S355J2: Steel Technical Specifications

01S355 Steel: Introduction and General Characteristics

S355 steel is one of the most widely used and versatile structural steels in the European industrial landscape, standardised by EN 10025-2 as a non-alloy steel for structural applications at room temperature. This ferrous alloy, characterised by an excellent combination of mechanical strength, weldability and machinability, is the benchmark technical solution for metal structures, heavy steelwork and mechanical components that require structural reliability and ease of processing.

S355 owes its designation to the minimum yield strength of 355 MPa according to the EN 10025-2 classification, which defines mechanical characteristics as a function of material thickness. The “S” designation stands for structural steels, while the number “355” specifies the minimum yield strength for thicknesses up to 16 mm. This European standardisation ensures uniformity in technical specifications and facilitates structural design according to the Eurocodes.

S355 properties derive from a balanced chemical composition that favours controlled carbon content and manganese to optimise the strength-weldability ratio. The limited presence of residual elements such as phosphorus and sulphur ensures good deformability properties and resistance to cold brittleness.

This formulation gives the material stable and predictable mechanical characteristics, essential for the design of structures according to codified calculation methodologies.

The broad spectrum of S355 applications includes civil and industrial steel construction, bridges, building structures, shipbuilding steelwork and components for earth-moving machinery. The versatility of this steel is demonstrated by its adoption as a standard material for structural sections (IPE, HE, UPN), plates for welded construction and mechanical components that require good strength characteristics without the need for complex heat treatments.

1.1S355 Differences vs Conventional Steels

The differences between S355 and conventional steels are mainly reflected in the superior metallurgical quality and the rigorous standardisation of mechanical properties. Compared to lower-grade carbon steels such as S235, S355 offers a yield strength about 50% higher (355 MPa vs 235 MPa), making it possible to reduce structural sections with consequent advantages in terms of weight and material costs.

The weldability of S355 steel is aided by a low carbon equivalent; the CEV limits are not fixed but depend on the variant (JR/J0/J2), product form and thickness according to Table 6 of EN 10025-2, and must therefore be verified on the specific product or against the delivery limits declared by the manufacturer, provided they comply with the standard.

Compared to special alloy steels, S355 keeps costs low thanks to its simplified chemical composition, while still ensuring mechanical performance adequate for most structural applications. Standardisation according to EN 10025-2 ensures constant availability and consistent quality from the various European producers.

1.2S355 Advantages for Industrial Applications

The advantages of S355 in industrial applications include the excellent strength-to-weight ratio, which makes it possible to optimise structures by reducing material costs and simplifying assembly operations. The yield strength of 355 MPa for standard thicknesses allows lighter structures to be designed compared to lower-grade steels, with significant benefits for foundations, transport and installation costs.

The excellent workability of S355 facilitates cutting, drilling, bending and cold-forming operations without the need for preliminary heat treatments. The controlled hardness (≤200 HB, for information) ensures good performance with standard tools and reduces tool wear compared to harder steels, translating into economic advantages for machining operations. The hardness quoted for S355 steel is to be understood as a typical informative delivery value from the manufacturer and not as a requirement prescribed by EN 10025-2, which establishes only the mechanical tensile and impact-toughness requirements for the grade and thickness considered.

The atmospheric corrosion resistance of S355 is standard for non-alloy steels but can be improved through protective coatings or galvanizing, keeping protection costs low compared to stainless steels for applications where corrosion resistance is not a critical requirement.

1.3S355 Standards and Certifications

The standards for S355 mainly follow the European standardisation EN 10025-2:2019, which defines the technical delivery conditions for non-alloy structural steels. The standard specifies requirements for chemical composition, mechanical properties, dimensions and tolerances, as well as testing and quality-control procedures to ensure conformity and traceability of the material.

