| Pages:
1
2 |
joseph6355
Hazard to Others
Posts: 144
Registered: 23-8-2017
Member Is Offline
Mood: Nitrated
|
|
[Metalurgy] Homemade steel body armor
Is anyone interested in the idea of making their own steel body armor?
First of all, lets pay attention to some principles when making hard body armor.
A lot of people talk about ar500 and ar600, but those are industrial nomenclatures, and not actually steel chemical standards. It means that ar500
isn't actually a steel alloy, but just a market-friendly way of describing a certain type of steel that has been exposed to certain heat treatments.
AR stands for abrasive resistant. It means that there are chemical additives (alloys) that are mixed within the molten steel in order to achieve
resistance to abrasion (it will suffer less from wearing when scratched with a harder element). Generally, Manganese, Phosphorus, Chromium and Boron
are added in certain quantities to obtain such characteristics.
500, 600 and so on, stands for the Brinell hardness of the metal. 400 is not enough if you want it to last, 500 is ok, 550 is good, 600 is ideal if
you chose the proper thickness for the armor plate. Don't go above 600 or else it will get so brittle that it will shatter (specially after a few
shots from a heavy hitter). Choosing the proper steel alloy is the key. The most important factor to stop a projectile is the final hardness, but the
added alloys also imply in a greater bullet-stopping capability, specially Manganese and Phosphorus in higher quantities, and also add toughness to
the hardened steel so it is hard but not as brittle as other less tough steel alloy would be at the same hardness.
Steel alloys
The most easy-to-get steel alloy that will suit these needs is the AISI 5160. It is frequently used in leaf springs, so it became readily available
and cheap. At 600 Brinell, you can get away with .210 gauge thickness, but back face deformation will also be greater, and thus, increase the chances
of an injury. The pro side is that it will be slightly lighter.
I would personally go for the 1/4" thick plate, it will be more robust and last longer, and also compensate for any human error that could be made
that would reduce its bullet-stopping capabilities. Another key factor is grain refining. Normalizing the steel will reduce the grain size and
increase the plate toughness, because the kinetic energy delivered by the projectile will be more evenly distributed among the greater number of
grains. Think about it as hitting a bucket filled with fine sand with a hammer, and then hitting another bucket filled with gravel. Which one do you
think that will result in a higher penetration depth? 
Heat treatment
In order to heat treat it correctly, you could send it to a heat treating company. But it would totally defeat the "homemade" purpose of the thing,
right? You could build a gas forge, and judge color by the eye.
Not a very accurate reading, but if its the best you can do...
AISI 5160 is very forgiving when heat treating though.
You will need to heat it to a red-orangeish color and then let it cool to black, and wait a few minutes then. Do it 3 times.
Next, heat it again to the same color and quench it in a fast coolant, like olive oil or parks 50 oil. Agitate it gently.
Next, put it in the oven and use an accurate temperature reading, like a good thermometer. Temper it to 200-210 ºC for 1 hour, and then let it cool
to room temperature.
And remember to curve or form the plate before you heat treat.
A lot of companies complain that 600 Brinell steel cant be bent and curved, so they don't use it.
Well, they shouldn't be bending the hardened steel in the first place, it will cause a lot of stress in the material and compromise toughness.
All forging, curving and cutting should be performed prior to normalizing and hardening.
The true reason why they do this is because they buy the steel from a proprietary company that don't disclose the alloy used neither how to heat treat
it, and then they don't have other option but to curve the hardened steel.
Common abrasive resistant borderline-proprietary alloys used in body armor are T1, T2, T3 and so on. AISI 5160 gets very close to some of these
abrasive resistant alloys, and it is both tough and capable to achieve high hardness.
Thickness
First of all, lets talk about what the NIJ standards call for.
https://www.ncjrs.gov/pdffiles1/nij/223054.pdf
Type III hard armor or plate inserts shall be tested in a conditioned state with 7.62 mm FMJ, steel jacketed bullets (U .S. Military designation
M80) with a specified mass of 9.6 g (147 gr) and a velocity of 847 m/s ± 9.1 m/s (2780 ft/s ± 30 ft/s).
