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Duffy
10-29-2009, 03:56 PM
I went to visit a water jet cutter today in an attempt to score some HRS drops from cutting pipe flanges. What I needed was a 10"x1/2" disc as a starting point for a faceplate, and an 8"x3/8" one as a match plate to mount an 8" 3-jaw chuck on a 6" D1-3 camlock plate. ANYWAY, he had no HRS drops but I did find a 10"x3/8" which I thought would do. The manager of the shop thought that it was armour plate and that it would be tough to machine. Will it be a problem?
While looking around, I asked to see the cutter in action-no luck. One had just finished some 1/2" fibergass board, and the other was being set up to cut a slab of 4130 that was 13" thick! He told me not to wait around until it was finished! He also said that he gets "a few" 4" and 6" hydraulic breaker points to sharpen. The small ones are $100.00 and the 6" are $150.00. Apparently the operators are not really interested in sharpening because they charge their machines out by the hour and there is no incentive to be quick.
One more bit of information:- water jet is more expensive than either plasma or flame cutting and it is mostly used where distortion or final finish are important factors. Duffy

tattoomike68
10-29-2009, 04:21 PM
Hard to say what he called Armour plate. He might have T1 and that stuff is tough and is a little tough to machine but not bad. It will make a small 1 HP mill grunt hard to drill it, even a 3 hp mill you have to lean on a drill hard to get it to make a chip.

bulldozers and logging skidders have belly armor made from AR50. its just abrasion resistant , a bit tough and will break if bent up bad. if it dont break when bent it will break when you put a 100 tons on it to straiten it out after its been beat up and all work hardend unless you use lots of heat.

when new AR plate machines great, its good stuff but not worth the price for a chuck backing.


Just find some good old hot roll plate and save yourself the hassle.

AD5MB
10-29-2009, 04:26 PM
armor plate is what tanks and ships are made out of.

it's amusing to watch people try to drill it with hardware store drill bits. drain the battery on a dewalt, barely make a dimple. Hand them a 190 and tell them not to punch through to the concrete and ruin your bit. smirk, sneer, what the fu...

hey, bud, I broke that drill bit you loaned me. as they hand you a $20.

lazlo
10-29-2009, 04:45 PM
From what I remember from when I was at the Army Research Laboratory (which was before I got into machining), the most common US armor plate is RHA 12560 -- wrought homogenous armor, which comes in various heat treat classifications, CL I, II, III (for hardness, for shock resistance,...).

It's specified by penetration at various oblique angles, so the vendors are allowed to have their own blends, as long as it meets the Mil Spec penetration tests and is weldable.

The ARL ballistics guys often used 4340 as a stand-in, but I think that's actually a more sophisticated alloy than standard 12560.

If your plate is annealed, it probably will machine OK, but it'll work harden easily. If it's hardened, have fun! :D

Steve Steven
10-29-2009, 05:09 PM
I just happened to do some work with military armor plate. There are two MilSpecs for it, I can't remember them off the top of my head, but both are similiar. One, aimed towards vehicle armor, is a hardened alloy steel plate (MILDTL-12560J) which has from 0.30 to 0.33 carbon, with manganese, silicon and chromium in small ammounts to create a carbon equilivance of about 0.80. It is heat treated and tempered to 29-33 Rockwell C.

The other spec is MIL-A-46100 which is a similiar composition plate, but is used for lighter weapons and is tested for resistance to up to 20mm API shells.

Both are very hard and difficult to machine, but can be.

Steve

Black_Moons
10-29-2009, 05:14 PM
AD5MB: whats a 190?

rantbot
10-29-2009, 05:29 PM
It doesn't mean much. It's like describing steel as "carbon steel."

At one time, armor plate was steel which had been through the mother of all case-hardening operations. Soak time (for carbon adsorption) was measured in weeks for typical applications, which in the good old days was for the armor belts of dreadnoughts.