Classification by impact toughness according to EN 10025-2 provides for the variants S355JR (impact test at +20 °C with KV≥27 J), S355J0 (impact test at 0 °C with KV≥27 J) and S355J2 (impact test at -20 °C with KV≥27 J), allowing the appropriate grade to be selected according to the expected service conditions and low-temperature toughness requirements.

Quality certifications for S355 provide for certificates of conformity according to EN 10204, typically 2.1 certificates for standard applications or 3.1 for critical structural uses. The specifications may include additional through-thickness requirements (Z properties according to EN 10164) for critical welded applications where resistance to lamellar tearing is decisive for structural safety.

02Chemical Composition of S355 Steel: Alloying Elements and Standard Specifications

The chemical composition of S355 is rigorously defined by EN 10025-2 to ensure the specified mechanical properties and the excellent weldability that characterises this structural steel. The formulation favours base elements such as carbon and manganese, keeping residual-element contents low to optimise machinability and structural performance.

The chemical limits of S355 steel depend on the variant (JR/J0/J2), the product form and the thickness as set out in EN 10025-2; it is not correct to use a single set of maximums for all variants and forms, since some grades (e.g. S355J2) adopt stricter limits for P and S and sometimes a lower maximum C than S355JR.

Application example (informative): for S355JR plates, C ≤ 0.24; Mn ≤ 1.60; Si ≤ 0.55; P ≤ 0.035; S ≤ 0.035; N ≤ 0.012 are often declared, whereas for S355J2 plates the limits for P and S are typically ≤ 0.025, with C possibly ≤ 0.22; in any case, adhere to the limits stated in the order specification and in the supplier's EN 10204 3.1 certificate.

The carbon equivalent must be calculated using the relation CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 and compared with the limits by variant/thickness in Table 6 of EN 10025-2 or with the manufacturer's delivery limits when these are more restrictive.

The carbon equivalent of S355 (CEV) is calculated according to the formula CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 and is ≤0.45% for thicknesses up to 30 mm (0.47% for 30-40 mm, see Table 6 of EN 10025-2), ensuring excellent weldability without the need for preheating in most applications. This parameter is essential for assessing susceptibility to hydrogen cracking during welding and for defining appropriate welding procedures. Refer to EN 10025-1/-2 for the use of the formula and the limits.

It is important to note that the chemical limits of S355 steel vary by variant JR/J0/J2 and by product form; for example, for S355JR (plates) they are typically C ≤ 0.24; Mn ≤ 1.60; Si ≤ 0.55; P ≤ 0.035; S ≤ 0.035; N ≤ 0.012, whereas for S355J2, P and S are generally limited to ≤ 0.025, as per EN 10025-2 and manufacturer technical datasheets.

2.1S355 International Equivalents

The correspondences with ASTM A572 Grade 50, BS 4360 (Grade 50B/50C) and UNI 7070 (Fe510) reflect long-standing commercial practice rather than a 1:1 normative equivalence; test methods, chemical limits and impact requirements may differ, and substitution requires project-specific technical and contractual verification.

ISO 630 designations use the “E” series and should not be assumed to be automatic synonyms of the EN “S” series; any use of ISO grades as alternatives to S355 requires a full comparison of the requirements (chemistry, mechanical properties, impact toughness) and of the product form.

The slight differences between the international equivalents mainly concern the test methods and the impact-toughness requirements, while the fundamental mechanical properties and the chemical composition remain substantially uniform, facilitating interchangeability for most standard structural applications. It should be noted that such correspondences are of a technical-commercial nature and not of a normative nature.

03Mechanical Characteristics of S355 Steel: Properties and Structural Performance

The mechanical characteristics of S355 are defined by EN 10025-2 as a function of material thickness, ensuring predictable structural performance for design according to codified methodologies. A detailed understanding of the mechanical properties of S355 is essential for structural engineers and designers working in the field of steel construction and industrial steelwork.

