What is the difference between S355J2 and S355J2+N?

S355J2 and S355J2+N are both variants of the same steel grade, S355J2, which is a non-alloy structural steel according to the EN 10025-2 standard. However, there is a significant difference between S355J2 and S355J2+N:

S355J2:

S355J2 is a normalized steel grade, meaning it has undergone a controlled heat treatment process called normalizing. Normalizing involves heating the steel to a specific temperature and then cooling it in air to obtain a desired microstructure and mechanical properties.

S355J2 has specified impact energy values for different temperatures and thicknesses, making it suitable for various applications in construction, engineering, and manufacturing industries.

The "J2" designation indicates that it has good impact toughness at -20 degrees Celsius.

S355J2+N:

S355J2+N is essentially the same as S355J2 but with the addition of "+N," which stands for "normalized rolled." It means that this variant has been further processed through controlled rolling or thermo-mechanical treatment after normalizing.

Thermo-mechanical treatment involves subjecting the steel to precise temperature and rolling processes to achieve improved structural and mechanical properties.

S355J2+N is generally delivered in a normalized or normalized rolled condition, providing enhanced strength and toughness compared to untreated S355J2.

The "+N" designation indicates that the steel is supplied in a normalized condition.

In summary, while both S355J2 and S355J2+N are based on the same steel grade, S355J2+N undergoes additional processing steps such as controlled rolling or thermo-mechanical treatment after normalizing. This results in improved properties, particularly in terms of strength and toughness. S355J2+N is often preferred for applications requiring higher performance and enhanced structural integrity. It is important to consult specific project requirements and design codes to determine the appropriate steel grade for a given application.