Carbon steel ERW pipe vs SSAW pipe

When choosing between carbon steel Electric Resistance Welded (ERW) pipes and Spiral Submerged Arc Welded (SSAW) pipes, it's important to understand their differences in production process, raw materials, procurement costs, and geometric size. Here’s a detailed comparison.

Production Process

ERW Carbon Steel Pipe:

Process: ERW pipes are produced by continuously roll-forming hot-rolled coils. High-frequency current is used to heat the edges of the coil, which are then fused together under pressure from squeeze rollers.

Residual Stress: ERW pipes have minimal residual stress, which is further reduced through heat treatment, sizing, straightening, and hydrostatic testing. Residual stress does not affect the pipe’s performance during storage or use.

Weld Quality: No welding wire is used, so the weld's physical and chemical properties match those of the base material. The quality of the ERW pipe depends on the quality of the coil.

SSAW Carbon Steel Pipe:

Process: SSAW pipes are produced by spirally welding hot-rolled steel strips. The process introduces complex geometric stresses, sometimes reaching the yield limit of the steel.

Residual Stress: SSAW pipes have significant residual tensile stress, which, combined with the hoop stress from internal pressure, weakens the pipe's structural integrity.

Weld Quality: The weld is made with welding wire, leading to differences in physical properties and chemical composition between the weld and the base metal. This can cause stress concentration and potential defects.

Raw Materials

ERW Carbon Steel Pipe:

Raw Materials: Made from regular hot-rolled coils with stable chemical composition and physical properties.

SSAW Carbon Steel Pipe:

Raw Materials: Often made from lower-grade hot-rolled strips with unstable composition and properties. High-quality SSAW pipes are produced from regular hot-rolled coils, primarily by major manufacturers in the oil and petrochemical industries to ensure quality and safety.

Procurement Costs and Difficulties

ERW Carbon Steel Pipe:

Cost: For small to medium diameters (Φ114mm ~Φ355.6mm), ERW pipes are generally 8% to 15% less expensive than SSAW pipes.

Availability: Widely available due to the large number of manufacturers.

SSAW Carbon Steel Pipe:

Cost: More cost-effective for large-diameter pipes but less so for small to medium diameters.

Availability: Large manufacturers often do not produce small-diameter SSAW pipes, making procurement more difficult.

Geometric Size of Steel Pipes

ERW Carbon Steel Pipe:

Accuracy: Higher geometric accuracy, facilitating easier weld joint alignment during construction.

Weld Coefficient: 100% weld efficiency, with welds that are nearly invisible to the naked eye.

Surface: Smooth internal and external surfaces with no significant weld protrusion, ensuring good corrosion resistance and fluid transmission efficiency.

SSAW Carbon Steel Pipe:

Accuracy: Lower geometric accuracy, complicating weld joint alignment.

Weld Coefficient: 130% - 200% weld efficiency, with longer weld seams and higher defect rates.

Surface: Internal and external welds protrude about 0.3 mm, creating gaps that reduce corrosion resistance and increase flow resistance, leading to reduced pipeline transport efficiency.