ensure the expandable ceramic fiber sealing gasket wraps tightly around all four sides of the filter plate.
Position the Filter: Place the filter plate flush into the filter bowl seat. Press down evenly to verify there are no gaps along the perimeter where un-filtered liquid metal could bypass.
Preheating Sequence: Preheating the filter plate using burner flames or electric heating elements is mandatory before casting starts:
- Target Preheat Temperature: 300°C to 500°C (572°F to 932°F).
- Purpose: Prevents thermal stress cracking upon contact with molten metal and ensures instant priming without freezing.
Priming & Flow Rate Control: Maintain an adequate metal head height (typically 50–150 mm) during initial pour to overcome surface tension and prime the filter pores.

6. Troubleshooting Common Filtration Failures

Issue / Symptom	Root Cause Analysis	Rencana Tindakan Korektif
Filter Floating / Displacement	Missing or incorrectly sized edge gasket; improper filter seating inside the bowl.	Use correct ceramic fiber gasket thickness to ensure tight mechanical wedge fit.
Metal Priming Failure (No Flow)	Filter temperature too low during pour; selected PPI too fine for available liquid metal head pressure.	Increase filter box preheat temperature; switch to a lower PPI filter (e.g., from 50 PPI to 30 PPI).
Filter Structural Cracking	Severe thermal shock due to non-uniform or insufficient preheating; physical impact during loading.	Standardize burner preheat sequence; handle filter plates carefully using thermal protective gear.
Inclusion Bypass / Downstream Defect	Damaged edge gasket allowing molten metal to bypass filter; cracks inside filter matrix.	Inspect gasket seal prior to casting; verify cold compressive strength specifications from supplier.

7. Frequently Asked Questions (FAQ)

Q1: What is the standard lifespan of an alumina ceramic foam filter?

Alumina ceramic foam filters are designed primarily for single-cast usage in continuous and semi-continuous casting runs. They should be replaced after every drop/cast or once maximum inclusion load capacity is reached to avoid channel clogging and pressure drops.

Q2: Why is the expandable gasket around the filter plate critical?

The ceramic fiber gasket serves two vital functions: first, it seals the perimeter to prevent liquid aluminum from leaking past the sides without being filtered; second, it expands under high casting temperatures to securely lock the filter plate in position, preventing it from floating.

Q3: How do I determine whether to use a 30 PPI or 50 PPI filter?

Base your selection on your end product quality specifications. If you are manufacturing standard industrial extrusions or billets, 30 PPI provides excellent flow efficiency and clean melt quality. If you produce foil stock, lithographic plates, or aerospace components, 50 PPI or 60 PPI is necessary to remove fine micro-inclusions.

Q4: What is the main difference between Alumina (Al2O3) and Silicon Carbide (SiC) foam filters?

Alumina (Al2O3) filters are specifically formulated for aluminum and non-ferrous alloy casting up to 1150°C. Silicon Carbide (SiC) filters exhibit much higher mechanical strength and temperature resistance up to 1500°C, making them suitable for iron, brass, and bronze foundry applications.

Technical Consultation & Procurement Solutions

Are you seeking to improve your casting yield, reduce dross rejection rates, or custom-engineer ceramic foam filter sizes for your aluminum furnace launder system?

Contact the metallurgical engineering team at AdTech today for technical datasheets, custom PPI configurations, and factory-direct volume quotes.

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filter busa keramik

Cara Membuat Filter Busa Keramik

12 September Cara Membuat Filter Busa Keramik