Cutting Stainless Steel

[rbmedic75]

OK guys trying to decide if I can do this with my plasmacam or if I am gonna have to farm it out or buy a CNC Mill. I have a plasmacam DHC2 with a hypertherm PM1000 hand torch keep in mind for some reason my plasma cuts slower than everyone says it should, for example to get a decent clean cut on .250 mild steel it cut at a rate of 32 IPM 3/16 mild steel at 40-45. SO I am going to be in the need for at stainless flanges (exhaust manifold flanges) 3/8 thick. Can I do these cuts with my plasmacam or do I need to seek alternative methods. I dont mind the slower cuts but need them to be complete and correct

[plain ol Bill]

shouldn't be a reason in the world you can't do it on your machine. Maybe Jim Colt will answer up also - he is the resident guru for all things Hypertherm.

[jimcolt]

Cutting stainless with an air plasma is not perfect....there will be more edge taper than you normally get when cutting carbon steel as the stainless is strictly a thermal process....no exothermic reaction. That being said, I have cut many 1/4" and 3/8" header flanges with my Powermax 1000 and Powermax45 on my PlasmaCam machine. The outside contour is pretty straightforward, however you need to experiment a bit with the bolt holes as they will be tapered (smaller at the bottom)....so either oversize the holes adequately so the bottom fits the bolt, or (this is what I do) ream the holes after cutting to the correct size. Use of a high quality drill or reamer (cobalt or coated for use on hard materials such as stainless or AR plate) is necessary as there is some hardening on the edge of the holes.

As far as your speed issue with your Powermax1000....I'd be happy to work with you on that. Are you following the specifications in the Hypertherm manual under "mechanized cutting"? regardless of whether you are using a hand torch or machine torch you need to use the mechanized shielded consumables (different than hand cutting) and you need to use the optimum speed settings as well as pierce height, pierce delay and cut height exactly as the manual describes. I will stand behind the specifications for speed in the Hypertherm manual.....if they cannot be achieved then we will have to find something wrong with your Powermax that is causing the slower speeds.

Your speed on 1/4" plate (mild steel) at 40 Amps will be 48 inches per minute, pierce height 1/8", cut height 1/16", pierce delay of 1 second. Nice clean cut with close to square edges. At 60 amps your speed will be 86 ipm.

On 3/8" SS, I would recommend the 60 Amp process, pierce and cut height as above, pierce delay .75 seconds, and cut speed of 41 ipm.

Jim Colt Hypertherm

[rbmedic75]

Jim I appreciate your offer to help and would be gald to take up some of your time. Im sure most of the issues Ihave are my own fault over all the cut quality 99% is very good. Seems very tempermental on life of the tips from VERY short to longer than I expect. I do a lot of odd cuts like bull skulls cut out of 1/4" plate so I know the intricate stuff on 1/4" is gonna add up fast. so tips I can deal with and dont need it to cut super fast but I want it to be right if that makes sense. Example today I cut about 20 4" oval flanges with a 1" hole cut in the middle and 4 tiny holes. each one probably 20" of cut plus the 4 holes My cut heights and pierce heights and times are on par with what your saying arc shift with a new tip is dead on at .125-.128 as the tips wears seems to be better @ .135 or so. The one that seems to fall way short is cut speeds. today I was actually able to cut the 1/4" at 40 IPM which is the best it has done but normally I cut it at 32 IPM which I can live with, again more worried about quality than quantity. The 20 pieces I cut today will last me a couple weeks. Wierd thing is it usually cuts 1/2 just as clean at 27-30 IPM which makes no sense to me. but VERY glad that I should be able to dial in for the stainless cuts.


One the holes yep that is what I do just use the plasma to pierce a marking point for consistency repeat parts and then drill them out on the drill press with cobalt bits.

Will try and be more prompt on checking back here, you guys know how it can be

Thanks again

[ross340]

go to your local welding supply store and ask them about plasma cutting stainless steel. Most likely, they're going to point you in the direction of nitrogen. Instead of using compressed air, nitrogen gives a cleaner and weldable cut.

[jimcolt]

Nitrogen only gives a more weldable cut on stainless if it is used in a dual flow plasma torch with either nitrogen or C02 as the shield gas. or in a single flow plasma torch submerged under water. Most air plasma torches are single gas, so unless you are cutting submerged with nitrogen there is no advantage. The dual gas torch and cutting submerged keeps the ambient air (20% oxygen, 80% nitrogen) from creating an oxide later on the stainless. Nitrogen will also cause slower cut speeds and more dross on stainless....as compared to air cutting. The only real advantage to using nitrogen in an air plasma torch is that the electrode will last 2 to 3 times longer!

Bottom line, in most cases on gauge materials, air is the best choice for plasma cutting.

Jim Colt Hypertherm

[MBG]

You make a note about cutting submerged. Is there a benefit to doing it? I didn't know it was even possible.

[jimcolt]

If you have a torch that is designed to cut underwater (consult with torch manufacturer) and you are using nitrogen as the plasma gas (on stainless steel) you will get an edge without oxidation (appears as a blackish or brownish edge on stainless) if you cut underwater. You may have to slow the cut speed 5 to 10% and there is a higher chance of dross formation, just the edges will be cleaner. This is only for stainless, and it essentially keeps air (20% oxygen) away from the molten cut face, eliminating the oxide formation.

Jim