Steels produced to EN standards – for example pressure vessel steels such as P355 or structural steels S275 have names that tell you a lot about the steel without having to look the details up in the relevant standard. The way that they are named in set out in EN 10027 and by following a few simple rules you should soon be a master of know steel properties from the grade alone
This page tells you about how to decipher these steel names for some common grade of pressure vessel and structural steels that we have in stock. Once you know how it works it is easy to use.
Structural and pressure vessel steels have a standardised naming convention and this is laid out in EN 10027 Designation System for Steels.
Whilst both are similar they are each subtly different and it is important to know what all the components of a steel name mean
EN Structural Steel Names to EN 10027
The first letter S standards for Structural. P stands for Pressure and this is the way you initially tell the grades apart.
The next set of 3 digits gives the steel’s minimum yield strength. So S355 has a minimum yield strength of 355 MPa for the smallest thickness range covered by the relevant standard – i.e. EN10025.
These are the basics. You can then have up to 3 groups of characters providing more information.
The first group concerns the impact testing of the steel – what joule value (J, K or L) and at what temperature. (R,0,2,3,4,5,6)
- J = 27J
- K = 40J
- L = 60J
- R = 20 °C (Room Temperature)
- 0 = 0 °C
- 2 = -20 °C
- 3 = -30 °C
- 4 = -40 °C
- 5 = -50 °C
- 6 = -60 °C
An easy way of remembering the temperatures is that each increase in the digit means another 10 degrees below zero.
So S355K2 Steel is a structural steel with 355 MPa yield strength with an impact test of 40J at -20 °C
Then you can get a number of additional symbols
- M – Thermomechanically rolled or produced by TMCP S355 M
- N – Normalised or normalised rolled S355 J2+N
- Q – Quenched – S690Q
- G – other characteristics – Usually used for offshore steels and followed by upto 2 digits – i.e. S355 G10
- L – Low Temperature – S355 NL
- W – Weather resistant – S355J0W
- +Z35 – through thickness property; minimum reduction of area = 35 %
- +AR – as rolled
EN Pressure Vessel Steel Names to EN 10027
The first letter P standards for Pressure. S stands for Structural and this is the way you initially tell the grades apart.
The next set of 3 digits gives the steel’s minimum yield strength. So P355 has a minimum yield strength of 355 MPa for the smallest thickness range covered by the relevant standard – i.e. EN10028
For pressure vessel steels you get fewer letters than for structural steels. These include:
- M – Thermomechanically rolled
- N – Normalised or normalised rolled – P355NL1
- Q – Quenched and tempered
- G – Other characteristics – P355GH
- H – High temperature – P355NH
- L – Low Temperature – P355NL2
- R – Room temperature
So P355 NL2 is a Pressure vessel steel with a 355MPa minimum yield which is normalised and is for low temperature use. The 2 indicates that it is the second category of low temperature use.
You can buy EN 10027 from the BSI website