Ferrosilicon 72 and 75 Selection Guide for Steelmaking and Casting

In the metallurgical and casting industries, ferrosilicon 72 (FeSi72) and ferrosilicon 75 (FeSi75) are the two most widely used high-silicon ferroalloys. Although the silicon content differs by only approximately 3%, their functions and roles in core steelmaking processes such as deoxidation, alloying, casting inoculation, and spheroidizing are significantly different.

The fundamental differences between ferrosilicon 72 and 75 stem from their silicon content and impurity control standards, which directly determine their physical properties and application scenarios:

This compositional difference gives Ferrosilicon 72# an advantage in impurity-sensitive processes, while Ferrosilicon 75#, thanks to its high silicon content, excels in efficient metallurgical reactions.

In the steelmaking process, the core functions of ferro silicon are deoxidation and alloying, but the application logic of FeSi72 and 75 differ significantly:

1. Deoxidation Function: A Trade-off between Efficiency and Cost

Silicon has a strong chemical affinity for oxygen, making it an indispensable deoxidizer in steelmaking. Due to its higher silicon content, 75# Ferrosilicon has a deoxidation efficiency 10%-15% higher than 72# Ferrosilicon. It can quickly remove oxygen from molten steel, reduce oxide inclusions, and significantly improve steel purity. In the production of high-strength steel and electrical steel, which require stringent purity requirements, 75% ferrosilicon is the preferred choice. For example, 4-5 kg ​​of 75% FeSi is required to produce one ton of electrical steel to ensure the steel's magnetic permeability and aging resistance.

Ferrosilicon72, due to its cost advantage, is widely used for deoxidation of conventional steel grades such as low-alloy structural steel and spring steel. Although its deoxidation rate is slightly slower, by precisely controlling the addition amount, it can meet basic deoxidation requirements while reducing the cost per ton of steel by 8-12 yuan. Data from a steel mill shows that after using 72% FeSi for deoxidation, the oxide inclusion content of low-alloy structural steel can still be controlled below 0.03%, meeting industry standards.

2. Alloying Effect: Precise Matching of Properties

As an alloying additive, silicon enhances the strength, hardness, and elasticity of steel. FeSi75, due to its stable composition, is often used in high-end steel grades requiring precise control of silicon content. For example, adding silicon ferro 75 to silicon steel can achieve uniform silicon distribution and reduce hysteresis losses by over 30%. FeSi72, on the other hand, is suitable for applications requiring moderate silicon content. For example, in bearing steel production, adding 72%fesi can stabilize the silicon content at 0.4%-0.8%, maintaining a balance between hardness and toughness.

In the casting industry, fesi alloy primarily serves as an inoculant and spheroidizing agent. Their applications differ depending on impurity control and reactivity:

1. Inoculation: The Key to Regulating Graphite Precipitation

The key to inoculation is promoting uniform graphite precipitation and improving casting properties. Ferro silicon 72, due to its low carbon content (≤0.08%) and strictly controlled total impurities, is an ideal choice for inoculation of ductile iron and malleable cast iron. Experiments have shown that adding 0.3%-0.6% ferrosilicon 72 alloy to ductile iron production can increase the proportion of type A graphite by 40% and raise the tensile strength of the casting to over 500 MPa.

Ferro silicon 75, due to its high aluminum content (≥1.5%), offers advantages in gray cast iron inoculation. The released aluminum combines with nitrogen in the molten iron to form AlN particles, which serve as the nuclei for graphite nucleation and extend the effective inoculation time to over 25 minutes. A water pump manufacturer using ferrosilicon alloy 75 inoculation reduced its casting scrap rate from 8% to 2% and improved wear resistance by 20%.

2. Spheroidization Assistance: A Synergistic Effect for Performance Optimization

In ductile iron production, 72ferrosilicon is often used in combination with magnesium alloys as a composite spheroidizing agent. Its low impurity content prevents consumption of spheroidizing elements and improves the roundness of graphite spheres by 35%. 75fesi is mostly used for secondary inoculation of thick-walled castings. By adding 75ferrosilicon, insufficient inoculation in the core of the casting can be compensated and shrinkage defects can be reduced.

The functional differences between Ferrosilicon 72 and 75 are essentially a matter of cost-effectiveness and high performance. fesi alloy 75, with its high silicon content and strong reactivity, dominates high-end steelmaking and thick-wall castings. fesi alloy 72, with its precise impurity control and cost advantages, dominates conventional metallurgy and precision casting. Companies must comprehensively select the right Ferrosilicon based on product positioning, process requirements, and cost budget to maximize profitability.

If you have questions about selecting, purchasing, or exporting ferrosilicon 72 or 75, we, a company with years of experience in ferrosilicon export, can provide one-on-one professional technical guidance to help you precisely match your production needs. Contact us now for a free customized quote and samples, helping you reduce costs and increase efficiency in production and seize opportunities in the international market! Feel free to contact us by private message or phone using the contact information provided on this page, and we will assist you promptly.