3.1S355 Mechanical Properties in the Annealed Condition

The mechanical properties of S355 in the annealed condition do not represent the standard delivery condition for this structural steel, which is normally supplied in the hot-rolled condition according to EN 10025-2. However, when required for specific machinability needs, annealing at 650-700 °C followed by slow cooling gives the material a spheroidised ferritic-pearlitic structure with reduced hardness.

In the annealed condition, S355 exhibits a reduced tensile strength of about 450-500 MPa with a yield strength of about 250-280 MPa, values lower than in the standard condition but with a significant improvement in deformability. The percentage elongation can reach 26-30%, facilitating complex cold-forming operations that require severe deformations.

The hardness of annealed S355 typically settles around 130-160 HB, ensuring excellent machinability for turning, milling and drilling operations with conventional tools. This metallurgical condition is rarely used for S355, with the hot-rolled condition generally preferred as it offers the best mechanical-properties-to-cost ratio for structural applications.

3.2S355 Mechanical Strength in the Quenched and Tempered Condition

S355 in the quenched and tempered condition does not represent a standard treatment for this structural steel, since quenching and tempering (hardening + tempering) is mainly applied to alloy steels to improve mechanical properties. However, for special applications requiring high mechanical strength, quenching and tempering can be applied to S355 with parameters adapted to its chemical composition.

Quenching and tempering of S355 with hardening from 850-880 °C in water followed by tempering at 550-600 °C can increase the tensile strength up to 650-750 MPa while maintaining good toughness. The yield strength can reach 450-550 MPa, values higher than in the standard condition but with an increase in process costs that must be justified by the required performance.

The deformability properties after quenching and tempering may decrease, with elongation of 18-22% and reduction of area of 40-50%, while still maintaining characteristics adequate for most mechanical applications requiring high strength combined with sufficient toughness for dynamic loads.

3.3S355 Hardness After Heat Treatment

In the standard hot-rolled condition, the hardness of S355 typically reaches up to about 200 HB (indicative manufacturer data; EN 10025-2 does not prescribe a hardness requirement), ensuring good machinability. This controlled hardness allows cutting, drilling and machining operations with standard tooling without the need for preliminary treatments in most applications.

After normalising of S355 at 880-920 °C followed by air cooling, the hardness can increase up to 180-220 HB depending on the cooling rate and section thickness. This treatment is applied to homogenise the microstructure after hot working or to improve toughness in critical applications where metallurgical quality must be optimised.

The hardness after hardening of S355 from temperatures of 850-880 °C can reach 300-450 HV depending on the quenching medium used, but this treatment leads to a drastic reduction in toughness and increased brittleness. Subsequent tempering at temperatures of 400-600 °C allows hardness and toughness to be balanced according to specific application requirements, although these treatments are not standard for S355.

3.4S355 Impact Strength and Toughness

The impact toughness of S355 is specified by the EN 10025-2 standard through Charpy V-notch impact tests at different test temperatures for the JR (+20 °C), J0 (0 °C) and J2 (-20 °C) variants. The minimum absorbed energy is specified as 27 J for all grades, ensuring adequate toughness for structural applications in various climatic conditions.

The toughness of S355J2 at -20 °C with a Charpy energy of at least 27 J ensures non-brittle behaviour even at low temperatures, an essential characteristic for structures exposed to severe climatic conditions or for critical applications where brittle fracture must be avoided. This property is particularly important for bridges, offshore structures and industrial plants in regions with harsh winter temperatures.

The crack propagation characteristics of S355 are influenced by metallurgical quality and by the presence of non-metallic inclusions. Strict control of the chemical composition according to EN 10025-2 ensures uniform and predictable toughness, a fundamental parameter for design based on fracture mechanics methodologies when required by critical applications.

3.5S355 Fatigue and Dynamic Behaviour

The fatigue behaviour of S355 under cyclic loads is defined by the structural Eurocodes (EN 1993-1-9), which specify the S-N curves for different categories of construction details and loading conditions. High-cycle fatigue strength depends significantly on the quality of the welds and on the presence of stress concentrators.

