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 |
