6 Key Factors Causing Damage to Torpedo Ladle Refractory Linings

The primary function of a torpedo ladle is to transport molten iron to basic oxygen furnaces (BOF) or electric arc furnaces (EAF). During this process, the refractory lining of the torpedo ladle undergoes various forms of wear and damage. The main factors contributing to this degradation are detailed below.

1. Mechanical Wear During Molten Iron Tapping

When molten iron flows from the blast furnace into the torpedo ladle, it first impacts and erodes the refractory materials on the ladle bottom and sidewalls. Additionally, the turbulence generated during the filling process causes further erosion and abrasion of the lining. Among all components, the refractory materials at the ladle bottom suffer the most severe mechanical wear during tapping.

2. Thermal Shock Damage from Cyclic Operation

The torpedo ladle operates in repeated thermal cycles, exposing the refractory lining to fluctuating temperatures:

• During tapping: Refractory surface temperatures reach approximately 1550–1650°C.
• During transportation: Temperatures drop to around 1400–1500°C.
• During empty return: Lining surfaces cool further to about 800–1200°C.
• Next tapping: Temperatures rise again to 1550–1650°C, continuing the cycle.

This cyclic temperature fluctuation subjects the refractory lining to repeated thermal stress, causing spalling and loss of material. Furthermore, during the empty return phase, carbon-containing refractories are exposed to air, making them prone to oxidation, which weakens the refractory structure and accelerates deterioration.

3. Structural Damage During Desulfurization

In some steel plants, desulfurization is performed directly inside the torpedo ladle. This introduces two major risks:

• Abrasion: Injection of desulfurizing agents with a lance induces molten iron flow, eroding the ladle bottom and sidewalls.
• Chemical attack: The use of CaO-CaF₂-CaC₂ based desulfurizers increases slag basicity, intensifying chemical penetration and corrosion of the refractory lining.

4. Molten Iron Infiltration Through Brick Joints

As the number of operating cycles increases, slag attack progressively thins the working lining, and joints between bricks widen. Molten iron can infiltrate these joints, attacking the backup lining and reducing the overall lining life. In severe cases, iron infiltration can create large accumulations behind the working lining, causing brick displacement and severe mechanical damage during tapping and desulfurization.

5. Damage During Slag and Iron Cleaning

When the temperature of molten iron in the ladle drops too much, iron and slag become viscous and adhere to the refractory lining. To maintain ladle capacity, operators often use mechanical slag and iron removal. This process leads to significant abrasion or spalling of the working lining, especially when slag build-up is severe or when brick joints are wide and iron infiltration has already compromised the lining integrity. This increases maintenance frequency and shortens the service life of the torpedo ladle.

6. Criteria for Refractory Material Selection

Based on the above analysis, refractory materials for torpedo ladle linings should meet the following criteria:

• Cold crushing strength (CCS): Sufficient mechanical strength at ambient temperature to ensure safe installation and transport.
• Hot modulus of rupture : High strength at elevated temperatures, especially for bottom refractories, to withstand molten iron impact and flow.
• Oxidation resistance: If carbon-containing refractories are used, excellent oxidation resistance is critical to prevent structural weakening during empty return cycles.
• Slag resistance and permeability resistance: Superior resistance to slag attack and molten iron infiltration is essential to preserve lining integrity and extend service life.

Conclusion

Understanding the wear mechanisms of torpedo ladle linings enables the selection of optimized refractory solutions to enhance performance and longevity. At Firebird New Material Co., Ltd., we specialize in providing high-performance refractory materials. With over 20 years of expertise, we help our clients improve operational efficiency and reduce maintenance costs. Visit our website to explore our comprehensive range of refractory solutions.