Michael Hall
10-29-2009, 05:45 PM
Duffy was it ferrous or non-ferrous? Alcoa makes a product called "Armor Plate" and it to can be tough to machine. I believe the Bradley personnel carriers is an example of a vehicle using aluminum armor plate.

Michael

lazlo
10-29-2009, 06:23 PM
Alcoa makes a product called "Armor Plate" and it to can be tough to machine.

I'd be interested in the alloy on that one -- is there any common (non-laboratory) aluminum alloy with higher yield strength than 7075?

You mean, the Bradley's armored with aircraft aluminum? :D

dockrat
10-29-2009, 06:37 PM
re alcoa armour plate:

http://www.alcoa.com/global/en/news/news_detail.asp?pageID=20071008005877en&newsYear=2007

The data sheet for ALCOA ALLOY 2519-T87: Weldable Cryogenic/Armor Plate Aluminum Alloy can be found here but it will cost ya $25.00

http://asmcommunity.asminternational.org/portal/site/www/AsmStore/ProductDetails/?vgnextoid=b800fdca43dce110VgnVCM100000701e010aRCR D

Looks like its a wrought al/cu

lugnut
10-29-2009, 06:40 PM
In Idaho in my other life, I worked at a nuclear reactor testing site, at the north end of the site, they (the Army) was said to be making armor plate for tanks from Depleted Uranium. OF course they did not advertize much about it. I guess it works I think they are still at it. A google search will get you some limited info on it.
Mel

JSGAuto
10-29-2009, 06:44 PM
All of the above is used, along with ceramic plate, composites, titanium, transparent armor (ballistic glass) and plain old mild steel.

As always, it depends on cost, weight, time, and level of protection.

Jim

lazlo
10-29-2009, 07:12 PM
(the Army) was said to be making armor plate for tanks from Depleted Uranium.

That's the Chobham armor -- modular armor boxes with laminations of ceramics, Kevlar, and depleted uranium in the front glacis for protection against long-rod penetrators.
That's why the turret on the M1 is flat and boxy.

When I worked for ARL, the tank crews used to tease the driver, because when the hatch is down, he's pressed up against the glacis, which is somewhat radioactive.

OSHA doesn't apply to the Armed Forces :)

loose nut
10-29-2009, 07:30 PM
Are the sides and rear of the turret just plain steel armor or the "good" stuff

lazlo
10-29-2009, 07:33 PM
Are the sides and rear of the turret just plain steel armor or the "good" stuff

Everywhere else besides the glacis and the turret is RHA. The top is surprisingly thin -- ~ 1/2", if I remember correctly. That didn't used to be a problem, but one of the projects I worked on at ARL were pop-up mines that fired an explosively-formed projectile into the top of the tank.

Duffy
10-29-2009, 09:23 PM
This stuff is definitely ferrous. I have not tried to drill it yet-that's for tomorrow. If it IS armour plate, I suspect that it came from one of our Defence Research labs. It is 3/8" or the metric equivalent. I am guessing that it might be protection on a APC. I have $10.00 invested in it and, if I cant work it, I will put it with the CTC barbell weight that I could not machine-in the garbage! I get too soon old and too late smart! Duffy

lazlo
10-29-2009, 10:09 PM
I suspect that it came from one of our Defence Research labs.

Ah, judging from your spelling of "Defence", either you're using Airsmith's spell checker, or you're British :)

If it's the latter, the American Milspec 12560 won't help -- I'm sure the Brits have their own armor plate specifications. Probably same deal: it's spec'd according to hardness, yield strength, ductility, and penetration, and not the actual alloy.

Michael Hall
10-29-2009, 10:27 PM
I didn't say aircraft aluminum, its a 7085.



I'd be interested in the alloy on that one -- is there any common (non-laboratory) aluminum alloy with higher yield strength than 7075?

You mean, the Bradley's armored with aircraft aluminum? :D

barts
10-30-2009, 02:05 AM
Back when I was part of a team that built a robotic laser guided cell to weld the Bradley turrets in the mid 1980's, the aluminum armor plate was two different alloys bonded (how, I have no idea) together to increase spalling and penetration resistance.

