Nitrogen is often used for excellent quality when cutting stainless steel or aluminum. Unlike oxygen, nitrogen is used as a shielding gas in lightweight materials to stop the combustion process and allow the laser to vaporize the material. This means that power is the determining factor in cutting speed; more power equals faster speed.

Laser cutting is a thermal process in which a laser beam is used as a tool. The specific parameters used in the process, such as laser power and assist gas type, will significantly affect the overall quality and processing time during operation. The most commonly used auxiliary gases are oxygen and nitrogen. Their selection depends on the type of material being cut, the thickness and the desired edge quality.

Traditionally, oxygen is most often used when cutting steel. Thin steel doesn't require a lot of power due to the combustion process, which involves an exothermic reaction -- a chemical reaction in which oxygen burns iron, releasing excess energy through heat and light. Oxygen will do about 60% of the work. This, in turn, is the limiting factor in the speed of cuts. Only so much power can be applied to the material before too much burn occurs, resulting in a poor cut. This means that the cutting speed using oxygen as an assist gas in thin steel will be the same for a 1500 watt to 6000 watt laser.

Nitrogen is often used for excellent quality when cutting stainless steel or aluminum. Unlike oxygen, nitrogen is used as a shielding gas in lightweight materials to stop the combustion process and allow the laser to vaporize the material. This means that power is the determining factor in cutting speed; more power equals faster speed.

Laser power is steadily increasing in various applications. This development gives the laser user a reason to choose his machining needs, as he can now see nitrogen assist gas as an efficient method for machining steel.

Factors to Consider

In order to make the right decision between oxygen and nitrogen, the following criteria must be considered:

(1) Processing speed

(2) Secondary operations, including the required edge quality

(3) Operating costs

Let's examine these three factors in detail:

processing speed. As mentioned earlier, oxygen cutting speed is limited by the power that can be applied, while nitrogen cutting speed is directly related to power. In some cases, the higher laser power for cutting thin steel with nitrogen allows laser users to expect processing speeds three to four times faster than when using oxygen. However, laser cutting steel with nitrogen is not limited to thin materials. Nitrogen can be used as an assist gas for thicker steels, and the maximum thickness depends on the laser power available. While nitrogen can provide faster machining in steel, up to 1/8 inch, this is not the case for thick materials, where oxygen will provide faster speeds as the thickness of the material increases .

secondary operation. Nitrogen will provide a premium edge quality without any impurities. This edge is very receptive to powder paint coatings and also ensures a proper welding surface. This cutting method usually does not require any secondary operations. However, oxide surfaces produced by oxygen cutting can affect powder coating coatings as well as welding. Typically, steel greater than 14 gauge requires the surface to be removed for powder coating paint.

operating costs. A major factor in operating costs is auxiliary gas consumption. There is a significant difference between oxygen and nitrogen. Treatment with oxygen can result in the lowest operating costs because the gas consumption rate can be 10 to 15 times lower than the nitrogen requirement. In general, nitrogen assist gas consumption increases as thickness increases.

The right choice

Taking all factors into consideration, the following decisions can be made:

In thin steel, if laser users can increase their machining speed and produce more and better quality parts at the same or slightly higher cost, nitrogen should be strongly considered as an assist gas. As the thickness of the material increases, the decision becomes more challenging. If the part to be produced requires a secondary operation, the user must weigh the cost of the additional process and handling to determine whether the cost of the additional nitrogen in the laser cutting process will provide a cost-effective solution.