Ferrosilicon Nitride
Pure-Si₃N₄ Performance, Half the Cost
FeSiN delivers β-Si₃N₄ high-temperature strength with an Fe₃Si iron phase that actively promotes sintering — not an inert filler. Refractory-grade powder for blast-furnace taphole clay, steelmaking-grade granules for controlled nitrogen alloying. Proven at Baosteel since 1994.
Product Overview
What Is Ferrosilicon Nitride?
A dual-track nitride alloy — β-Si₃N₄ on an Fe₃Si core — engineered for both refractory bonding and steel nitrogen alloying
Ferrosilicon Nitride (FeSiN) is a composite nitride whose main crystalline phase is β-Si₃N₄, grown around an Fe₃Si metallic core during flash combustion synthesis of FeSi75 powder under nitrogen. The result is a material that behaves like pure silicon nitride where it matters — but costs about half as much.
It serves two industrial fields from one product family. As a refractory-grade powder, FeSiN is the key nitrogen-bonding additive in blast-furnace taphole clay, iron-runner castables, and Al₂O₃-SiC-C refractories. As a steelmaking-grade granule, it is a controlled nitrogen source for HRB400 rebar, grain-oriented silicon steel, and specialty steels.
Unlike inert additives, the Fe₃Si iron phase actively promotes sintering and acts as a plastic phase during hot processing — densifying the matrix, resisting slag penetration, and keeping the taphole easy to open. That is performance a mechanical Si₃N₄ mix cannot replicate.
What it is
β-Si₃N₄ main phase on an Fe₃Si core; gray-white/tan-brown powder or gray-white granules.
Where it’s used
Taphole clay, iron-runner castables, ASC refractories; HRB400 rebar & silicon-steel nitriding.
Why it wins
Fe₃Si promotes sintering & anti-hardening; β-Si₃N₄ gives hot strength and thermal-shock resistance.
Cost edge
~50% the price of pure Si₃N₄ with comparable in-service performance.
Why FeSiN
Three Reasons Buyers Switch to FeSiN
The commercial case in numbers — cost, performance, and supply working together
~50%
Cost of Pure Si₃N₄
Flash combustion synthesis produces FeSiN at 1/10 to 1/3 the cost of conventional silicon nitridation. You get β-Si₃N₄ performance at roughly half the price — the single biggest lever on refractory and alloy budgets.
2× tracks
One Product, Two Fields
Refractory-grade fine powder for taphole clay and castables; steelmaking-grade granules for nitrogen alloying. A single qualified supplier covers both your refractory and melt-shop nitrogen needs.
30+ yrs
Field-Proven Reliability
In continuous blast-furnace taphole-clay service at Baosteel since 1994. This is not a lab curiosity — it is a mature, industrially validated additive with documented process gains.
Composition
Dual-Grade Selector
Two precisely controlled nitride grades — choose by your nitride-content and thermal-performance target
A
Grade A — Premium
Maximum Si₃N₄ for critical refractories
Best for: critical taphole clay, blast-furnace refractories and any formulation demanding the highest nitride content and thermal-shock resistance. Bulk density ≥3.6 g/cm³.
B
Grade B — Cost-Optimized
Best cost-performance for standard use
Best for: standard taphole clay, steelmaking nitriding and cost-sensitive refractory formulations where value dominates the spec. Bulk density ≥3.6 g/cm³.
Typical Properties
Chemical & Physical Specification
FerrumX’s exact composition limits for both grades, plus the handling properties that make FeSiN easy to formulate and dose
| Grade | Si₃N₄ (%) | Si (%) | N (%) | Fe (%) | Al+Ca (%) | Bulk Density |
|---|---|---|---|---|---|---|
| Grade A | 75–80 | 47–51 | 30–33 | 12–16 | <2.5 | ≥3.6 g/cm³ |
| Grade B | 70–75 | 49–52 | 28–30 | 12–16 | <2.5 | ≥3.6 g/cm³ |
Refractory grade: gray-white or tan-brown powder · Steelmaking grade: gray-white granular material
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β-Si₃N₄ Main Phase
Columnar/needle β-Si₃N₄ delivers high-temperature strength, oxidation resistance, and thermal-shock resistance in service.
