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Chemical and mechanical properties of Q355NE grade spiral steel pipe
1、 Chemical composition
The chemical composition of Q355NE spiral steel pipe must meet the following requirements (taking normalized or normalized rolling state as an example):
Carbon (C): ≤ 0.18%~0.20% (some standards require ≤ 0.18%);
Silicon (Si): ≤ 0.50%;
Manganese (Mn): 0.90%~1.65% (optimized strength and toughness);
Phosphorus (P): ≤ 0.035%;
Sulfur (S): ≤ 0.035% (Z-direction performance requirements are stricter, such as Z25 requiring ≤ 0.007%);
Microalloying elements: niobium (Nb) 0.005%~0.05%, vanadium (V) 0.01%~0.12%, titanium (Ti) 0.006%~0.05% (grain refinement);
Other elements: Chromium (Cr) ≤ 0.30%, Nickel (Ni) ≤ 0.50%, Copper (Cu) ≤ 0.40%, Molybdenum (Mo) ≤ 0.10%.
2、 Mechanical performance
Strength indicators (different thickness ranges):
Yield strength (σ s):
Thickness ≤ 16mm: ≥ 345 MPa；
16~40mm：≥ 335 MPa；
40~63mm：≥ 325 MPa；
63~80mm：≥ 315 MPa；
80~100mm：≥ 305 MPa；
100~150mm：≥ 285 MPa；
150~200mm：≥ 275 MPa；
Tensile strength (σ b): 450-630 MPa;
Qu Qiang ratio: not explicitly defined, but must meet the requirements of plastic reserve.
Plasticity and toughness:
Elongation rate (δ 5):
Thickness ≤ 63mm: ≥ 21%~22%；
63~80mm：≥ 21%；
80~400mm：≥ 17%~20%；
Impact toughness:
-40 ℃ low-temperature impact energy ≥ 31 J (longitudinal), ≥ 20 J (transverse);
Z-directional performance (such as Z25): elongation at break ≥ 15%, sulfur content ≤ 0.007%;
Corrosion resistance: not explicitly mentioned, but alloying elements such as Cu and Ni can enhance corrosion resistance.
Manufacturing process and standards:
Delivery status: normalized or normalized rolling (optimized grain structure);
Execution standard: GB/T 1591-2018 (Low alloy High strength Structural Steel);
Testing requirements: Ultrasonic testing (with optional levels of primary, secondary, and tertiary testing).
3、 Application Fields
Engineering structure: wind turbine tower, crane frame, bridge load-bearing components;
Low temperature environment: Heavy machinery and polar facilities operating at -40 ℃;
Z-direction performance requirement scenario: thick plate welded structures that prevent layer tearing (such as offshore platforms).
(Note: Specific parameters may be adjusted due to differences in delivery status, thickness range, and Z-direction performance level.)
ADD：Chengnan Industrial Development Zone, Yanshan County, Hebei Province
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