- Bart

Oblig. Bradley joke: "Why do they paint Bradleys tan?... so they can hide at the bottom of ponds"

Duffy
10-30-2009, 06:06 PM
I tried to drill this stuff. I used an ex-Boeing bit, which I think is cobalt alloy. In any case, it formed a little dimple and stopped. Using low cunning, I switched to a 3/16" carbide drill, also ex-Boeing. It did NOTHING! Being old and wise, I then gave up. Well not REALLY wise, otherwise I would have left the plate where I found it! Duffy

Evan
10-30-2009, 06:26 PM
When I worked for ARL, the tank crews used to tease the driver, because when the hatch is down, he's pressed up against the glacis, which is somewhat radioactive.

OSHA doesn't apply to the Armed Forces

OSHA doesn't care about the radiation level of DU either. It's so low that the natural background count swamps it. You will get a bigger dose from standing next to a granite surface plate which normally contains undepleted uranium. DU is used for radiation shielding in medical equipment.

lazlo
10-30-2009, 07:08 PM
OSHA doesn't care about the radiation level of DU either. It's so low that the natural background count swamps it.

Depleted uranium is about 60% of the radioactivity of pure uranium ore -- it's considerably higher than background radiation. It's still ~.7% U235. That's why the Europeans have banned live fire exercises with DU shells. I actually participated in the last "Reforger" Nato live fire exercise in '93. It's an amazing sight to see a battalions of M1's firing DU shells in the Fulda Gap...

The front glacis of an M1 tank will set a geiger counter off, although it's primarily alpha.

Why do I have the funny feeling there's going to be a flood of Google quotes? :rolleyes:

Evan
10-30-2009, 07:34 PM
A geiger tube won't detect alpha. For that you need a unpressurized/unevacuated thin window ionization chamber. Alpha is so weak it can't penetrate a piece of paper. Background radiation is composed of mainly beta from daughter products of radioative elements and some gammas from cosmic ray secondaries. Even undepleted uranium generates a very low level of radiation but the difference in DU is that the U235 has been almost completely removed along with the normal daughter products of decay. It requires no shielding or other measures to protect workers from radiation, only from the fact that it is a toxic heavy metal.

The extremely low radiation level is directly reflected in the very long half life of U238, 4.5 billion years. That means that if you are observing an atom of U238 you will have to wait, on average, 4.5 billion years before it decays and emits an energetic particle. If it is vaporized as in munitions use then it becomes inhalable and that presents a radiation hazard because the alpha particles can then impinge directly on tissues that matter, unlike skin.

Ordinary lead is actually more dangerous than DU. Uranium including it's oxides is almost completely passed through the digestive system if eaten while lead may be bioavailable.


Why do I have the funny feeling there's going to be a flood of Google quotes

Not likely. I used to work in quality control for a company that produced radiation counters and monitors. As well I worked with my father at the Lawrence Radiation Laboratory in Berkeley. I also have two counters that I use to check the background from time to time especially during solar flares which can produce what are called "ground level events".

lazlo
10-30-2009, 07:48 PM
A geiger tube won't detect alpha.

Huh, that's funny. 'Cause mine does:

http://scientificsonline.com/product.asp?pn=3017006&cm_mmc=Mercent-_-Google-_-NULL-_-3017006&mr:trackingCode=1B6D1735-DB81-DE11-8C0A-000423C27502&mr:referralID=NA&bhcd2=1256946506

lugnut
10-30-2009, 07:51 PM
Duffy I think if you want a hole in the stuff you will have to buy some depleted uranium bullets and shoot a hole through it:eek:
Mel

AD5MB
10-30-2009, 08:25 PM
AD5MB: whats a 190?

http://www.emisupply.com/catalog/imagemagic.php?img=images/UPLOAD/Image/Products/Norseman/190-AG-Jobber.jpg&w=500&h=101&page=popup

Norseman Jobber AG 190 (http://www.emisupply.com/catalog/190ag-magnum-super-premium-jobber-length-drill-p-2164.html)

ferocious drill bit. goes through 1/2" armor plate like its 6061 T6. makes a remarkable improvement in productivity when you need to drill and tap 50 4-40s in a day.

note antique brass outer coating, black in the flutes.

does not give you spirals from armor plate. fine spray of little flakes.

wierdscience
10-30-2009, 08:47 PM
For normal "punch and hole in it work" good quality masonary bits will drill it,just touch up the bits tip with a green wheel.

