Frequently Asked Questions
Technical answers about silicon metal, aluminum alloys, degassing, cryolite and importing metallurgical materials from China.
Everything You Need to Know About Silicon Metal
Welcome to AL-LINX's silicon metal FAQs. Here you'll find comprehensive answers to common questions about our industrial silicon products and technical specifications. Whether you're looking to understand the differences between silicon grades like 553, 441, or 2202, learn about impurity controls (Fe, Al, Ca), or discover the right grain size for your application, our technical FAQs cover everything you need to know.
AL-LINX supplies premium silicon metal directly from our facility in Anyang, China, ensuring consistent quality and traceability across all grades. Explore our FAQs to make an informed decision about which silicon grade is best for your industrial needs.
Common Questions
Silicon Metal
What is the difference between Silicon 553 and Silicon 441?
Silicon 553 and Silicon 441 differ primarily in their purity levels and impurity content. Silicon 553 has a purity of ≥98.5% with Fe ≤0.5%, Al ≤0.5%, and Ca ≤0.3%, making it ideal for aluminum alloy applications where standard purity is sufficient. Silicon 441, with ≥99% purity and lower impurity limits (Fe ≤0.4%, Al ≤0.4%, Ca ≤0.1%), is preferred for non-ferrous alloy production and organosilicon compounds where slightly higher purity is required.
Which silicon grade should I buy for aluminum alloying?
Grade 553 covers most aluminum alloying applications. Move to 441 or 3303 when your alloy chemistry requires lower iron, aluminum, or calcium content.
What is Silicon 2202 and what is it used for?
Silicon 2202 is our highest purity grade with ≥99.5% silicon content and extremely tight impurity controls (Fe ≤0.2%, Al ≤0.2%, Ca ≤0.02%). It is specifically designed for applications that demand very low iron and aluminum content, including electronic component manufacturing, high-purity chemical synthesis, and solar silicon feedstock applications. Its superior purity makes it essential for specialized industries where impurity levels directly impact product quality.
When should I use Off-Grade Si 97 instead of higher-purity grades?
Off-Grade Silicon 97 is a cost-effective option designed for applications where ultra-high purity is not required. With ≥97% silicon content and higher impurity tolerance (Fe ≤1.5%, Al ≤0.9%, Ca ≤0.3%), it is widely used in steel deoxidation, ferrosilicon production, and cost-sensitive alloy applications. If your process can tolerate higher impurity levels, Off-Grade Si 97 offers significant cost advantages without compromising performance for your specific needs.
What do Fe, Al and Ca mean in silicon metal specifications?
Fe, Al, and Ca represent the primary impurity elements in silicon metal:
- Fe (Iron): Affects mechanical properties and corrosion resistance. Lower Fe content is critical for electronics and high-purity applications.
- Al (Aluminum): Influences thermal and electrical conductivity. Critical in semiconductor and chemical synthesis applications.
- Ca (Calcium): Affects material brittleness and processing behavior. Very tight control required for medical-grade and specialty applications.
Silicon purity grades are classified and named based on their maximum allowable impurity levels for these three elements.
What grain sizes are available for silicon metal?
We offer silicon metal in multiple standard particle sizes to suit different applications:
- 10–50mm: Standard lump size for most industrial applications.
- 50–100mm: Larger chunks for specific processing requirements.
- 10–100mm: Mixed size for flexible processing.
- Custom sizing: We can provide custom specifications to meet your exact requirements.
For inquiries about custom sizing, please contact our sales team.
How is silicon metal produced?
Silicon metal is produced through a well-established industrial process: high-purity silica (quartzite) is reduced with carbon in large electric arc furnaces at extremely high temperatures. This reduction process removes oxygen and other impurities, resulting in crystalline silicon metal. The purity of the final product depends on the quality of raw materials, furnace conditions, and post-processing refinement.
Where does AL-LINX source its silicon metal?
AL-LINX supplies silicon metal directly from our Anyang factory in China, a renowned leader in silicon production and processing. We control the full production cycle, from briefing to delivery, with no middlemen.
