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Both in Russia and abroad homogeneous low-alloy
armor steels are mostly used for combat equipment protection.
1. Steels
for Heavy Combat Vehicles (Tank Armor)
Such steels shall not crack under impact of
large-caliber shells (survivability requirement); they also
shall meet the welding requirements (no tempering of welds
is allowed).
For the most part Cr-Ni-Mo alloy steels are
used with the upper allowable limit of carbon content (no
more than 0.30% for thicknesses up to 100mm).
Such steels are supplied after hardening and
high-temperature tempering to 280…388 ÍÂ. The main specifications
and acceptance requirements abroad are stated in MIL-A-12560
“Armor plate, steel, wrought, homogeneous. For use in combat-vehicles
and for ammunition testing”.
The hardness requirements depend on the plate
thickness, namely:
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for 6.2…12.6mm: ÍÂ 341…388
for 12.7…19.0mm: ÍÂ 331…375
for 19.1…31.7mm: ÍÂ 321…375
for 31.8…50.5mm: ÍÂ 293…331
for 50.5…101.3mm: ÍÂ 269…311
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The typical armor steels of this grade are MARS
190 (France), ARMOX 370S (Sweden).
ARMOX 300S and ARMOX 400S also belong to the above strength
class, but because of lower carbon content the required strength
(hardness) is achieved by hardening and low-temperature tempering.
Domestic steels usually feature higher carbon content which
imposes heavier requirements on the choice of welding materials
and armored structure welding methods.
Acceptance Requirements
According to MIL-A-12560 armor plates shall be checked for
their hardness, Charpy impact energy at -40°Ñ and ballistic
resistance (V50).
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Plate thickness range, mm
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Ammunition caliber and type
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Impact angle, deg.
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6.3 … 14.3
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7.62mm ÀÐ, Ì2
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0
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14.4 …28.6
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12.7mm ÀÐ, Ì2
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0
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28.7 … 69.8
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20mm ÀÐ-Ò, Ì602
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0
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70.0 … 100
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57mm ÀÐ, Ì70
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0
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90mm ÀÐÑ, Ì82
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45
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In Russia the acceptance requirements are different.
In the ballistic resistance tests by small arms instead of
V50 the non-perforation angle is defined; 20mm
ammunition is not used; 100mm ammunition is used instead of
90mm ammunition etc. Besides, instead of impact energy the
specimen fracture mode is checked.
These differences are only conditional and there
is no problem to agree on the acceptance requirements acceptable
for both parties.
Typical foreign steels belonging to this class
are given below in Tables 1 and 2. The strength of domestic
hardened and tempered cannonproof armor steels is about 1000…1400
MPa.
2. Armor Steels for Light Armored Vehicles
(APC, IFV)
Such steels shall resist without cracking hits
of large-caliber small arms bullets (survivability requirement)
and meet the welding requirements (in case of welds tempering).
For such applications steels with the upper
allowable limit of carbon content (no more than 0.32%) are
used.
Such steels are supplied after hardening and
low-temperature tempering to 477…534 ÍÂ. The main specifications
and acceptance requirements abroad are regulated by MIL-A-46100
“Armor plate, steel, wrought, high-hardness”.
The most typical armor steels of this grade
are MARS 240 (France), ARMOX 500S (Sweden).
Domestic steels of this grade are Grade 2P and
Grade 7. Besides, steel Grade “7” does not require welds tempering.
According to MIL-A-46100 armor plates shall
be checked for their hardness, Charpy impact energy at -40°Ñ
and ballistic resistance to 7.62mm, 12.7mm and 14.5mm AP bullets.
The differences in foreign and Russian acceptance tests have
been mentioned before.
Typical Russian and foreign steels of this grade
are given in Tables 1, 2 and 3.
3. Steels of Wide Application Range
Such steels shall not crack under impact of
20mm ammunition.
Such steels are supplied after hardening and
low-temperature tempering to 534…601 ÍÂ (for 4.7…25.4mm thicknesses)
and 477…534 ÍÂ (for 25.5…76.2mm thicknesses). The armor of
Class 2 is supplied with 302…352 ÍÂ.
The main specifications and acceptance requirements
abroad are regulated by MIL-A-46173 “Armor steel, plate, wrought,
(ESR). (3/16 through 3 inches, inclusive)”.
The most typical armor steels of this grade
are MARS 270 (France), ARMOX 560S (Sweden).
