Basic Concepts and Process Differences
ERW steel pipe
The raw material of ERW steel pipe is hot-rolled coil, which adopts cold bending forming process. High-frequency current is used to heat and weld the edge of steel plate. During the production process, the temperature must be kept constant at room temperature, and the welding length must be consistent with the length of the steel pipe.
Seamless steel pipe
Seamless steel pipe is a steel pipe without any welding seam on the whole pipe body. It is processed by hot rolling and cold drawing to perforate the solid steel billet. If there are defects on the surface of the billet, it needs to be polished in the finished product stage. The forming temperature is as high as 800℃.
ERW vs Seamless Pipe：Comparison of Physical Properties
ERW pipe vs seamless pipe：dimensional accuracy
- Outside diameter tolerance
ERW steel pipes adopt cold bending forming process combined with 0.6% diameter reduction and sizing technology. Thanks to the stable forming temperature and standardized production process at room temperature, the outer diameter tolerance can be accurately controlled within the range of ±0.05mm.
Seamless steel pipes adopt high-temperature hot rolling forming process above 800℃. Affected by the thermal expansion and contraction of materials and roller wear, the outer diameter fluctuation range increases significantly, and the tolerance range is difficult to accurately control.
- Wall thickness tolerance
ERW steel pipes are made of high-precision hot-rolled strip coils. Through continuous cold rolling process, the wall thickness tolerance is ≤0.05mm, and the transverse wall thickness uniformity error is less than 0.05mm/m.
Seamless steel pipes are limited by the round billet perforation process, and the wall thickness deviation can reach ±5-10%, especially at the pipe end. Local thickening or thinning is prone to occur.
ERW pipe vs seamless pipe：Surface quality
- Surface quality comparison
ERW steel pipe adopts high-frequency resistance welding technology. During the forming process, precise mechanical processing is used to achieve smooth inner and outer walls without marks. There is no obvious bulge in the weld area after annealing.
However, due to the hot rolling perforation process, the seamless steel pipe is prone to residual spiral rolling lines, subcutaneous pores and inclusions and other original defects on the pipe body, which need to be polished or cut by grinding wheel for surface finishing.
- Geometric accuracy difference
ERW steel pipe is formed by cold bending and combined with 0.6% diameter reduction and sizing process. The outer diameter tolerance can be controlled within ±0.05mm, and the roundness error is ≤0.25% 14.
Seamless steel pipes are affected by temperature fluctuations (above 800℃) and mold wear in the hot rolling process, and are prone to outer diameter deviations of ±0.1-0.3mm, and ovality defects of 0.5-1.2% may be formed under asymmetric cooling conditions.
ERW vs Seamless Pipe：Differences in mechanical properties
Seamless pipe vs ERW pipe：tensile properties
- Strength
Seamless steel pipes are usually at the upper limit of the standard and have relatively high strength.
ERW steel pipes have more balanced strength indicators due to microalloying smelting and controlled rolling processes. - Plasticity:
The elongation of ERW steel pipes is 33.3% higher than the API standard,and the plasticity of seamless steel pipes is inferior to other steel pipes.
Seamless vs ERW pipe：weld quality
- ERW steel pipes use ultrasonic online detection and weld annealing hormones, so the weld toughness is very high, and the FATT (ductile-brittle transition temperature) value is close to the parent material (-70~-80℃)
- Although seamless steel pipes have no welds, the internal structure may be uneven due to the use of hot rolling process.
Application Scenario Selection
Application scenario selection
ERW steel pipe application areas
Scenarios requiring high-precision dimensions and surface quality, such as automobile transmission shafts and furniture structural parts;
Medium and low-pressure fluid transportation (oil, gas, water treatment) and building support structures.
Core advantages of seamless steel pipes
High-pressure and high-temperature environments (such as boiler pipes and oil drilling casings);
Mechanical parts with high overall uniformity requirements (bearings, hydraulic cylinders).
ERW vs Seamless Pipe
index | ERW Steel Pipe | Seamless steel pipe |
cost | High production efficiency and low price | The process is complicated and the cost is high |
reliability | Weld quality is controllable and defect rate is low | No risk of stress concentration in welds |
Applicable scenarios | Medium and low pressure conventional environment | Extreme working conditions (high pressure/high temperature) |
Identifying Seamless or ERW pipe
If you want to identify seamless pipe or ERW pipe, you can use the markings on the side of the pipe. For example, in the ASTM A53 standard, type S indicates seamless pipe, and type E indicates ERW pipe. However, different standards have different markings, so please consult our pipe experts for assistance.
You can also make a preliminary judgment by observing the uniformity of the wall thickness. Seamless pipe has uneven thickness due to the perforation process, while ERW pipe is formed through high-precision molding with a uniform thickness.
Pandapipe is a pipe supplier with over 20 years of experience in pipe manufacturing. Our products meet international standards such as ASTM, API, and EN, and are customizable for diameters from DN15 to DN2000. If you require ERW, seamless pipe, or other types of pipe, please contact us using any of the contact methods at the bottom of this website.
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