⚙️
Fe₃Si Sintering Core
The iron phase promotes sintering and acts as a plastic phase — densifying the matrix and preventing over-hardening.
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No Free Silicon
Flash combustion achieves complete conversion — no residual free silicon contamination in the finished product.
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Dual-Track Sizing
Powder distributions for refractory bonding and granule sizes for controlled melt-shop nitrogen release.
Particle Size System
Dual-Track Particle Sizing
Powder distributions for refractory dispersion, granules for steelmaking nitrogen release — matched to how each field actually uses the material
Refractory Track
Powder Grades — 3 Distributions
| Grade | -45μm | -45 to -75μm | +75 to -150μm | +150μm | -75μm Passing |
|---|---|---|---|---|---|
| Fine Powder | >80% | 5–15% | <3% | 0 | 95–100% |
| Standard Powder | 70–80% | 10–20% | 8–15% | <3% | 85–95% |
| Coarse Powder | 60–70% | 10–16% | 10–16% | <8% | 65–80% |
Appearance: gray-white or tan-brown powder. Fine powder maximizes surface area for taphole-clay bonding; coarse powder controls packing density in castables.
Steelmaking Track
Granule Grades — 3 Sizes
| Grade | Particle Size Range | Passing Rate | Typical Use |
|---|---|---|---|
| Fine Granule | 3–5 mm | >90% | Rapid dissolution in smaller ladles |
| Standard Granule | 3–10 mm | >90% | General-purpose nitrogen alloying |
| Coarse Granule | 10–50 mm | >90% | Sustained release in large converters / LF |
Appearance: gray-white granular material. Custom sizes of 0–3 mm and 3–8 mm are available on request — contact FerrumX for tailored particle-size specifications.
Production
Flash Combustion Synthesis
A continuous, self-sustaining process that converts FeSi75 into high-purity FeSiN — at a fraction of traditional nitridation cost
Raw Material
FeSi75 ferrosilicon fine powder, milled to ≤0.088 mm for optimal gas-solid contact and complete nitridation.
FeSi75 · ≤0.088 mm
Reactor Charging
Powder is fed into a vertical reactor against an ascending nitrogen stream; counter-current flow maximizes N₂ exposure.
Vertical · counter-current N₂
Self-Sustaining Burn
At ~1,400°C, the FeSi + N₂ reaction self-sustains under just 0.2 MPa nitrogen pressure; 24–36 h for full conversion.
~1,400°C · 0.2 MPa · 24–36 h
Product Harvest
Loose, porous honeycomb product — each particle an Fe₃Si core wrapped in β-Si₃N₄ crystals — is crushed and classified.
Honeycomb · Fe₃Si + β-Si₃N₄
1/10 – 1/3
Cost vs Traditional
Dramatically lower production cost than conventional silicon nitridation — the foundation of FeSiN’s ~50% price advantage.
No Free Si
Cost vs Traditional
Dramatically lower production cost than conventional silicon nitridation — the foundation of FeSiN’s ~50% price advantage.
1/10 – 1/3
Cost vs Traditional
Dramatically lower production cost than conventional silicon nitridation — the foundation of FeSiN’s ~50% price advantage.
Microstructure
β-Si₃N₄ on Fe₃Si — A Composite Born from Combustion
FeSiN is not a simple mixture. Each phase plays a defined functional role — this is why it outperforms mechanically blended alternatives
| Phase | Content | Crystal Form | Functional Role |
|---|---|---|---|
| β-Si₃N₄ | Main | Columnar / needle-like | High-temperature strength, thermal-shock resistance |
| α-Si₃N₄ | Small amount | Equiaxed | Sintering activity, densification driver |
| Fe solid solution | Minor | Fe₃Si core | Promotes sintering, plastic phase, anti-hardening |
β-Si₃N₄ Matrix
The dominant phase — columnar/needle crystals delivering high-temperature mechanical integrity, thermal-shock resistance, and strength at blast-furnace temperatures.
