[TheForge] why doesn't cast iron oxidize and burn in the same way?(was: oil/wax finish, blackened steel) OT:

[peter fels & phoebe palmer]

Jerry;
When you earned your gray beard
the tree excuse became redundant.
You have more brains left than most
of us had to begin with.
A bit of handicapping is only fair.

On 11/2/2010 11:20 AM, Jerry Frost wrote:
> Endothermic is right.. Cast iron is much higher C content than steel which
> separates to an extent when molten outside controlled conditions. The iron
> molecules tend to bond more tightly while the C tends to form a skin of
> graphite.
>
> The black leading edges and belly of the space shuttles is " Reinforced
> Carbon Carbon" or graphite refractory reinforced with graphite fibers with a
> working temp well above 3,000f.
>
> Anyway, cast iron slag has a melting temp higher than it's burning temp so
> it just blocks the oxy jet and that's all she wrote.
>
> Funny how someone with a decent size chunk of gray matter turned to rust
> remembers the darndest things. This bit came right to mind when you asked
> Andy but I can't recall one of my niece's name for nothing. Damn TREE!
>
> Jer
> ----- Original Message -----
> From: "peter fels&  phoebe palmer"<artgawk at thegrid.net>
> To: "Blacksmithing List Sponsored by ABANA"<theforge at mailman.qth.net>
> Sent: Tuesday, November 02, 2010 5:58 AM
> Subject: Re: [TheForge] why doesn't cast iron oxidize and burn in the same
> way?(was: oil/wax finish, blackened steel)
>
>
>> I inquired and got a helpful
>> Cast iron is endothermic, steel in exothermic...
>> Yeah thanks.
>> As a guess, and as Andy speculates, it's the clumps and lumps of carbon
>> and carbon compounds
>> that act in a refractory manner. Think carbon arc lights.
>> To cut cast with a torch, one needs to feed in sacrificial exothermic
>> steel above the cast.
>> Jim B will straighten us out on this, most likely.
>>
>> On 11/1/2010 8:45 PM, Andy Gladish wrote:
>>> Yeah, just wondering on a chemical level exactly what's happening with
>>> the
>>> oxygen stream, seems to be a lot going on.
>>> I think of carbides as being flammable but apparently they only interfere
>>> if
>>> anything. Carbon content per se doesn't seem to be a factor in the
>>> burning
>>> reaction.
>>>
>>> -----Original Message-----
>>> From: Bruce Freeman
>>> Sent: Monday, November 01, 2010 8:10 PM
>>> To: Blacksmithing List Sponsored by ABANA
>>> Subject: [TheForge] why doesn't cast iron oxidize and burn in the same
>>> way?(was: oil/wax finish, blackened steel)
>>>
>>> Andy,
>>> Yes, when you "burn" steel, the iron is oxidizing.
>>> I'm not sure I follow the question about cast iron.  It certainly will
>>> oxidize (rust).  Does this question refer to cutting with an oxygen
>>> stream?
>>>
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