[TheForge] Re: Burning Metal

Thu Nov 6 18:37:01 2003

        Chuck, I couldn't agree with you more on proper pre-heats.
        My experience with a cutting torch has found that a "cold flame" is
a good thing for lack of slag.  Now how to define a cold flame on the torch
would depend on the material thickness your cutting vs rate of cut.  When
you are cutting and have the very top of the plate melting and puckering
back looking like the very top edges are melted and rolled(sloppy kerf that
I think you refer to)........you need to cut the preheat a bit so your not
melting the top edge of the plate/piece.   This means developing a knack for
proper cut rate in certain thicknesses.........then when your used to that -
the ability to fine tune the flame so you don't get that top melt is when
you start to save yourself hours of grinding and clean up on fabrication
projects.  A good thing to remember is a cutting torch is just
that.......your cutting with an oxidizing stream and if you enter the
equation of melting steel into that.......you got a mess you gotta clean up.
        Don't get me wrong, I still have to fine tune things with a couple
trails before diving into the project if I want accuracy and lack of slag.
It's just like forging a study or sample, or doing a weld test to set the
heat and feed speed on your welder to "tune it in".......sometimes the test
piece is to tune you into running a torch - and if it's one of those days,
you certainly don't want to be making your first cut on your expensive plate
layout or parts which you have JUST the right amount of material for.
        Making simple guides and fixtures for flame cutting plate, wide
flats, beams, flanges, and circles are also a good idea as the less energy
you put into your alignment and distance of tip to stock........the more you
can focus on the cut rate and clean cold flame so you don't spend the day
grinding.  A day of heavy slag grinding these days is right at the bottom of
my list of fun things to do for a day.

Ralph
----- Original Message -----
From: "Chuck Robinson" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 06, 2003 1:59 PM
Subject: Re: [TheForge] Re: Burning Metal


> Hey Jerry,
> What I have observed during cutting operations, is that after setting up
the
> torch properly, it is critical to use the right preheat flame to heat the
> steel enough to start the cutting action; but not over heat the area so
that
> the kerf gets sloppy. Once the cut gets sloppy, the slag diverts the
cutting
> action to the sides of the kerf. And the cut is kaput. The higher the O2
> pressure and thicker the metal, the more slag is formed. Once the slag
> oxides have clogged the cut. its a real pain to restart the cut at that
> point. It's like the slag is forming an insulating barrier.
> I've heard that the allstate is a really good torch, but havent tried one
> yet.
> Chuck
> ----- Original Message -----
> From: "Jerry Frost" <[email protected]>
> To: <[email protected]>
> Sent: Thursday, November 06, 2003 3:19 AM
> Subject: Re: [TheForge] Re: Burning Metal
>
>
> > Hi Chuck:
> >
> > I'm not sure how my muddled ramblings lead to your question except
perhaps
> I
> > didn't say the iron/steel is burning under the oxy jet. Once the steel
is
> > hot enough to initiate burning under the oxy it is self supporting.
> Properly
> > set and guided by a steady hand you can certainly shut down the acet
after
> > cutting starts and continue just with the oxy.
> >
> > Oxides and slag inclusions that shield the iron/steel from the oxy jet
> stop
> > the combustion. Iron and steel within the cutable range of alloys
produces
> > an oxide with a much lower melting temp than the unoxidized metal and is
> > literally blown out of the cut by the "pressure" of it's own combustion.
> >
> > Ayup, improper regulator settings and tip selection is the #1 reason for
> > poor torch cutting. (Oh okay, dirty tips are right up there too.) I use
an
> > Allstates oxy/prop rig at home and the regulators are self metering but
at
> > work I'm always resetting the regulators. Everybody seems to want to run
> > 5lbs acet and 40lbs oxy.  What really kills me is somebody will
compliment
> > me on a torch cut, then rag on me for not having the regs set "right".
> > <sigh>
> >
> > Frosty
> > ------------------------
> > If it ain't forged
> > it ain't real.
> > Wrought iron is.
> > The FrostWorks
> >
> > Meadow Lakes, AK.
> >
> >
> > ----- Original Message -----
> > From: "Chuck Robinson" <[email protected]>
> > To: <[email protected]>
> > Sent: Monday, November 03, 2003 7:37 PM
> > Subject: Re: [TheForge] Re: Burning Metal
> >
> >
> > > Jerry,
> > > If this is true, how can I shut the Acetylene valve off when the cut
> > starts
> > > and complete a cut in metal 1/2" thick  with out the fuel supply?
> > > When I first started cutting  my 5+" thick steel anvil billets, I had
> > major
> > > problems with slag build up and sloppy wide kerfs or incomplete cuts.
> > > After reviewing my O/A cutting text books. I lowered the O2 pressure
and
> > the
> > > cutting action improved dramatically. The higher the O2 pressure the
> more
> > > slag formed in the kerf
> > > The cutting action is exothermic.
> > > I believe poor O/A torch performance is mostly due to not adhering to
> > proper
> > > gas pressure for the tip size recommended for the steel thickness.
> > > Chuck
> >
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