I. Introduction to Carbon Steel Welded Pipes
Carbon steel welded pipes, also known as carbon steel pipes, are a widely used industrial material that plays an indispensable role in numerous fields.
Carbon steel steel pipes, with their excellent mechanical properties and cost-effectiveness, play a significant role in industries such as construction, municipal engineering, chemicals, oil, and natural gas.
This article will provide a detailed overview of the specifications, materials, and national standards for carbon steel welded pipes. By thoroughly analyzing these key elements, the aim is to help readers gain a comprehensive understanding of the characteristics and applications of carbon steel welded pipes.
Additionally, this article will offer detailed reference guidelines for engineering selection and project implementation, thereby facilitating the smooth progress and efficient execution of related engineering projects.
II. Carbon steel welded pipes standards in various countries
| Country/Region | Standard Number | Standard Name / Applicable Scope |
|---|---|---|
| China | GB/T 3091 | Welded steel pipes for low-pressure fluid conveyance |
| China | GB/T 9711 | Pipeline steel for petroleum and natural gas industries |
| USA | ASTM A53 | Carbon steel welded steel pipes for pipeline conveyance and structural use |
| USA | ASTM A252 | Carbon steel welded pipes for steel piles |
| USA | ASTM A500 | Carbon steel welded square and rectangular steel pipes for structural use |
| API | API 5L | Pipeline steel for petroleum and natural gas conveyance |
| Europe | EN 10217 | Welded steel pipes for pressure purposes |
| Japan | JIS G3444 | Carbon steel welded steel pipes for general structural use |
| Japan | JIS G3452 | Carbon steel welded steel pipes for piping |
| Germany | DIN 2440 | Carbon steel welded steel pipes for piping |
| UK | BS 1387 | Welded steel pipes for piping (metric thread) |
III. Chemical composition table for carbon steel welded pipes made of different materials
| Material | C (%) | Si (%) | Mn (%) | P (%) | S (%) |
|---|---|---|---|---|---|
| Q195 | ≤0.12 | ≤0.30 | 0.30 – 0.60 | ≤0.035 | ≤0.035 |
| Q215 | ≤0.15 | ≤0.30 | 0.35 – 0.70 | ≤0.035 | ≤0.035 |
| Q235 | ≤0.22 | ≤0.35 | 0.35 – 0.80 | ≤0.035 | ≤0.035 |
| Q345B | ≤0.20 | ≤0.50 | 1.00 – 1.60 | ≤0.035 | ≤0.035 |
| ASTM A53 Gr.B | ≤0.30 | ≤0.25 | ≤1.20 | ≤0.05 | ≤0.045 |
| API 5L Gr.B | ≤0.26 | – | ≤1.20 | ≤0.030 | ≤0.030 |
| API 5L X42 | ≤0.28 | – | ≤1.40 | ≤0.030 | ≤0.030 |
| API 5L X52 | ≤0.28 | – | ≤1.40 | ≤0.030 | ≤0.030 |
| API 5L X60 | ≤0.28 | – | ≤1.40 | ≤0.030 | ≤0.030 |
| API 5L X70 | ≤0.28 | – | ≤1.40 | ≤0.030 | ≤0.030 |
IV. Classification of Carbon Steel Welded Pipes
i. Classification by Welding Process
A. Resistance Welded (ERW) Carbon Steel Welded Pipes
High-frequency welding produces neat weld seams and is widely used for structural and fluid conveyance applications.
B. Submerged Arc Welded (SAW/LSAW) Carbon Steel Welded Pipes
Includes straight seam submerged arc welding (LSAW) and spiral submerged arc welding (SSAW), suitable for large-diameter high-strength pipelines.
C. Oxy-fuel Welded Carbon Steel Welded Pipes
Traditional process, currently less commonly used.
D. Furnace Welded Carbon Steel Welded Pipes
Commonly used for low-pressure water and gas transportation or certain structural applications.
ii. Classification by Application
A. Carbon Steel Welded Pipes for Conveyance
Used for conveying fluids such as water, gas, and oil.
B. Carbon Steel Welded Pipes for Structural Applications
Used in building steel structures, mechanical components, etc.
C. Carbon Steel Welded Pipes for Mechanical Manufacturing
Used for mechanical parts, automotive components, drums, brackets, etc.
D. Carbon Steel Welded Pipes for Pile Foundations
Used in foundation support and pile foundation engineering.
iii. Classification by Weld Type
A. Straight Seam Welded Pipes
The weld runs along the longitudinal axis of the pipe.
B. Spiral Seam Welded Pipes
The weld is spiral-shaped, enabling the production of large-diameter pipes using narrow steel strips.
iv. Classification by end form
A. Plain end (PE)
Directly cut without beveling.
B. Beveled end (BE)
Pre-machined beveled end for easy welding and installation.
C. Threaded end (Threaded)
End machined with threads for connection with fittings.
v. Classification by surface treatment
A. Black pipe (Bare)
No coating treatment.
B. Oiled Pipe (Oiled)
Surface coated with anti-rust oil.
C. Galvanized Pipe (Galvanized)
Hot-dip or electrogalvanized treatment to enhance corrosion resistance.
D. Corrosion-Resistant Coated Pipe (FBE, 3LPE, 3LPP, etc.)
Suitable for buried or corrosive environments.
V. Common Corrosion Protection Types for Carbon Steel Welded Pipes
A. Oil Coating
A layer of anti-rust oil is applied to the surface of the steel pipe to prevent oxidation and rusting during short-term storage and transportation.
B. Black Pipe
No corrosion protection coating is applied; the surface retains the hot-rolled black oxide scale, suitable for indoor structures with no corrosion protection requirements.
C. Hot-Dip Galvanizing
A thick zinc layer is formed on the surface of the steel pipe, offering strong corrosion resistance, suitable for outdoor or humid corrosive environments.
D. Electrogalvanizing
Features a thinner zinc layer with a bright surface, offering slightly weaker corrosion resistance than hot-dip galvanizing but at a lower cost.
E. Fusion-Bonded Epoxy Powder Coating
A single-layer epoxy powder coating with strong adhesion and chemical corrosion resistance, commonly used for buried pipelines.
F. Three-Layer Polyethylene Coating
Composed of an epoxy base layer + adhesive layer + polyethylene outer layer, it offers corrosion resistance and impact resistance, suitable for buried oil and natural gas pipelines.
G. Three-layer polypropylene coating
Structure similar to 3LPE, with a polypropylene outer layer, offering better high-temperature resistance, suitable for hot-water transmission pipelines.
H. Internal epoxy coating
Epoxy coating sprayed on the inner wall of steel pipes to enhance corrosion resistance and flow efficiency of transported fluids.
