I. Definition of steel pipes for construction
Steel pipe for construction refer to steel pipes used in construction and structural engineering as load-bearing, conveying, or supporting materials. Depending on their specific applications, steel pipes for construction can serve as part of the main structural components of a building or as core components of temporary construction facilities (such as scaffolding or support frames).
They typically possess the following characteristics:
High load-bearing capacity: capable of withstanding significant pressure and weight.
Good corrosion resistance: Extended service life through galvanization, coating, and other methods.
Flexible installation: Can be assembled using various methods such as welding, bolt connections, and coupling connections.
II. Main Categories of Steel Pipes for Construction
(1) Classification by Production Process
Seamless Steel Pipes
Made by piercing a solid piece of steel, with no welded seams.
High strength, suitable for load-bearing structures and high-pressure pipelines.
Welded Steel Pipes
Made by rolling steel plates into tubes and then welding them.
Low cost, fast processing speed, commonly used in scaffolding, railings, and other non-high-pressure environments.
(2) Classification by Surface Treatment
Galvanized Steel Pipes
Galvanized on the surface to enhance corrosion resistance.
Commonly used in outdoor scaffolding and water supply/drainage systems.
Plastic-Coated Steel Pipes
Coated with plastic on both inner and outer surfaces, offering excellent wear resistance and corrosion protection.
Commonly used in water supply and fire protection pipelines.
(3) Classification by application
Structural steel pipes
Used for load-bearing components such as building frames, trusses, and supports.
Scaffolding steel pipes
Typically have a diameter of 48 mm and a wall thickness of 3.0–3.5 mm, used for temporary construction supports.
Pipe steel pipes
Used for conveying water, gas, steam, and other media.
III. Common Standards for Steel Pipes Used in Construction
| Standard Code | Standard Name (EN) | Scope of Application | Main Content | Remarks |
|---|---|---|---|---|
| GB/T 3091 | Welded Steel Pipes for Low-Pressure Fluid Conveyance | Water supply & drainage, firefighting, HVAC | Longitudinal welded pipe, galvanized or black, for pressures ≤1.6 MPa | Widely used in building water supply & drainage |
| GB/T 13793 | Straight-Seam Electric-Welded Steel Tubes | Structural supports, steel structures, scaffolding | Q195–Q235 material, ordinary or precision welded tubes | Commonly used for scaffolding & supports |
| GB/T 8162 | Seamless Steel Tubes for Structural Purposes | Trusses, frame structures | OD 6–630 mm, seamless structural tube | Higher mechanical-property requirements |
| GB/T 8163 | Seamless Steel Tubes for Fluid Transport | Water, gas, steam transport | OD 6–630 mm, suitable for medium- & high-pressure fluids | Used in critical piping systems |
| GB/T 21835 | Welded Steel Tubes for Scaffolding | Building scaffolding | OD 48.3 mm, wall thickness 3.0–3.5 mm | Made from hot- or cold-rolled steel strip |
| GB/T 18248 | Seamless Steel Tubes for Gas Cylinders | High-pressure gas transport | High-strength seamless tubes | Special building gas systems |
| GB/T 14980 | Spiral-Submerged-Arc Welded Steel Pipes for Urban Construction | Municipal water supply & drainage, gas transmission | Spiral welded, large diameter | Common in large municipal projects |
| GB/T 700 | Carbon Structural Steels | Raw material for steel pipes | Q195, Q235, etc. | Base material for many steel pipes |
| GB/T 1591 | High-Strength Low-Alloy Structural Steels | High-strength steel pipes | Q345 series | For heavy-duty structures |
| EN 10255 | Non-Alloy Steel Tubes Suitable for Welding and Threading (European) | Building, water supply & drainage, firefighting | Low-pressure welded tubes, galvanized optional | Frequently used in international projects |
| EN 10219 | Cold-Formed Welded Structural Hollow Sections | Trusses, frame structures | Square, rectangular, and circular tubes | European structural steel tubes |
| EN 10210 | Hot-Finished Structural Hollow Sections | Construction steel structures | High-strength hot-formed tubes | Used in large-scale projects |
| ASTM A53 | Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless (U.S.) | Water supply & drainage, structural support | Black or galvanized pipe | Common in U.S. engineering projects |
| ASTM A500 | Cold-Formed Welded and Seamless Carbon Steel Structural Tubing | Trusses, frames, railings | Round, square, and rectangular tubes | Widely used in North-American steel structures |
| ASTM A252 | Standard Specification for Welded and Seamless Steel Pipe Piles | Bridge & foundation piles | Spiral or straight-seam welded piles | Foundation engineering applications |
| JIS G3444 | Carbon Steel Tubes for General Structural Purposes (Japan) | Trusses, building structures | Structural support tubes | Japanese engineering standard |
| JIS G3454 | Carbon Steel Pipes for Pressure Service (Japan) | High-pressure piping systems | Steam & gas transport | Commonly used in Japanese projects |
