Understanding Silicon Metal Grade Numbers

Industrial silicon is commonly classified according to the maximum content of its main metallic impurities, especially iron, aluminum and calcium.

You may see commercial names such as 441 and 553, while the current GB/T 2881-2023 standard uses four-digit grade designations such as Si4410 and Si5530.

What Do the Numbers Mean?

The digits indicate the maximum Fe, Al and Ca limits.

For Si3303, the limits are Fe ≤0.30%, Al ≤0.30% and Ca ≤0.03%. For Si2202, they are Fe ≤0.20%, Al ≤0.20% and Ca ≤0.02%.

This is why the grade code is more useful than looking only at the silicon percentage: it immediately shows which impurity limits are being controlled.

Grade-by-Grade Breakdown

Silicon Metal 441 — Common Aluminum Alloy Grade

Silicon Metal 441, corresponding to Si4410 in the four-digit system, has a nominal silicon content of approximately 99.10%, with Fe ≤0.40%, Al ≤0.40% and Ca ≤0.10%.

441 is commonly considered where aluminum alloy production requires tighter Fe, Al and Ca control than lower-cost general-purpose grades.

If you are comparing 441 with a more economical grade, see our

Silicon Metal 441 vs 553 comparison
.

Silicon Metal 553 — General-Purpose Industrial Grade

Silicon Metal 553, commonly corresponding to Si5530, has a nominal silicon content of approximately 98.70%, with Fe ≤0.50%, Al ≤0.50% and Ca ≤0.30%.

Because its impurity limits are less restrictive than 441, 3303, 2202 or 1101, 553 is commonly considered for applications where very low Fe, Al or Ca levels are not required.

Silicon Metal 3303 — Lower-Calcium Chemical Grade

Silicon Metal 3303 has a nominal silicon content of approximately 99.37%, with Fe ≤0.30%, Al ≤0.30% and Ca ≤0.03%.

The lower calcium limit makes 3303 attractive for chemical and organosilicon applications where impurity control can affect reaction efficiency and downstream product quality.

You can review the detailed

Silicon Metal 3303 specification

for available particle sizes and packing options.

Silicon Metal 2202 — Higher-Purity Industrial Silicon

Silicon Metal 2202 has a nominal silicon content of approximately 99.58%, with Fe ≤0.20%, Al ≤0.20% and Ca ≤0.02%.

Compared with 3303, 441 and 553, 2202 provides tighter control of all three major impurity elements. It can therefore be considered where downstream chemical or refining processes require cleaner feedstock.

See our

Silicon Metal 2202

page for current product information.

Silicon Metal 1101 — High-Purity Industrial Feedstock

Silicon Metal 1101 has a nominal silicon content of approximately 99.79%, with Fe ≤0.10%, Al ≤0.10% and Ca ≤0.01%.

Among these common industrial silicon grades, 1101 offers the tightest Fe, Al and Ca limits.
It can be used as a higher-purity industrial feedstock where further refining or downstream purification is required.

GB/T 2881-2023 Chemical Composition Reference

The current GB/T 2881-2023 standard classifies industrial silicon by chemical composition. The table below summarizes the five grades covered in this guide.

Application Matching Guide

The correct silicon metal grade depends on which impurities matter most to your process. A higher-purity grade is not automatically necessary if your downstream specification can accept a more economical grade.

Aluminum Alloys

Silicon metal is widely used as a silicon source in aluminum-silicon alloys. Grades such as 441 are commonly evaluated where controlled Fe, Al and Ca levels are required.

The final grade should be selected according to the alloy chemistry and the maximum impurity contribution your melt can accept.

Organic Silicon and Siloxanes

Organosilicon production can be sensitive to impurity composition, especially Fe, Al and Ca. Grades such as 3303 or cleaner material may be considered where tighter impurity control supports downstream reaction and product requirements.

Particle size can also affect reaction behavior, so chemical composition and size specification should be confirmed together.

Polysilicon and Further Purification

Higher-purity industrial silicon grades such as 2202 and 1101 may be used as feedstock where subsequent purification is required.

However, Fe, Al and Ca alone are not enough to determine suitability for photovoltaic or electronic material production. Trace elements such as boron, phosphorus and other metallic impurities may also require specific limits.

Refractory and Foundry Applications

Silicon metal lumps or powders can also be used in selected metallurgical, refractory and foundry processes. In these applications, particle size, reactivity and the acceptable impurity range may be as important as nominal Si content.

Do not select the grade from the application name alone. Send us the target chemistry and particle size if your process has a specific requirement.

How Impurities Affect Downstream Processing

Iron

Iron contributes directly to the total Fe level introduced into downstream alloys or chemical processes. If your final product has a tight Fe specification, moving from 553 or 441 to 3303, 2202 or 1101 can reduce the impurity contribution from the silicon feedstock.

Aluminum

Aluminum limits can influence alloy balancing and chemical processing. Do not assume two grades with similar Si content are interchangeable if their Al limits are different.

Calcium

Calcium is one of the clearest differences between grades such as 553 and 3303. The maximum Ca limit decreases from 0.30% in Si5530 to 0.03% in Si3303, 0.02% in Si2202 and 0.01% in Si1101.

What to Specify When Ordering Silicon Metal

To receive a quotation that matches your actual process, send us more than just “441” or “3303”.

Silicon Metal Grade FAQ