Quality	Material-No.	Standard
S275N	1.0490	DIN EN 10025-3	Details
S275NL	1.0491	DIN EN 10025-3	Details
S275M	1.8818	DIN EN 10025-4	Details
S275ML	1.8819	DIN EN 10025-4	Details
S355N	1.0545	DIN EN 10025-3	Details
S355NL	1.0546	DIN EN 10025-3	Details
S355M	1.8823	DIN EN 10025-4	Details
S355ML	1.8834	DIN EN 10025-4	Details
S420N	1.8902	DIN EN 10025-3	Details
S420NL	1.8912	DIN EN 10025-3	Details
S420M	1.8825	DIN EN 10025-4	Details
S420ML	1.8836	DIN EN 10025-4	Details
S460N	1.8901	DIN EN 10025-3	Details
S460NL	1.8903	DIN EN 10025-3	Details
S460M	1.8827	DIN EN 10025-4	Details
S460ML	1.8838	DIN EN 10025-4	Details

Fine-grain structural steels belong to the advanced types of construction steels specifically developed for demanding applications in construction and mechanical engineering. These steels are characterized by their fine microstructure and good weldability, making them particularly attractive for constructions that require high strength, formability, and toughness. Depending on the manufacturing process and standards, the properties and application areas of these steel grades differ significantly. Below, the characteristics of fine-grain structural steels according to DIN EN 10025-3 and DIN EN 10025-4 are presented.

Normal-annealed or normalized rolled fine-grain structural steels are specified according to DIN EN 10025-3 and undergo a normalizing process during production. This process involves controlled annealing, where the steel microstructure is homogenized and stresses are relieved to achieve optimal mechanical properties. Normalization improves toughness and ensures a uniform structure, making the steel particularly resilient and workable.

Normalized rolled fine-grain structural steels are particularly suitable for welding work, as their chemical composition and the normalizing process reduce the risk of cracking. This makes them ideal for demanding construction projects, such as bridges, high-rise buildings, and large structures that must withstand heavy loads. The steel grades in this category, such as S275N or S355N, provide a high level of safety and reliability in structural applications due to their strength and toughness.

Thermomechanically rolled fine-grain structural steels according to DIN EN 10025-4 are produced using a special process that combines mechanical rolling with controlled cooling. This thermomechanical treatment creates an exceptionally fine-grained and homogeneous microstructure, which gives the steel high strength and toughness. In addition, the mechanical properties remain stable even at low temperatures, making thermomechanically rolled steels ideal for use in cold environments.

One of the key advantages of thermomechanically rolled fine-grain structural steels is the reduced carbon equivalence, which improves weldability and minimizes the risk of hardening cracks. As a result, these steels can be welded with minimal preheating effort, which reduces both processing time and costs. Typical steel grades such as S420M and S460M are found in this category and are frequently used in projects that require high strength and toughness while maintaining good weldability, such as offshore platforms, power plants, and heavy steel construction.

Both groups of fine-grain structural steels – both the normalized and the thermomechanically rolled steels – feature excellent mechanical properties, but they are optimized for different applications. While normalized rolled steels are particularly suitable for complex construction due to their uniform structure and weldability, thermomechanically rolled steels offer advantages for applications in extreme environments due to their high strength and toughness.