The fatigue strength of S355 for the base material is characterised by a fatigue limit (at 2×10⁶ cycles) of about 160-180 MPa for alternating stresses (see EN 1993-1-9 for details), a value that is significantly reduced in the presence of welds or critical geometric details. Fatigue design must consider not only the properties of the base material but also the construction details and the execution quality of the welded joints.

The dynamic behaviour of S355 under impact loads is characterised by its ability to absorb energy through plastic deformation before fracture, a property quantified through Charpy impact toughness tests. The ferritic-pearlitic microstructure typical of hot-rolled steel provides a good balance between strength and toughness for structural applications subjected to variable loads.

04Physical Characteristics of S355 Steel: Thermal and Structural Properties

The physical characteristics of S355 represent fundamental parameters for structural design and for the analysis of the thermomechanical behaviour of components. These technical data are essential for calculations of thermal expansion, conductivity, self-weight of structures and finite element analyses that consider thermostructural coupling.

The density of S355 is standardised at 7.85 g/cm³, a value typical of carbon steels that reflects the simplified chemical composition without heavy alloying elements. This parameter is fundamental for calculating the self-weight of metal structures and for determining permanent actions in structural design according to the Eurocodes.

The modulus of elasticity of S355 is specified as 210 GPa according to EN 1993-1-1 for all structural steels, a value used for calculating elastic deformations and for structural stability analysis. The shear modulus stands at 81 GPa, a parameter required for torsional buckling analysis and for the calculation of structural members subjected to torsion.

The thermal properties of S355 include a melting temperature of about 1520-1540 °C, typical of non-alloy carbon steels. The thermal conductivity varies from 54 W/(m·K) at room temperature down to about 27 W/(m·K) at 600 °C, parameters relevant for thermal analyses and for the design of structures subjected to significant thermal gradients or fire protection.

The coefficient of linear thermal expansion of S355 is specified as 12 × 10⁻⁶/K according to EN 1993-1-1, a value that must be considered in the design of structures subjected to thermal excursions in order to avoid excessive restraint stresses. This parameter is particularly critical for bridges, large-span roofing and industrial structures where thermal variations can generate significant forces if not adequately compensated by expansion joints.

The specific heat of S355, equal to 465 J/(kg·K) at room temperature, is an important value for fire protection calculations and for modelling the thermal behaviour of metal structures subjected to fire. The electrical resistivity of about 0.20 Ω·mm²/m indicates electrical properties typical of carbon steels, a parameter relevant for applications involving leakage currents or for the design of cathodic protection systems.

05Heat Treatments of S355 Steel: Processes and Optimal Parameters

The heat treatment of S355 is generally not a necessity for this structural steel, which is supplied in the hot-rolled condition with mechanical properties that are optimal for most applications. However, specific treatments can be applied for particular needs such as structural homogenisation, improved machinability, or optimisation of properties for specialized mechanical applications.

5.1S355 Hardening: Temperatures and Techniques

The hardening of S355 is not a standard treatment for this structural steel due to its relatively low carbon content (≤0.22%), which limits its hardenability. However, for special applications requiring a localized increase in hardness, surface hardening techniques can be applied with parameters adapted to the material's chemical composition.

The hardening temperature for S355 lies in the range 850-880 °C, corresponding to the austenitic zone for this chemical composition. Cooling in water or polymers can generate martensitic structures with a hardness of 300-450 HV, but it entails high risks of cracking and brittleness that limit its practical applicability for structural components.

The quenching media for S355 hardening mainly include water to maximise the cooling rate, polymer solutions to control distortion on complex geometries, or oil to reduce residual stresses. Localized hardening by induction heating can be applied to surface-harden contact areas while maintaining core toughness, although this application is rare for S355.

