A572 Gr.50 steel pipe is a high-strength low-alloy (HSLA) columbium-vanadium structural steel pipe compliant with the ASTM A572/A572M standard. The designation "50" denotes a minimum yield strength of 50 ksi (approximately 345 MPa), a key metric that distinguishes it from conventional carbon steel pipes. Renowned for its exceptional strength-to-weight ratio, superior weldability, and reliable atmospheric corrosion resistance, it is extensively adopted in heavy-duty structural projects and fluid transport systems. Available in both seamless and welded variants, this steel pipe strikes an ideal balance between mechanical performance and cost-effectiveness, catering to diverse industrial demands.
I. Basic Definition & Executive Standard
Full Standard Name: ASTM A572/A572M - Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel (applicable to steel pipes when combined with pipe-specific manufacturing standards)
Material Type: High-Strength Low-Alloy (HSLA) structural steel pipe, strengthened by microalloying elements including niobium (Nb) and/or vanadium (V), which enhance strength, toughness, and weldability without compromising formability.
Product Forms: Primarily includes seamless steel pipes, ERW (Electric Resistance Welded) pipes, EFW (Electric Fusion Welded) pipes, and fabricated pipes. Common cross-sections are round, square, and rectangular, with hot-dip galvanized variants available for improved corrosion resistance.
Grade Classification: The ASTM A572 series comprises five grades (42, 50, 55, 60, 65) differentiated by yield strength. Gr.50 is the most versatile and cost-effective grade for steel pipes, offering an optimal balance of strength and processability for most structural and transport applications.
Typical Manufacturing Processes: Seamless pipes are produced via hot rolling or cold drawing, ensuring uniform wall thickness and high structural integrity. Welded pipes are manufactured using ERW (Electric Resistance Welded), EFW (Electric Fusion Welded), or LSAW (Longitudinal Submerged Arc Welding) technologies. Supply conditions include as-rolled, normalized, thermo-mechanically controlled processed (TMCP), and quenched & tempered (Q&T), which can be tailored to meet specific project requirements for toughness and strength.
II. Chemical Composition (%)
| Element |
Maximum Content |
Notes |
| Carbon (C) |
0.23 |
Controls weldability and ductility |
| Manganese (Mn) |
1.35 |
Enhances strength and hardenability |
| Phosphorus (P) |
0.04 |
Restricted to avoid brittleness |
| Sulfur (S) |
0.05 |
Minimized to improve toughness and weld quality |
| Silicon (Si) |
0.40 |
Deoxidizer and strength enhancer |
| Niobium (Nb) |
0.05 |
Alternative to vanadium (0.15% max) or Nb+V ≤0.15% |
| Vanadium (V) |
0.15 |
Microalloying element for grain refinement |
| Copper (Cu) |
0.50 |
Optional addition to improve atmospheric corrosion resistance |
Note: Composition may vary slightly based on pipe wall thickness, manufacturing process (seamless/welded), and mill specifications. Always refer to the mill test certificate (MTC) and ASTM A572/A572M standard for exact values.
III. Mechanical Properties (Minimum Values)
| Property |
Value |
Unit |
Notes |
| Yield Strength (YS) |
345 |
MPa (50 ksi) |
Applicable for wall thickness ≤16mm; decreases by ~5% per 25mm thickness increase |
| Tensile Strength (TS) |
450 |
MPa (65 ksi) |
Actual values typically range from 490-600 MPa for seamless/welded pipes |
| Elongation |
18 |
% (50mm gauge length) |
Minimum 21% for pipes with wall thickness >40mm |
| Charpy V-Notch Impact Energy |
27 |
J |
At -40ºC, optional per project specifications |
IV. Key Characteristics & Advantages for Steel Pipes
High Strength-to-Weight Ratio: 1.5 times stronger than ordinary carbon steel pipes (e.g., A36), reducing structural weight and material consumption in large-scale projects.
Excellent Weldability: Low carbon equivalent enables welding without preheating (for thin-walled pipes), compatible with common welding methods (SMAW, GMAW, GTAW) for on-site fabrication.
Good Formability: Maintains flexibility for bending, flanging, and other forming operations, suitable for customized pipe fittings and complex structural designs.
Corrosion Resistance: Optional copper addition and hot-dip galvanization enhance atmospheric and mild chemical corrosion resistance, extending service life in outdoor and industrial environments.
Cost-Effectiveness: Balances high performance with lower costs compared to high-alloy steel pipes, delivering optimal value for structural and transport applications.
Structural Integrity: Seamless variants offer uniform wall thickness and no weld seams, ideal for high-pressure fluid transport; welded pipes meet strict weld quality standards (e.g., AWS D1.1) for structural use.