IV. What are the common specifications, dimensions, and wall thickness ranges?
| Steel Pipe Type | Outer Diameter Range (mm) | Wall Thickness Range (mm) | Standard Length (m) | Common Standards |
|---|---|---|---|---|
| Structural Welded Steel Pipe | 21.3 – 219.1 | 1.5 – 10 | 6 / 9 / 12 | GB/T 3091, ASTM A53 |
| Structural Seamless Steel Pipe | 21.3 – 426 | 2 – 40 | 6 / 12 | GB/T 8162, ASTM A106 |
| Galvanized Steel Pipe (Hot/Cold Dip) | 21.3 – 165 | 2 – 6 | 6 | GB/T 3091, BS EN 10255 |
| Square/Rectangular Tube (Structural) | 20×20 – 500×500 (Rectangular) | 1.5 – 16 | 6 / 12 | GB/T 6728, ASTM A500 |
V. How to choose the appropriate specifications?
(1) Based on load-bearing requirements
High load-bearing or structural main components → Select large outer diameter + thick-walled steel pipes (e.g., Φ168×6mm)
Lightweight support or enclosure structures → Select small outer diameter + thin-walled steel pipes (e.g., Φ60×3mm)
(2) Based on the application location
Main frames, columns → Large-diameter thick-walled
Stair railings, guardrails → Medium to small-diameter thin-walled
Scaffolding → Medium-diameter medium-wall thickness (e.g., Φ48×3.25mm, commonly used scaffolding steel pipe specification)
(3) Consider processing and weldability
Areas requiring extensive welding → Select low-carbon steel with good weldability (Q235, Q355)
Areas requiring bending → Select thin-walled materials with good ductility
(4) Balancing economic considerations
Avoid over-specifying while ensuring strength and safety
Using standard lengths reduces cutting waste
(5) Compliance with standards and testing requirements
Confirm applicable standards (GB, ASTM, EN)
Require suppliers to provide material certificates + third-party test reports
VI. The differences between welded pipes, seamless pipes, and galvanized pipes, three types of steel pipes used in construction
| Item | Welded Pipe | Seamless Pipe | Galvanized Pipe |
|---|---|---|---|
| Manufacturing Process | Formed from steel plate and then welded | Hot-rolled or cold-drawn from a solid billet without any weld seam | Base pipe is either welded or seamless; surface is hot-dip or electro-galvanized |
| Structural Strength | Good strength, but slightly lower at the weld seam | Highest strength, no weld seam, excellent pressure resistance | Zinc coating mainly improves corrosion resistance; strength equals that of the base pipe |
| Corrosion Resistance | Moderate; requires additional coating or anti-corrosion treatment | Needs extra anti-corrosion measures | Inherent zinc coating provides strong corrosion resistance, ideal for outdoor or humid environments |
| Cost | Lowest cost, most economical | Highest cost due to complex manufacturing process | Moderately high; zinc coating increases the cost |
| Fabrication & Workability | Easy to cut and weld, suitable for mass production | Difficult to process, requires specialized equipment | Protect zinc coating during fabrication to avoid damage that would reduce corrosion resistance |
| Purchase Considerations | Check weld quality, applicable standards, and material certificates | Require strict material certification and seamless-pipe inspection reports | Pay attention to zinc layer thickness, uniformity, and corrosion-resistance grade |
| Typical Applications | General building structures, scaffolding, non-pressure pipelines | Critical load-bearing structures, high-pressure pipelines | Outdoor structures with high anti-corrosion requirements, water supply and drainage pipes |
