S355K2 Carbon Steel Plate — Factory Direct Supplier | Huaxia-Steel

Huaxia-Steel supplies S355K2 structural steel plate rolled to EN 10025-2, the European standard for non-alloy structural steels. S355K2 is the higher-toughness member of the S355 family: it guarantees a 355 MPa minimum yield together with a 40 J impact energy at −20°C, making it the grade of choice for structures that must resist brittle fracture in cold climates or under dynamic loading. It is widely specified in European-designed bridges, offshore structures, heavy machinery and cold-region construction.

This page sets out the thickness range, chemistry, mechanical properties, impact requirements, international equivalents, applications, quality assurance and packing for S355K2 plate. Send your thickness, size, quantity and destination for a firm quotation within 24 hours.

Product Overview

S355K2 belongs to the EN 10025-2 family of hot rolled non-alloy structural steels. The designation reads: S for structural, 355 for the minimum yield strength in MPa at the thinnest section, and K2 for the impact quality — 40 J minimum absorbed energy at −20°C. The higher K-grade impact requirement distinguishes it from the more common S355J2 (27 J at −20°C) and makes it suitable where a higher margin against brittle fracture is required.

Because S355K2 is a European grade, it is often specified on drawings exported from the EU and on projects with European engineering standards. We supply it from mills producing to EN 10025-2 with 3.1 certification, and can provide an equivalence comparison against Chinese Q355D or Q355E where a cross-reference is needed.

Specifications: Size, Weight and Tolerance

S355K2 plate is supplied in the structural thickness range, with tolerances to EN 10029. Thickness tolerance class and flatness should be stated on the order because they affect both weight and fabrication fit-up.

Parameter	Range	Tolerance
Thickness	6–150 mm	Per EN 10029
Width	1500–3500 mm	Mill standard
Length	6000–12000 mm	Per order
Theoretical weight	7.85 g/cm³ basis	Calculated
Flatness	Per EN 10029	Class by agreement
Edge	Mill edge or cut	Per order

Thicker plate in the K2 impact grade is more demanding to roll and test, so availability and lead time depend on thickness. We confirm the achievable thickness and impact-test capability before quoting, rather than promising a size the mill cannot certify to −20°C at 40 J.

Available Grades and Chemistry

EN 10025-2 controls S355K2 chemistry to balance strength, toughness and weldability. Carbon and carbon equivalent are capped, and the steel is fully killed with fine grain practice to support the impact requirement.

Element	S355K2
Carbon (C)	≤0.22%
Manganese (Mn)	≤1.60%
Silicon (Si)	≤0.55%
Phosphorus (P)	≤0.030%
Sulfur (S)	≤0.030%
Carbon equivalent (CEV)	≤0.45% typical

The K2 impact designation is the defining feature. Where a drawing specifies S355J2 (27 J at −20°C), S355K2 exceeds that requirement and is an acceptable upgrade; the reverse is not true, so a J2 plate should never be substituted for a K2 requirement without engineering approval. For colder service, S355K2 is not the lowest-temperature option — the L grades (S355ML, S355NL) extend toughness to −50°C and beyond.

Mechanical Properties

Yield and tensile requirements fall with thickness, while the impact requirement is fixed by the K2 designation. The values below are the EN 10025-2 requirements for common structural thicknesses.

Property	Requirement (≤16 mm)	Requirement (16–40 mm)
Yield strength	≥355 MPa	≥345 MPa
Tensile strength	470–630 MPa	470–630 MPa
Elongation	≥20%	≥20%
Impact (K2, −20°C)	≥40 J	≥40 J
Impact test	Charpy V, longitudinal	Per EN 10025-2

Impact testing is performed on Charpy V-notch specimens at −20°C and reported on the mill certificate. For critical structures, buyers should confirm the test direction (longitudinal or transverse) and the sampling frequency, since these affect how representative the reported energy is of the whole plate.

Manufacturing Standards

S355K2 plate is rolled and tested to EN 10025-2, with dimensions and tolerances to EN 10029. Delivery conditions include as-rolled, normalized (N) and thermomechanically rolled (M); the condition affects both toughness and weldability and is stated on the certificate. The steel is fully killed and fine grain treated to meet the impact requirement.