Grade indicating -40°C Charpy V-notch impact test requirement with minimum 34J impact energy
This grade offers an optimal balance of high strength, excellent low-temperature toughness, good weldability, and cost-effectiveness, making it ideal for structural and pressure applications in cold environments.
Core Standards & Specifications
Primary StandardsKey Dimensional Range
Outer Diameter: 21mm ~ 762mm (custom sizes available)
Wall Thickness: 2.0mm ~ 140mm
Length: 3m ~ 12m (fixed or random length)
Chemical Composition (GB/T 1591-2018)
Mechanical Properties (GB/T 1591-2018)
| Property |
Value |
Notes |
| Yield Strength (σs) |
≥345 MPa (for ≤16mm wall)≥335 MPa (16-40mm)≥325 MPa (40-63mm)≥295 MPa (>63mm) |
Decreases with increasing wall thickness |
| Tensile Strength (σb) |
470-630 MPa |
Higher than carbon steel (e.g., Q235: 370-500 MPa) |
| Elongation (δ) |
≥21% |
Ensures good ductility and deformability |
| Impact Energy (Akv) |
≥34 J at -40°C |
Charpy V-notch test, critical for low-temperature applications |
| Brinell Hardness (HB) |
≤235 |
Indicates good machinability |
Low-Temperature Performance Advantage
The "E" grade designation signifies Q345E's exceptional resistance to brittle fracture at sub-zero temperatures:
· Successfully passes -40°C impact testing (vs. Q345D at -20°C, Q345C at 0°C)
· Microalloying with Nb/V/Ti creates a fine-grained ferrite-pearlite microstructure that enhances toughness
· Strict control of P/S impurities (≤0.025% P, ≤0.020% S) minimizes brittle phase formation
Manufacturing & Quality Control
Production Methods
Seamless: Hot rolling, cold drawing, or hot expansion processes ensuring uniform wall thickness and no longitudinal welds
Welded: ERW (Electric Resistance Welding) or SAW (Submerged Arc Welding) with proper heat treatment
Critical Quality Inspections
Chemical analysis: Verify alloy composition meets GB/T 1591-2018 requirements
Mechanical testing: Tensile, yield, elongation, and -40°C Charpy V-notch impact tests
Non-destructive testing (NDT):
Ultrasonic testing (UT) for internal defects
Eddy current testing (ECT) for surface defects
Hydrostatic pressure test (1.5× working pressure) for leak-tightness
Microstructure examination: Ensure fine-grained structure free of harmful phases
Applications
A572/A572M steel pipe is widely used in demanding low-temperature environments:
Petrochemical Cryogenic storage tanks, ethylene plants, propane dehydrogenation units
Power Generation Nuclear power plants, LNG-fired power stations, cold region power transmission towers
Oil & Gas Arctic oil/gas pipelines, offshore platforms, low-temperature gathering lines
Chemical High-pressure fertilizer equipment, cryogenic separation systems
Construction Bridges, buildings, and infrastructure in cold regions (e.g., Northeast China, Mongolia)
Shipbuilding & Marine Vessels operating in polar waters, LNG carrier cargo systems
Machinery Low-temperature pressure vessels, refrigeration equipment components
Q1: Why choose us?
A: Our company, as an internationally experienced and professional supplier, has been engaged in steel business for more than ten years. We can provide a variety of steel products with high quality to our clients.
Q2: Can you provide OEM/ODM service?
A: Yes. Please feel free to contact us for more details.
Q3:What is your terms of payment?
A: 100% T/T advance.
30% T/T and balance against copy of documents.
30% T/T advance, balance L/C at sight.
Q4: Can we visit your factory?
A: Warmly welcome. Once we have your schedule, we will arrange the professional sales team to follow up your case.
Q5: Can you provide sample?
A: Yes. Sample is free for regular sizes, but the buyer needs to pay freight cost.
Q6: How long is your delivery time?
A: Regular lead time is 15 to 30 days after receiving deposit.
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A572 Gr.50 steel pipe is a high-strength low-alloy (HSLA) columbium-vanadium structural steel pipe compliant with the ASTM A572/A572M standard. The designation "50" denotes a minimum yield strength of 50 ksi (approximately 345 MPa), a key metric that distinguishes it from conventional carbon steel pipes. Renowned for its exceptional strength-to-weight ratio, superior weldability, and reliable atmospheric corrosion resistance, it is extensively adopted in heavy-duty structural projects and fluid transport systems. Available in both seamless and welded variants, this steel pipe strikes an ideal balance between mechanical performance and cost-effectiveness, catering to diverse industrial demands.
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