Evan
10-30-2009, 09:29 PM
Huh, that's funny. 'Cause mine does:


Yes it will if the energy is above 4 mev. That is what the spec says but what it doesn't say is that it isn't a hard threshold. While the characteristic energy of the decay of each daughter species is always the same the chance of the particle making it through the window and then ionizing the chamber is a matter of probability. The decay energies of uranium 238 decay are only slightly above the stated 4 mev value. Your counter will detect some alpha from U238 but without knowing what the spec is based on as to the probability of a 4 mev particle getting through the window there is no way to tell how well it will detect alpha.

You have a very good counter ($900). It probably has a beryllium window tube and I presume it has a movable shield that you open to detect alpha particles. Garden variety counters will not detect alpha particles except at much higher energies than uranium emits.

A good test of your counter would be to do a 24 hour background count using the audio output to pulse a totalizer so you can get a long term average. The background should be around 16 to 30 counts per minute in a location away from local sources.

Then place the tube on your surface plate and do another 24 hour count. It should read at least 3 to 4 times as high to perhaps as much as ten times higher depending on the source of the granite.

John Stevenson
10-30-2009, 09:43 PM
I used to work in quality control for a company that produced radiation counters and monitors. As well I worked with my father at the Lawrence Radiation Laboratory in Berkeley.

Bloody hell Evan how many jobs have you had ?

You must have had more jobs than Yosser Hughes.

.

dp
10-30-2009, 09:50 PM
This is as good a place as any to say Armour plate is that thing that keeps your slices of honey-baked ham off the table linen.

boslab
10-30-2009, 10:04 PM
any plate irrispective of chemical analysis can be considered to be 'armour plate' if it provides a barrier, theres a whole pile of aluminium armours [least there was when i worked at hawker siddley high duty alloys, all the ali armours are laminated, different grades of ali alloy rolled sandwich style.
most of the inner constituents were classified as they were the defense peoples property, a lot came as unmarked slabs of about 12-15 ton for homogonisation and rolling.
post roll heat treatment was usually bizzare to say the least, some aspects actually modified the structure some were put there for no other reason than to hide the ones that did make a difference, eg percipitation, age hardening, cryo etc
steel is the same. there is no 'better' steel than another, just different ones.
laminar plate rolling is usually sandwich style, very rarely would an armour plate for say a tank be monolithic unless its a casting [you can modify a casting to behave like a laminated plate by playnng with cooling rates aka chill casting/ slurry casting etc]
hastelloys are fascinating things to play with, spose they could be 'armour plate' depending on use
wasnt yosser a charicter from boys from the blackstuff?, my memory is not what it was
mark

wierdscience
10-30-2009, 10:22 PM
Yes it will if the energy is above 4 mev. That is what the spec says but what it doesn't say is that it isn't a hard threshold. While the characteristic energy of the decay of each daughter species is always the same the chance of the particle making it through the window and then ionizing the chamber is a matter of probability. The decay energies of uranium 238 decay are only slightly above the stated 4 mev value. Your counter will detect some alpha from U238 but without knowing what the spec is based on as to the probability of a 4 mev particle getting through the window there is no way to tell how well it will detect alpha.

You have a very good counter ($900). It probably has a beryllium window tube and I presume it has a movable shield that you open to detect alpha particles. Garden variety counters will not detect alpha particles except at much higher energies than uranium emits.

