I. Classification of ERW Steel Pipes
There are numerous types of welded steel pipes, among which ERW steel pipes are widely used in production processes. The following is a core classification method to help you quickly understand the key points of selection:
i. By Core Application
Fluid Conveyance Pipes: Used for conveying low-pressure fluids such as water, gas, and oil (municipal, gas, irrigation).
Oil and gas industry pipes: Used in oil and gas extraction, transportation, and gathering systems (oil well pipes, gathering pipelines).
Construction structural pipes: Used for building support, frameworks, and piling (bridges, docks, high-rise buildings).
Mechanical manufacturing pipes: Used to manufacture automotive chassis, mechanical brackets, and other structural components.
Other specialized pipes: Such as exhaust systems, boilers, chemical equipment, etc.
ii. By key material
Carbon steel pipes (ERW carbon steel pipes): Such as Q195/Q215/Q235, with good weldability and moderate strength, the most widely used.
Low-alloy high-strength steel pipes: Such as L245/L360/L555, enhanced in strength and toughness by adding alloy elements (commonly used in oil and gas, structural applications).
Stainless steel pipes: such as 304/316, with strong corrosion resistance, used in corrosive environments.
Other special material pipes: such as alloy steel, heat-resistant steel, meeting specific performance requirements.
iii. By weld seam type
Straight seam welded pipes (ERW LSAW pipe): the weld seam is parallel to the pipe axis, with a simple and efficient process, suitable for medium and small diameter pipes.
Spiral welded pipes: The weld seam is spiral-shaped, with a longer weld length, enhancing the strength and toughness of large-diameter pipes.
iv. By surface protection
Hot-dip galvanized steel pipes: Zinc coating for corrosion protection, suitable for humid environments.
Plastic-coated pipes: Plastic coating for corrosion resistance and wear resistance.
Painted pipes: Enhances weather resistance and appearance.
Uncoated pipes (untreated): Suitable for general dry environments.
v. By execution standards
Domestic standard pipes: Compliant with national standards such as GB/T 3091, GB/T 14980, etc.
International standard pipes: Compliant with API 5L (pipeline pipes), API 5CT (casing pipes), ASTM A53, EN 10217, etc.
II. Core Process Advantages of ERW Steel Pipes
The high-frequency resistance welding (ERW) process utilizes the principle of electromagnetic induction, leveraging the unique effects of high-frequency current (skin effect, proximity effect) to instantly heat the edges of the tube blank to a molten state, followed by compression to achieve solid-state bonding. Compared to traditional welding methods, its significant advantages include:
(1) Ultra-fast welding: The fusion process takes only a few seconds, with production line speeds exceeding 80 meters per minute, far surpassing the efficiency of arc welding.
(2) Superior strength: Rapid heating significantly reduces the heat-affected zone, minimizes oxidation, and typically achieves weld strength exceeding 95% of the base material, ensuring reliable performance.
(3) Wide application: It can efficiently process various materials such as carbon steel and stainless steel, perfectly meeting diverse needs from high-pressure oil and gas transmission pipelines to building structural supports (structural welded pipes). As one of the most mainstream production methods for circular welded pipes, it is particularly suitable for large-scale production of standardized building welded pipes and fluid transmission pipes.
III. ERW steel pipe specification sheet
| Model | Outer Diameter (mm) | Wall Thickness (mm) | Length (m) | Steel Grade | Applicable Standard | Application Field |
|---|---|---|---|---|---|---|
| ERW-1 | 21.3 | 1.5 - 3.0 | 6 - 12 | Q195/Q215 | GB/T 3091 | Construction, Decoration |
| ERW-2 | 33.4 | 2.0 - 4.0 | 6 - 12 | Q235 | GB/T 3091 | Low-pressure Fluid Conveyance |
| ERW-3 | 48.3 | 2.5 - 5.0 | 6 - 12 | Q345 | GB/T 3091 | Mechanical Manufacturing |
| ERW-4 | 60.3 | 3.0 - 6.0 | 6 - 12 | L245 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-5 | 88.9 | 3.5 - 8.0 | 6 - 12 | L290 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-6 | 114.3 | 4.0 - 10.0 | 6 - 12 | L360 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-7 | 168.3 | 5.0 - 12.0 | 6 - 12 | L415 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-8 | 219.1 | 6.0 - 16.0 | 6 - 12 | L450 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-9 | 323.9 | 8.0 - 20.0 | 6 - 12 | L485 | GB/T 9711 | Oil and Gas Conveyance |
| ERW-10 | 406.4 | 10.0 - 25.0 | 6 - 12 | L555 | GB/T 9711 | Oil and Gas Conveyance |
IV. Differences between straight seam high-frequency resistance welded steel pipes and seamless steel pipes
| Characteristics | ERW Straight Seam Welded Pipe | Seamless Pipe |
|---|---|---|
| Dimensional Precision | High control precision of outer diameter and wall thickness, small size fluctuation, uniform wall thickness | Difficult to control outer diameter and wall thickness, wider size fluctuation range |
| Mechanical Properties | Strength and ductility are well matched, high elongation | High strength, but difficult to balance strength and ductility |
| Grain Structure | Fine grains, dense structure, no columnar crystal zone | Larger grain structure, slightly poorer uniformity of structure |
| Weld Quality | Short weld seam, fast welding speed, small heat-affected zone, high quality | No weld seam, uniform overall performance |
| Production Efficiency and Cost | High production efficiency, low cost | Complex production process, high cost |
| Application Scenarios | Urban gas, crude oil pipelines, structural pipes, etc. | High-pressure oil and gas transportation, offshore platforms, etc. |