5.2S355 Stress Relieving: Optimal Parameters

The stress relieving of S355 is applied mainly to relieve residual stresses after intensive machining operations or complex welding, rather than to optimise mechanical properties as in alloy steels. Stress-relieving temperatures are chosen to maintain the mechanical properties specified by EN 10025-2 while avoiding any degradation of structural performance.

The stress-relieving temperatures for S355 typically lie in the range 580-650 °C for complete relief of residual stresses while maintaining the original mechanical characteristics. Lower temperatures (400-500 °C) can be used for partial stress relieving when strict retention of the original mechanical properties is required, whereas higher temperatures entail risks of reduced mechanical strength.

The tempering time of S355 varies between 1-2 hours for standard thicknesses (≤40 mm), ensuring complete thermal homogenisation of the section. Cooling is carried out slowly in the furnace or in still air to avoid thermal shocks that could generate new residual stresses, negating the effectiveness of the stress-relieving treatment.

5.3S355 Normalising: Conditions and Applications

The normalising of S355 is the most commonly applied heat treatment for this steel when microstructure homogenisation is required after irregular hot working, or to improve toughness in critical applications. The process consists of heating into the austenitic region followed by air cooling to obtain a fine, homogeneous ferritic-pearlitic structure.

The normalising temperatures for S355 range between 880-920 °C depending on the specific chemical composition and section thickness. Heating must be carried out at a controlled rate (50-100 °C/h) to avoid excessive thermal gradients that could cause stresses and distortion, which is particularly important for components of complex geometry or thin sections.

The cooling after S355 normalising is carried out in still air to achieve intermediate cooling rates that favour the formation of fine ferritic-pearlitic structures with a good strength-toughness balance. For thick sections (>80 mm), forced-air cooling may be necessary to prevent the formation of coarse structures that would compromise the mechanical properties.

5.4Quality Control of S355 Heat Treatments

The quality control of S355 heat treatments involves systematic checks of the mechanical and metallographic properties to ensure compliance with the original specifications of EN 10025-2 or with any additional requirements defined for specialized applications. The control methods include standardised mechanical tests and microstructural analyses on representative samples.

The verification of S355 mechanical properties after treatment includes tensile tests to ISO 6892-1, Charpy V-notch impact tests to ISO 148-1, and HB hardness measurements to ISO 6506-1. The values must remain within the limits specified by EN 10025-2 for the specific grade (S355JR, J0 or J2), ensuring that the heat treatment has not compromised the structural performance of the material.

The metallographic inspection of S355 after heat treatment analyses the homogeneity of the microstructure, the ferritic grain size, and the distribution of pearlite by means of optical microscopy and, where appropriate, scanning electron microscopy. The absence of anomalous structures (bainite, martensite) must be verified to confirm the effectiveness of the treatment and its suitability for standard structural applications.

5.5Common Defects and Solutions in S355 Heat Treatments

The common defects in S355 heat treatments mainly include geometric distortions, surface oxidation, and occasional local variations in mechanical properties associated with non-uniform heating or cooling. Early identification and correction of these problems is essential to maintain the quality of the treated material.

The distortions from S355 heat treatment can be minimised through appropriate supports during heating, strict control of the heating and cooling rates, and the possible use of hot presses to maintain the geometry during phase transformations. The design of dedicated fixtures to support components during treatment is often necessary for complex geometries.

The surface oxidation of S355 during heat treatments can be controlled through protective atmospheres (nitrogen, argon) or by applying temporary protective coatings that are removed after treatment. Excessive oxidation may require chemical pickling or sandblasting operations to restore the surface characteristics needed for subsequent machining or painting.

06Industrial Applications of S355 Steel: Sectors and Strategic Uses

The applications of S355 dominate the structural steelwork and industrial fabrication sector, where its combination of structural strength, excellent weldability, and low cost makes it the preferred choice for a wide range of structural applications. This steel is the reference material for structural engineers and designers working in the civil and industrial construction sector.