Importing from China
What is the minimum order quantity for silicon metal from China?
Most producers work in full-container lots of about 20 to 25 tonnes. Smaller trial quantities are possible through consolidators, at a price premium.
How long does it take to import silicon metal from China?
Production and loading typically take 2 to 4 weeks from order confirmation, plus 3 to 5 weeks of ocean transit to Latin America or Europe, plus customs clearance at destination.
Do I need a pre-shipment inspection for every lot?
Yes, until a supplier has earned a long track record, and most experienced buyers keep inspecting even then. The cost is marginal compared with the cost of one off-spec container.
Do you provide certificates of analysis (CoA)?
Yes, every lot ships with full documentation and CoA matching the agreed specification. Our on-site teams test final products before shipping.
CIF or FOB: which Incoterm is better for silicon metal imports?
FOB is often better if you import regularly and have a freight forwarder you trust; CIF is simpler for first-time or occasional importers. Under CIF the seller arranges freight and insurance to your port in a single invoice, but you have less control over carrier and freight cost. Under FOB you arrange freight and marine insurance yourself, and control rates and policy terms. Under CIF the seller's insurance obligation is minimal, typically ICC(C), so high-value shipments may need supplemental coverage.
Which Incoterms do you support?
We manage international shipping under your preferred Incoterms: CIF, FOB, DAP and more, door-to-door, including customs documentation.
Can AL-LINX handle the entire import process?
Yes. AL-LINX manages supplier verification, quality control at origin, export documentation, and freight coordination, delivering under the Incoterm that fits your operation.
Which countries do you serve?
We have been collaborating with clients in more than 15 countries for over 18 years, with offices in Querétaro (Mexico), Panama City, Shenzhen and Hong Kong, a new office opening soon in Florence (Italy), and commercial representations in Colombia and the Netherlands.
Aluminum Alloys
What are 6000 series (6xxx) aluminum alloys?
6000 series alloys are aluminum alloyed with magnesium and silicon. The combination gives a remarkable balance of mechanical strength, corrosion resistance, weldability and ease of extrusion, which makes them the most versatile and most widely used aluminum alloys worldwide.
What is the difference between 6063 and 6061 aluminum?
6063 is chosen when appearance and extrusion matter; 6061 when structural strength matters. 6063 has a higher silicon-to-magnesium ratio, which gives superior extrudability, surface finish and anodizing quality. 6061 contains more magnesium and adds 0.15 to 0.40% copper, which raises its strength (310 MPa ultimate tensile strength in T6, against 241 MPa for 6063-T6) at the cost of slightly lower corrosion resistance and extrudability.
Why is silicon metal used in aluminum alloys?
Silicon is one of the main alloying elements of aluminum: grade 553 is primarily used in aluminum alloy production, where it improves strength and reduces weight in die-casting applications. In the 6000 series, silicon combines with magnesium to give the balance of strength, corrosion resistance and extrudability those alloys are known for.
Degassing and Graphite Rotors
Why does molten aluminum need degassing?
Degassing removes the hydrogen that molten aluminum absorbs from humidity and combustion atmospheres, which otherwise forms porosity that weakens castings on solidification. In rotary degassing, a spinning graphite rotor injects inert gas and shears it into fine bubbles that strip hydrogen as they rise.
Why are degassing rotors made of graphite?
Graphite survives immersion in molten aluminum at 700 °C and above, resists thermal shock, and is not wetted by the melt. No practical alternative matches that combination at consumable-part cost.
How long do graphite rotors last in aluminum degassing?
Typically 4 to 8 weeks in continuous service, depending on graphite grade, anti-oxidation treatment, melt temperature, and rotation speed. Oxidation at the melt line is the usual failure zone, and shafts usually outlast rotors.
What graphite properties matter for a degassing rotor?
