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UFi911 (Military)
24 Jan 11 16:10
Does anyone have any information regarding forming 1/2" and under armor plate?

We are a fabrication shop with lots of experience forming more traditional materials, but armor is new to us.  We have successfully laser cut armor, but not formed it.

I'm interested in methods, practices, and technical data (minimum bend radii, tons per foot required, etc).

The specific materials we are interested in are MIL-A-12560H(MR) and MIL-A-46100D(MR)

Thank you for any help you can provide.

-John
 
KENAT (Mechanical)
24 Jan 11 16:29
This isn't the busiest forum on the site, if you don't get the answer you need, you may want to repost somewhere like forum330: Metal and Metallurgy engineering or elsewhere.  

If you do, may be a good idea to red flag this one for deletion.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

MiketheEngineer (Structural)
24 Jan 11 18:25
Its armor - good luck!!
Wrenchbender (Mechanical)
28 Jan 11 12:47
Should behave like any other steel in that regard.  Same elastic modulus; put enough force on it and it goes plastic.  Yield strengths are in moderate ranges as given by hardness in the specs you mentioned.  One is for Hi-hard, other for RHA; neither is face hardened.  While bending, forming, welding are possible, machining is usually difficult due to the austenitic nature.  The specs also include chem composition and minimum bend radii.  Also google search 'forming armor plate', contact the steel maker, or maybe an MRAP vehicle contractor.    
UFi911 (Military)
31 Jan 11 10:37
Thanks for the info BestWrench.  Your info seems to align with the other information I've been able to gather as well.  

Looks like we are going to have to get some of it and just give it a try.

Thanks,

-John
 
boo1 (Mechanical)
31 Jan 11 12:05
MIL-A-12560H[MR) see attached
3.2.4.3 Forming. Forming after the final quenching and tempering
operations shall not be done except when authorized by the procuring activity.

MIL–A-46100 steel plate is a military spec armor steel exhibits high-hardness (HH).  Surface hardness of this material is between 477 and 534 brinell.  While the material can be formed, it is important to note that due to its ductile limitations, it should not be bent improperly. What we had on forming MIL–A-46100 was from ATI:

COLD FORMING
Cold forming can be performed with the proper techniques and suitable equipment in a highly controlled environment. Given the
high strength nature and material properties of ATI 500-MIL plate, set up should be thoroughly evaluated before cold forming.
Although cold forming is not recommended, it is possible. ATI 500-MIL plate up to 0.375" gauge has been successfully cold formed.
The following precautions should be taken when cold forming this material:
1. Grind edges, grind outside surface which will be in tension and grind to create round corners.
2. Use lubricant.
3. Nearly five times as much power is required compared with mild steel.
4. Forming across grain direction is preferred but not mandatory.
5. Allow for greater "spring-back" due to higher yield strength.

HOT FORMING
Hot forming is recommended with the following guidelines:
1. Plate should be heated to the 1550ºF to 1650ºF (843ºC to 899ºC) temperature range prior to forming.
2. To maintain ballistic quality, toughness, and metallurgical integrity, the temperature of the plate should
not exceed 1650ºF (899ºC.)
3. Grind edges and create round corners.
4. After forming allow steel to cool uniformly with unrestricted air flow (still air recommended) to the top and bottom of
plate until plate temperature is <300º F (149ºC.) Do not cool using water quenching or forced air cooling methods.
Steel will re-harden to approximately 500 BHN.

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