Silicon metal is sold by grade, and those grades are defined by their maximum impurity content. The three-digit or four-digit number is not arbitrary:
each digit represents the maximum percentage of iron (Fe), aluminum (Al), and calcium (Ca), in that order.
So Silicon 553 means: max 0.5% Fe, max 0.5% Al, max 0.3% Ca.
Understanding this system is the first step to sourcing the right grade for your process.
The most common industrial grades
Silicon 553
The workhorse of the industry. Used heavily in aluminum alloy production and chemical synthesis. It offers a strong balance between purity and cost,
making it the default choice for most applications that do not require tight impurity control.
Silicon 441
A step up in purity, with tighter aluminum limits. Preferred in applications where aluminum contamination is a concern, particularly in certain
aluminum alloys and silicone chemical production.
Silicon 411 and 421
These grades differ mainly in their calcium content. 411 has tighter Ca limits, making it preferable for processes sensitive to calcium, including some
silicone and polysilicon feedstock applications.
Silicon 3303
Higher iron tolerance, lower aluminum and calcium. Often used in steel deoxidation and ferrosilicon production where iron is not a contaminant concern
but aluminum needs to be controlled.
Silicon 2202
Used in more demanding chemical and silicone applications. The tighter spec on both Al and Ca makes it suitable as a feedstock for silicone polymers
and high-purity chemical intermediates.
Silicon 1101
Near the top of the industrial-grade pyramid. Used in advanced silicone production and as a stepping stone toward semiconductor-grade silicon when
further purification is applied.
Off-Grade Si 97
Not a standard grade but widely used in metallurgy, particularly for steel deoxidation and cast iron production. Lower purity, lower cost.
How to choose the right grade
The key variables are your application, your tolerance for each impurity, and your budget. A few questions that help narrow it down:
– Is aluminum a contaminant in your process? Avoid 553 and consider 441 or lower.
– Are you producing silicone polymers? 2202 or 1101 are typical starting points.
– Is this for aluminum alloys? 553 or 441 depending on your alloy spec.
– Steel deoxidation? 3303 or off-grade 97 are cost-effective choices.
A note on sizing and packaging
Grade is only half the specification. Silicon metal is also sold by particle size, typically 10-50mm, 50-100mm, or 10-100mm, and packaged in big bags
or drums. Make sure your supplier can match both the grade and the sizing to your charging equipment.
At AL-LINX, we supply all major grades directly from our certified facility in Anyang, China, with full CoA documentation and custom sizing on request.
Contact us (https://al-linx.com/contacts/) to discuss your specification.