Producing high-quality, corrosion-resistant alloy and stainless steel requires secondary refining processes to be carried out under extremely demanding conditions. Temperatures typically range from 1,600°C to 1,800°C, and operations are often performed under high-vacuum environments. In these conditions, equipment must be capable of withstanding severe thermal, chemical, and mechanical stresses while maintaining reliable performance.
The Heavy Concrete Lance is an indispensable tool in critical refining processes such as Vacuum Oxygen Decarburization (VOD) and Vacuum Arc Degassing (VAD). Its exceptionally thick refractory concrete coating provides the durability and protection needed to ensure safe, efficient, and precise refining under extreme temperatures and vacuum conditions encountered in alloy and stainless-steel production.
What Makes Heavy Concrete Lances Suitable for Use During Alloy and Stainless-Steel Production?
Source: Daiwa Lance International
What is the Heavy Concrete Lance?
Heavy Concrete Lance, also known as a refractory-lined oxygen or injection lance, is a specialized pipe used to inject oxygen or inert gases during the VOD and VAD refining processes.
Unlike conventional lances, a Heavy Concrete Lance is manufactured using a heat-resistant calorized steel pipe coated with an exceptionally thick refractory concrete layer. This coating is typically 15 to 30 times thicker than standard protective coatings, providing superior resistance to heat, thermal shock, and chemical attack.
Structure of a Heavy Concrete Lance
The Heavy Concrete Lance consists of:
A heat-resistant calorized steel pipe core capable of withstanding temperatures exceeding 2,000°C.
A special thick refractory concrete coating made from high-performance materials like aluminium oxide plus silica (Al₂O₃).
A durable construction designed to protect the lance from extreme operating conditions while maintaining structural integrity throughout the refining process.
How Does a Heavy Concrete Lance Work in VOD and VAD Processes?
The Heavy Concrete Lance plays a vital role in the secondary refining of alloy and stainless steels, particularly in the VOD and VAD processes.
In the VOD Process
| Primary Function
The lance is used to inject pure oxygen directly onto the surface of the molten metal or into the steel bath.
| Mechanism of Action
- Within a vacuum environment, oxygen injection promotes the decarburization reaction, reducing the carbon content of the steel to extremely low levels required for the production of stainless and specialty alloy steels.
- The thick refractory concrete coating protects the internal steel pipe from:
- Extreme temperatures ranging from 1,600°C to 1,800°C
- Thermal shock caused by rapid temperature fluctuations
- Chemical corrosion from slags rich in Cr₂O₃, NiO, and FeO
- Mechanical stress and vacuum operating conditions
- In addition, the lance ensures a stable and controlled oxygen flow, which is essential for achieving efficient decarburization and maintaining the quality of the final steel product.
In the VAD Process
| Primary Function
In the VAD process, the lance is commonly used to inject inert gases such as argon.
| Mechanism of Action
- The injected inert gas creates vigorous stirring within the molten steel bath. This stirring action is critical for:
- Homogenizing temperature throughout the steel
- Achieving a uniform chemical composition
- Optimizing degassing process under vacuum.
- Improving overall refining efficiency
- As in the VOD process, the refractory coating protects the lance from excessive heat, pressure, and thermal stress, preventing warping, burn-through, and premature failure. This allows the stirring and degassing process to be carried out safely and continuously.
As a result, Heavy Concrete Lances can reliably convey both oxygen and inert gases depending on the specific refining requirements.
What Makes Heavy Concrete Lances Suitable for Alloy and Stainless-Steel Production?
The demanding conditions of alloy and stainless-steel production require equipment that can deliver exceptional durability, reliability, and performance. The following characteristics make Heavy Concrete Lances particularly suitable for these applications.
High-Temperature Resistance
Alloy and stainless-steel refining processes operate at temperatures between 1,600°C and 1,800°C.
The refractory concrete layer is manufactured using high-temperature-resistant materials such as: High-alumina refractories, Magnesia-based compounds, Zircon-containing materials.
These materials maintain their strength and structural integrity under extreme heat while protecting the internal steel pipe from thermal damage.
Excellent Thermal Insulation
The thick refractory concrete layer provides outstanding thermal insulation due to its low thermal conductivity.
This helps to:
- Reduce heat transfer to the steel pipe
- Prevent pipe softening and deformation
- Protect surrounding equipment from excessive heat exposure
- Maintain stable gas temperature and pressure during operation
As a result, the lance delivers more consistent injection performance and longer service life.
Chemical and Slag Corrosion Resistance
During alloy and stainless-steel production, the lance is exposed to highly corrosive slags containing oxides such as: Chromium oxide (Cr₂O₃), Nickel oxide (NiO), Iron oxide (FeO).
Heavy Concrete Lances utilize refractory materials specifically designed to resist chemical attack and slag penetration. This significantly reduces wear and extends operational lifespan.
Mechanical Strength and Erosion Resistance
The dense refractory concrete coating provides excellent resistance to:
- Erosion from high-velocity oxygen streams
- Impact from splashing molten metal
- Mechanical shock during handling
- Pressure fluctuations during operation
This robust construction helps maintain lance integrity even under severe operating conditions.
Safety and Process Reliability
Safety and operational stability are critical in steel refining environments.
The thick refractory layer serves as a protective barrier that helps prevent:
- Burn-through of the internal steel pipe
- Equipment damage caused by molten steel exposure
- Unplanned shutdowns and process interruptions
By ensuring stable and continuous operation, Heavy Concrete Lances contribute to improved productivity, reduced downtime, and enhanced workplace safety
Conclusion
Heavy Concrete Lances are essential components in the production of high-quality alloy and stainless steels. Their exceptionally thick refractory concrete coating provides superior resistance to extreme temperatures, thermal shock, chemical corrosion, and mechanical wear.
These properties enable safe, stable, and efficient operation in both VOD and VAD refining processes, helping steel manufacturers achieve consistent product quality while extending equipment service life and reducing operational risks.
As steelmaking technology continues to evolve, Heavy Concrete Lances remain a reliable solution for meeting the demanding requirements of modern alloy and stainless-steel production.
For more information, please contact our sales team at sales@daiwaanayasteel.com
Daiwa Anaya Steel Private Limited is a part of Anaya Steel, LLC (US parent company). Our company has over 30 years of involvement in steel products. It mostly deals in:
- Specialized steel hardware – punched, pressed, galvanized, powder-coated.
- Steel pipes and tubing – specialized, color coated, galvanized, and structural.
- Our products are produced by Daiwa Lance International in Vietnam.
