Ferrosilicon is a ferroalloy of iron and silicon produced in submerged electric arc furnaces by reducing quartz with coke, with iron added as scrap or iron ore. High-purity grades are used where silicon content, impurity control and consistency matter more than cost. This article explains the grade designations 441 and 553, shows how ferrosilicon differs from metal silicon, reviews the main application fields, and includes a dated price reference table recorded on July 14 to help buyers interpret historical quote levels.
What Do the Grades 441 and 553 Mean
In the international silicon trade, the three-digit designations 441 and 553 describe the maximum permitted content of iron, aluminum and calcium in the product, expressed in weight percent. For grade 441, the limits are 0.4 percent iron, 0.4 percent aluminum and 0.1 percent calcium, which leaves a silicon content of about 99 percent. For grade 553, the limits are 0.5 percent iron, 0.5 percent aluminum and 0.3 percent calcium, and the silicon content is typically specified at or above 98.5 percent. The same notation is used across the metallurgical silicon industry, and buyers should confirm the exact limits in the applicable national standard or the mill certificate, because the boundaries can vary slightly between standards.
The digits therefore describe impurity control rather than a fixed silicon number. A 441 grade is tighter on calcium and slightly tighter on iron and aluminum than 553, which makes it a preferred input for aluminum-silicon alloys and chemical uses where calcium interferes with the process.
Ferrosilicon and Metal Silicon: How They Differ
Ferrosilicon and metal silicon are often confused because both are silicon-iron products, but they differ in silicon level and production target. Ferrosilicon is a ferroalloy whose grades are named by silicon content, such as FeSi72 and FeSi75, meaning a nominal silicon content of 72 and 75 percent respectively. It is produced in large quantities and consumed mainly as a deoxidizer and alloying agent in steelmaking and foundry iron. Metal silicon, also called industrial silicon, is a purer product with silicon content above 98.5 percent, and the 441 and 553 designations are most commonly applied to this category. In trade documents the two product families are frequently mixed, so it is important to check whether the specification refers to a ferrosilicon grade such as FeSi75 or a metallurgical silicon grade such as 441.
Main Applications of High-Purity Ferrosilicon
Steelmaking: silicon removes oxygen from molten steel and raises strength and hardenability; low-aluminum ferrosilicon is preferred for specialty steel grades.
Foundry: ferrosilicon is used as an inoculant in gray and ductile iron to control graphite structure.
Aluminum alloys: silicon improves casting fluidity and mechanical properties of aluminum-silicon alloys.
Chemical industry: silicon metal is the raw material for silicones, fumed silica and other organosilicon products.
Solar and electronics: high-purity silicon is further refined for photovoltaic and semiconductor applications.
Price Reference Snapshot: July 14
The tables below were recorded on July 14 as a single-day reference snapshot. They are historical quote levels, not current offers, and actual transaction prices depend on quantity, delivery terms, payment conditions and quality.
Export ferrosilicon reference prices, USD per metric ton:
| Product | Grade | Quote | Basis |
|---|---|---|---|
| Ferrosilicon | 72 | 1000-1030 | FOB Tianjin Port |
| Ferrosilicon | 75 | 1080-1100 | FOB Tianjin Port |
Domestic low-aluminum ferrosilicon reference prices, yuan per metric ton, natural block, ex-factory cash price including tax:
| Specification | Region | Price |
|---|---|---|
| Si75 Al below 0.1 percent | Qinghai | 6700-6750 |
| Si75 Al below 0.5 percent | Qinghai | 6400-6450 |
| Si75 Al below 0.1 percent | Inner Mongolia | 6700-6750 |
| Si75 Al below 0.5 percent | Inner Mongolia | 6400-6450 |
The export table shows the premium of FeSi75 over FeSi72, which reflects the higher silicon content and the tighter specifications buyers attach to the 75 grade. The domestic table shows a clear premium for the lower-aluminum variant, because low aluminum content is valued in high-grade steel production.
What Moves Ferrosilicon Prices
Several factors drive ferrosilicon price movements. Electricity is the largest production cost, so regional power tariffs and hydroelectric availability directly affect supply. Quartz, coke and iron input prices set the raw-material cost floor. Export demand from steel producers in Southeast Asia, Japan, Korea and Europe absorbs the surplus of Chinese capacity, and logistics costs at ports such as Tianjin add to the delivered price. Exchange rates also matter because most export contracts are settled in USD. Finally, environmental and production restrictions in the main producing provinces can tighten supply quickly and push prices up.
Frequently Asked Questions
What is the difference between ferrosilicon 441 and 553? The digits describe the maximum iron, aluminum and calcium content. Grade 441 permits up to 0.4 percent iron, 0.4 percent aluminum and 0.1 percent calcium, while grade 553 permits 0.5 percent iron, 0.5 percent aluminum and 0.3 percent calcium. The 441 grade therefore has higher silicon content and tighter impurity control.
Is ferrosilicon the same as metal silicon? No. Ferrosilicon grades such as FeSi72 and FeSi75 contain 72 to 80 percent silicon, while metal silicon contains 98.5 percent or more. Both come from electric furnace reduction of quartz, but they serve different applications and are traded as separate products.
What is ferrosilicon used for in steelmaking? Ferrosilicon is the standard deoxidizer for molten steel and an alloying agent that raises strength and hardenability. Low-aluminum grades are used when aluminum inclusions must be minimized in specialty steels.
Why does low-aluminum ferrosilicon cost more? Lower aluminum requires tighter process control and sometimes special raw materials or refining steps. The cost difference appears clearly in the domestic reference table, where the low-aluminum variant is quoted roughly 250 to 300 yuan per ton above the standard grade.
How should a buyer specify ferrosilicon? purchase specification should state the product family, the grade, the silicon range, the maximum iron, aluminum and calcium content, the size range, the packing method and the standard to be applied, so that the mill certificate can be checked against the order.