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

[Jerry Frost]

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?
>>