Q355 Seamless Carbon Steel Pipe
Product Overview
Q355 seamless carbon steel pipe is a low-alloy high-strength structural steel pipe. The "Q" stands for yield strength, and "355" indicates a minimum yield strength of 355 MPa. As the upgraded replacement for the Q345 grade, Q355 features comprehensively optimized chemical composition and mechanical properties, making it a mainstream choice in fluid transportation, engineering structures, and petrochemical applications.
Mechanical Properties
| Property | Standard Requirement |
|---|---|
| Yield Strength (≤16mm) | ≥ 355 MPa |
| Tensile Strength | 490 – 670 MPa |
| Elongation | ≥ 21% |
| Impact Energy (0℃, Longitudinal) | ≥ 40J |
Yield strength adjusts with increased wall thickness: 16–40mm ≥345MPa, 40–63mm ≥335MPa.
Key Advantages
1. High Strength & Toughness
Yield strength ≥355MPa, tensile strength reaches 490–670MPa, over 50% higher than ordinary carbon steel. Excellent low-temperature impact toughness, suitable for cold regions and winter construction.
2. Excellent Weldability
Strict carbon equivalent control (CEV≤0.45%) enables high-quality welding without complex preheating or post-weld heat treatment, significantly reducing construction difficulty and costs.
3. Seamless Process, Safe & Reliable
Manufactured by hot-rolled or cold-drawn seamless process, free from weld defects, effectively eliminating leakage risks. Each pipe undergoes ultrasonic flaw detection and hydrostatic testing to ensure quality compliance.
4. High Temperature & Pressure Resistance
Withstands pressures ≥20MPa and temperatures above 500℃. Creep rupture strength at 450℃ reaches 150MPa, suitable for long-term high-temperature applications such as hydrogenation units.
Application Fields
Petrochemical: High-pressure pipelines (ethylene, hydrogen), reactors, and heat exchanger tube bundles
Fertilizer Production: High-pressure pipelines for ammonia synthesis units and urea equipment
Marine Engineering: Subsea oil pipelines and offshore platform structural components
Power Industry: Boiler superheaters and turbine components
General Fluid Transportation: Water, oil, gas, and seawater pipelines
Delivery Condition
Multiple delivery conditions available upon request:
Hot Rolled
Normalized (N)
Normalized + Tempered
Quenched + Tempered (Q&T)
Pipes with wall thickness ≤14mm are typically delivered in normalized condition; those >14mm can be normalized or quenched and tempered to refine grain structure and eliminate internal stresses.
Quality Assurance
100% Ultrasonic flaw detection per pipe (Acceptance Level U2)
Hydrostatic testing (Pressure ≤20MPa)
Complete mill test certificates provided, including chemical composition, mechanical properties, and inspection reports
With its high strength, excellent low-temperature toughness, superior weldability, and reliable pressure resistance, Q355 seamless carbon steel pipe has become an ideal piping solution for petrochemical, fluid transportation, marine engineering, and power construction industries. We are committed to providing high-quality, full-size seamless steel pipe products and professional technical support to our customers.
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