6.1S355 Automotive Applications

The automotive applications of S355 are limited compared to other specialized steels, focusing mainly on structural chassis components and body elements that require mechanical strength combined with ease of machining and welding. The automotive sector generally favours advanced high-strength steels (AHSS) to optimise weight, but S355 finds use in specific applications where cost and machinability are the priority.

Commercial vehicle chassis in S355 benefit from good weldability and an excellent strength-to-cost ratio for applications where weight is not the critical design parameter. The yield strength of 355 MPa ensures adequate structural safety for high payloads while keeping production costs competitive compared with more sophisticated steels.

The applications in the S355 automotive sector also include engine mounts, structural crossmembers, and floor-pan components for commercial vehicles, where robustness and ease of repair are preferable to weight optimisation. The standard corrosion resistance can be improved through surface treatments (galvanizing, painting) to ensure adequate durability in the automotive environment.

6.2S355 Machine Tool Sector

The S355 machine tool sector uses this steel for bases, beds, and load-bearing structures that require high rigidity and dimensional stability under machining loads. Its good weldability makes it easier to produce complex welded structures at a lower cost than casting, while maintaining mechanical properties suitable for structural applications.

Machine tool bases in S355 exploit the high elastic modulus (210 GPa) to minimise deformation under load and ensure machining precision. Although steel offers lower inherent damping than cast iron, welded S355 bases achieve the required dynamic stability through stiffness-driven design and, where needed, concrete or polymer filling.

Load-bearing structures for CNC machining centres in S355 benefit from ease of machining for the fabrication of guides, slots and precision holes. The controlled hardness (≤200 HB for information) allows milling and grinding operations with standard tooling while maintaining the strict tolerances required for the assembly of precision components.

6.3S355 in Mechanical Engineering and Construction

The S355 mechanical engineering and construction industry represents the primary field of application for this structural steel, where it is used for structural steelwork, bridges, industrial buildings, and civil structures. Its standardisation to EN 10025-2 and its compatibility with the structural Eurocodes make it the reference material for structural design across Europe.

Steel constructions in S355 include industrial buildings, warehouses, plant structures and infrastructure where structural strength and ease of assembly are priority parameters. Availability in standard profiles (IPE, HE, UPN, L, T) and plates facilitates modular design and structural optimisation according to codified methodologies.

Bridges and viaducts in S355 exploit the toughness properties (J0, J2 variants) to ensure structural safety even at low temperatures, an essential requirement for transport infrastructure exposed to severe climatic conditions. Fatigue strength according to EN 1993-1-9 makes it possible to design structures subjected to cyclic traffic loads with design lives of 100+ years.

6.4S355 Specialist Sectors

The S355 specialist sectors include marine, oil and gas, energy, and mining applications, where robustness, weldability, and commercial availability are more important than sophisticated mechanical properties. These sectors often require additional certifications and rigorous quality control to ensure reliability under severe operating conditions.

The S355 shipbuilding industry uses this steel for hulls, superstructures and structural components of commercial vessels, where marine corrosion resistance is ensured through cathodic protection systems and specific coatings. Variants with through-thickness properties (Z-quality) can be requested for critical applications where resistance to lamellar tearing is essential for navigation safety.

S355 energy applications include support structures for wind farms, mounting frames for solar panels and steelwork for power plants, where standardisation and low costs facilitate the delivery of large-scale projects. Resistance to dynamic wind loads and ease of maintenance represent significant advantages for energy-sector applications.

6.5Performance Comparison vs Other Steels

The comparison of S355 with other structural steels highlights specific advantages that justify its widespread use in the steel construction sector. Compared to S235, S355 offers 50% higher yield strength, allowing structural optimisation and weight reduction with significant economic benefits.

