Comparison between seamless pipe and erw pipe

When selecting the appropriate type of steel pipe for a specific application, understanding the differences between seamless pipes and ERW pipes is crucial. Both types are widely used in various industries, but they differ significantly in terms of production processes, material properties, and performance characteristics. Below is a detailed comparison between seamless pipes and ERW pipes, highlighting their key differences.

1. Appearance
Seamless steel pipes often retain surface defects from the original billet that cannot be fully removed during the hot rolling process. These defects can only be partially polished after the pipe is produced, leaving behind traces such as spiral paths from piercing. On the other hand, ERW steel pipes are made from hot-rolled coils, which have a consistently high surface quality. As a result, ERW pipes generally have a much better surface finish compared to seamless pipes.

2. Outer Diameter Tolerance
ERW steel pipes are cold-formed, with the sizing process completed by a 0.6% reduction at room temperature. This method allows for precise control of the outer diameter, resulting in minimal fluctuations. In contrast, seamless steel pipes are formed through a hot-rolling process at approximately 800°C, making it difficult to control the outer diameter accurately. Factors such as raw material composition and cooling conditions contribute to a wider fluctuation range in diameter.

3. Wall Thickness Tolerance
ERW steel pipes are manufactured using hot-rolled coils, which can achieve a thickness tolerance within 0.05mm due to modern hot-rolling techniques. Seamless steel pipes, however, are produced through round steel perforation, leading to greater deviations in wall thickness. Even with subsequent hot rolling, the best achievable control is within ±5-10% of the target thickness.

4. Ovality
ERW steel pipes are cold-formed, resulting in a precise outer diameter and small fluctuation range. Seamless steel pipes, being hot-rolled, are subject to variability in outer diameter due to the raw material composition and cooling conditions, leading to greater ovality.

5. Tensile Test
Both seamless and ERW steel pipes meet API standards for tensile properties, but seamless pipes typically exhibit higher strength at the upper limit and lower plasticity. ERW pipes, however, achieve a better balance of strength and plasticity due to advanced metallurgical processes such as microalloying, refining, and controlled rolling.

6. Hardness
The controlled rolling process used in producing ERW steel pipes ensures uniform performance across all parts of the coil, resulting in consistent hardness.

7. Grain Structure
ERW steel pipes, made from hot-rolled strips with a compact structure and fine grains, benefit from controlled rolling techniques. These ensure a uniform grain size, unlike seamless pipes, where the grain structure can vary significantly.

8. Collapse Resistance
Due to the uniform wall thickness and superior ellipticity of ERW steel pipes, they exhibit higher collapse resistance compared to seamless steel pipes.

9. Impact Test
ERW steel pipes typically have better impact toughness than seamless pipes. By optimizing parameters like welding speed and heating power, the welds in ERW pipes can achieve impact energy close to that of the base metal, enhancing their overall toughness.

10. Blasting Test
ERW steel pipes perform better in blasting tests due to their uniform wall thickness and outer diameter, often exceeding standard requirements.

11. Straightness
ERW steel pipes benefit from cold working and online straightening, resulting in better straightness. Seamless pipes, formed in a plastic state, often have less consistent straightness, especially at the ends.

12. Steel Usage Efficiency
ERW steel pipes have uniform wall thickness, leading to negligible tolerance differences. In contrast, seamless pipes require an increased wall thickness to meet minimum standards, resulting in 5-10% more steel usage for the same casing length. Therefore, ERW pipes can be more cost-effective, saving up to 10% in material costs.

This comparison highlights the advantages and disadvantages of seamless and ERW pipes, providing valuable insights for making informed decisions based on specific application requirements.