Vacuum Degassing
What is vacuum degassing?
Vacuum degassing is a process used in different industries, especially the metallurgical industry, to remove dissolved gases from liquids or molten materials. In steel production, it is used to remove gases such as hydrogen, oxygen and nitrogen, which can harm the mechanical properties and quality of steel. The process involves exposing the material to a vacuum (low pressure) environment to facilitate the release and removal of these gases. This method is essential for manufacturing high-quality steels, as residual gases can cause defects such as porosity, brittleness, and strength problems.
History of vacuum degassing
Vacuum degassing has evolved significantly since its inception. In the 1930s, the steel industry began researching how to remove harmful gases from molten steel, but it was not until the 1950s that efficient technologies were developed for this purpose. Technological progress and the increasing demand for high-quality steels prompted the creation of more sophisticated methods, such as the Ruhrstahl-Heraeus (RH) process and the Vacuum Oxygen Decarburization (VOD) process, which optimized gas removal and significantly improved properties. of steel.
Vacuum degassing technologies
Vacuum degassing technologies in the metallurgical industry are diverse and have been developed to optimize the removal of gases dissolved in steel and other molten metals. Some of the most important technologies include:
1. Vacuum Oxygen Decarburization (VOD) Process:
- Combines vacuum degassing with oxygen to reduce carbon content and remove dissolved gases.
- Widely used in the production of stainless steels.
2. Ruhrstahl-Heraeus (RH) process:
- Uses a combination of vacuum and agitation to degas the steel.
- Effective in removing hydrogen and nitrogen from molten steel.
3. Vacuum Degassing (VD) Process:
- The molten steel is kept in a container under vacuum, often with electromagnetic stirring.
- Effective in removing hydrogen, nitrogen and oxygen from steel.
Other less used processes are: Vacuum Tank Degassing (VTD) Process, Vacuum Ladle Degassing (VLD) Process, Vacuum Carbon Deoxidation (VCD) Process and the Electroslag Remelting Process (ESR).
Each of these technologies offers specific advantages and is chosen according to the requirements of the final product and the characteristics of the steel or alloy to be produced. Proper selection of the degassing process is crucial to obtain high-quality materials with optimal mechanical and chemical properties.
Steel degassing process
The process of degassing steels under vacuum involves several steps and these can vary depending on the technology used. An example of a typical process could be:
- Transfer of molten steel: The molten steel is transferred to a vacuum degassing chamber.
- Vacuum creation: The pressure inside the chamber is reduced using vacuum pumps.
- Degassing: The steel is kept in the chamber under vacuum conditions for a certain time. In some cases, steel can be agitated by electromagnetic methods or injection
of inert gases to improve the removal of dissolved gases. - Cooling and solidification: Once degassing is completed, the steel cools and solidifies, becoming ready for subsequent forming and treatment processes.
Degassing machinery
Machinery used for vacuum degassing includes:
- Vacuum chambers: Where the molten steel is placed for treatment.
- Vacuum pumps: Essential to create the required low pressure environment. They can be mechanical, liquid ring, diffusion or turbomolecular, depending on the degree of vacuum required.
- Agitation equipment: Used to improve the homogeneity of the degassing process. This includes electromagnetic systems and inert gas injection equipment.
- Sensors and controllers: To monitor and control parameters such as pressure, temperature and degassing time.
Utilities of vacuum degassing
Vacuum degassing has multiple applications and benefits in the industry, including:
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- Improved steel quality: By removing dissolved gases, cleaner steel is produced with better mechanical properties and fewer defects.
- Increased durability: Removing gases reduces brittleness and increases the strength of steel, making it more suitable for critical applications.
- Optimization of forming processes: A more homogeneous and cleaner steel improves subsequent processes such as rolling, forging and welding.
- High technology applications: Vacuum degassed steels are essential for the manufacture of components in the aerospace, automotive, energy and other industries that require high reliability materials.