Selecting the wrong type of steel pipe can lead to equipment failure, project delays, or even safety incidents—a scenario no engineer wants to face. In industrial manufacturing and mechanical engineering, pipe selection is critical. While ERW (Electric Resistance Welded), DOM (Drawn Over Mandrel), and seamless pipes may appear similar at first glance, they differ significantly in manufacturing processes, performance characteristics, and application scenarios.
ERW pipes are manufactured through resistance welding, a process widely used for producing round, square, and rectangular pipes. The manufacturing process involves:
- Steel strip preparation: Uncoiling and edge trimming for proper width and weld preparation
- Roll forming: Shaping the strip through rollers into the desired cross-section
- Resistance welding: Heating edges to over 2000°F (1093°C) under pressure to create the weld
- Weld flash removal: Eliminating excess weld material from the outer surface
- Sizing and straightening: Final dimensional adjustment and straightening
- Cutting: Cutting to required lengths
ERW pipes typically use SAE 1010 steel, with cold-rolled (CREW) steel preferred for wall thicknesses below 0.060 inches (1.52mm) and hot-rolled (HREW) for thicknesses above 0.083 inches (2.11mm). Internal weld flash is often retained ("flash-in"), which may affect fluid flow in certain applications.
- Pros: High production efficiency, lower cost, mature welding technology, wide applications in structural support and fluid transport
- Cons: Lower pressure capacity and corrosion resistance compared to seamless pipes, internal flash affects fluid flow, strict welding quality requirements
DOM refers to a finishing process rather than a steel type, typically using SAE 1020 or 1026 steel. The manufacturing process begins like ERW but includes additional refinement:
- ERW welding: Initial pipe formation identical to standard ERW process
- Complete flash removal: Both internal and external weld flash elimination
- Cold drawing over mandrel: The key differentiator—drawing the pipe through a die with internal mandrel support to enhance dimensional accuracy, surface finish, and mechanical properties
The cold drawing process optimizes grain structure, improving strength and toughness while achieving superior dimensional precision. The refined weld seam often makes DOM pipes appear seamless.
- Pros: Excellent dimensional accuracy, superior surface finish, enhanced mechanical properties, good weldability; ideal for hydraulic cylinders, bearings, and precision components
- Cons: Higher production costs, remains technically a welded pipe with potential limitations in extreme pressure environments
True seamless pipes contain no weld seam, created by piercing solid steel billets. They come in two main variants:
Typically made from SAE 1018 steel, CDS pipes undergo additional cold drawing after hot rolling for exceptional dimensional accuracy and surface finish—perfect for precision applications.
Usually made from SAE 1026 steel, HFS pipes have rougher, scaled surfaces and lower dimensional precision but offer cost advantages for non-critical applications.
- Pros: Superior strength and pressure capacity, excellent corrosion resistance, no weld-related defects, ideal for high-pressure/temperature environments
- Cons: Highest production costs, lower dimensional precision than DOM pipes, complex manufacturing with lower efficiency
Consider these factors when choosing pipe types:
- Budget: ERW for cost-sensitive applications with moderate requirements
- Precision: DOM or CDS for high-accuracy needs
- Pressure capacity: Seamless for high-pressure or extreme conditions
- Application: Match pipe characteristics to specific use cases (hydraulics, automotive, construction, etc.)
ERW pipes offer economical solutions for general purposes, DOM provides precision for demanding applications, while seamless pipes deliver maximum strength for critical environments. Understanding these differences enables informed material selection decisions.