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GENERAL
DESCRIPTION
RB plates are available as Quenched and Tempered plates. The steel
is produced to provide an optimal combination of hardness, toughness and
weldability. This is a fully killed fine grain steel that is also
calcium treated and vacuum degassed to achieve low sulphur levels and a
very low inclusion content. These processes insure adequate
toughness in addition to the high hardness.
The plates are heat treated
in a roller quenching plant that subjects the entire plate to a rapid high
volume water quench. The high cooling rate ensures maximum exploitation of
the alloying elements to give the required properties throughout the plate
thickness. The 3.5mm and 4.5mm RB 390 plates are heated and then
quenched in a water cooled press. These plates are not subsequently
tempered.
CHEMICAL
COMPOSITION
The composition of armour plate is determined by the requirements for
ballistic protection and is not fixed as such.
However, the following
maximum aim as well as typical percentage for specific elements shall
apply:
Chemical Composition (%
ladle analysis) of RB 390
|
Element
|
Typical
|
Maximum
|
Element
|
Typical
|
Maximum
|
|
C
|
0.30
|
0.33
|
AD
|
0.040
|
0.080
|
|
Mn
|
0.60
|
0.70
|
V
|
0.09
|
0.11
|
|
P
|
0.010
|
0.015
|
Nb
|
0.003
|
0.01
|
|
S
|
0.003
|
0.007
|
Ti
|
0.020
|
0.03
|
|
Si
|
0.35
|
0.50
|
B
|
0.002
|
0.004
|
|
Cu
|
0.04
|
0.080
|
Zr
|
0.003
|
0.015
|
|
Ni
|
1.45
|
1.60
|
N
|
0.006
|
0.012
|
|
Cr
|
1.55
|
1.70
|
H
|
0.0003
|
0.0005
|
|
Mo
|
0.55
|
0.65
|
Sn
|
0.008
|
0.015
|
Note:
RB390 plates with thickness 3.5mm to 60.0mm are produced to meet specific
ballistic and hardness requirements only.
HARDNESS
|
NOMINAL
THICKNESS (mm)
|
BRINELL
HARDNESS RANGE (3000 Kg)
|
|
3.5
|
460 - 532
|
|
4.5
|
444 - 532
|
|
6.0 to 8.0
|
402 - 495
|
|
10.0 to 15.0
|
364 - 418
|
|
16.0 to 35.0
|
304 - 387
|
|
36.0 to 60.0
|
321 - 375
|
HOT
WORKING
Local or general heating should not be performed after the final
quenching and/or tempering heat treatment, as it will have a detrimental
effect on the mechanical properties.
PREHEATING
AND WELDING
The objective of preheating is to minimise the adverse effect of welding
and flame cutting on the microstructure of the heat affected zone (HAZ) by
reducing the cooling rate in the HAZ. Rapid cooling after welding
and flame cutting results in a hard and brittle martensitic
microstructure, which is susceptible to hydrogen cracking.
RB material is a weldable steel.
MACHINABILITY
Machining can be performed using high speed tool steel and reducing
cutting speed to about 50% of speeds used for normal carbon steels.
BENDING
No bending specification for armour plate is available and it is not
recommended. If, however, any form of bending is done, it is
advisable to do all bending transverse to the rolling direction.
LENGTH
AND WIDTH TOLERANCES:
|
Thickness range
(mm)
|
Width tolerance
(mm)
|
Length tolerance
(mm)
|
Side condition
(mm)
|
|
3.5 to 4.5
|
-0.0
|
+ 50.0
|
-0.0
|
+ 50.0
|
Untrimmed
|
|
6.0 to 60.0
|
-0.0
|
+ 50.0
|
-0.0
|
+ 20.0
|
Trimmed
|
|
6.0 to 60.0
|
-0.0
|
+ 50.0
|
-0.0
|
+ 20.0
|
Untrimmed
|
Note:
- RB390, 6.0 to 15.0mm plates, sides trimmed on
application only
- RB390, 18.0 to 60mm plates, sides untrimmed on
application only
THICKNESS TOLERANCE
|
Nominal thickness
range
(mm)
|
Tolerances
|
|
Minimum
|
Maximum
|
|
3.5 + 4.5
|
- 0.0
|
+ 0.5
|
|
6.0
|
- 0.0
|
+ 1.2
|
|
8.0 - 12.0
|
- 0.1
|
+ 0.8
|
|
15.0
|
- 0.2
|
+ 1.3
|
|
20.0 - 25.0
|
- 0.5
|
+ 1.3
|
|
30.0 - 35.0
|
- 1.0
|
+ 1.5
|
|
40.0
|
- 1.0
|
+ 2.0
|
|
50.0 - 60.0
|
- 1.5
|
+ 2.5
|
SURFACE
DEFECTS
|
Nominal
thickness (mm)
|
Maximum
depth of rolled in scale (mm)
|
|
< 15
|
0.4
|
|
> 15 to 30
|
0.8
|
|
> 30 to 60
|
1.5
|
WAVINESS
TOLERANCE
|
Thickness
(mm)
|
Number
of waves in one metre
|
Tolerance
1) (mm)
|
|
RB 390 3.5 - 5.0
|
1
2
3
|
6
5
3
|
|
RB 390 > 6.0
|
1
2
3
|
3
2
1
|
1)
Maximum deviation from a flat surface in any 1 000mm length.
DEVIATION
FROM FLATNESS (width, < 1500mm)
|
Nominal
thickness (mm)
|
Deviation
from flat surface per metre (mm/m)
|
|
3.5 to 4.5
|
6
|
|
6.0 to 60
|
3
|
Note:
- If a maximum plate width of 1520mm is exceeded, the
above table does not apply.
DEVIATION
FROM FLATNESS (width > 1500mm)
|
Thickness range
(mm)
|
Deviation from flat
surface for specified widths in millimetres per metre (mm/m)
|
|
1501 to 1830
|
1831 to 2130
|
2131 to 2400
|
|
6.0 to 10.0
|
6
|
-
|
-
|
|
12.0 to 15.0
|
6
|
12
|
12
|
|
20.0 to 60.0
|
6
|
9
|
12
|
APPLICATIONS
-
Combat vehicles
-
Security vehicles
-
Bullet-proof jacket
-
Security doors and
rooms
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