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Heat treatment of metals
Nitrogen is highly desirable in heat and thermo-chemical treatment of metals, because it allows to obtain the required high parameters of end products.
During heat treatment, nitrogen is used among others for:
- Annealing - in this process, the nitrogen atmosphere provides a high quality and bright colour of the metal surface.
- Carburising - In thermochemical processes such as carburising and carbonitriding, nitrogen is used as an atmosphere promoting the desired technical parameters of the workpiece.
- Hardening - Nitrogen is used to obtain the optimal atmosphere of the furnace, preventing oxidation and decarburisation of the workpiece.
- Nitriding and carbonitriding- These processes increase the surface resistance to wear.
- Sintering metal powders - to effectively prevent decarburization this process requires specific parameters of the gas atmosphere, including nitrogen.
- Furnace brazing - nitrogen is used to improve the quality of surface and solder joints.
- Normalisation –for shielding during repairs.
- Tempering - for shielding while removing structural tensions in the metal structure.
Typically, nitrogen with a residual oxygen content of 10ppm-1% is used for this type of applications.
Cięcie laserem - en
In laser cutting processes a laser beam focuses on the workpiece surface and heats up the material beyond the ignition temperature. That triggers an exothermic reaction that contributes to initiating the cutting process. Shielding gases are used to protect the processed material. Nitrogen or argon are fed into the cutting head nozzle at a pressure of up to approx. 20 bar.
For our applications we recommend using nitrogen that is cheaper to obtain. Specific properties of this gas cool the material and prevent oxidation on the edges of workpieces. A nitrogen blanket is suitable for cutting thin sheets and in applications where ready products must meet high visual requirements without further processing. Usually, nitrogen with a residual oxygen content of 10 ppm to 0.5%. is used for this type of applications. Typical nitrogen feeding pressure is 25 bar.
Liquid metal casting and processing
In high-temperature processes such as liquid metal casting and processing, nitrogen is an excellent barrier preventing oxidation of molten surfaces. For alloys that are not sensitive to nitrogen uptake it is a highly cost-effective method for shielding the melting surface.
Nitrogen helps prevent metal oxidation and gas absorption in the metal. When using an inert shield, oxygen and water vapour contained in the atmospheric air are replaced by a dry and neutral nitrogen atmosphere. By reducing the oxygen content over the molten material to just 1%, it is possible to:
- lower the costs of the alloy,
- reduce the amount of slag,
- increase liquidity of the metal and efficiency of the casting process,
- reduce the amount of inclusions and porosity of the casting,
- improve processability and the quality of surface finish,
- extend the lifetime of the coatings / crucible.