What is the difference between seamless and welded (ERW) pipe?

The core distinction between seamless and welded (ERW) pipe is their manufacture. Seamless pipe is produced by perforating and rolling solid steel billet, without any welding line, offering uniform structure and superior pressure capacity for harsh conditions with high pressure, high temperature and strict safety requirements. Welded pipe is made by coiled and welded steel strips with a longitudinal welding line, is cost-effective and efficient for common applications such as building structures, low pressure fluid transportation.

	Seamless Pipe	Welded Pipe
Manufacture Process	Round steel billet → Heating → Piercing → Rolling → Straightening	Steel strip → uncoiling → leveling → shearing&end welding → forming → ERW welding
Core Feature	Uniform structure Superior pressure capacity *Production cost relatively high	With a longitudinal welding line High production efficiency *Welds are potential weak links
Fatigue Strength	Very high (Uniform structure makes stress distribution uniform and less prone to fatigue cracks)	Relatively low (The welding line is a stress concentration point)
Pressure-bearing Capacity	Very high	Relatively high
Dimension Range	Limitation (common diameter range less than 660mm)	Flexible and extensive
Production Cost	Relatively high cost (energy consumption is high, the scrap rate is relatively high)	Low cost (continuous production, high efficiency, high material utilization)
Applications	Critical, high pressure, harsh working conditions	General pressure, structure, transportation conditions