Primary strength
Thermal-shock resistant
Fe₃Si Core
An iron-silicide core acts as a sintering promoter. During firing it softens plastically, filling pores to form a denser, less-permeable matrix that resists slag penetration.
Plastic phase
sintering promoter
anti-hardening
α-Si₃N₄ Nuclei
A small fraction of equiaxed α-Si₃N₄ provides sintering activity — its higher surface energy drives densification at lower temperatures than β-Si₃N₄ alone.
Sintering-active phase
densification driver
Porous Honeycomb Microstructure
The hallmark of flash-combustion FeSiN: a loose, porous, honeycomb-like structure where short columnar β-Si₃N₄ crystals surround each Fe₃Si core. This architecture is functionally critical — the porosity allows nitrogen infiltration and bonding within refractory matrices, while the metallic iron core drives plastic-phase sintering in service. The result is a material that strengthens taphole clay through nitride bonding and controlled metal-phase flow, rather than acting as an inert filler.
Porous honeycomb structure
Fe₃Si core + β-Si₃N₄ shell
Columnar crystal morphology
Promotes nitride bonding
Proof of Performance
Taphole Clay ROI — Baosteel Since 1994
Over three decades of continuous blast-furnace service. Here is what the industrial data shows.
18 → 6–12
Taphole Openings / Day
Fewer openings mean fewer interruptions, higher furnace availability, and lower labor cost per campaign.
1.2 → 0.5
Clay Use (kg / t Hot Metal)
More than 50% lower clay consumption per tonne of hot metal — direct material-cost savings.
Significant ↑
Iron Throughput / Runner
Longer campaign life and less frequent maintenance from higher iron throughput before relining.
Recommended addition: 5–9% FeSiN in the taphole-clay formulation — simultaneously improving strength, oxidation resistance, and slag-penetration resistance while keeping the taphole easy to open. The ideal balance of performance and cost.
Applications
Application Deep Dives
Where FeSiN delivers measurable performance and cost advantage across refractories and the melt shop
Blast-Furnace Taphole Clay
The flagship application. β-Si₃N₄ provides hot strength and slag resistance while the Fe₃Si core prevents over-hardening — so the taphole opens cleanly. Validated at Baosteel for 30+ years.
Al₂O₃-SiC-C Iron-Runner Castables
At 5–9% addition in ASC iron-runner castables, FeSiN improves both erosion resistance and mechanical strength. β-Si₃N₄ raises hot strength; the Fe₃Si core densifies the matrix against slag and iron penetration.
HRB400 Rebar Microalloying
The FeV50 + FeSiN composite scheme is a proven cost-reduction route for HRB400 rebar. FeSiN supplies stable nitrogen for V(C,N) precipitation strengthening — cutting total alloy cost by $5–20 per tonne of steel.
Grain-Oriented Silicon & Specialty Steel
FeSiN granules act as a controlled nitrogen source for grain-oriented silicon steel and other specialty grades — delivering stable nitrogen recovery without the handling hazards of gaseous nitrogen or the premium of pure Si₃N₄.
Competitive View
FeSiN vs Alternative Nitrogen Sources
How ferrosilicon nitride stacks up against pure Si₃N₄ and other nitride additives on cost and behavior
| Additive | Relative Cost | Sintering Behavior | Taphole Opening | Where FeSiN Wins |
|---|---|---|---|---|
| FeSiN (FerrumX) | ~50% | Fe phase promotes sintering | The iron phase prevents over-hardening | Half cost, active sintering, easy opening |
| Pure Si₃N₄ | Baseline (100%) | Needs higher sintering temperature | Hardens — harder to open | FeSiN ~50% cheaper, comparable in service |
| Gaseous N₂ Injection | Low material cost | N/A (melt only) | N/A | Stable, safe solid nitrogen source |
| Vanadium Nitride (VN) | High (scarce V) | N/A (melt only) | N/A | Cheaper N supply in FeV50 + FeSiN scheme |
| Mechanical Si₃N₄ Blend | Variable | Inert filler, no sintering aid | No anti-hardening benefit | Integral Fe₃Si core, not a loose mix |
The trade-off: FeSiN’s maximum strength is marginally below pure Si₃N₄ — a difference that is negligible in most refractory and steelmaking applications where cost and sintering behavior dominate the value equation.