A good test of your counter would be to do a 24 hour background count using the audio output to pulse a totalizer so you can get a long term average. The background should be around 16 to 30 counts per minute in a location away from local sources.

Then place the tube on your surface plate and do another 24 hour count. It should read at least 3 to 4 times as high to perhaps as much as ten times higher depending on the source of the granite.

For added fun,find a piece of Fiestaware china with the DU glaze and do a count.:)

http://www.youtube.com/watch?v=qk9vHQrKMdk

boslab
10-30-2009, 10:51 PM
Go to Cornwall on holiday, watch your kids glow in the dark!, and a bit of Radon too just for fun.
I remember going to an old dock [built by Brinnel] in South Wales, turned out that there was a big pile of crap that was old ballast of sailing ships, it was Pitchblend [Uranium ore] well it was dense!, now i know why the rats were sooo big!
im still wondering how the hell my badge in work picked up a Neutron dose, thats a puzzle, all the sources were locked away in thier wax bottles.
we make scintillatioin counters for the rolling mills out of big 6" thick slabs of perspex with a titanium window over them for protection, a source [Co], tracks over the steel sheet as its being rolled [between the roll stands] and gives you a graphical output of the shape of the steel sheet called wedge and crown, steel ciols ate not flat across thier width, if they were you wouldent be able to get them to go through a rolling mill at 60 Km/h!
mark

Evan
10-30-2009, 11:00 PM
The problem with those uranium glazes is that they weren't depleted uranium. They were made with undepleted uranium and are quite a bit hotter than DU. While the statistic is that DU is 60% as radiactive as Un-DU that doesn't tell the entire story. That 40% is entirely due to the U235 and daughter products and the energies from those are much higher and penetrate more.

U238 decays to thorium 234 which has a half life of about 24 days and emits a beta particle when it decays. The next decay emits an alpha of very low energy and then the decay stalls for 25,000 years. This is important because DU has the daughter products removed so when it stalls at U234 that's it for a long time.

U235 decays with an alpha to thorium 231 and then to Protactinium via beta decay but the half life is ony 25 hours. That means it emits 25 times as many beta particles as U238. Un-depleted uranium emits virtually all of the extra radiation as beta particles which are penetrating particles so there is a big difference in the hazard level compared to depleted uranium.

loose nut
10-31-2009, 02:12 PM
Back in the late '30s, when Britain started to rearm, one of the main armor plate suppliers, most where gone and much of the armor for British battleship was imported from Czechoslovakia, big problem there, was Vickers.

In the steel mill where they were founding the plate there was a catwalk above the big converters and in those less safety conscious days where only made out of wood. One of the employees was a Chinese man and one day while on the cat walk he looked over the railing and it broke, the man plunging into the molten steel being almost instantly incinerated. The supervisor knowing nothing could be done kept production going and made a note on the spec. forms that the man had fallen into the vat.

After the rolled plate had been delivered to the ship yard the metal inspector read the mill test report saw the note about the man falling into the vat of molten metal and rejected the whole shipment of armor plate.

The steel mill superintendent called the shipyard with an indigent voice asking why the plate had been rejected and was flatly told "we don't want ships with a chink in the armor":D :D

boslab
10-31-2009, 03:11 PM
that is so bad on so many levels...lol, clever thing is if you do happen to fall in you float, apparently worse for the onlookers than the victim, a friend of mine in schools father fell into a slag pot at dupont steel, they buiried the whole pot at the site [some 40 tons], thats his grave now, the steelplant has long gone, sad, i can say from expirience that a splash of molten steel will knock you off your feet and leave you broken as well as burnt, steel density
about 7.8 ish tons per cubic metre, imagine being hit by a bucketfull!
the joys of liquid sunshine
still laughing as i think i have a somewhat black sense of humor
mark

loose nut
11-01-2009, 10:08 AM
The bit about having to buy there armor from Skoda (Czechoslovakia) is true. The Brits had to reinvent the art of armor making for WW2 as most or all of the steel works that could make it where closed down by then.