1. Core Mechanical Property Comparison Table
| Steel Type | Yield Strength (≥MPa) | Tensile Strength (MPa) | Elongation (≥%) | -20℃ Impact Toughness (KV≥J) | Core Highlight |
|---|---|---|---|---|---|
| Q355NH (Weathering) | 355 | 470~630 | 21 | 34 | Weather corrosion resistance + high strength + good toughness |
| Q355B (Low-alloy) | 355 | 470~630 | 21 | 34 (≥0℃ standard, -20℃ optional) | High strength, no weather resistance |
| Q235B (Carbon steel) | 235 | 375~500 | 26 | - (no mandatory impact requirement) | Low strength, poor corrosion resistance |
| SPA-H (JIS Weathering) | 345 | 480~620 | 22 | 34 | Similar weather resistance, slightly lower yield strength than Q355NH |
| A588 Gr.B (ASTM Weathering) | 345 | 480~650 | 21 | 27 (-30℃) | Better low-temperature toughness, matching weather resistance with Q355NH |
2. Key Performance Differences & Positioning
▶ VS Ordinary Carbon Steel (Q235B)
▶ VS General Low-alloy Steel (Q355B)
▶ VS Imported Weathering Steel (SPA-H/A588 Gr.B)
VS SPA-H (Japanese standard): Q355NH has a 10MPa higher yield strength, with almost the same tensile strength and weather resistance; both are suitable for landscape/architectural applications, and Q355NH is more cost-effective for domestic projects.
VS A588 Gr.B (American standard): A588 Gr.B has better ultra-low-temperature toughness (-30℃ KV≥27J vs Q355NH's -20℃), and slightly higher tensile strength upper limit; Q355NH is more matched with Chinese engineering standards and has lower procurement costs.
3. Comprehensive Performance Positioning
It makes up for the defects of Q235B/Q355B (no weather resistance, high maintenance cost) and has equivalent or slightly better structural strength than imported weathering steel (SPA-H);
Compared with high-alloy corrosion-resistant steel (e.g., 304 stainless steel), its strength is close but the cost is only 1/3~1/2, and it has better formability/weldability (stainless steel is prone to intergranular corrosion during welding);
The only limitation is that its corrosion resistance is lower than stainless steel, and it is not suitable for severe corrosive environments (high-salt/acid mist).