Quality & Logistics
Quality, Certification & Packaging
Every lot is tested and packed to keep nitride content and particle sizing consistent from our plant to your line
Certification & Testing
ISO 9001 & ISO 45001 certified manufacturer — quality and occupational-safety management.
Chemical analysis of Si₃N₄, Si, N, Fe, Al+Ca on every batch against the grade specification.
Sieve analysis confirms powder distribution and granule size compliance.
Density & appearance checks ensure a density≥3.6 g/cm³ and a uniform product color.
Packaging & Supply
25 kg bags or 1-ton jumbo bags, moisture-proof for safe storage.
Refractory powder (3 distributions) and steelmaking granules (3 sizes) as standard.
Custom sizing: 0–3 mm and 3–8 mm granules available on request.
Backed by 120,000 t/yr integrated silicon-based capacity for supply stability.
Why FerrumX
Why Choose FerrumX
An integrated silicon-based and nitride-alloy producer built for consistent, cost-effective supply
Certified Quality
ISO 9001 & ISO 45001 certified, with batch-by-batch chemical and sieve verification.
Integrated Capacity
120,000 t/yr of silicon carbide and silicon-based production secures raw material stability.
Dual-Track Grades
Grade A / Grade B and refractory-vs-steelmaking sizing matched to your exact process.
Technical Support
Metallurgical guidance on addition rate, sizing, and dosing to maximize performance.
FAQ
Frequently Asked Questions About Silicon Carbide
Direct answers to common questions about silicon carbide for refractory applications.
Ferrosilicon nitride (FeSiN) is a composite nitride alloy whose main crystalline phase is β-Si₃N₄ grown around an Fe₃Si metallic core, produced by flash combustion synthesis of FeSi75 powder under nitrogen. It is used in two main fields: as a refractory-grade powder additive in blast-furnace taphole clay, iron-runner castables, and Al₂O₃-SiC-C refractories; and as a steelmaking-grade granular nitrogen source for HRB400 rebar, grain-oriented silicon steel, and specialty steels. Its key commercial advantage is delivering performance close to pure silicon nitride at roughly half the cost.
Ferrosilicon nitride costs approximately 50% of pure Si₃N₄, making it the most cost-effective bulk nitride source for refractory and steelmaking use. Flash combustion synthesis produces FeSiN at roughly 1/10 to 1/3 the cost of conventional silicon-nitridation routes. Beyond raw price, the Fe₃Si iron phase actively promotes sintering — lowering firing energy and improving densification — so total installed cost in taphole clay and castables drops further while performance stays close to pure Si₃N₄.
FerrumX offers two grades. Grade A contains Si₃N₄ 75–80%, Si 47–51%, N 30–33%, Fe 12–16%, with Al+Ca under 2.5% — recommended for critical taphole clay and blast-furnace refractories demanding the highest nitride content and thermal-shock resistance. Grade B contains Si₃N₄ 70–75%, Si 49–52%, N 28–30%, Fe 12–16%, with Al+Ca under 2.5% — a cost-optimized balance for standard taphole clay and steelmaking formulations. Both grades share a bulk density of ≥3.6 g/cm³ and the Fe₃Si core + β-Si₃N₄ shell microstructure.