Compared to high-strength steels (S460, S690), S355 maintains significantly lower costs and superior weldability, factors that make it preferable for most standard structural applications where weight optimisation does not justify the additional costs of special steels. High commercial availability and well-established standardisation represent additional advantages for designers and fabricators.

07Frequently Asked Questions About S355 Steel: Technical Answers for Professionals

The most frequently asked questions about S355 reflect the practical needs of structural engineers, qualified welders and technicians working in the steel construction sector. This chapter gathers the most recurring queries, providing precise technical answers based on European standards and official specifications to support the correct application of this structural steel.

7.1What is the difference between S355JR, S355J0 and S355J2?

The S355JR/J0/J2 variants differ in guaranteed impact toughness (27 J at +20 °C/0 °C/-20 °C respectively); for some product forms, J2 also adopts stricter chemical limits (typically lower P and S) and, in some cases, a lower maximum C than JR, according to the manufacturer's product specifications and in compliance with EN 10025-2.

7.2Does S355 require preheating for welding?

The weldability of S355 is excellent thanks to the controlled carbon equivalent (CEV ≤ 0.45% for thicknesses ≤30 mm and 0.47% for 30-40 mm, see table 6 of EN 10025-2). For thicknesses up to 30 mm and standard welds, preheating is generally not required with low-hydrogen electrodes under normal ambient conditions (>5 °C). For thicknesses above 30 mm, severe ambient conditions (temperatures <0 °C, high humidity) or highly restrained geometries, preheating of 100-150 °C may be recommended to prevent cold cracking.

Correct preheating is determined according to EN 1011-2 as a function of CEV/CET, thickness, diffusible hydrogen of the filler material, heat input and restraint. It is advisable to avoid fixed rules based on thickness alone and to determine the temperature using method A of the preheating curves, adopting low-hydrogen consumables and qualified WPS/PQR.

7.3What are the international equivalents of S355?

The international equivalents of S355 include ASTM A572 Grade 50 (USA), BS 4360 Grade 50B (United Kingdom), ISO 630 E355 (international) and UNI 7070 Fe510C (Italy). It should be noted that these cross-references are commercial rather than normative; therefore, in regulated projects it is mandatory to fully compare the chemical and mechanical requirements, impact toughness and test methods.

While the mechanical properties are substantially equivalent, slight differences may exist in impact toughness requirements and test methods. For international projects, it is advisable to verify the specific requirements of the destination country and any additional certifications required.

7.4Can S355 be used for high-temperature applications?

S355 for high-temperature applications is not recommended above 200-250 °C for continuous use, since the mechanical properties degrade significantly as temperature increases. For structural applications at higher temperatures, special high-temperature steels (P235GH, P355GH according to EN 10028) are preferable, as they maintain adequate mechanical properties up to 400-500 °C with chemical compositions optimised for creep resistance.

7.5How is the carbon equivalent of S355 calculated?

The calculation of the carbon equivalent of S355 follows the formula CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 according to EN 10025-2. For a typical S355 composition (C=0.20%, Mn=1.40%, Si=0.30%, other elements negligible), the CEV is approximately 0.43%, a value that ensures excellent weldability without the need for preheating in most standard structural applications.

7.6Is S355 suitable for thick welded structures?

S355 for thick-section welded structures maintains good properties up to thicknesses of 80-100 mm according to EN 10025-2, although the mechanical properties progressively decrease as thickness increases. For thicknesses above 40 mm, the S355J2 variant is recommended to ensure adequate toughness, while thicknesses >80 mm may require special steels with compositions optimised for heavy sections (S355N, S355NL according to EN 10025-3).

08Siderticino's Offering for S355 Steel: Specialist Solutions

The Siderticino offering for S355 steel stands out for the completeness of its product range and specialized commercial support, meeting the varied needs of the steel construction market, industrial steelwork and structural engineering. Following the well-established approach for structural steels, Siderticino guarantees quality certified to EN 10025-2 and full traceability for applications where structural reliability is a non-negotiable requirement.