That is what a level 3 body armor should be able to stop.
Commercial body armor are mostly 1/4" thick and have a hardness of 500 to 550 Brinell. At this hardness and thickness, it will stop most projectiles
traveling under 2900 ft/s (for 5.56) and 2800 ft/s (for 308 win).
Newer plates though have an increased hardness at about 600 Brinell, and some going even further till 650 Brinell.
Spartan armor plates have a thickness of .210 inches, and 600 Brinell hardness, and will stop 5.56 projectiles traveling under 3200 ft/s. That is a
huge improvement, since a 55 grain projectile traveling that fast would penetrate a common ar500 plate.
The problem with a hardness like this is that the plate will be prone to shattering. To counteract that, we can try to refine the grain and increase
the thickness. A thicker plate will accept an increased hardness better.
It is also proven that ar500 1/2" thick plates will stop a .50 BMG FMJ traveling under 3200 ft/s. But if you are going to get hit with a .50 BMG, the
kinetic energy itself would probably kill you anyway, because there isn't enough surface are to distribute this energy that would allow it to be
reduced to an acceptable level. So just take your armor off and die like a man.
Anti-spalling coatings
You can always pay someone to coat your plate with bedliner. There are places that will offer this kind of service. But I'm gonna focus on the fun
part, which is making it yourself.
You could coat it with bedliner yourself, but it is kind of expensive, messy and complex. So we will use fiberglass.
You see, fiberglass and epoxy are perfect for this. The final product will be a hard plate that will not only help with slowing down the projectile,
but contain its spalling.
The projectile will penetrate the fiberglass plate and hit the steel, which will make it basically pulverize, but the surrounding fiberglass will
catch all of the fragments.
The fragments usually fly at a 20º angle from the plate, so I eyeball a 1/2" thick fiberglass plate to be enough to catch all the fragments.
I think I covered the basics and now we can start a discussion about it. Maybe testing too.
I can't test it with rifles because I live in a country where it's not possible to own it legally, but I'm sure that there are a lot of Americans here
that can test it properly.
I've shot a small 10x10 cm plate before with a .38 SPL and .40 SW. No dents, no bending, no back face deformation, no nothing. It wasn't even fun.
[Edited on 3-1-2018 by joseph6355]
Oh, hello! |
|
|
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
Honestly, if I were going to build a set of body armor, I'd make it from UHMWPE. Far lighter, and just as strong.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
unionised
International Hazard
Posts: 5102
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
Is it just me who thinks this makes roughly as much sense a a DIY parachute?
|
|
|
walruslover69
Hazard to Others
Posts: 216
Registered: 21-12-2017
Member Is Offline
Mood: No Mood
|
|
how are you creating your steel alloy plate in the first place? if you are already buying a steal plate, why not just buy a bullet proof plate?
|
|
|
joseph6355
Hazard to Others
Posts: 144
Registered: 23-8-2017
Member Is Offline
Mood: Nitrated
|
|
I don't know. I hasn't been tested.
Are you sure it will sustain multiple hits from a 5.56 projectile traveling at 3200 ft/s?
Oh, hello! |
|
|
joseph6355
Hazard to Others
Posts: 144
Registered: 23-8-2017
Member Is Offline
Mood: Nitrated
|
|
Quote: Originally posted by walruslover69  | how are you creating your steel alloy plate in the first place? if you are already buying a steal plate, why not just buy a bullet proof plate?
|
For the sake of experimenting and creating something with my own hands.
What if some day you are not allowed to buy armor plate anymore? What if the government requires it to have a serial number? What if...
Nothing wrong with testing and having the knowledge.
I don't want to depend on the government or any private company to protect myself from rifle threats.