FeSiN improves taphole clay through a dual-phase mechanism: β-Si₃N₄ delivers high-temperature strength, oxidation resistance, and slag-penetration resistance, while the Fe₃Si metallic core promotes sintering and prevents excessive hardening so the taphole opens cleanly. Industrial data from Baosteel (in continuous use since 1994) shows taphole opening frequency cut from 18 to 6–12 times per day, clay consumption reduced from 1.2 to 0.5 kg per tonne of hot metal, and significantly increased iron throughput per runner. Recommended addition is 5–9% FeSiN in the taphole-clay formulation.
Flash combustion synthesis feeds FeSi75 fine powder (≤0.088 mm) into a vertical reactor against an ascending nitrogen stream. At approximately 1,400°C the FeSi + N₂ reaction becomes self-sustaining under just 0.2 MPa nitrogen pressure, completing in 24–36 hours. It produces high-purity FeSiN with no free silicon, in a porous honeycomb microstructure ideal for refractory bonding. Advantages: 1/10 to 1/3 the production cost of traditional nitridation, no free-silicon contamination, continuous scalable output, and consistent quality across tonnage quantities.
FerrumX supplies three refractory-grade powder distributions. Fine Powder: >80% at -45μm, 5–15% at -45 to -75μm, <3% at +75 to -150μm, 0% at +150μm, -75μm passing 95–100%. Standard Powder: 70–80% at -45μm, 10–20% at -45 to -75μm, 8–15% at +75 to -150μm, <3% at +150μm, -75μm passing 85–95%. Coarse Powder: 60–70% at -45μm, 10–16% at -45 to -75μm, 10–16% at +75 to -150μm, <8% at +150μm, -75μm passing 65–80%. Appearance is gray-white or tan-brown powder.
FerrumX supplies three steelmaking-grade granule sizes. Fine Granule: 3–5 mm, >90% passing. Standard Granule: 3–10 mm, >90% passing. Coarse Granule: 10–50 mm, >90% passing. Custom sizes of 0–3 mm and 3–8 mm are available on request. Appearance is a gray-white granular material. Finer granules dissolve rapidly in smaller ladles; coarser granules give slower, sustained nitrogen release in large converters and ladle furnaces.
FeSiN from flash combustion synthesis contains β-Si₃N₄ as the main phase (columnar/needle-like, providing high-temperature strength and thermal-shock resistance), a small amount of equiaxed α-Si₃N₄ (sintering activity), and minor iron solid-solution phases forming an Fe₃Si core at each particle center. The overall structure is porous and honeycomb-like, with short columnar β-Si₃N₄ crystals surrounding each Fe₃Si core. This architecture allows nitrogen infiltration and bonding within refractory matrices while the iron core drives plastic-phase sintering during service.
FerrumX supplies three steelmaking-grade granule sizes. Fine Granule: 3–5 mm, >90% passing. Standard Granule: 3–10 mm, >90% passing. Coarse Granule: 10–50 mm, >90% passing. Custom sizes of 0–3 mm and 3–8 mm are available on request. Appearance is a gray-white graIn HRB400 rebar, FeSiN is used in a FeV50 + FeSiN composite microalloying scheme, cutting total alloy cost by $5–20 per tonne of steel versus FeV50 alone or VN12. FeSiN supplies a stable nitrogen source for vanadium-nitride precipitation strengthening to reach the ≥400 MPa yield requirement, while its iron matrix integrates cleanly into the melt. FeSiN granules also serve grain-oriented silicon steel and other specialty steels as a controlled nitrogen addition without the handling hazards of gaseous nitrogen.nular material. Finer granules dissolve rapidly in smaller ladles; coarser granules give slower, sustained nitrogen release in large converters and ladle furnaces.
FerrumX is an ISO 9001 and ISO 45001 certified integrated silicon-based and nitride-alloy producer with 120,000 t/yr silicon-carbide capacity securing raw-material stability. FeSiN is offered in two grades and dual-track particle systems (refractory powder and steelmaking granules), with batch-by-batch chemical and sieve verification, custom sizing on request, and metallurgical support on addition rate and dosing. Decades of proven taphole-clay performance back the product.
