As structural steels under different standard systems, S275 and Q235B pipes have significant differences in mechanical properties, composition control and application scenarios. The specific comparison is as follows:
Core performance differences
- Strength grade
S275: yield strength ≥ 275MPa (thickness ≤ 16mm), tensile strength 430-580MPa;
Q235B: yield strength 235MPa (thick plate performance attenuation is more obvious), tensile strength 370-500MPa.
S275 can reduce the pipe wall by 10%-15% under the same load, but has higher requirements for welding process.
- Low temperature toughness
S275J0: -20℃ impact energy ≥27J, suitable for cold region projects; Q235B: only guarantees 20℃ performance, easy to become brittle at low temperature111, Q235D supports -20℃ but the impact energy requirement is lower than S275.
- Ingredient Control
| Element | S275 Upper limit | Q235B Upper limit | Functions |
|---|---|---|---|
| P | ≤0.035% | ≤0.045% | High phosphorus increases cold brittleness |
| S | ≤0.035% | ≤0.045% | High sulfur causes welding hot cracks |
| C | ≤0.21% | ≤0.20% | Carbon equivalent affects weldability |
Adaptability to special working conditions
Corrosion resistance requirements
Due to the controlled rolling process and low sulfur and phosphorus characteristics, the salt spray corrosion rate of S275 is 18% lower than that of Q235, and it is preferred for offshore platforms;
Q235 needs to rely on galvanized layer for corrosion protection (such as 45μm zinc layer for 500 hours of corrosion resistance).
Dynamic load scenario
The fatigue life of S275 is 42% higher than that of Q235 (actual measurement of port machinery);
Q235 welded pipe is suitable for static structures (such as building supports).
Key points for selection decision
| Scene | Material | Key basis |
|---|---|---|
| High pressure fluid delivery | S275 | Higher pressure redundancy (test pressure ≥ 1.5 times) |
| Low temperature environment (below -20℃) | S275J0 | The impact energy is up to standard and stable |
| Low-cost conventional pipeline | Q235B | 15%-20% lower price |
