Gunning mass for converter
Gunning mass for converters, particularly Basic Oxygen Furnaces (BOF), is a specialized refractory material used for the maintenance and repair of the converter lining. Converters are subjected to extreme thermal, chemical, and mechanical stresses during the steelmaking process, making it essential to maintain the refractory lining to extend the converter's service life and ensure efficient operations.
Key Characteristics of Gunning Mass for Converters
1.High Temperature Resistance
The gunning mass must withstand the high temperatures inside the converter, typically reaching up to 1700°C. Materials like magnesia, alumina, and carbon are commonly used for their ability to endure these extreme conditions.
2.Slag and Metal Resistance
The gunning mass needs to be highly resistant to basic slags, which are prevalent in the BOF process. The material should prevent slag penetration and erosion, which can weaken the refractory lining.
3.Thermal Shock Resistance
Converters undergo rapid temperature changes, especially during the charging of cold scrap metal. The gunning mass must resist thermal shock to avoid cracking or spalling, which could lead to premature lining failure.
4.Adhesion and Cohesion
Good adhesion to the existing lining and cohesive properties are critical for the gunning mass to form a strong, durable repair layer that integrates well with the existing refractory material.
5.Low Rebound Loss
During the gunning process, it’s important that the material adheres well to the surface, minimizing the amount of rebound (material that bounces off rather than sticking). This reduces waste and ensures that the repair is efficient and effective.
Applications and Benefits
1.Spot Repairs
Gunning mass is commonly used for spot repairs in high-wear areas of the converter, such as the slag line, trunnion areas, and mouth. This allows operators to address localized damage without requiring a full shutdown for relining.
2.Maintenance Between Campaigns
Regular gunning maintenance can extend the life of the refractory lining between major relining campaigns, reducing overall maintenance costs and downtime.
3.Enhanced Converter Life
By maintaining the integrity of the lining with gunning mass, the overall service life of the converter is extended, allowing for more efficient steel production with fewer interruptions.
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Types of Gunning Mass for Converters
1.Magnesia-Carbon Gunning Mass
Composition: Typically made from high-purity magnesia (MgO) with a carbon content that helps resist slag penetration and provides excellent thermal shock resistance.
Applications: Used in the slag line and high-wear zones where basic slag attack is most aggressive.
2.Alumina-Magnesia Gunning Mass
Composition: A blend of alumina (Al?O?) and magnesia, offering a balance between slag resistance and thermal stability.
Applications: Suitable for areas with lower slag impact but where high thermal resistance is required.
3.Magnesia-Alumina Spinel Gunning Mass
Composition: Contains magnesia and alumina in a spinel phase (MgAl?O?), which provides excellent resistance to both slag and thermal shock.
Applications: Ideal for use in converters where both acidic and basic slags may be present.
Application Process
1.Preparation
The area to be repaired is cleaned to remove any loose material or debris. The surface should be free of contaminants to ensure good adhesion of the gunning mass.
2.Gunning
The gunning mass is applied using pneumatic equipment that sprays the material onto the targeted areas. The process is carried out quickly, often while the converter is still hot, to minimize downtime.
3.Curing
After application, the gunning mass undergoes a curing process, where it hardens and integrates with the existing lining. The converter may be brought back to operating temperature gradually to prevent thermal shock.
Gunning mass for converters is an essential tool in the maintenance of BOF and similar steelmaking furnaces. It provides a cost-effective way to repair and extend the life of the refractory lining, ensuring that the converter can continue to operate efficiently and safely. By selecting the appropriate type of gunning mass and applying it correctly, steel producers can reduce downtime, minimize maintenance costs, and improve the overall performance of their converters.