Surface Hardening or Case-Hardening
Steel
Steels for carburizing and case hardening typically have a relatively low carbon level,
0.10-0.25% C, and are used when there is a demand for varying properties, such as for
components in transmissions.
Case hardening entails the treatment of a finished component in a carburizing atmosphere at a high
temperature, typically 850–950°C, which increases the carbon content at the surface of the component. The
carburized layer is typically 0,5–1,0 mm deep but can be deeper. Following carburization, the part is quenched
and thereby hardened. During quenching the carburized layer is transformed to martensite with hardness
determined by the carbon content. The result is thus a component with a hard surface and a comparably soft
core. Typical components made out of carburizing steel, are gears in transmissions.
EN- Ovak
Typical analysis
standard o
O
S M C M N
C th
i n r o i
er
0
0 1 1
234, .
16MnCr5 . . .
4306 1
2 2 0
6
20MnCr5 236, 0 0 1 1
.
. . .
4326 2
2 3 2
0
0
0 0 1 0
18CrMo8 .
-5* 225 . . . .
1
3 8 8 5
8
0
0 0 0 0
.
20MoCr4 124 . . . .
2
2 8 5 4
0
0
0 0 0 0 0
20NiCrM 152, .
o2-2 . . . . .
4548 2
3 9 6 2 5
0
0
0 1 1 0
146, .
16NiCrS4 . . . .
4730 1
1 0 1 8
6
0
0 0 0 0 1
20NiCrM .
157 . . . . .
o7 2
2 6 5 2 7
0
0
0 0 1 0 1
18CrNiM 159, .
o7-6 . . . . .
4761 1
2 7 7 3 6
8
0
0 0 1 0 3
12NiCr14 .
-6* 245 . . . . .
1
3 5 5 1 3
3
0
0 0 1 0 3
18NiCrM .
255 . . . . .
o14-6 1
3 5 4 2 3
8
0
0 0 1 0 2
22NiCrM .
253 . . . . .
o12-5* 1
2 6 2 2 9
4
0
0 0 1 0 3
24NiCrM .
256 . . . . .
o15-5* 2
3 7 2 3 6
4
0
0 0 0 0 2
20NiMo9 .
158 . . . . .
-7* 2
1 3 4 7 3
0
0
0 0 1 1
30MoCr .
499 . . . . V
V20-7* 3
2 3 7 8
0
0
16CrMn 0 1 2 0 0
.
NiMo9-5- 277 . . . . . V
1
2* 2 3 1 5 5
6
EN-standard designation followed by “*” is not an official EN standard grade but named according to the rules
in EN 10027.
