Composition of Tundish Metering Nozzle: Materials, Structure, and Performance in Continuous Casting

Introduction
In modern continuous steel casting, the tundish plays a critical metallurgical role as a buffer, distributor, and refining vessel between the ladle and the mold. Among all tundish functional refractories, the tundish metering nozzle is one of the most important flow control components. Its material composition, internal design, and microstructure directly influence steel cleanliness, flow stability, nozzle clogging behavior, and casting safety.

Understanding the composition of a tundish metering nozzle is essential for steelmakers seeking to optimize casting performance, reduce operational interruptions, and improve product quality. This article provides a detailed, SEO-optimized explanation of the raw materials, phase composition, structural layers, additives, and functional zones of tundish metering nozzles used in continuous casting operations worldwide.


What Is a Tundish Metering Nozzle?
A tundish metering nozzle (TMN) is a precision-engineered refractory component installed at the bottom of the tundish to regulate the flow of molten steel from the tundish into downstream components such as:

Sub-Entry Shrouds (SES)
Submerged Entry Nozzles (SEN)
Direct mold feeding systems
Unlike tundish well blocks or impact pads, the metering nozzle performs active flow control, requiring high dimensional accuracy, erosion resistance, and chemical stability. Its composition is therefore significantly more sophisticated than that of conventional monolithic tundish refractories.

Functional Requirements Driving Material Composition
The composition of a tundish metering nozzle is designed to meet multiple demanding service conditions:

Continuous contact with molten steel (1550–1600°C)
High thermal gradients and thermal shock
Mechanical stress from stopper rods or slide gate systems
Chemical attack by steel, slag, and inclusions
Resistance to nozzle clogging and alumina buildup
Gas permeability control (in argon-purged systems)
These requirements dictate the selection of raw materials, carbon content, bonding system, and additives.

Main Material Systems Used in Tundish Metering Nozzles
1. Alumina-Carbon (Al₂O₃-C) System
The most widely used composition for tundish metering nozzles is alumina-carbon.

Typical Composition Range
Al₂O₃: 70–90%
Carbon (graphite): 5–20%
Metallic additives: 2–6%
Resin or pitch binder: 2–4%
Role of Alumina (Al₂O₃)
High refractoriness (>2050°C)
Excellent resistance to steel erosion
Low solubility in molten steel
Structural backbone of the nozzle
Role of Carbon
Improves thermal shock resistance
Reduces wettability by molten steel
Suppresses inclusion adhesion
Enhances resistance to alumina clogging
Al₂O₃-C compositions are especially effective for aluminum-killed steels and long casting sequences.

2. Zirconia-Based (ZrO₂) Inserts and Hybrid Structures
High-performance tundish metering nozzles often incorporate zirconia inserts, particularly in the bore region.

ZrO₂ Content
ZrO₂ purity: 94–99%
Stabilizers: CaO, MgO, or Y₂O₃
Advantages of Zirconia
Extremely low wettability to steel
Outstanding corrosion resistance
Minimal alumina buildup
Superior resistance to clogging
Due to high cost, zirconia is typically used as a localized insert rather than a full-body material.

3. Magnesia-Based (MgO) Compositions
In some specific steel grades or operating environments, magnesia-carbon (MgO-C) materials are used.

Characteristics
High resistance to basic slags
Good performance in high-CaO environments
Lower resistance to thermal shock than Al₂O₃-C
MgO-based compositions are less common for metering nozzles but may be selected in special applications.

Carbon Sources in Tundish Metering Nozzles

flow control refractory
Carbon plays a critical role in nozzle performance.

Types of Carbon Used
Flake graphite
Expanded graphite
Synthetic graphite
Carbon black (minor amounts)
Functions of Carbon
Reduces steel adhesion
Improves thermal shock resistance
Lowers friction with stopper rods
Minimizes crack propagation
Carbon content must be carefully optimized to avoid oxidation loss, particularly during preheating.

Metallic Additives and Antioxidants
To protect carbon and enhance high-temperature performance, tundish metering nozzles contain metallic additives.

Common Additives
Aluminum (Al)
Silicon (Si)
Magnesium (Mg)
Boron carbide (B₄C)
Silicon carbide (SiC)
Functions
Formation of protective oxide layers
Reduction of carbon oxidation
Improvement of hot strength
Enhanced resistance to slag penetration
The selection and dosage of additives significantly influence nozzle lifespan.

Binder Systems and Bonding Phases
Resin-Bonded Systems
Most tundish metering nozzles use phenolic resin bonding, which provides:

High green strength
Controlled carbon yield
Dimensional stability during curing
Pitch-Bonded Systems
Used in some traditional designs but less common due to environmental concerns.

After firing or coking, the binder transforms into a carbon bond, strengthening the microstructure.

Structural Zones and Layered Composition
Modern tundish metering nozzles are multi-zone components, each optimized with different compositions.

1. Bore Zone
High-purity Al₂O₃-C or ZrO₂
Low porosity
Anti-clogging optimized
2. Working Zone
High erosion resistance
Balanced thermal shock performance
3. Backup Zone
Cost-optimized refractory
Lower carbon content
Structural support function
This graded composition design improves overall performance and cost efficiency.

Manufacturing Methods and Their Influence on Composition
Isostatic Pressing
High density
Uniform microstructure
Precise dimensional control
Superior corrosion resistance
Conventional Pressing
Lower cost
Suitable for short casting sequences
Isostatic pressing allows higher carbon and additive optimization due to better structural integrity.

Quality Control Parameters Related to Composition
Key quality indicators include:

Bulk density
Apparent porosity
Carbon content
Cold crushing strength (CCS)
Oxidation resistance
Thermal shock cycles
Consistent composition is essential for predictable performance.


Relationship Between Composition and Performance
Composition FeaturePerformance Impact
High Al₂O₃ purity Improved erosion resistance
Optimized carbon Reduced clogging
ZrO₂ insert Extended casting sequence
Metallic additives Longer nozzle life
Graded structure Reduced failure risk
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Conclusion
The composition of a is a carefully engineered balance of alumina, carbon, zirconia, metallic additives, and bonding systems, tailored to meet the extreme demands of continuous steel casting. By selecting the correct material system and structural design, steelmakers can significantly reduce clogging, stabilize steel flow, extend nozzle life, and improve overall steel cleanliness.

A deep understanding of tundish metering nozzle composition enables informed decisions in procurement, design optimization, and operational control, ultimately contributing to safer operations and higher-quality steel production.More information please visit Henan Yangyu Refractories Co.,Ltd

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