Real or Urban Myth ?

[Arcfire]

Calling any Mythbusters out there.

Some years ago I heard that using air plasma to cut caused nitrides to form in the cut edges. This then caused you to used up grinding disks faster due to the extra hardness in the metal.

I have not noticed any real difference but is this because of better abrasives or not being able to compare cuts together or is it a myth ?

I'm just curious to find out.

 

[pedrobedro]

Was that in the days when nitrogen was used as well ?

 

[Arcfire]

Nitrogen is still used :-) but no, it was after the "pre air plasma" era.

 

[gridley51]

No,it`s not a myth,the cut edge is harder.The nitrogen comes from the air and causes slight nitriding of the edges.I don`t know if it uses more grinding discs though.
Mark.

 

[TechnicAl]

Air is 70%Nitrogen, 20% Oxygen, 8% CO2 plus other bits and bobs. Before anyone pulls me up I mean roughly.
So cut faces will have Oxides and Nitrides which can lead to hardening, embrittlement and possibly porosity. If its high integrity work you should clean the faces.
In fact if its a quality job you need, you should always clean the surfaces before welding regardless of how its been prepped.

 

[Arcfire]

At the last Essen Expo in Germany I came across a small cutter that used steam generated from distilled water as the plasma gas.

Do you think this might be worthy of development as an alternative to air, no nitrites ?

I know you would have to wait for a good boil, but no air needed.

Steam powered cutting ! ;-))

 

[mike os]

does it offer any advantages?

you are still cutting in a nitrogen rich environment some contamination of the hot and or molten metal is inevitable.....

 

[rtbcomp]

At the last Essen Expo in Germany I came across a small cutter that used steam generated from distilled water as the plasma gas.

Do you think this might be worthy of development as an alternative to air, no nitrites ?

I know you would have to wait for a good boil, but no air needed.

Steam powered cutting ! ;-))

Is this what Shadowwu was on about here (Post #14)

http://www.mig-welding.co.uk/forum/showthread.php?t=21550&page=2

 

[Arcfire]

The cutter I saw was Germany I think, a research machine. They were trying to sell it as a cutter/welder sort of thing. It caught my eye because they were cutting glass with it in non-transfer mode, though not very well.

 

[rikrobson]

Air is 70%Nitrogen, 21% Oxygen, 8% CO2 plus other bits and bobs.

Err 8% CO2 would be hazardous to health we'd all be sick/dead
Air is 78%Nitrogen, 21% Oxygen, 0.9% Argon plus .03% CO2 and the rest is trace.

 

[TechnicAl]

Err 8% CO2 would be hazardous to health we'd all be sick/dead
Air is 78%Nitrogen, 21% Oxygen, 0.9% Argon plus .03% CO2 and the rest is trace.

I told you all that someone would pull me up

OK but its the N2 and the O2 that matters in this instance


Oh and Steam still contains H2 and O2 so it wouldnt really be any better. I cant think why steam would be preferred over air, perhaps the moisture helps the plasma.

 

[mike os]

so really a different process..... as water kills current plasma setups

 

[Arcfire]

From what I saw the steam had to purge the torch line of water before the arc could be started.

 

[Sparkey]

Is this what Shadowwu was on about here (Post #14)

http://www.mig-welding.co.uk/forum/showthread.php?t=21550&page=2

OOooops! i think he got scared off when he read our replies.....

 

[Arcfire]

Reviewing the thread we seem to have gone off mark.

Can we say that air plasma does harden edges and cause the use of more grinding discs, and if so can we then lobby grinding disc sellers to discount the cost of air plasma machines due to the extra profit they make from the discs :-) ?

 

[rtbcomp]

OOooops! i think he got scared off when he read our replies.....

You could always send him a PM and apologise

 

[rtbcomp]

Blowing steam onto red-hot steel produces rust and hydrogen and more heat, so it could be a good way of cutting steel.

 

[paulmowers]

hi al

As already said, the edges are harder after plasma cutting, if you need proof just try running a file over it!!!!
As to using up grinding discs quicker I cant say ive noticed any difference but small intricate bits that you need a file or a little dremmel type stone thing definately wear out quickly!

Paul..

 

[jugs]

1
Real or Urban Myth ?
Whats the difference between a Real or Urban Myth ? - its in the country



2

Err 8% CO2 would be hazardous to health we'd all be sick/dead
Air is 78%Nitrogen, 21% Oxygen, 0.9% Argon plus .03% CO2 and the rest is trace.

Interestingly the atmosphere contains almost the same amount of Argon as Water !!! now if only we could collect it

Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxideand small amounts of other gases.
Air also contains a variable amount of water vapor, on average around 1%.

 

[pedrobedro]

A real myth? That is an oxymoron if ever I heard one You could have an urban myth, a suburban myth or a rural myth