gwh%earthquake.Berkeley.EDU@ucbvax.Berkeley.EDU (George William Herbert) (06/28/90)
From: gwh%earthquake.Berkeley.EDU@ucbvax.Berkeley.EDU (George William Herbert) In article <1990Jun27.021037.1449@cbnews.att.com> creps@silver.ucs.indiana.edu (Steve Creps) writes: > I thought Sheffield was lost because she was made of aluminum, which was >ignited by the burning missile (metallic Al will burn at high enough >temperature- you can ignite an aluminum can with a blowtorch, for example). >This isn't going to happen with a steel ship like the Iowa. I would like to know where this rumor started... 8-) Aluminum in ship structures does not burn in shipboard fires. It has once, maybe, it's suspected, but it is not a general consideration at all. What _is_ a concern is the thermal conductivity and resistance of structural aluminum in ships. It apparently lets heat though better than the steel that it would be replacing, letting fires jump from compartment to compartment better, and thus Aluminum ships are less resistant to fires than Steel ones. It also melts at a lower temperature, which will let fires propogate _much_ more readlily if they get this hot. It's strength in general drops more in a fire also, leading to a higher likelyhood of structural problems. == George William Herbert == I support Open-Access Computing! UCB OCF == JOAT for Hire: Anything, === ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ =======Anywhere, My Price.======= Quantum Mechanics can explain everything == gwh@ocf.berkeley.edu == except Madonna, Flame Wars, and NASA's space == ucbvax!gwh%ocf%lilac == Policy. We're working on the first two...
raymond%carme@uunet.UU.NET (Raymond Man) (06/29/90)
From: raymond%carme@uunet.UU.NET (Raymond Man)
In <1990Jun28.025954.19601@cbnews.att.com> George William Herbert maintained
that
>Aluminum in ship structures does not burn in shipboard fires.
We need to talk to chemists here. I believe (from what remain of my
high school chemistry) that Al reaction with O is exothemric. So
given a high enough initial temp., the reaction will sustain itself,
in other words, burn. For steel, I believe it is endothermic, so
it will not burn. There is no reason to suppose shipboard fires
burn cooler than any fire and I imagine the materials on a warship
give much hotter flame than usual.
[mod.note: Will a metallurgist do ? 8-) Yes, the oxidation of aluminum
is exothermic, very much so. The thing is, Al2O3 (blasted ASCII...) forms
a very stable, thin film over the aluminum, which greatly inhibits further
oxidation, even when the aluminum is molten. Hence, aluminum can be (and
routinely is) melted and cast in open air. So long as it doesn't become
finely divided, it's quite resistant to uncontrolled oxidation (fire,
y'all 8-)
This is not true for the more reactive titanium and zirconium families.
Thermite (a mixture of powdered aluminum and iron oxide, which generates
great heat in the exchange reaction forming iron and aluminum oxide)
works because of the fine division of the components. The process is
known as "aluminothermic reduction," for vocabulary buffs. - Bill ]
The rest of Mr. Herbert article I tend to agree.
Disclaimer: Nothing more than explicitly stated is intended to be conveyed.
Just call me `Man'.
"And why take ye thought for " -- Matt. 6:28
raymond@jupiter.ame.arizona.edujharkins@uunet.UU.NET (Jim Harkins) (06/30/90)
From: sagpd1!jharkins@uunet.UU.NET (Jim Harkins)
In <1990Jun28.025954.19601@cbnews.att.com> George William Herbert says
>Aluminum in ship structures does not burn in shipboard fires.
I don't know if you mean aluminum in general, or when cast to look like a
ship :-), but the current issue of Scientific American has an article on
fireworks. Turns out one of the ingredients for bright displays is aluminum
because it burns so brightly. Then again, I seem to remember from my child-
hood chemistry set that iron would burn also. Just make iron filings and
sprinkle them over your alcohol lamp. Nobody has yet claimed that we lost
ships in Nasty Number 2 because the steel superstructure caught fire :-)
--
jim jharkins@sagpd1
I hate to see you go, but I love to see you walk away.henry@zoo.toronto.edu (Henry Spencer) (06/30/90)
From: henry@zoo.toronto.edu (Henry Spencer) >From: raymond%carme@uunet.UU.NET (Raymond Man) >We need to talk to chemists here. I believe (from what remain of my >high school chemistry) that Al reaction with O is exothemric... >... For steel, I believe it is endothermic... Not so. Any metal reacting with oxygen is exothermic, often highly so. Steel wool can burn quite impressively. Differences lie in how easy the metals are to ignite. Steel wool is an extremely favorable case because it's finely-divided steel with lots of oxygen around it. It is *very* difficult to ignite bulk steel, to the point where it essentially never happens. And it is actually very difficult to ignite bulk aluminum, for that matter -- last I heard, there are *no* known confirmed cases of aluminum fires in warship accidents. As our moderator mentions, one important factor in the case of aluminum is its very tough oxide film. You've never touched aluminum. For that matter, you have probably never touched steel or magnesium. What you touch is the oxide film on the surface. But the physical properties of that oxide film vary a lot depending on the metal (which is why, for example, steel rusts -- spontaneously "burning" at an infinitesimal rate -- and aluminum doesn't). Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry
leipold@uunet.UU.NET (Walt Leipold) (07/03/90)
From: eplrx7!leipold@uunet.UU.NET (Walt Leipold) In article <1990Jun30.053925.4579@cbnews.att.com> sagpd1!jharkins@uunet.UU.NET (Jim Harkins) writes: >I don't know if you mean aluminum in general, or when cast to look like a >ship :-), but the current issue of Scientific American has an article on >fireworks. Turns out one of the ingredients for bright displays is aluminum >because it burns so brightly. And the fuel for most solid-propellant rocket motors (including the SRBs on the Shuttle) is aluminum (finely divided, of course). -- "As long as you've lit one candle, Walt Leipold you're allowed to curse the darkness." (leipolw%esvax@dupont.com) --
wrf@mab.ecse.rpi.edu (Wm Randolph Franklin) (07/05/90)
From: wrf@mab.ecse.rpi.edu (Wm Randolph Franklin) Metals in general soften (i.e. turn to putty) at about half their melting point. A consideration in the design of steel buildings on land is to shield the steel to protect it (for awhile) in case of fire. E.g., insulating foam is sprayed on skyscraper beams. In fact a solid wood beam is more fire resistant than an uninsulated steel beam of equal strength. The point of all this is that if the weakening of steel is a problem in a fire, I'd think that aluminum would be absolutely terrible since it melts at a much lower temp. -- Wm. Randolph Franklin Internet: wrf@ecse.rpi.edu (or @cs.rpi.edu) Bitnet: Wrfrankl@Rpitsmts Telephone: (518) 276-6077; Telex: 6716050 RPI TROU; Fax: (518) 276-6261 Paper: ECSE Dept., 6026 JEC, Rensselaer Polytechnic Inst, Troy NY, 12180