"why not just buy a bullet proof plate?"
Why buy it in the first place if I can make my own?
It will be far cheaper and have the same efficiency.
Oh, hello! |
|
|
joseph6355
Hazard to Others
Posts: 144
Registered: 23-8-2017
Member Is Offline
Mood: Nitrated
|
|
Yeah, lets just rely on the government and private companies to protect ourselves.
Nothing wrong with going online and buying a steel plate. But remember that not so long ago it was possible to buy nitric acid otc, nowadays it became
more expensive and hard to get, forcing people to make their own.
Oh, hello! |
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
...Somehow I doubt that.
I'm not sure what you're trying to do here. Are you trying to make medieval plate armor that's bulletproof?
If you do and you can demonstrate it works just as well as commercial products, definitely post it here. It would be quite the achievement.
|
|
|
Fulmen
International Hazard
Posts: 1693
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
| Quote: Originally posted by joseph6355 |
You will need to heat it to a red-orangeish color and then let it cool to black, and wait a few minutes then. Do it 3 times. |
What would be the purpose of this? Normally one only needs to heat to uniform heat plus 15-30minutes soak time.
| Quote: |
Temper it to 200-210 ºC for 1 hour, and then let it cool to room temperature. |
This will most likely produce a brittle product. While I haven't worked with 5xxx steel I do know a little bit about 4xxx, and it is seldom annealed
below 400°C.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
walruslover69
Hazard to Others
Posts: 216
Registered: 21-12-2017
Member Is Offline
Mood: No Mood
|
|
you could just stock up and buy plates. they are less than $100. You wont be able to make anything like that for $100. You never answered, how do you
plan on making the steel alloy plates in the first place?
|
|
|
unionised
International Hazard
Posts: 5102
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
I guess you make your own bullets, make your own powder + make your own guns too.
|
|
|
Twospoons
International Hazard
Posts: 1280
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
@joseph6355 Don't listen to the nay-sayers. Have a go.
Its right there are the top of the page: "The Art and Science of Amateur Experimentalism". I'd have thought everyone would be more supportive.
I build or make a lot of stuff I could just go out and buy - but where's the fun in that? What would I learn?
[Edited on 3-1-2018 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
OldNubbins
Hazard to Others
Posts: 136
Registered: 2-2-2017
Location: CA
Member Is Offline
Mood: Comfortably Numb
|
|
Support should not be conflated with encouragement. What I am seeing are people supporting the OP in a way that ultimately leads away from a misguided
effort to solve a problem that does not exist using methods that are likely to be flawed and inefficient, perhaps even ultimately dangerous.
I appreciate the ‘do-it-yourself’ mentality, not for a conspiratorial distrust of large organizations but for a sense of self-improvement and
satisfaction. However, in the context of this thread, how much chemistry and how much ‘make-it-yourself’ is actually involved? In my opinion, not
much.
In order to experiment and learn, you would need detailed knowledge of the chemical composition of the steel being used. This requires it to be
purchased from an organization that can provide material test reports that are generated in accordance with large, untrustworthy organizations such as
NIST, ANSI, ISO, etc. That aspect removes the majority of the DIY.
Where will you get your 5160 steel from? Can you guarantee the beat up old Chevy that spring steel was removed from is indeed 5160?
How will you control the heat treating process on something you are entrusting your life to? I used to work at a shop that made gear components for
limited-slip differentials. The gears required a combination of through-hardening for overall toughness with a case hardness at a critical depth (too
deep and the whole tooth was brittle, too shallow and it would deform). The heat treating process is difficult to control, and really more of an art
form with myriad variables. Our vendor was really quite good and yet we would still see over 50% failure rate. Torching your steel to whatever-ish
color, saturated with garage atmosphere and quenched in used motor oil with a pad of butter will give me a whatinistic crystal structure of the
correct grain size? Will the leaf springs off my Aston-Martin be austen-martensitic enough?
