What the S275JR Designation Means
S275JR is a weldable, non-alloy structural steel plate covered by EN 10025-2, the European standard for hot-rolled products of structural steels. Each symbol in the designation carries a defined meaning: the letter S identifies structural steel, the figure 275 states the minimum specified yield strength in megapascals for material up to and including 16 mm thick, and the letters JR define the impact toughness class, which requires a minimum Charpy V-notch absorbed energy of 27 J at a test temperature of +20 °C. The steel number allocated to S275JR is 1.0044.
Because every mechanical value in EN 10025-2 is tied to nominal thickness, S275JR data must always be read against the plate section actually ordered. A 10 mm plate and a 200 mm plate carry the same grade name but different guaranteed minima, and that difference matters as soon as a designer works close to the allowable stress limit.
Chemical Composition of S275JR Plate
EN 10025-2 controls the ladle analysis of S275JR within the limits below. Values are maximum percentages by mass.
| Element (max %) | t ≤ 16 mm | 16 < t ≤ 40 mm | t > 40 mm |
|---|---|---|---|
| C | 0.21 | 0.21 | 0.22 |
| Mn | 1.50 | 1.50 | 1.50 |
| P | 0.035 | 0.035 | 0.035 |
| S | 0.035 | 0.035 | 0.035 |
| N | 0.012 | 0.012 | 0.012 |
| Cu | 0.55 | 0.55 | 0.55 |
The tight limits on phosphorus and sulphur keep the steel weldable at the plate thicknesses used in general construction, while the nitrogen ceiling protects toughness in the heat-affected zone. Copper is permitted as a residual element up to 0.55 %. For plates above 30 mm the standard additionally controls the carbon equivalent, so heavy S275JR sections can still be welded without special approval.
Mechanical Properties of S275JR
Minimum yield strength ReH decreases with increasing thickness, reflecting the slower cooling rate and coarser microstructure of heavy plate.
| Nominal thickness (mm) | ReH min (MPa) |
|---|---|
| ≤ 16 | 275 |
| > 16 to 40 | 265 |
| > 40 to 63 | 255 |
| > 63 to 80 | 245 |
| > 80 to 100 | 235 |
| > 100 to 150 | 225 |
| > 150 to 200 | 215 |
| > 200 to 250 | 205 |
Tensile strength and elongation follow the same thickness logic.
| Nominal thickness (mm) | Tensile strength Rm (MPa) | Elongation A min (%) |
|---|---|---|
| < 3 | 430–580 | 23 |
| 3 to 100 | 410–560 | 23 at ≤ 40, 22 at > 40 to 63, 21 at > 63 to 100 |
| > 100 to 150 | 400–540 | 19 |
| > 150 to 250 | 380–540 | 18 |
Toughness is verified by Charpy V-notch testing on longitudinal specimens. The JR designation guarantees a minimum absorbed energy of 27 J at +20 °C, which suits indoor and moderate-climate structures. Where lower service temperatures are expected, an impact-tested variant such as S275J0 should be selected instead of S275JR.
Delivery Condition, Dimensions and Tolerances
Delivery condition: normally as-rolled; normalized delivery can be agreed when a finer, more uniform grain structure is required.
Dimensional tolerances: thickness, width, length and flatness in accordance with EN 10029 for hot-rolled plate.
Surface and edge condition: requirements of EN 10163-2 for the relevant surface class.
General delivery requirements: EN 10025-1, with inspection documents issued to EN 10204; a 3.1 certificate is the usual commercial option.
Optional testing that can be agreed at order stage: ultrasonic examination of the plate body to EN 10160, additional Charpy tests, and dimensional verification.
Fabrication and Welding Notes
Cutting: S275JR can be cut by flame, plasma, laser or waterjet. Mechanically sheared edges are acceptable for most structural joints, although the sheared zone should be removed before welding on thick plate.
Welding: the grade is readily welded by shielded metal arc, gas metal arc, submerged arc and flux-cored processes using consumables of matching strength class. Low-hydrogen consumables are preferred for thick sections, restrained joints and low ambient temperatures.
Forming: cold bending is widely used, and the minimum bend radius increases with plate thickness. Hot forming is possible, and heavy hot working is best followed by normalizing so that the specified properties are restored.
Machining: the as-rolled microstructure machines easily with high-speed steel or carbide tooling, which keeps secondary operations economical.
Storage: plates should be stored flat and dry, clear of standing water, to limit edge corrosion before fabrication.
Typical Applications
Building frames, industrial halls and mezzanine floors
Road and pedestrian bridges, bridge bearing plates and diaphragms
Transmission towers, substation structures and telecom masts
Storage tanks, silos and general pressure-free vessels
Machine bases, crane runway beams and equipment support frames
Secondary ship structures, dock fenders and offshore ancillary structures
S275JR is often the most economical choice when a structure needs dependable strength and weldability rather than high strength. Designers comparing it with other grades should confirm that the yield strength at the governing thickness, not the headline 275 MPa figure, is used in the calculation.
Frequently Asked Questions
Q: What does the designation S275JR stand for?
S means structural steel, 275 is the minimum yield strength in MPa for thickness up to 16 mm, and JR indicates a minimum Charpy V-notch energy of 27 J at +20 °C.
Q: What is the minimum yield strength of S275JR plate?
It falls from 275 MPa at 16 mm and below to 205 MPa at thickness above 200 mm up to 250 mm, so the value used for design must match the section thickness.
Q: What impact energy does the JR suffix guarantee?
27 J minimum absorbed energy in the Charpy V-notch test at +20 °C, tested on longitudinal specimens.
Q: Is S275JR equivalent to Q275B or ASTM A36?
They are comparable strength classes rather than identical grades. Q275B in GB/T 700 and ASTM A36 in the American system are widely used as substitution options, but chemistry, impact requirements and tolerances differ, so the substitution should be checked against the governing design code.
Q: Can S275JR be welded without preheating?
For thin and medium plate welded with low-hydrogen consumables in normal workshop conditions, no preheating is usually needed. Thick sections, high restraint and cold ambient conditions call for a qualified welding procedure that may include preheating.
Q: What is the steel number of S275JR?
The European steel number for S275JR is 1.0044.
