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Nitrogen vs. Oxygen: Which Should You Use to Cut Steel?

To make the most cost effective decision on the choice between these assist gases, several important factors must be weighed.

Posted: November 26, 2012

Nitrogen is generally used when cutting stainless or aluminum in order to achieve excellent quality. Unlike oxygen, nitrogen serves as a shielding gas in light gauge material to stop the burning process and allow the laser to vaporize the material. This means that power is the determining factor in cutting speed; more power equals more speed.

Laser cutting is a thermal machining process where the laser beam serves as a tool. Specific parameters used in this process, such as laser power and assist gas type, will significantly impact the overall quality and processing time during operation. The most common assist gases used are oxygen and nitrogen. They are selected based on the type of material being cut, its thickness and the edge quality required.

Traditionally, oxygen is most commonly used when cutting steels. Thin steel does not require a significant amount of power due to the burning process, which involves an exothermic reaction – a chemical reaction of oxygen-burning iron which releases excess energy through heat and light. The oxygen will do approximately 60 percent of the work. This, in turn, is the limiting factor to cutting speed. Only so much power can be applied to the material before too much burning occurs, resulting in a poor cut. This means that the cut speed, using oxygen as an assist gas in thin steel, would be the same for a 1500 watt to a 6000 watt laser.

Nitrogen is generally used when cutting stainless or aluminum in order to achieve excellent quality. Unlike oxygen, nitrogen serves as a shielding gas in light gauge material to stop the burning process and allow the laser to vaporize the material. This means that power is the determining factor in cutting speed; more power equals more speed.

Laser powers have been steadily increasing in various applications. This development has given the laser user a justifiable choice for his processing needs as he can now consider nitrogen assist gas as a valid method to process steel.

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

(1) Processing speeds

(2) Secondary operations, including edge quality required

(3) Cost of operation

Let’s examine these three factors in some detail:

Processing speeds. As previously stated, oxygen cutting speeds are limited by the power that can be applied, whereas nitrogen cutting speeds are directly related to power. In some cases, higher laser powers where nitrogen is employed in cutting thin steel allow the laser user to expect processing speeds three times to four times faster than what can be achieved when using oxygen. However, laser cutting of steel with nitrogen is not limited to thin material. Nitrogen can be used as an assist gas for thicker steels, with the maximum thickness depending on the available laser power. While nitrogen will provide faster processing speeds in steel up to 1/8 in, this is not the case in thicker materials, in which case oxygen will provide faster speeds as material thickness increases.

Secondary operations. Nitrogen will provide a superior edge quality free of any impurities. This edge is highly receptive to powder coat paint, and it also ensures a proper weld surface. This method of cutting generally eliminates the need for any secondary operations. However, the oxide surface produced by an oxygen cut can affect powder coat paint as well as welding. In general, steels greater than 14 gage require this surface to be removed for powder coat paint.

Cost of operation. The primary contributing factor to operating costs is assist gas consumption. There is a significant difference between oxygen and nitrogen. Processing with oxygen can result in the lowest cost of operation, as the consumption rate of gas can be up to 10 times to 15 times less than the requirements for nitrogen. Generally speaking, as thickness increases nitrogen assist gas consumption increases.

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

In thin steels, if a laser user can increase their processing speeds and produce more parts with better quality at either the same or slightly greater cost, then nitrogen should be strongly considered as the assist gas. As material thickness increases, the decision becomes more challenging. If the parts to be produced require secondary operations, the user must weigh the costs of the additional processes and handling in order to determine if the cost of the additional nitrogen in the laser cutting process will provide the most cost effective solution.

In order to make the most cost effective decision, all of these factors must be weighed. But what it all boils down to – and what is most important – is that laser users do indeed have a choice.

  • Jim Ward wrote:

    This was a great insight for the case of which gas to use. We are currently having complaints of our powder coat not sticking to the edges of oxygen cut parts. We have a Bystronic 3000 watt. would you happen to know how thick we could go using nitrogen?

    • Brian Welz wrote:

      The cutting process with nitrogen is dictated by the power of the laser. In general, steel reacts differently than stainless steel when processed with nitrogen. Unfortunately, you cannot reach the same thickness and quality in steel as you can in stainless. Based on a 3kw CO2 resonator, the maximum thickness you would process is 11 gage steel for it to still be considered a reliable and quality part.  

