Ferro Silicon 72 (FeSi 72) is a mainstream medium-grade silicon alloy specially formulated for general steelmaking and conventional foundry applications. Sitting between low-grade ferrosilicon and high-purity FerroSilicon (FeSi 75), FeSi 72% delivers a perfect balance of reliable metallurgical performance, stable pricing, and low melting volatility. It avoids the high cost of FeSi 75% and the unstable impurity control of low-grade FeSi, making it the most cost-effective solution for mass production of carbon steel, structural low-alloy steel, gray cast iron, and common ductile iron.
Basic Specification & Core Functions of FeSi 72
Qualified industrial FerroSilicon 72 strictly follows international and Chinese national standards (GB/T 2272-2017), with fixed chemical composition and low harmful impurities to ensure consistent smelting results across different batches. Its core technical parameters are as follows:
Silicon content: 72%–74%
Low impurities: S ≤ 0.04%, P ≤ 0.04%
Stable recovery rate: 82%–86% in normal smelting conditions
Thanks to its stable silicon content and ultra-low sulfur and phosphorus impurities, FeSi 72# performs three irreplaceable core functions in steelmaking and foundry production, solving common production pain points such as insufficient deoxidation, unstable mechanical properties, and casting surface defects:
Primary deoxidizer: Effectively removes dissolved oxygen from molten steel and molten iron, inhibits the formation of harmful oxide inclusions, improves metal compactness, and reduces internal porosity and crack defects in finished products.
Basic alloying agent: Silicon elements dissolve into the steel matrix to form solid solution strengthening, significantly improving the tensile strength, hardness, wear resistance and structural stability of carbon steel and low-alloy steel.
Foundry inoculant: Acts as an efficient graphite nucleating agent in cast iron production. It promotes uniform and fine graphite precipitation, eliminates undercooled graphite, improves molten iron fluidity, and reduces shrinkage cavities, porosity and cold shut defects in castings.
Correct Usage in Steelmaking
72% FeSi is widely used in the smelting of ordinary carbon steel, building structural steel, mild steel and general low-alloy steel. Unlike high-purity FeSi 75 used for high-end spring steel and precision alloy steel, Ferro silicon 72 is more suitable for large-scale conventional steel production. Standardized adding procedures are essential to maintain stable silicon recovery rate and consistent steel composition.
Adding Timing
FeSi 72 must be added in the later stage of steelmaking. Operators should complete oxidation slag removal first, then add FeSi 72 during molten steel tapping or LF ladle refining. Adding FeSi72 in the early oxidation stage will cause severe silicon oxidation and burning loss, greatly reducing the recovery rate and leading to insufficient deoxidation.
Recommended Dosage
- Ordinary carbon steel: 3–5 kg per ton of molten steel
- Low-alloy structural steel: 5–7 kg per ton of molten steel
Operation Tips
- Spread FeSi72% evenly into the molten steel flow to ensure rapid melting and uniform diffusion, avoiding local silicon concentration differences.
- Stabilize molten steel temperature between 1540–1590°C. Too low temperature causes incomplete melting, while excessive high temperature accelerates silicon burning loss.
- Strictly control the total addition amount. Excess silicon residue will increase steel brittleness, reduce impact toughness, and affect subsequent rolling and forging performance.
Application Method in Foundry
In the foundry industry, FeSi 72 serves as a cost-effective inoculant and nucleating agent, mainly applied to gray cast iron, ordinary ductile iron, and mechanical casting parts with conventional performance requirements. It is the most commonly used ferrosilicon inoculant for mass casting production.
- Inoculation addition standard: Add 0.2%–0.4% of molten iron total weight during ladle pouring or stream inoculation to achieve the best graphite refinement effect.
- Core improvement effects: Refines cast iron grain structure, eliminates coarse graphite, significantly improves casting surface smoothness, and effectively solves common defects such as porosity, shrinkage cavity and cold shut.
- Cost advantage: Compared with high-grade FeSi 75, FeSi 72 has lower unit price and stable inoculation performance, helping foundries reduce raw material costs while maintaining qualified casting quality, ideal for standardized mass production.
Size Selection Guide
FerroSilicon72% size directly affects melting speed, silicon recovery rate and smelting stability. Selecting a matched size according to furnace type and process can effectively reduce material waste and improve production efficiency:
- 10–50mm large particles: Suitable for large-capacity induction furnaces and ladle tapping deoxidation, with slow melting and long-lasting deoxidation effect.
- 3–15mm fine particles: Suitable for medium and small furnaces and stream inoculation processes, featuring fast melting and uniform mixing for precise composition control.
Ferro Silicon 72 is a cost-effective and highly practical metallurgical auxiliary material for conventional steelmaking and foundry industries. With its stable chemical index, low impurity content and flexible applicability, it can fully meet the production needs of carbon steel, low-alloy steel and ordinary cast iron. By adopting standardized adding timing, scientific dosage control, matched size and standardized storage management, manufacturers can maintain stable silicon recovery rate, reduce product defects, and effectively control production costs. For most steel mills and foundries that balance quality and cost, FeSi 72 is the most reliable daily-use silicon alloy option.