We supply EN 10204 3.1 mill certificates as standard and can arrange 3.2 certification or third-party inspection. Because S355K2 is often specified alongside Chinese equivalents, we provide an equivalence comparison — typically Q355D or Q355E for the impact level — so the buyer’s engineer can approve the cross-reference formally rather than relying on a verbal assurance.

Applications

S355K2 plate is specified where a structural steel must combine high strength with reliable toughness at low temperature: bridges and infrastructure in cold climates, offshore and port structures, heavy machinery and crane components, mining and earthmoving equipment, and dynamically loaded frames. The −20°C impact guarantee gives designers a margin against brittle fracture that the J2 grade, with its lower energy requirement, does not provide to the same degree.

The grade is not intended for elevated-temperature pressure service, where a pressure vessel standard applies, nor for severe corrosive environments without protection. Within structural and mechanical fabrication, it is a dependable choice wherever the design code demands K2 toughness, and we recommend confirming the code requirement and impact temperature before ordering.

Quality Assurance

Quality control covers chemistry, mechanical properties including impact energy, dimensions and surface. Each heat is verified against EN 10025-2, tensile and Charpy tests are taken per lot, and plate is inspected for thickness, flatness, edge condition and surface defects before dispatch. Records and traceability travel with the shipment.

• Heat chemistry and mechanical results, including −20°C impact energy, on 3.1 certificate.
• Delivery condition (AR, N or M) stated on the certificate.
• Dimensional inspection: thickness, width, length, flatness.
• Surface and edge inspection; optional UT for critical plate.
• Optional third-party inspection before shipment.

Packing and Shipping

Plate is shipped in strapped bundles or as loose plate, with edges protected and bundles marked with grade, heat number, size and quantity. Heavy plate is loaded by magnet or clamp. We arrange container, breakbulk or project cargo shipping depending on thickness and tonnage, and apply rust-preventive coating where the plate will be stored before fabrication.

For European destinations and projects with strict documentation requirements, we prepare the certificate package and shipping documents to the contract or letter of credit. Tell us the destination, the required impact grade proof and the handling equipment at the receiving end, and we will confirm the packing and loading method that protects the plate in transit.

Welding, Fabrication and Impact Grade Selection

S355K2 welds with standard low-hydrogen practice, but the K2 impact requirement means the welding procedure must be qualified to preserve toughness in the heat-affected zone, not merely to achieve strength. Preheat of 100–150°C is typical for thicker sections, with controlled interpass temperature and a matching low-hydrogen consumable. Where the structure will see low-temperature service, the procedure qualification should include impact testing of the weld and HAZ, mirroring the base plate requirement.

The most common specification error with this grade is confusing the impact designations. S355K2 requires 40 J at −20°C, which is higher than S355J2’s 27 J at the same temperature. A J2 plate can never be substituted for a K2 requirement without engineering approval, because the toughness margin the design assumed would be lost. Equally, K2 should not be used where the design temperature is lower than −20°C; the ML and NL grades extend toughness further down the temperature range.

For heavy fabrication, plate flatness and edge quality affect fit-up and weld quality as much as chemistry does. Specify the flatness class and edge condition on the order, and consider ultrasonic testing for thick plate in critical structures to detect laminations before fabrication begins. A plate that passes tensile and impact tests can still carry an internal defect that only UT reveals, which is why critical projects pair the mill certificate with independent inspection.

Ordering Checklist

1. State the grade with impact designation (S355K2) and the governing EN 10025-2 edition.
2. Give thickness, width, length and quantity, and the tolerance class (EN 10029).
3. Specify delivery condition (as-rolled, normalized, or thermomechanically rolled).
4. Confirm the impact test requirement and whether transverse testing is needed.
5. State cutting, edge and flatness requirements, and whether UT is required.
6. Agree packing, protection and the certificate package for the destination.

What is the difference between S355K2 and S355J2?

Both are S355 structural steels with the same strength, but they differ in impact toughness. S355J2 requires 27 J minimum absorbed energy at −20°C, while S355K2 requires 40 J at the same temperature. K2 therefore offers a higher margin against brittle fracture and is specified where the design demands it; it can replace J2, but J2 cannot replace K2 without engineering approval.

Where a project specifies S355K2 alongside Chinese grades, the closest impact equivalents are Q355D (−20°C) and Q355E (−40°C). Confirm the required impact temperature and energy on the certificate rather than relying on a grade name alone, since the difference between a compliant and a non-compliant plate often comes down to the Charpy result at the service temperature.