  • RKU wrote:

    Hi, really good article. Now the main question: how do you calculate the gauge according laser power. As for us, we have laser cutting machine that has 2 kw of power. So what maximum gauge would you offer for us when using oxygen? Is there any rule?

    • Brian Welz wrote:

      There are other factors that help to determine the maximum thickness that a laser can cut besides power and assist gas. Based on cutting with oxygen, the most important factor is which focal length lens has been applied. In general some typical lens lengths offered are 3.75”, 5” and 7.5”. If a 3.75” lens is applied, the max thickness would be 11 gage. With a 5” lens applied, the maximum thickness would be 7 gage. With a 7.5” lens 3/8” thickness can be considered.

  • Marco Josep wrote:

    Hi Brian, I’m from Israel and I have a question about the laser machine, we are working with nitrogen gas and we do not have specific problems, only thick brass metal processing 0.3 We do not have perfect cuts. Could you please offer us some guidance or direction?

    • Brian Welz wrote:

      Hi Marco,
      Cutting results will depend on the type of laser you are using and if the thickness in questions is 0.3mm or 0.3 inches. If it is a CO2 laser, be aware that you are taking a risk in regards to back reflection that could potentially harm your system. If it is a system with a solid state laser, you should consider the use of oxygen as an assist gas. For 0.3mm you should use 3 to 5 bar of oxygen with about a 2mm nozzle. If the material is 0.3 inches, it would require a minimum of a 3 to 4 kW solid state resonator with about 10 bar of oxygen. You will get a gold to brown edge but this is only on the surface.

  • Chuck Johnson wrote:

    What sort of cut rates should be expected using a 4000 watt machine on .06 G60 galvanized? Any safety issues?

    • Brian Welz wrote:

      You can consider the use of nitrogen or air as an assist gas. There are no safety concerns with these gases as there is no burning process involved. In general with nitrogen, you would apply the full power of the system and treat it with similar cutting parameters as you would stainless steel. With a 5” lens you could potentially reach up to about 300 ipm. With air as an assist gas, you would apply full power using a 2 mm or larger nozzle and about 5 bar of pressure. With this gas applied you could potentially reach 400 ipm.

  • Steven Hoiland wrote:

    I got a 4050 5000watt Trumpf laser having troubles cutting 7/8 A514 very liney Cutting with oxygen

  • Huzefa wrote:

    Sir, can we use nitrogen and air in one time to cut stainless steel on a 2kW fiber laser? 

  • Diala wrote:

    Please advise if it is better to cut corten steel using nitrogen or oxygen?

  • Tom Gatz wrote:

    Cutting steel with oxygen leaves the material we are cutting (HR P+O) with a semi hard surface, which makes it hard to do some secondary operations like machining or drilling or tapping. Will this
    also happen if we try to cut with nitrogen?

    • Ian Frank wrote:

      Hello Tom,

      My name is Ian Frank. I am an Applications Engineer at TRUMPF and I would like to help answer your question.

      This hardened material will not happen with Nitrogen – or at least it won’t be as extreme. While there is always heat involved with laser cutting, the type of cutting differs with Nitrogen vs Oxygen. When cutting with Oxygen, you are using a technique known as flame cutting. The melted metal reacts with the oxygen and creates a small flame that drives through the material. As with most chemical reactions there is a lot of heat energy created. This causes the hardening of your material. Cutting with Nitrogen, however, uses a technique known as fusion cutting. With this process, the laser melts the material and the high pressure Nitrogen ejects the material through the cut. Because Nitrogen is an inert gas, it does not react with the molten metal and therefore your cut is much cooler than if it was cut with Oxygen. There is a draw back with cutting with Nitrogen however, and that is a higher chance of dross left behind. This increases with the material thickness. I hope this helps answer your question!

  • Daniel Hubbard wrote:

    I’m cutting .104 HSLA with nitrogen. Is there any way to get rid of the dross left behind? I have a 2500 watt C02 laser.

    • Mickey Lawson (Trumpf Laser Applications Supervisor) wrote:

      HSLA will be tougher to cut without a dross on the back with a 2500 watt resonator. Typically what you will try to attain is a draws that is brittle and breaks off easily. With higher power resonators this thickness can be cut draws free. If you want to try a couple of things that might help, try bringing the cutting gas pressure much lower than typical, maybe as low as 4 bar. Also, burying the focus 1 or 2 mm below the bottom of the material can help.