This topic may be better suited to a gun enthusiast or blacksmithing forum. However, if there are some methods for creating some interesting alloys
using thermite that don’t result in a large portion of the product violently erupting from an old paint can an a few slaggy chunks of iron, I am all
ears.
|
|
|
XeonTheMGPony
International Hazard
Posts: 1636
Registered: 5-1-2016
Member Is Offline
Mood: No Mood
|
|
I have, it really isn't that hard you know.
|
|
|
joseph6355
Hazard to Others
Posts: 144
Registered: 23-8-2017
Member Is Offline
Mood: Nitrated
|
|
OP here.
I see that you guys are not willing to even consider the idea.
I'll try it somewhere else.
I will not answer anymore questions, I don't think it's worth it since people here seem to be very close-minded.
Oh, hello! |
|
|
SWIM
National Hazard
Posts: 970
Registered: 3-9-2017
Member Is Offline
|
|
You weren't really answering questions in the first place.
Fulmen tried to discuss the metallurgy with you and ask about your annealing procedure but you wouldn't deign to answer.
Walruslover69 actually went full walrus and asked repeatedly for information you wouldn't supply about plate sources.
Your few answers were primarily aimed at justifying your survivalist aims, not explaining the project.
Hard to see what you were expecting.
Unquestioning and universal approval?
Besides, your post reads like you culled your information about armor from PMJB, or the Poor Man's Armorer, or other sources like that as opposed to
actually going to the effort to find legitimate, reliable information.
[Edited on 4-1-2018 by SWIM]
|
|
|
Fulmen
International Hazard
Posts: 1693
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
He's a quitter, good riddance.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
donalderrand8
Harmless
Posts: 3
Registered: 7-9-2017
Member Is Offline
Mood: No Mood
|
|
Tell me it was just for experiement! right?
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Please explain how something simple and inexpensive as taking many small bags and filling it with peddles (technical speak for small rocks), and
inserting it into a wired or otherwise constructed body frame, would not deflect or possibly stop most high speed projectiles? I would envision the
need for similar taylormade arm, neck and head protection.
Yes, granted, after testing with real bullets, you may need, worst case, a few new bags and more peddles, but that is to be expected. The
fragmentation of the rocks may also injury the person, or persons, shooting at you from close range, and any cloud of particles could obscure your
shooter's view along with surprising the hell out of them while the shooter tries to understand what the f**k just happened, but these are likely all
positives, not offered by other conventional body armor geared to possibly(?) stopping (and not deflecting) projectiles!
[Edited on 31-1-2018 by AJKOER]
|
|
|
Sulaiman
International Hazard
Posts: 3555
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Online
|
|
Technically;
peddles = sells
pebbles = small rounded rocks 
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
I bet Damascus steel makes great plate armor.
|
|
|
Fulmen
International Hazard
Posts: 1693
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
Ajoker: A bag of rocks will be better than nothing, but it won't be uniform in thickness/resistance. And what prevents the rocks from moving out of
the way of the projectile? Another important function of ballistic armor is to spread the impact out over a larger area, I don't see how your idea
would accomplish this. As for fragments, remember that this will occur a few inches below your face, so the risk of you being hurt by this would be
greater than the risk to the shooter.
JJay: Why? As far as I understand, damascus steel can mean two things. The first is blades made from Wootz steel, a legendary Indian steel that
contained certain beneficial alloying elements. The second is any patterned steel made by two or more distinct alloys. Neither has any properties that
would rival modern steel.
A good choice would be a low alloy steel, for instance a chromium/molybdenum/manganese steel with a low/medium carbon content. These can be heat
treated to fairly high strength while retaining excellent impact resistance.
