[TheForge] Re: Burning Metal

Thu Nov 6 19:58:00 2003

        Good point on rusted and heavy scaled plate........that is a great
way to get a mess.........and heavy scale plate really sends hot flakes
flying as well.  I gave up on goggles and went to face shields for that
reason........I'm already ugly enough without the burn scars.  My favorite
shop atire for cutting is a set of shaded glasses and a face shield for full
protection from flake and back blow if it occurs.   Back blow is not
something that in line arrestors stop.....it is when the cut stops for some
wonderful reason.......(like a ball bearing in the middle of your
beam!)........and the old faithful blow back of molten metal occurs.  I
actually have that ball bearing I dug out of the middle of a beam flange
when that occured.
         This surface cleaning is especially important on cutting bevels at
a 45 degree angle by hand.......that's the only way to get decent results in
that process.

Ralph
----- Original Message -----
From: "Chuck Robinson" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 06, 2003 7:10 PM
Subject: Re: [TheForge] Re: Burning Metal


> Right on Ralph,
> Another no-no is not cleaning the cut line surface on the plate.
> When I get lazy and don't pre clean the plate the cut has to pre- heat the
> surface scale, an so the cut is more ragged.
> One technique I use, is to turn my side grinder 90 degrees, and use the
disk
> edge to grind a 1/8" de scaling cut along the pencil line.
> Chuck
> ----- Original Message -----
> From: "Ralph Sproul" <[email protected]>
> To: <[email protected]>
> Sent: Thursday, November 06, 2003 5:43 PM
> Subject: Re: [TheForge] Re: Burning Metal
>
>
> >         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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