  • Stephen wrote:

    Hi Brian,
    I have a 160 W Chinese laser that I would like to cut mainly 1.2 mm mild steel, 1.2 mm stainless steel and up to 1.6 mm HR steel. With Nitrogen as an assist gas, can you advise starting settings, pressure, power and speed? Many thanks.

  • Marvin Benjamin wrote:

    Hi Brian,

    Will a fiber laser cut create a hardened edge on the part? If so, do you have any data on how deep it will go? We currently water jet parts and then perform additional machining and I would like to know what affect, if any, fiber laser cutting would have vs. the water jet? Thanks in advance for your answer.

    • Shannon Mason - Laser Applications Engineer wrote:

      Hi Marvin,

      Fiber lasers do not create a hardened edge. Essentially, the laser is melting away the material down through what we call the kerf (or beam width gap) and out the bottom. However, the edge will look very different (not quite as smooth) from a water jet edge as you’re typically cutting it much faster on a laser and without an abrasive medium. If you are curious as to what a typical fiber laser cut may look like in various materials you should take a look at our 2D laser product line info

      • seb wrote:

        …and how it is cutting Hardox with fiber lasers? Does anyone have any experience?

  • Kyle Gray wrote:

    Very insightful indeed! I still have a few questions though. I’m currently having issues with corners melting on small parts and I believe the issue is too much heat in that small surface area. Would nitrogen instead of oxygen allow a cooler cut and not hinder the quality of the corners? Parts we are currently having issues with is 11 gauge mild steel. Specs of machine are as follows: Mazak STX-510 MKII 4KW.

  • Khursheed Anwar wrote:

    Hi Brian, I want to cut 11 gauge brass sheet with a 1 kW fiber laser. Please advise the cutting parameters, like speed, nozzle size, oxygen pressure etc.

  • Paul wrote:

    We have 4.4 kW Bystronic CO2 laser and are trying to cut 1.5″ W x 72″ L strips out of 3/8 in HR steel with 7.5 in head/oxygen assist and keep getting severe metal warpage. Width remains at 1.5 in on the extreme ends, while the middle of this bar measures as low as 1.25 in at times. What do you suggest? Will cutting with N2 help?

  • Cesar Giraldo wrote:

    Mr. Brian

    We have a small shop of signs, our laser is a 300 watt CO2-assisted by oxygen with capacitive sensor of altitude, I read your article and have some questions i wonder you may review:

    Can we change the O2 bottles for N2 to have a better quality? What do you think will be the thicker stainless steel we were able to cut if so? Does this change of gas represent any other upgrade in hardware?

    Attached the link to our machine…

    Thanks for your advice. Best regards.

  • Prakash wrote:

    We have 1 kW Bodor fiber laser machine and we are cutting GI on the same machine. Our maximum thickness is 3 mm. We are cutting the material on air, but due to some impurities in the air we are not getting the desired finish. Also, we found that pressure required during cutting is also 22 bar. Kindly suggest us proper method which suits our operation.

  • Osvaldo Maccari wrote:

    In order to improve laser cutting quality and precision, is there any gas or mixture of gases used instead of Nitrogen? Is there any quality standard for the Nitrogen quality which should be considered in order to achieve high quality cuts and precision?

  • arham wrote:

    Why don’t we use compressed air for cutting? It might be cheaper than nitrogen.

    • Raj wrote:

      Compressed air results in reduction in life of torch wear parts. It’s not a good option

  • Ramanathan wrote:

    Dear Mr.Brian Welzz : I am a private technical consultant with an air compressor background. have a client who uses oxygen cylinders for laser cutting 15 mm MS door and window frames. He wants me spell out the advantages of shifting from 3 # 7 cubic meters oxygen cylinder they use to nitrogen. I request your support with technical inputs.

  • Santosh Kund wrote:

    How to cut galvanised sheeet on laser machune, which gas and what type nizzle to use, wwhat should be power and current setting for 1.5 mm thickness

  • Pawel B wrote:

    Would anyone has ever testes hardness of material after using those both assist gases. I wonder if there is any difference?

  • shyam wrote:

    Dear Sir,

    What will be the per mm per thickness price of cutting cost considering machine price? what will be the machine hour rate?

    28 % speed is ok but what will be the higher thickness speed difference ?

    with regards

  • Swarup Maiti wrote:

    hi sir,i have Bystronic 4kw CO2 laser,i try to cut MS plate by using Nitrogen pressure .is this possible?

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