The real challenge of any steel armor would be weight. I have a Lv4 composite ceramic insert lying around, it is appr. 260x300mm, 18mm thick. It
weighs 3.5kg (density appr. 2.5g/cm^3). It's rated for a 166grs 30-06 armor piercing round, which is pretty darn impressive. A steel plate of the same
weight would be less than 6mm thick, and I doubt there's a steel available that would stop even a regular .30 FMJ at that thickness.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
clearly_not_atara
International Hazard
Posts: 2691
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
The problem with a bag of rocks is that it's too heavy to move in. You could achieve better protection by simply, I don't know, standing inside of a
building. It does stop the bullet, because the bullet has to hit a specific pebble, and so about 50% of its kinetic energy will be transferred to this
pebble, likely traveling in an oblique direction towards other pebbles, while the bullet ricochets towards the other pebbles. But such a suit would
weigh 1m tall * 5 dm wide * 5 cm thick * 5 kg/L -> 125 kg! Good luck moving with 125 kg of rocks on your back, and those are generous numbers.
Anyway IIRC boron carbide is preferred for this application is it not? At least you don't have to worry about the "grade" as much with B4C. According
to this:
https://www.researchgate.net/profile/Robert_Ritchie/publicat...
the most damage-tolerant material is a palladium-based metallic glass with composition Pd79Ag3.5P6Si9.5Ge2. For more practical purposes, there's an
interesting alumina-PMMA composite which imitates seashells:
"Recently, synthetic, yet bioinspired, bulk ceramic materials havebeen made in the image of the nacre structure 25 . Using alumina ceramic powders
mixed with water and frozen using a freeze-casting (ice-templating) technique 25,26 , ceramic scaffolds can be processed with layer thicknesses (of
~1–100 μm) controlled by the rate of cooling, and interlayer roughnesses controlled in part by the addition of dopants (sugar, salt or alcohol).
After cold pressing and infiltrating with a polymeric lubricant phase (poly(methyl methacrylate), PMMA), ‘brick-and-mortar’ 85 vol.% alumina
ceramic–PMMA hybrid materials have been made in bulk form in the image of nacre (Fig. 5b). The resulting mechanical properties of these bioinspired
ceramics are nothing short of remarkable, with strengths comparable to pure alumina but fracture toughnesses an order of magnitude larger (Fig. 5c).
Indeed, toughness values can exceed 30 MPa m 1/2 (Fig. 5d) making these materials the highest toughness ceramics on record 25 ."
So maybe you can take your seashells down to the seashore and storm the beaches of Normandy, or something.
[Edited on 04-20-1969 by clearly_not_atara]
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
| Quote: Originally posted by Fulmen |
JJay: Why? As far as I understand, damascus steel can mean two things. The first is blades made from Wootz steel, a legendary Indian steel that
contained certain beneficial alloying elements. The second is any patterned steel made by two or more distinct alloys. Neither has any properties that
would rival modern steel.
|
Wootz steel is not really damascus. Damascus steel has very thin layers of different steel alloys laminated together, so it resists cracking and
shattering the same way that bulletproof glass does.
Damascus steel certainly does rival modern steel, especially if it the steels chosen for the laminate are modern alloys. Some people pay thousands of
dollars for a single Damascus chef's knife.
|
|
|
Fulmen
International Hazard
Posts: 1693
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
The prices modern pattern Damascus can fetch is mainly due to the look and the incredible craftmanship involved. As most patterns will end up crossing
the edge both alloys need to have similar mechanical properties to retain a useful cutting edge.
Laminated blades have been made for a long time (Japanese swords for instance), these did combine soft and hard steel for several reasons. One was
cost, a good edge-holding carbon steel has historically been expensive. But shatter resistance was also important, the old carbon steels were quite
brittle compared to modern steels.
The historical Damascus blades were not forged from different alloys, they did have dark lines/bands but afaik these were formed by precipitated
carbides.
I guess part of the disagreement is around the term Damascus. In a more broad sense you could be right, a metal composite could have interesting
properties. But at the same time there are probably simpler ways to achieve such properties. One would be case hardening, this produces a hard outer
skin while keeping the core ductile.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
| Pages:
1
2 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