The most typical armor steels of this grade
are Grade 77 and Grade 88. Steel Grade 77 does not require
welds tempering.
According to MIL-A-46173 armor plates shall
be checked for their hardness, Charpy impact energy at -40°Ñ
and ballistic resistance to 7.62mm, 12.7mm and 14.5mm AP bullets,
as well as to 20mm ammunition (only for 25-50mm thick plates).
The differences in foreign and Russian acceptance tests have
been mentioned before.
Table 1. Main French Armor Steel Grades
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Steel Grade
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Nominal Chemical Composition
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Thickness, mm
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Carbon, % by weight
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σÂ, MPa average
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Hardness, HB
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Production method features
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Standard
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MARS 190
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0.30C-1.10Cr-2.0Ni-0.45Mo
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2 - 50
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≤ 0.30
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1100
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≤ 388
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out-of-furnace treatment
S ≤ 0.005%
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MIL 12560
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51 - 500
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≤ 0.33
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900
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MARS 240
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0.285C-1.50Cr-1.50Ni-0.30Mo
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≤ 38
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≤ 0.32
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1700
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477 - 534
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same S ≤ 0.004%
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MIL 46100
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38 - 50
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1650
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450 - 534
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MARS 270
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0.35C-0.75Cr-3.10Ni-0.40Mo
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< 25
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≤ 0.37
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2000
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534 - 601
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same S ≤ 0.002%
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MIL 46173
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25 - 75
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1700
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477 - 534
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MARS 300
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0.50C-0.80Si-4.0Ni-0.40Mo
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≤ 8
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≤ 0.54
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2180
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578 - 655
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Table 2. Main Swedish Armor Steel Grades
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Steel Grade
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Nominal Chemical Composition
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Thickness, mm
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Carbon, % by weight
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σÂ, Mpa average
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Hardness, HB
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Production method features
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Standard
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ARMOX 300 S
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0.18Ñ-1.5Mn-0.4Cr-0.65Mo-0.003B
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5 - 60
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≤ 0.20
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900
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280 - 340
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Out-of-furnace treatment
S ≤ 0.010%
Thermo-mechanical treatment
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MIL 12560
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ARMOX 400 S
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1150
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360 - 420
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ARMOX 370 S
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0.28-1Mn-0.8Cr-1.1Ni-0.65Mo-0.002B
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5 – 12.9
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≤ 0.30
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1300
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390 - 440
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MIL 46100
MIL 12560
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13 – 22
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350 – 400
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22.1 – 34.9
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330 – 380
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35 – 59.9
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300 – 350
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60 - 80
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265 - 315
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ARMOX 500 S
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Òî æå
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6 – 13
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≤ 0.30
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1600
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480 - 540
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MIL 46100
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13.1 - 50
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450 - 520
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ARMOX 560 S
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0.35-1Mn-1.2Cr-3Ni-0.65Mo-0.002B
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6 – 20
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≤ 0.38
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1850
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534 - 601
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MIL 46173
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ARMOX 600 S
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0.45-0.8Mn-0.8Cr-2.5Ni-0.65Mo-.002B
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4 – 10
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≤ 0.50
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2150
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570 - 640
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Table 3. Armor Steels with Low-Temperature-Tempered
Martensite Structure (Russia)
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Steel Grade
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Alloy System
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Thickness, mm
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Carbon, % by weight
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σÂ, MPa average
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Hardness, HB
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Production method features
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Similar standard
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«2P»
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Si-Mn-Mo
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4 – 7
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≤ 0.29
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1550
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444 – 514
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Out-of-furnace treatment S ≤ 0.010%
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(MIL 46100)
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8 – 14
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1450
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388 – 495
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15 – 22
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1400
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363 – 495
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«7»
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Si-Cr-Ni-Mo
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4
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≤ 0.24
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1550
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444 - 514
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Same
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Same
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5 – 6
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1500
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429 – 514
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8 – 13
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1450
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388 – 495
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15 – 22
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1400
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375 – 495
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«77»
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8 - 20
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≤ 0.37
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1900
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477 - 532
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electroslag remelting
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(MIL 46173)
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«88»
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8 - 20
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≤ 0.42
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2000
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495 - 540
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electroslag remelting
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(MIL 46173)
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«44»
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Cr-Ni-Mo-V
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2 - 15
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≤ 0.47
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2100
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511 - 555
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Electric arc remelting, electroslag remelting
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