EN 10025-2 S355K2 is a high-strength low-alloy structural steel plate with exceptionally balanced overall performance. While ensuring high strength (355 MPa yield strength), it also combines good low-temperature toughness (-20°C impact resistance) and excellent weldability, making it one of the indispensable "workhorse" steels in fields such as heavy industry, construction, and bridge engineering. When selecting this steel, its suitability must ultimately be determined based on the structural design requirements, the service environment (particularly the minimum temperature), and the welding process.

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.

Carbon Equivalent of S355K2 High-strength Low-alloy Steel Plate

* The carbon equivalent value varies depending on the thickness.For detailed information, please contact us for inquiries.

* Carbon equivalent (CEV) is calculated using the International Institute of Welding (IIW) formula:

CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

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. Building Structures: Load-bearing structures for high-rise buildings, industrial plants, and sports venues.

2. Bridge Construction: Main beams and components of bridges.

3. Heavy Machinery: Frames for cranes, mining equipment, and engineering machinery.

4. Shipbuilding and Marine Engineering: Hull structures and offshore platform modules.

5. Others: Pressure vessels and storage tanks (when compliant with relevant standards).

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.