[StephanusThie]

Hi guys, need you to share your experience in cutting 4mm thick alum or ssteel plate using plasma cutter. Is the cut clean enough to tig weld?
Please share. Thank you.

Steve.

[AKweldshop]

I have done some Plasma cutting somewhat like this and it works okay, The best thing you can do for Plasma cutting is get a straight edge , a piece of square tubing or angle and clamp it along where you are going to cut . Drag that torch nice and steady and you should get a decent cut that would need minimal grinding to be able to tig it. But with your plate being only 4mm thick I would shear it , of course if you've got access to a big shear do it , it depends on how long of cut you have to make . If your going to be doing lots of this kind of work I would for sure look into getting into shearing your metal. But hey you can get good fit ups working with a plasma cutter any day of the week .So try it if it doesn't work shear it . good luck , John

[noddybrian]

I only use compressed air for cutting so the cut on those materials is not as good as with nitrogen - but however straight or good the cut looks the edge is always ragged & full of oxides & other crap - to weld this without grinding is asking for problems even at a hobby level as most of this will end up in the weld pool - if the job needs to look good or falls within any coding / testing then you really need to grind it clean - I think the only cutting method not needing some cleanup would be water jet or laser.

[Otto Nobedder]

I regularly cut aluminum sheet/plate up to 3/8" with a 7 1/4" circular saw and 24-32 tooth carbide blade. I'm sure with patience I could cut thicker.

Perfectly clean, if that's all you use the blade for.

Put on your safety glasses, grinding shield, and sleeves (the chips go everywhere), use a fence for a straight cut, and cut slowly, letting the blade do the work. If one side is "drop", you can bevel at the same time using the miter adjustment.

You won't dull a carbide blade unless you force it. I've gotten several hundred feet from a single $25 blade.

Steve S

[Oddjob83]

You must completely clean the cut, I recently tried to weld over a cut and even though i removed the dross with a SS wire wheel, the contaminates and oxides left a clear mark at the top of the puddle. i can be done, just don't do it if it is code or structural.

[steve-l]

I do this all the time, but like others state, the edges must be cleaned. I use a 60 grit slap disc and it's fast. I have successfully used a 40 amp machine, but 4mm alu is at its limit. It is better to use a 60 amp machine. I only use air. perhaps nitrogen would work better, but I would still sand the edges. Stainless is really easy with a plasma, but again edge sanding is prudent.

[Dirtbag]

"I do this all the time, but like others state, the edges must be cleaned. I use a 60 grit slap disc and it's fast."
I've paid diligent attention to the advise about using a dedicated SS brush to clean aluminum to avoid contaminates. I always wondered about the flap discs for that purpose and if they would leave any undesirable material behind. Looks like the question is answered.

[Jason_alex]

Okay, as far as the Stainless Steel plate I have been doing some reading has any one cut SS under water using nitrogen and and argon (or other gasses) to prevent oxidation, and check weld ability?

[noddybrian]

Dude - if you read about cutting underwater with either gas either I missed the memo or you've been smoking some really good stuff ! the only cutting process typically used underwater is oxy-arc or thermic lanse - I've used both - but trust me it's not neat or done to anything your going to weld ! - maybe I mis-read this post - stainless can be cut with water jet ( well suspended micro abrasive ) very cleanly & can be welded without any clean up - maybe we are talking at cross purposes ?

[Otto Nobedder]

I've never cut under water, or with argon. Argon would be costly outside of an industrial setting, I'd think, for the volume of gas needed. Nitrogen does improve the cut on stainless, but even if it were under water, I'd think a dressing would be in order due to nitrogen embrittlement. I'm not quite sure, though. I'd have to read up on it a bit. Argon, of course, would avoid this possibility.

The cleanest cuts I've seen are from a water-jet cutter. Those cuts are weld-ready as soon as the parts are rinsed (an abrasive is in the water) and dried.

Steve S

[weldin mike 27]

Hi everyone,

Time for me to weigh in,

Plasma cutting under water is a automated process, and the water is used to control the fumes. Maybe also controls the distortion but that may be secondary. We used to have a large system at work, that was 2 x "beds" that were, maybe 5 meters x 10 meters, give or take. The cutting head had a plasma and oa cutter. For plasma the water level was brought about 1" over the plate, and for oa it was left level with the underneath of the plate. Nitrogen and comp air were used in varying combinations depending on the material, ie mild, ss or alum.

http://www.youtube.com/watch?v=zN-YujXhHKY

Mick

[Jason_alex]

Dude - if you read about cutting underwater with either gas either I missed the memo or you've been smoking some really good stuff ! the only cutting process typically used underwater is oxy-arc or thermic lanse - I've used both - but trust me it's not neat or done to anything your going to weld ! - maybe I mis-read this post - stainless can be cut with water jet ( well suspended micro abrasive ) very cleanly & can be welded without any clean up - maybe we are talking at cross purposes ?

Sorry my chart I have here is calling for nitrogen plasma and co2 secondary. Above water or Ar/H2 plasma with N2 secondary. This information is in Thermal Dynamics Pak 15XC Merllin book.

I know you can cut SS under water and I can not find the articular right now about minimizing oxidation on the edge cutting under water.

[noddybrian]

Interesting video - I have to admit I'd never heard of submerged plasma - I've seen a water table that kept the underside of plate wet - but the top was dry where the cutting head is & I'd seen true submerged oxy / fuel cutting ( I believe JCB 's main profiling facility used this ) which was done to provide better tolerance by reducing thermal movement & preventing any dross adhering to the cut pieces so that no grinding or other clean up was needed - just proves how little I know - & how tech stuff sneaks up on you ! - never too late to learn things - but I doubt many of us will get to see this cool stuff first hand.

[Jason_alex]

The reason that the industrial plasmas can do this is because they use high frequency and there are no moving parts inside the head (It is not recommend for a normal plasma). Where most of the cutmaster and power max units have starter cartridges and moving parts, the benefit to the industry is that it will not smoke with the exception of a little bubbling and it knocks down the glare under 2 to 4" of water. It knocks down the noise it makes by quite a bit.

OOOO Yea and as always don't cut aluminum this way!!!

Thanks,
Jason