Density, grain size, anti-oxidation treatment and machining tolerance. A density of 1.75 to 1.85 g/cm³ slows oxidation and erosion, a fine and uniform grain gives uniform wear and stable balance at speed, impregnation or coating extends life at the melt line, and threads and runout machined to drawing prevent vibration and early breakage.
What gas is used with graphite degassing rotors?
Argon or nitrogen. Argon is more effective per volume and chemically inert; nitrogen is cheaper and adequate for many alloys and process windows.
Can I buy graphite rotors and shafts separately?
Yes. Shafts generally outlast rotors, so most operations consume rotors at a higher rate. Threads must match exactly, which is why both should be machined to the same drawing standard.
Does AL-LINX supply custom-machined graphite rotors?
Yes. AL-LINX works from your drawing or your degassing unit's specification, with dimensional inspection at origin and full documentation on every lot.
Cryolite
What does cryolite do in aluminum production?
Cryolite (Na3AlF6) is the flux that makes electrolytic aluminum smelting viable: in the Hall-Héroult process, alumina dissolved in a molten cryolite bath is reduced at around 950 to 980 °C, instead of the more than 2,000 °C it would need on its own. The bath works as solvent, as conductor of the electrolysis current, and as density separator, since molten aluminum sinks below it for clean tapping.
Is natural cryolite still available?
Commercially, no. The main natural deposit in Ivittuut, Greenland, was exhausted in the 20th century. Industrial buyers today purchase synthetic cryolite manufactured from fluorite-derived chemistry.
What is the difference between sandy and powder cryolite?
Sandy (granular) cryolite flows better, doses more precisely, and generates less dust at the cell line. Powder grades are usually cheaper and are common in flux blends for secondary aluminum.
Can cryolite be used in secondary aluminum and foundries?
Yes. Beyond electrolysis, cryolite works as a flux component that helps separate oxides from molten metal and improves recovery when remelting scrap and dross.
How is cryolite packed for export?
Typically in 25 kg woven bags with moisture-proof liners, or 1,000 kg big bags on pallets. The critical requirement is moisture protection throughout the sea voyage.
Magnesium, Ceramic Blanket and Other Materials
Which magnesium ingot grades are most common?
The most common commercial grades are Mg9990 (99.90%), Mg9995 (99.95%) and Mg9998 (99.98%). Mg9990 is the standard for die casting alloys such as AZ91, AM60 and AM50 and for desulfurization; the higher grades are used where impurities such as iron, nickel and copper must be tightly controlled.
Are magnesium ingots dangerous goods for shipping?
Yes. Magnesium is classified as a flammable solid under IMDG regulations (UN 1869, Class 4.1), so it needs certified packaging, a dangerous goods declaration and a packing certificate for sea freight. Because it reacts with moisture, packaging should include sealed polyethylene inner bags, desiccant and steel-banded wooden pallets.
What temperature can ceramic fiber blanket withstand?
Standard grades are classified at 1,260 °C, with high-alumina and zirconia grades reaching 1,360 to 1,430 °C. Continuous operating temperature should stay 150 to 250 °C below classification temperature.
Which ceramic fiber blanket density should I choose?
96 kg/m³ suits most backup insulation and covers; 128 kg/m³ offers better strength and lower conductivity for hot-face and structural applications.
Besides silicon, what other materials do you supply?
We also supply synthetic cryolite, magnesium ingots, ceramic fiber blankets, graphite shafts and rotors, and custom-sourced metallurgical materials like fluorite, bauxite, alumina, antimony, tin and zinc ingots.
Quotes
How do I request a quote from AL-LINX?
Send your requirements through the contact form or to info@al-linx.com: product and grade, quantity, delivery terms and timeline. For graphite rotors, include your drawing or degassing unit model and consumption rate. AL-LINX can quote freight-inclusive or ex-works, depending on your logistics setup.
What are your prices and minimum order quantities?
Every order of aluminum, silicon, magnesium and other supplies for the metallurgical industry is quoted based on the product, packaging, volume and destination. Contact us and we will prepare a proposal for you.