Understanding Assist Gases in Metal Laser Cutting

The role of assist gas when fiber cutting metals

  • Ejecting Molten Material: As the laser beam melts the metal, the assist gas helps to eject the molten material from the kerf (the cut path created by the laser). This ejection is crucial for ensuring a clean cut and preventing the molten material from re-solidifying in the cut path, which can affect the quality of the cut and the final appearance of the material.
  • Reduced Heat Affected Zone (HAZ): Assist gases help to minimize the heat-affected zone (the area around the cut that undergoes thermal stress) by cooling the area and quickly removing excess heat.
  • Improved Beam Quality: By blowing away particulates or debris that could interfere with the laser’s path, assist gasses ensure that the laser beam remains unobstructed, which is critical for maintaining consistent cuts.
  • Increased Cutting Speed: Certain gases, like oxygen, actively participate in the cutting process by reacting chemically with the metal. This reaction increases the energy in the cutting zone and can significantly speed up the cutting process.

Oxygen is an Oxidizing Agent

When laser cutting, oxygen reacts with the metal being cut and the laser. This reaction is exothermic, meaning it releases heat, which helps to melt and vaporize the metal more efficiently than the laser beam alone.

Preventing Oxidation

Oxidation causes certain metals to become brittle and sometimes deform. Inert assist gases, like nitrogen and argon, prevent oxidation by displacing oxygen at the cut area and not reacting with the process..

Using Compressed Air

The air we breathe is composed of approximately 21% oxygen, a highly reactive element, and 78% nitrogen, which is inert. For most fiber metal cutting applications, either oxygen or nitrogen is recommended as an assist gas. Using compressed air (21% Oxygen,78% Nitrogen) as an assist gas when fiber cutting aluminum or stainless steel, can deliver excellent results without the inconvenience and high cost of nitrogen or oxygen tanks.