EN 10025-2 S355K2 is a European standard for hot-rolled structural steels. 

Standard and Grade Designation

EN 10025-2: Specifies the technical delivery conditions for hot-rolled structural steels (non-alloy and fine-grain steels).

S355JR:

S = Structural steel

355 = Minimum yield strength of 355 MPa (at thickness ≤16mm)

K2 = Indicates impact toughness at -40°C (Charpy V-notch test)

Delivery Condition: To achieve the required toughness properties (the "K2" designation), the steel is typically delivered in a normalized rolled condition.

Key Advantages of S355K2:

Good weldability (low carbon equivalent).

High toughness at low temperatures (suitable for cold environments).

Cost-effective compared to alloy steels.

Note: The actual yield strength value decreases as the material thickness increases.

Used in heavy-duty structural components requiring good weldability and toughness in cold climates, such as:

1.Bridges, buildings, cranes.

2.Offshore structures, pressure vessels.

3.Machinery and transport equipment.

Process Performance

Weldability: Excellent, can be welded without preheating (or with only slight preheating). Compatible with common processes such as manual arc welding (MMA), gas shielded welding (MIG/MAG), and submerged arc welding (SAW). The toughness of the welded joint can match that of the base material after welding.

Formability: Capable of undergoing cold bending, stamping, shearing, and other processing. The cold bending test requirement (mandrel diameter = 3 × steel thickness, bending angle 180°) is met without cracking.

Delivery Condition: To achieve the required toughness properties (the "K2" designation), the steel is typically delivered in a normalized rolled condition.

Precautions for Procurement and Use

Certification Requirements: When procuring, require the steel mill to provide a "Type 3.1B Certificate" compliant with EN10204 standards, clearly stating chemical composition, mechanical properties, and impact test results (including data at -40°C). Avoid "non-standard S355" (e.g., materials that only meet yield strength requirements but fail to meet low-temperature toughness standards).

Thickness Considerations: For S355K2 with thickness >63mm, pay attention to "Z-direction properties" (resistance to lamellar tearing). If used in welded structures (e.g., thick plate splicing), additional requirements for "Z15/Z25/Z35" grades must be specified, indicated after the grade designation (e.g., S355K2-Z25).

Low-Temperature Environments: If the service environment temperature is below -40°C, upgrade to S355M/S355ML (impact test temperature -50°C) to avoid the risk of low-temperature brittle fracture.

Comparable Standards

ASTM: Similar to A572 Gr. 50 (but with different impact requirements).

Comparison with Other S355 Grades:

Summary

EN10025-2 S355K2 is a non-alloy, hot-rolled structural steel with a minimum yield strength of 355 MPa, guaranteed to have good impact toughness at temperatures as low as -20°C. It is supplied in a normalized rolled condition to achieve these properties and is a preferred choice for critical structures in cold climates.