S235JR in EN 10025-2
S235JR is a non-alloy structural steel grade in EN 10025-2, delivered in the hot-rolled condition. The designation is compact but carries three separate facts: S for structural, 235 for the minimum yield strength in megapascals at the reference thickness, and JR for the Charpy impact class, tested at room temperature with a minimum absorbed energy of 27 J. That last suffix is the part most often dropped in quotations, and dropping it changes the toughness duty of the order.
S235JR is a weldable low-carbon steel used for bolted, riveted and welded structures: mining machinery, metallurgical plant, construction machinery frames, general fabrication and structural hollow sections.
Chemical Composition Limits
| Element | Limit for S235JR, cast analysis |
|---|---|
| Carbon | 0.17% maximum for thickness up to 40 mm |
| Manganese | 1.40% maximum |
| Phosphorus | 0.035% maximum |
| Sulphur | 0.035% maximum |
| Nitrogen | 0.012% maximum |
| Copper | 0.55% maximum |
The JR suffix and the phosphorus and sulphur limits move together. A buyer who accepts a grade with 0.045% phosphorus and 0.045% sulphur is not buying S235JR, whatever the quotation says.
Yield Strength by Thickness
| Thickness range | Minimum yield strength |
|---|---|
| Up to 16 mm | 235 MPa |
| Over 16 to 40 mm | 225 MPa |
| Over 40 to 63 mm | 215 MPa |
| Over 63 to 100 mm | 215 MPa |
| Over 100 to 150 mm | 195 MPa |
| Over 150 to 200 mm | 185 MPa |
| Over 200 to 250 mm | 175 MPa |
Tensile strength is 360-510 MPa across the covered range. This thickness table is the reason a substitution claim needs the actual wall thickness: a 20 mm wall tube at 225 MPa is not equal to a 10 mm wall tube at 235 MPa, and the difference matters once a safety factor is applied.
Equivalent Designations
| Standard | Designation | Note |
|---|---|---|
| GB/T 700 | Q235B | Yield 235 MPa, tensile 370-500 MPa, chemistry fixed |
| JIS G3101 | SS400 | Yield 245 MPa, tensile 400-510 MPa, chemistry by agreement |
| ASTM A36/A36M | A36 | Yield 250 MPa, tensile 400-550 MPa |
| ISO 630-2 | E235 | Strength class aligned with the 235 MPa level |
| DIN 17100 | St37-2 | Withdrawn designation; replaced in practice by EN 10025-2 S235JR |
Older quality designations such as J2G3 and K2G4 belonged to the superseded EN 10025 edition. They still appear on legacy drawings and in supplier catalogues, but new orders should be written against EN 10025-2 with the impact class stated explicitly.
Hollow Sections and Pipe under Other Standards
When S235JR is required as a structural hollow section, the pipe standard changes the grade symbol: EN 10219-1 covers cold-formed welded hollow sections and uses S235JRH, while EN 10210-1 covers hot-finished hollow sections and also uses S235JRH. Seamless pressure pipe is a different family. A designer who writes "S235JR pipe" without naming the product standard leaves open whether the tube is hot-finished, cold-formed or seamless, and the delivery tolerance and impact test regime differ between them.
Substitution Checks Before Release
Confirm the yield value at the supplied thickness, confirm that the impact energy class matches the service temperature required by the design, and confirm the phosphorus and sulphur limits on the product analysis. Where a grade with a higher nominal yield is proposed as a replacement, check that the higher strength has not been obtained at the cost of weldability, and re-check the welding procedure, especially for thick wall joints.
Frequently Asked Questions
Q: What does the JR suffix in S235JR mean?
A: It is the impact class. JR material is Charpy tested at room temperature with a minimum absorbed energy of 27 J under EN 10025-2.
Q: Is S235JR the same as St37-2?
A: St37-2 is the withdrawn designation from the older DIN and EN 10025 editions. New orders should reference EN 10025-2 S235JR with the impact class stated.
Q: Which hollow section grade equals S235JR?
A: S235JRH, used in both EN 10219-1 for cold-formed hollow sections and EN 10210-1 for hot-finished hollow sections.
Q: Is Q235B a direct replacement for S235JR?
A: The strength level is close, but Q235B permits up to 0.045% phosphorus and 0.045% sulphur while S235JR caps both at 0.035%, so toughness and weldability differ.
Q: Why is a thickness table needed for S235JR?
A: Minimum yield falls as thickness rises, from 235 MPa up to 16 mm down to 175 MPa over 200 to 250 mm, so the design value depends on the wall actually supplied.