Both mild steel S235JR and S235J2 steel are under technical standard EN10025-2. They are low carbon structural steel which can be readily welded to other weldable steel. S235JR and S235J2 steel possess good cold-forming properties, and produced by fully killed steel process. The properties of S235JR and S235J2 steel have much in common. But very important difference of them is the impact requirements.
Impact ToughnessS235JR:
| Grade | Yield strength ReH/(N/mm2) (t≤16mm) min | Tensile strength Rm/(N/mm2) (3mm≤t≤16mm) | Elongation A/% (3mm≤t≤40mm) min | Charpy V test | |
| Temperature/℃ | Impact energy (Longitudinal)/J min | ||||
| S235JR | 235 | 360-510 | 26 | +20 | 27 |
| S235J2 | 235 | 360-510 | 24 | -20 | 27 |
S235JR is designed to provide impact resistance at room temperature. The "JR" in its designation indicates that it has a specified impact energy requirement at +20°C. It is suitable for applications where the structure is not likely to be exposed to very low temperatures.
S235J2:
The "J2" in the S235J2 grade means that it has a better impact toughness compared to S235JR. S235J2 is required to meet impact energy requirements at a lower temperature, typically -20°C. This makes it more suitable for use in environments where the risk of brittle fracture due to low - temperature exposure is higher, such as in cold - climate regions or for structures that may experience significant temperature variations.
Chemical CompositionS235JR:
| Grade | C (t≤16mm) | Si | Mn | P | S | Cu | N |
| S235JR | 0.19 max | - | 1.5 max | 0.045 max | 0.045 max | 0.60 max | 0.014 max |
| S235J2 | 0.19 max | - | 1.5 max | 0.035 max | 0.035 max | 0.60 max | - |
In terms of chemical composition, S235JR has relatively standard limits for elements such as carbon (C), manganese (Mn), phosphorus (P), and sulfur (S). For example, the carbon content is usually up to around 0.20% (depending on thickness), manganese up to 1.40%, phosphorus up to 0.045%, and sulfur up to 0.045%.
S235J2:
S235J2 generally has more restrictive limits on impurities like phosphorus and sulfur to enhance its toughness. The maximum allowable content of phosphorus is often 0.035% and sulfur is 0.035%, which are lower than those of S235JR. This stricter control of impurities helps to improve the material's ability to withstand impact loads, especially at low temperatures.
Applications
S235JR:
S235JR is commonly used in general - purpose structural applications where cost - effectiveness is a major consideration and the service temperature is not extremely low. Examples include the construction of ordinary buildings, simple machine frames, and some non - critical components in the manufacturing industry.
S235J2:
S235J2 is preferred for applications where there is a risk of exposure to lower temperatures or where a higher level of impact resistance is required. It can be used in the construction of structures in cold regions, such as bridges, industrial buildings, and equipment in cold - storage facilities
