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EN 10025-2 S355K2 High-strength Low-alloy (HSLA) Steel Plate

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EN10025-2 S355K2 is a high-strength non-alloy structural steel plate under the European standard. It features high strength, excellent low-temperature toughness, and good processability, making it commonly used in load-bearing structures such as construction and machinery manufacturing.

Standard :
EN 10025-2
Grade :
S355K2
Thickness :
0.8-30.0 mm
Width :
800-2500 mm
Length :
3000-12000 mm

Special thickness, width, and length can be negotiated separately.
We also provide customized processing services.If you have any questions, please contact us.

Overview

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.

Chemical Composition

Grade	S335K2
Element	C		Si	Mn	P	S	N	Cu
Content (max, %)	thickness ≤ 40 mm	thickness ＞40 mm
	0.20	0.22	0.55	1.60	0.025	0.025	0.012	0.55

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

Grade	Thickness (t) [mm]	CEV [max, %]
S355K2	t ≤ 40	0.43
	40 < t ≤ 63	0.45
	63 < t ≤ 80	0.46
	80 < t ≤ 100	0.48
	100 < t ≤ 150	0.48

* 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

Mechanical Properties

Grade	Thickness (t) [mm]	Yield Strength (ReH) [min, MPa]	Tensile Strength (Rm) [MPa]	Elongation (A) [min, %]	Impact Energy (KV) [min]
S355K2	t ≤ 16	355	470 - 630	22	40J (at -20°C)
	16 < t ≤ 40	345	470 - 630	21	40J (at -20°C)
	40 < t ≤ 63	335	470 - 630	20	40J (at -20°C)
	63 < t ≤ 80	325	470 - 630	18	40J (at -20°C)
	80 < t ≤ 100	315	470 - 630	17	40J (at -20°C)

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

Applications

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).

Other Information

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:

Grade	Impact Test Temp.	Key Difference
S355JR	+20°C	Lower strength, suitable for light structures with smaller loads.
S355J0	0°C	Good toughness at room temperature, suitable for structures in non-low temperature regions.
S355J2	-20°C	Better low-temperature toughness, suitable for structures in cold regions.
S355K2	-20°C	Higher guaranteed impact energy (≥40J at -20°C)

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.

FAQ

Q1:

What are the weldability characteristics of high-strength low-alloy steel plates?

High-strength low-alloy steel plates offer excellent weldability. As their carbon content is typically low (below 0.2%), they present a lower risk of cracking during welding compared to standard high-strength steel plates and generally do not require complex preheating treatments.

Q2:

Why are high-strength low-alloy steels the preferred choice in construction and automotive manufacturing?

The key advantage of high-strength low-alloy steels is weight reduction. As they offer greater strength, thinner sheets can be used to withstand the same loads, thereby reducing the overall weight of the structure; in the automotive sector, this leads to improved fuel efficiency.

Q3:

What is high-strength low-alloy steel (HSLA)?

High-strength low-alloy steel (HSLA) is a type of steel in which small amounts of alloying elements (such as niobium, vanadium, titanium or copper) are added to enhance its mechanical properties. Compared to traditional carbon steel, it offers higher yield strength and better corrosion resistance whilst maintaining good weldability and formability.