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Nitrogen for plasma cutting aluminum?

Rocketdc

Aluminum
Joined
May 24, 2020
I've only cut 1/8" aluminum on my plasma table a few times with compressed air and the cut edge was pretty rough and grainy. Would using nitrogen for the gas produce a similar edge to carbon steel cut with compressed air? Would submerging the part on the water table help the cut quality in addition to the nitrogen? Would there be excessive dross cutting underwater?

I'm considering 1/4" aluminum to reduce the weight of a part I make out of steel. I need to get a cut quality that's clean enough for powder coating straight off the plasma table with minimal secondary ops. Knocking the edges down with a grinder is fine, I already have to do that with the carbon steel version I make now.
 
My Hypertherm HD XT-100 machine seems to cut aluminum about the same with or without N2 @ 99.99%. The amount of effort required to supply it with N2 would seem prohibitive unless you were going to do a lot of it. On stainless it's a different story and it doesn't have to do with the quality of the cut, just how clean and shiny it is. My opinion is it's not going to make much difference at all. The XT-100 does spray water around the cut which does cool the part so that may also have some kind of effect on the outcome. Thanks.
 
I was curious to see what CHAT GPT-4 had to say about it even though I don't trust it.

This is its response:

Yes, nitrogen can be used as a plasma gas in place of air while plasma cutting aluminum. In fact, nitrogen is often a preferred choice for cutting aluminum and other non-ferrous metals. The choice of plasma gas can have a significant impact on the cut quality, speed, and overall performance of the plasma cutting process.

Using nitrogen as a plasma gas offers several advantages when cutting aluminum:

  1. Cleaner cuts: Nitrogen is an inert gas, which means it does not readily react with aluminum during the cutting process. This results in cleaner, more precise cuts with reduced oxidation and a smoother edge compared to using air as the plasma gas.
  2. Reduced oxidation: Nitrogen reduces the formation of aluminum oxide during the cutting process. Aluminum oxide can form a hard, tenacious layer on the cut surface, which can be challenging to remove and affect subsequent processes such as welding or painting.
  3. Higher cutting speeds: Nitrogen can offer higher cutting speeds compared to air when cutting aluminum. This can result in increased productivity and efficiency.
  4. Less dross: Nitrogen can help reduce the formation of dross, which is a byproduct of the cutting process that consists of re-solidified molten aluminum. Dross can affect the quality of the cut edge and often requires additional post-processing for removal.
However, it's essential to note that using nitrogen as a plasma gas can come with higher operational costs, as nitrogen is generally more expensive than compressed air. Additionally, using nitrogen may require specialized equipment for storage and handling. Despite these factors, the improved cut quality and other benefits often outweigh the additional costs for many applications, especially when cutting aluminum and other non-ferrous metals.
 
That's pretty cool. Straight from the horse's mouth. How could you go wrong?
I was curious to see what CHAT GPT-4 had to say about it even though I don't trust it.

This is its response:

Yes, nitrogen can be used as a plasma gas in place of air while plasma cutting aluminum. In fact, nitrogen is often a preferred choice for cutting aluminum and other non-ferrous metals. The choice of plasma gas can have a significant impact on the cut quality, speed, and overall performance of the plasma cutting process.

Using nitrogen as a plasma gas offers several advantages when cutting aluminum:

  1. Cleaner cuts: Nitrogen is an inert gas, which means it does not readily react with aluminum during the cutting process. This results in cleaner, more precise cuts with reduced oxidation and a smoother edge compared to using air as the plasma gas.
  2. Reduced oxidation: Nitrogen reduces the formation of aluminum oxide during the cutting process. Aluminum oxide can form a hard, tenacious layer on the cut surface, which can be challenging to remove and affect subsequent processes such as welding or painting.
  3. Higher cutting speeds: Nitrogen can offer higher cutting speeds compared to air when cutting aluminum. This can result in increased productivity and efficiency.
  4. Less dross: Nitrogen can help reduce the formation of dross, which is a byproduct of the cutting process that consists of re-solidified molten aluminum. Dross can affect the quality of the cut edge and often requires additional post-processing for removal.
However, it's essential to note that using nitrogen as a plasma gas can come with higher operational costs, as nitrogen is generally more expensive than compressed air. Additionally, using nitrogen may require specialized equipment for storage and handling. Despite these factors, the improved cut quality and other benefits often outweigh the additional costs for many applications, especially when cutting aluminum and other non-ferrous metals.

Alu Chat gpt4.JPG
 
I've only cut 1/8" aluminum on my plasma table a few times with compressed air and the cut edge was pretty rough and grainy. Would using nitrogen for the gas produce a similar edge to carbon steel cut with compressed air? Would submerging the part on the water table help the cut quality in addition to the nitrogen? Would there be excessive dross cutting underwater?

I'm considering 1/4" aluminum to reduce the weight of a part I make out of steel. I need to get a cut quality that's clean enough for powder coating straight off the plasma table with minimal secondary ops. Knocking the edges down with a grinder is fine, I already have to do that with the carbon steel version I make now.
nitrogen doesn't change the cut quality much.
if you want it clean, laser cut it.
with nitrogen you also loose cutting thickness capacity.
then talking with a hyperthem rep why small machines suck for cutting alum and stainless is because the energy density isnt possible with a low voltage/amp power supply as compared to a large industrial unit that can cut super clean on it.
 
