UNI ISO 898-1:2009
STEELS

Property
class

Material and heat treatment Chemical composition limits
(cast analysis %)
Tempering

temperature
C P S B
  min max max max max C min
4.6 Carbon steel
or carbon steel
with additives
- 0.55 0.050 0.060 Not
Specified
-
4.8 - 0.55 0.050 0.060
5.6 0.13 0.55 0.050 0.060
5.8 - 0.55 0.050 0.060
6.8 0.15 0.55 0.050 0.060
8.8 Carbon steel with additives
(e.g. Boron or Mn or Cr)
quenched and tempered
0.15 0.40 0.025 0.025 0.003 425
Or  
Carbon steel quenched
and tempered
0.25 0.55 0.025 0.025
Or
Alloy steel quenched and tempered 0.20 0.55 0.025 0.025
9.8 Carbon steel with additives
(e.g. Boron or Mn or Cr)
quenched and tempered
0.15 0.40 0.025 0.025 0.003 425
Or  
Carbon steel quenched
and tempered
0.25 0.55 0.025 0025
Or  
Alloy steel quenched and tempered 0.20 0.55 0.025 0.025
10.9 Carbon steel with additives
(e.g. Boron or Mn or Cr)
quenched and tempered
0.20 0.55 0.025 0.025 0.003 425
Or        
Carbon steel quenched
and tempered
0.25 0.55 0.025 0.025
Or        
Alloy steel quenched and tempered 0.20 0.55 0.025 0.025
12.9 Alloy steel quenched and tempered 0.30 0.50 0.025 0.25 0.003 425
12.9 Carbon steel with additives
(e.g. Boron or Mn or Cr)
quenched and tempered
0.28 0.50 0.025 0.025 0.003 380