I. What is a Submerged Entry Nozzle?

The Submerged Entry Nozzle is one of the “Three Major Pieces” in continuous casting, installed at the bottom of the tundish and submerged below the steel level in the mold. As the final gateway for molten steel entering the mold, its core functions include:

• Preventing secondary oxidation and splashing of molten steel.
• Optimizing flow and temperature fields within the mold to prevent slag entrapment.
• Promoting the flotation of non-metallic inclusions to improve steel cleanliness.
• Ensuring uniform solidification of the strand to enhance yield.

The performance of the SEN directly determines the smooth operation of continuous casting and the quality of the cast strand.

II. Structure and Classification

Based on casting processes, steel grades, and flow control methods, Submerged Entry Nozzles are primarily classified into the following structures:

• Side-Port Type: Commonly used in slab casting; molten steel flows out from bottom side ports, allowing for controllable flow fields.
• Straight-Through Type: Simple structure where steel falls directly to the mold bottom; suitable for certain bloom/billet casting operations.
• Bowl Type: Used in conjunction with the upper tundish nozzle to provide flow stabilization and buffering.
• Spiral/Whirl Type: Features an internal spiral structure to induce rotational flow, optimizing flow patterns.

III. Material Selection and Technical Highlights

SEN materials have evolved from fused silica to Alumina-Carbon (Al₂O₃-C) and Alumina-Zirconia-Carbon (Al₂O₃-ZrO₂-C).

• Fused Silica: Low thermal conductivity and excellent thermal stability allow for use without preheating. However, it is unsuitable for steel grades with >0.5% Manganese and has poor resistance to high-basicity mold flux. Ideal for ordinary carbon steel and low-manganese steel.
• Alumina-Carbon (Al₂O₃-C): Strong adaptability to various steels with good mechanical strength. However, it is prone to clogging when casting Al-killed steel or Ti-bearing stainless steel, and the slag line is susceptible to “necking.” Suitable for general special steel and silicon steel.
• Alumina-Zirconia-Carbon (Al₂O₃-ZrO₂-C): Uniform structure with excellent erosion and thermal shock resistance. The slag line shows significantly improved corrosion resistance. Ideal for stainless steel, calcium-treated steel, and high-alloy steel, though at a higher cost.

Typical Physical and Chemical Indicators:

• Alumina-Carbon: Bulk Density 2.35~3.15 g/cm³, Apparent Porosity 12%~18%, Cold Crushing Strength 20~35 MPa, Modulus of Rupture 6~14 MPa.
• Alumina-Zirconia-Carbon (Slag Line): ZrO₂ Content 65%~81%, C Content 12%~17%, Bulk Density 3.25~3.75 g/cm³, Apparent Porosity 14%~18%, Cold Crushing Strength 20~27 MPa, Modulus of Rupture 6~8 MPa. Higher ZrO₂ content correlates with stronger erosion resistance.
• Dimensional Tolerance: Standard tolerances range from ±1.5mm to ±1.5% (depending on dimension range), with wall thickness relative deviation ≤2.5.

IV. Manufacturing Process

Our company employs Cold Isostatic Pressing (CIP) technology to ensure uniform, dense internal structure and prevent lamination. Key processes include:

• Mixing: Homogeneous blending of graphite, alumina, zirconia, binders, and anti-oxidant additives.
• Isostatic Pressing: Uniform compaction under 100~150 MPa pressure to form dense green bodies.
• High-Temperature Sintering: Non-oxidizing firing at 1000~1350°C in a reducing atmosphere.
• Finishing & Inspection: Precision machining, Non-Destructive Testing (NDT), and application of anti-oxidation glaze on the outer surface.

The immersion nozzle is the “key” component that ensures the smooth operation of continuous casting and the quality of the cast billet. Whether you are a large steel mill or a special steel production enterprise, we can provide you with cost-effective products.