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Chemical and Mechanical Properties of Q550D Steel Grade Spiral Steel Pipe
1、 Chemical composition
The chemical composition of Q550D spiral steel pipe is based on GB/T 16270-2009 and GB/T 1591-2018 standards, with the main elements as follows:
Carbon (C): ≤ 0.18% (low-carbon design optimized weldability);
Manganese (Mn): 1.00%~1.60% (core strengthening element, enhancing strength and toughness);
Silicon (Si): ≤ 0.55% (deoxidation effect, auxiliary strength enhancement);
Phosphorus (P) and sulfur (S): both ≤ 0.030% (strictly limit harmful impurities);
Aluminum (Alt): ≥ 0.015% (refine grain size, improve toughness);
Trace alloying elements: titanium (Ti), chromium (Cr), nickel (Ni), etc. (enhance comprehensive performance, such as corrosion resistance and fatigue resistance).
2、 Mechanical performance
Strength and plasticity:
Yield strength (σ s): ≥ 550 MPa；
Tensile strength (σ b): 670~830 MPa;
Elongation rate (δ 5): ≥ 16% (elongation at break).
Low temperature impact toughness:
-20 ℃ impact energy: ≥ 40 J (structural stability under low temperature environment);
Thickness directional performance: Z15/Z25/Z35 grades, with a cross-sectional shrinkage rate of ≥ 15%/25%/35% respectively (to prevent layer tearing).
Process performance:
Weldability: Low sensitivity to welding cracks, supporting processes such as arc welding and submerged arc welding;
Testing requirements: Ultrasonic testing levels can be selected (first probe, second probe, third probe).
3、 Application Fields
Q550D spiral steel pipe is suitable for high load and harsh environmental scenarios:
Heavy machinery: mining supports, load-bearing components of engineering machinery;
Energy and ships: offshore platform structures, critical connections of ship hulls;
Pressure vessels: high-pressure storage tanks, nuclear reactor shells;
Low temperature engineering: structural components in environments below -20 ℃ (such as polar facilities).
(Note: Specific parameters may be adjusted due to thickness, flaw detection level, and Z-direction performance requirements.)
ADD：Chengnan Industrial Development Zone, Yanshan County, Hebei Province
Domestic phone number：0086-317-6689999
International call：0086-317-6165555
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