Key Refractory Products Used in the Tundish System of Continuous Casting

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1. Introduction
In modern continuous casting steelmaking, the tundish is not merely an intermediate vessel between the ladle and the mold; it is a metallurgical reactor that plays a crucial role in steel cleanliness, temperature control, and flow optimization. To achieve these objectives, a series of functional refractory products are installed in and around the tundish. These refractory items must operate under extreme conditions, including high temperature, aggressive molten steel and slag, thermal shock, erosion, and chemical corrosion.


Among the most critical tundish-related refractories are the ladle shroud, stopper rod, seating block, and associated flow-control components such as tundish nozzles and https://hyrefr.com/product/submerged-entry-nozzle/ (SENs). Each of these items performs a specific function and must be designed with appropriate material composition, structure, and performance characteristics.

This article provides a detailed technical overview of these key refractory products, focusing on their functions, materials, working conditions, failure mechanisms, and performance requirements.

2. Ladle Shroud

2.1 Function of thehttps://hyrefr.com/product/ladle-shroud/
The ladle shroud is a tubular refractory component installed between the ladle slide gate and the tundish impact zone. Its primary function is to protect the molten steel stream from reoxidation and nitrogen pickup during transfer from the ladle to the tundish.

Key functions include:

Creating a closed pouring system

Preventing air aspiration and secondary oxidation

Reducing inclusion formation

Stabilizing the steel flow into the tundish

Minimizing temperature loss

The ladle shroud is especially critical in the production of clean steels, such as automotive grades, IF steels, and bearing steels.

2.2 Materials and Structure
Ladle shrouds are typically manufactured from high-purity alumina-based or zirconia-containing refractories. Common material systems include:

Al₂O₃–C (alumina-carbon)

Al₂O₃–ZrO₂–C

ZrO₂–C (for high-end applications)

Key material requirements:

High thermal shock resistance

Excellent resistance to steel and slag corrosion

Low wettability with molten steel

High mechanical strength at elevated temperature

Carbon is often added to improve thermal shock resistance and reduce steel adhesion, while zirconia enhances corrosion resistance and dimensional stability.

2.3 Failure Mechanisms
Typical failure modes of ladle shrouds include:

Oxidation of carbon at high temperature

Erosion by high-velocity steel stream

Cracking due to thermal shock

Joint leakage caused by improper gasket sealing

Advanced ladle shrouds may incorporate anti-oxidation coatings and optimized inner bore designs to extend service life.

3. Stopper Rod

3.1 Role of the Stopper Rod in Tundish Flow Control
The stopper rod is a critical flow-control refractory used in tundishes equipped with stopper-controlled casting systems. By moving vertically, the stopper rod regulates the flow rate of molten steel from the tundish to the mold through the tundish nozzle.

Main functions:

Precise control of steel flow

Stable casting speed

Quick response during start and end of casting

Emergency shut-off capability

Compared with slide gate systems, stopper rods offer finer flow control and are widely used in slab and bloom casting.

3.2 Stopper Rod Construction and Materials
A typical stopper rod assembly consists of:

Stopper head (tip) – directly contacts molten steel

Rod body – connects the head to the actuator

Protective coatings or sleeves

Material systems for stopper heads commonly include:

Al₂O₃–C

Al₂O₃–ZrO₂–C

MgO–C (for specific steel grades)

The stopper head must exhibit:

Excellent erosion resistance

High thermal shock resistance

Minimal steel adhesion

Dimensional stability during long casting sequences

The rod body is often made from dense alumina or fiber-reinforced refractories, sometimes protected by insulating sleeves.

3.3 Wear and Failure Issues
Common problems include:

Erosion of stopper tip leading to unstable flow

Build-up of alumina inclusions

Cracking due to repeated thermal cycling

Misalignment with the seating block

Advanced stopper designs optimize tip geometry and material gradients to improve service life and flow stability.

4. Seating Block
4.1 Function of the Seating Block
The seating block (also known as the upper nozzle block) is installed at the bottom of the tundish and serves as the mounting interface between the tundish lining and the tundish nozzle.

Its primary functions include:

Supporting the tundish nozzle

Ensuring precise alignment with the stopper rod

Providing a tight seal to prevent steel leakage

Withstanding high mechanical and thermal stresses

Although relatively small in size, the seating block is a critical safety component.

4.2 Material Characteristics
Seating blocks are typically produced from high-density, high-strength refractory materials, such as:

Dense alumina

Alumina-spinel composites

Alumina–zirconia materials

Key performance requirements:

High compressive strength

Excellent thermal shock resistance

Minimal deformation at casting temperature

Good compatibility with nozzle and tundish lining materials

The bore accuracy and surface flatness of the seating block are extremely important for leak-free operation.

4.3 Failure Risks
Potential issues include:

Cracking caused by thermal gradients

Steel leakage due to poor machining tolerance

Chemical attack from aggressive slags

Misalignment leading to uneven stopper wear

Precision manufacturing and proper installation practices are essential to avoid these problems.

5. Other Important Tundish Refractory Items
5.1 Tundish Nozzle

The tundish nozzle is installed below the seating block and guides molten steel into the mold or SEN. It must resist:

Severe erosion

Chemical attack

Clogging by non-metallic inclusions

Common materials include Al₂O₃–C and ZrO₂–C, often with anti-clogging additives.

5.2 Sub-Entry Nozzle (SEN)
The SEN connects the tundish to the mold and controls steel delivery into the mold cavity. It plays a vital role in:

Mold flow pattern control

Slag entrainment prevention

Surface quality improvement

Zirconia-based SENs are widely used due to their superior corrosion resistance.

5.3 Impact Pad
Installed in the tundish impact zone, the impact pad absorbs the kinetic energy of incoming steel from the ladle shroud, reducing lining erosion and turbulence.

Materials are usually:

High-alumina castables

Spinel-containing refractories

5.4 Dams and Weirs
These flow-control refractories optimize steel residence time and inclusion flotation. They are usually made from insulating or alumina-based materials and are often disposable.

6. Integration and System Performance
The performance of tundish refractories should not be evaluated individually but as a complete functional system. Proper matching of ladle shroud, stopper rod, seating block, and nozzles ensures:

Stable casting

Improved steel cleanliness

Reduced breakout risk

Lower refractory consumption

Advanced steel plants increasingly work with https://hyrefr.com/ to develop system-based solutions rather than standalone products.

7. Conclusion
Refractory products such as the ladle shroud, stopper rod, and seating block are indispensable components of the tundish system in continuous casting. Each item serves a distinct function, yet all must work together under extreme thermal, chemical, and mechanical conditions.

With the increasing demand for clean steel, longer casting sequences, and higher productivity, the design and material selection of tundish refractories continue to evolve. Innovations in composite materials, anti-oxidation technologies, and precision manufacturing are pushing the performance of these refractory items to new levels.