We been CNC cutting different thickness of aluminum for years with both standard and hi-deff plasma
The two standard air plasma's are hypertherm units, with everything set correctly, that is to say good condition consumables, correct nozzle to work distance through voltage control and travel speed.
We get very nice results. We tried nitrogen some time back with the standard plasma cutting aluminum and determined cut quality was satisfactory with compressed air, actually we did not see that much of a difference, surely not enough to justify the additional cost of nitrogen.
 
We been CNC cutting different thickness of aluminum for years with both standard and hi-deff plasma
The two standard air plasma's are hypertherm units, with everything set correctly, that is to say good condition consumables, correct nozzle to work distance through voltage control and travel speed.
We get very nice results. We tried nitrogen some time back with the standard plasma cutting aluminum and determined cut quality was satisfactory with compressed air, actually we did not see that much of a difference, surely not enough to justify the additional cost of nitrogen.
Don't ya just love all those nifty consumables you get to acquire for your fancy smancy HD plasma cutter? With all the tiny model numbers you get to read to figure out what goes with what? At what thickness? When my Thermal D XT-100 was being installed by Dynatorch I asked the technician which machine he would get - he said a simple 80 amp machine. Experience is expensive.
 
You bet for a home/small shop a simple 80 amp air plasma generator is truely fine, stap it to your Dynatorch, Plasma cam, Torch mate etc and away you go. Do you think for one moment if in my production world I wouldn't love to preform all my sheet cutting with an 80 amp air plasma on an inexpensive CNC cutting table (Coincidencally I like Dyna torch I have one of there early tables, before the sell out) That said, We operate Air Plasma, HI def Plasma and Laser why, because speed, finish / cut /kerf/ quality demand it.
 
If you are cutting 1/4 and less a 45xp or 80 might be superior to Hydef 260/300. When you need pre qualified holes and go thru sheets of 3/8 to 1 1/2 you use the big dogs.
Different machines really, they just happen to be both plasma family.
 
I've run about 100 dewars of nitrogen through a plasma table and it absolutely makes a huge difference in cut quality on 1/8-1/4 5052. You get less taper, less porosity, less dross, and longer/more repeatable consumable life.
This was on a hypertherm powermax 85
 
I've run about 100 dewars of nitrogen through a plasma table and it absolutely makes a huge difference in cut quality on 1/8-1/4 5052. You get less taper, less porosity, less dross, and longer/more repeatable consumable life.
This was on a hypertherm powermax 85
I've also got a powermax 85. Were you cutting on a downdraft table? I've got a bladder on my water table and found out it's risky to cut aluminum as the hydrogen can get trapped underneath the table instead of bubbling to the surface on a standard water table. If I tried cutting with nitrogen I'd have to drain the water first and cut it dry.

Did you cut with hypertherms recommended settings or did you tweak them at all?
 
Why would nitrogen make you run the table dry ?
FWIW hypertherm had published an article addressing the hydrogen problem.
Showing a manifold with compressed air in the bottom of the water table to make bubbles, to eleviate the problem.
 
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I've read what hypertherm has written regarding hydrogen and many other articles about it. For the most part it's a non issue, you don't even need a bubbler installed, most of the hydrogen can escape if there's a gap between the water level and the aluminum sheet. As I mentioned above, I'm talking specifically about a water table with a bladder, which mine has. Doesn't mean you can't do it, but there's potential for hydrogen to get trapped under the table over time. Direct quote from hypertherms site:

"This production of hydrogen is most likely harmless, but there are some water table designs that utilize a submerged tank or chamber. This tank or chamber is used to raise and lower the water table rapidly by displacing water with low pressure compressed air. If this type of water table is in use, it is possible for some of the aluminum oxide particles to get stuck inside the lower chamber. Once inside the chamber, the aluminum oxide will absorb the oxygen leaving just the hydrogen. Over time and much use, a relatively large bubble of hydrogen could form, and this could potentially cause an explosion in the presence of an ignition source."

Hypertherm also recommended cutting 1/4" aluminum with nitrogen and h2o as a secondary gas which seems like the cutting should be done with the water level covering the plate, unless I interpreted that wrong. I mentioned cutting it dry with nitrogen to a) see if the water is really necessary for a cleaner cut using nitrogen and b) to mitigate the potential for any aluminum oxide particles to collect in the bladder chamber underneath the table.
 
One of the comments that gave me pause was from Hypertherms Jim Colt on the plasma spider forum. He said:

"if you have a raise lower type water table with an enclosed chamber (bladder) for storing water....and it was not designed specifically for aluminum cutting...then I would recommend against its use."
 
I've also got a powermax 85. Were you cutting on a downdraft table? I've got a bladder on my water table and found out it's risky to cut aluminum as the hydrogen can get trapped underneath the table instead of bubbling to the surface on a standard water table. If I tried cutting with nitrogen I'd have to drain the water first and cut it dry.

Did you cut with hypertherms recommended settings or did you tweak them at all?
Water table. It explodes a lot. Fill the table up to sheet level. Do not load the sheet until you are ready to cut, and begin cutting as soon as the sheet is loaded, and don't stop. If you have to stop for a long time either take the sheet off to air out or move the gantry out of the way and burp it with a torch. Either way you will get loud bangs, but not enough to lift the sheet.

Be aware the hydrogen production continues after cutting, especially when the table warm up, so you'll be committed to not leaving sheets of steel on the table either.

The reaction is exothermic. I got the water table hot after several days of long hours of cutting aluminum, and the water ended up boiling and I had to stop until the reaction petered out and then added more cold water. It was very inconvenient.
 








 
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