S235JR and S355JR steel -
properties, differences and sheet selection
S235JR and S355JR are non-alloy structural steels to EN 10025-2 that differ mainly in strength. The minimum yield strength is 235 MPa for S235JR and 355 MPa for S355JR (for thicknesses up to 16 mm), which is 51 per cent more. Both grades carry the JR designation, which guarantees an impact energy of at least 27 J at +20°C. In practice, S355JR makes it possible to reduce the thickness and weight of a load-bearing part, while S235JR is easier to bend and weld and cheaper to buy.
What the S235JR designation means
The designation follows EN 10027-1. The letter S indicates structural steel, the number is the minimum yield strength in megapascals for the lowest thickness range, and JR defines the impact class: 27 J at +20°C. Higher classes are J0 (27 J at 0°C), J2 (27 J at -20°C) and K2 (40 J at -20°C). More on how sheet grade designations are built can be found in the article on steel sheet grade designations.
Impact testing is carried out on products 6 mm thick and above. For thinner sheet, impact requirements are not verified by testing, and the grade is selected on the basis of yield strength, tensile strength and elongation.
Mechanical properties
| Parameter to EN 10025-2 | S235JR | S355JR |
|---|---|---|
| minimum yield strength ReH, thickness up to 16 mm | 235 MPa | 355 MPa |
| minimum yield strength ReH, thickness 16-40 mm | 225 MPa | 345 MPa |
| tensile strength Rm, thickness below 3 mm | 360-510 MPa | 510-680 MPa |
| tensile strength Rm, thickness 3-100 mm | 360-510 MPa | 470-630 MPa |
| minimum elongation A, thickness 3-40 mm, longitudinal | 26% | 22% |
| minimum impact energy KV at +20°C | 27 J | 27 J |
For thicknesses below 3 mm the standard gives separate, lower elongation values measured on an 80 mm gauge length. The modulus of elasticity of both grades is the same, around 210 GPa, as is the density of 7.85 kg/dm³. The weight of a sheet or coil is therefore identical, so requirements can be calculated with the same sheet metal weight calculator.
Chemical composition and weldability
| Element (cast analysis, max) | S235JR | S355JR |
|---|---|---|
| carbon C, thickness up to 16 mm | 0.17% | 0.24% |
| manganese Mn | 1.40% | 1.60% |
| silicon Si | not specified | 0.55% |
| phosphorus P | 0.035% | 0.035% |
| sulphur S | 0.035% | 0.035% |
| nitrogen N | 0.012% | 0.012% |
| copper Cu | 0.55% | 0.55% |
| carbon equivalent CEV, thickness up to 30 mm | 0.35 | 0.45 |
Both grades are considered readily weldable. The difference shows in the carbon equivalent CEV: S235JR lies in a range where preheating is practically unnecessary, while for S355JR the need for preheating depends on thickness, heat input and joint restraint. With thin sheet, typical for enclosures, profiles or machine components, both grades are welded with standard MAG processes without any additional measures.
When to choose S355JR instead of S235JR
The load-bearing capacity of a member in tension or bending within the elastic range increases in proportion to yield strength. A HEN-STOL calculation example: a 60 mm wide flat bar made from sheet carrying a tensile force of 50 kN requires a cross-section of 213 mm² in S235JR and 141 mm² in S355JR. This means a thickness of around 3.55 mm instead of 2.35 mm, or 34 per cent less steel in the same part (simplified calculation, without safety factors).
| Option | Required cross-section | Thickness at 60 mm width | Weight per 1 m of part |
|---|---|---|---|
| S235JR | 213 mm² | approx. 3.55 mm | approx. 1.67 kg |
| S355JR | 141 mm² | approx. 2.35 mm | approx. 1.11 kg |
The benefit of higher strength does not appear everywhere. Where dimensions are governed by stiffness, deflection or the stability of a thin wall, both steels behave in the same way, because they have the same modulus of elasticity. In such parts S235JR does the job equally well and at a lower cost. S355JR pays off in load-bearing members, brackets, frames and structures where self-weight or the cost of transporting the finished product matters.
Forming and cutting
The higher strength of S355JR means greater bending forces, more springback and usually a larger minimum bending radius than S235JR. In series bending on a press brake this should be reflected in the program and tooling. Laser, plasma and shear cutting work without significant differences in both grades. For pressing and deep forming, both grades give way to DD and DC steels, as described in more detail in the article on hot-rolled and cold-rolled steel sheet.
S235JR and S355JR without a mill certificate
Both steels are part of the HEN-STOL hot-rolled sheet offer as material without a mill certificate, sold without a steelworks certificate. Overrolled steel and surplus production in these grades have the same parameters as certified steel, and the lower price results solely from the absence of the certificate. This is a solution for production where product documentation does not require an inspection certificate, for example machine components, enclosures, equipment or metal products. Where a certificate is mandatory, the rules are described in the article on EN 10204 inspection documents.
Available steel grades, coating types and coil, strip and sheet formats are presented in the HEN-STOL steel sheet offer, with separate pages for galvanized steel sheet, cold-rolled steel sheet and hot-rolled steel sheet.
See how we can help
HEN-STOL supplies hot-rolled sheet in S235JR and S355JR in coils, strip and sheets, from 5 tonnes. Send us the specification with thickness, format and application, and we will check the available lots and advise which grade will be more favourable for the part.
Frequently asked questions
What is the difference between S235JR and S355JR steel?
The main difference is strength. S235JR has a minimum yield strength of 235 MPa and S355JR 355 MPa (thickness up to 16 mm). S355JR also has a higher tensile strength, 470-630 MPa compared with 360-510 MPa, and a slightly higher carbon equivalent CEV, 0.45 compared with 0.35. Both steels have the same JR impact class, 27 J at +20°C.
What does JR mean in S235JR?
JR is the impact class to EN 10025-2: a V-notch specimen must absorb at least 27 J of energy at +20°C. The higher classes J0 and J2 require the same energy at 0°C and -20°C, and K2 requires 40 J at -20°C. The test is carried out on products 6 mm thick and above.
Is S355JR steel weldable?
Yes, S355JR is readily weldable. Its carbon equivalent CEV is at most 0.45 for thicknesses up to 30 mm. Thin sheet is welded with standard processes without preheating, while for thick and restrained joints the need for preheating is determined by thickness and heat input.
Can S235JR be replaced with S355JR?
Usually yes, because S355JR meets and exceeds the strength requirements of S235JR. When substituting, higher bending forces and springback should be taken into account, as well as the higher CEV when welding thick parts. The reverse substitution, S355JR with S235JR, requires the load-bearing capacity of the part to be rechecked.
What is the equivalent of S235JR in old Polish standards?
The closest equivalent of S235JR is St3S to the former Polish standard PN-88/H-84020. For S355, 18G2A is most often quoted, although it is closer to S355J2. When updating designations in documentation, it is worth comparing requirements, not just names.
How much does S235JR and S355JR sheet weigh?
The same. Both grades have a density of 7.85 kg/dm³, so one square metre of 1 mm sheet weighs 7.85 kg, and a 1250 x 2500 mm sheet 3 mm thick weighs around 73.6 kg. A difference in product weight only arises when the higher strength of S355JR allows thinner sheet to be used.
Sources
- EN 10025-2, Hot rolled products of structural steels - technical delivery conditions for non-alloy structural steels, 2019
- EN 10027-1, Designation systems for steels - steel names, 2016
- EN 10204, Metallic products - types of inspection documents, 2004
- EN 1090-2, Execution of steel structures and aluminium structures - technical requirements for steel structures, 2018