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Chemical and mechanical properties of Q355ND grade spiral steel pipe
1、 Chemical composition
The chemical composition of Q355ND spiral steel pipe is based on the GB/T 1591-2018 standard, and the main elements are as follows:
Carbon (C): ≤ 0.20%~0.24%;
Silicon (Si): ≤ 0.50%;
Manganese (Mn): 0.90%~1.65% (optimized strength and processability);
Phosphorus (P): ≤ 0.030% (strictly limit impurities);
Sulfur (S): ≤ 0.025% (low sulfur controls thermal brittleness);
Micro alloy elements:
Niobium (Nb): 0.005%~0.05% (refined grain);
Vanadium (V): 0.01%~0.12% (improves toughness);
Titanium (Ti): 0.006%~0.05% (enhances corrosion resistance).
2、 Mechanical performance
Strength index (thickness related):
Yield strength (σ s):
Thickness ≤ 16mm: ≥ 345 MPa；
16~40mm：≥ 335 MPa；
40~63mm：≥ 325 MPa；
Tensile strength (σ b): 490~630 MPa (typical high strength range);
Bending strength ratio: not explicitly defined, but must meet plasticity requirements.
Plasticity and toughness:
Elongation rate (δ 5): ≥ 21%~22% (elongation at break);
Low temperature impact toughness:
-20 ℃ impact energy ≥ 27 KJ (some standards require -40 ℃ longitudinal impact energy ≥ 31 J);
Z-direction performance: Z25 grade elongation at break ≥ 15% (sulfur content ≤ 0.007%).
Process performance:
Weldability: Low carbon design supports multiple welding processes, with welding joint strength ≥ 355 MPa;
Cold formability: suitable for bending, bending and other processing.
3、 Application Fields
Q355ND spiral steel pipe is suitable for the following scenarios:
Energy infrastructure: wind power towers, high-voltage transmission towers;
Low temperature environment: polar facilities and ocean platforms operating at -40 ℃;
Bridges and heavy machinery: load-bearing components of highway bridges, crane frames.
4、 Production and Standards
Delivery status: normalized or normalized rolling (optimized grain structure);
Execution standard: GB/T 1591-2018 (corresponding to international standards such as European standard S355J2+N and American standard A572Gr50);
Surface quality: No defects such as bubbles or cracks, slight oxidation of iron scale is allowed.
(Note: Some parameters may be adjusted due to thickness range or Z-direction performance level.)
ADD：Chengnan Industrial Development Zone, Yanshan County, Hebei Province
Domestic phone number：0086-317-6689999
International call：0086-317-6165555
E-mail:9905791@qq.com
