The difference between erw and seamless black steel pipe

In steel pipe manufacturing, ERW steel pipe and seamless black steel pipe are the two most common types of steel pipe. Although they appear similar, they differ significantly in manufacturing processes, performance, applications, and cost. Understanding the differences between the two will help you select the most appropriate steel pipe during engineering design and project procurement.

What is ERW Steel Pipe?

Electric Resistance Welded (ERW) steel pipe is formed by rolling steel and then welding it longitudinally along its length. Therefore, ERW steel pipe has a welded joint along its cross section.

1. Manufacturing Standards

Common standards include ASTM A500, A53, EN 10217, and GB/T 3091.

2. Length and Size

Common factory lengths are 6m or 12m, with wall thicknesses typically ranging from 1.0mm to 25mm.

3. Surface Treatment

Common options include black, galvanized, and epoxy-coated.

What is Seamless Black Steel Pipe?

Seamless black steel pipe is a hollow steel pipe made directly from a billet through piercing, hot rolling, or cold drawing, without welds. Seamless pipe is produced by extruding the metal to the desired length. Therefore, it has no joints along its entire cross-section.

1. Manufacturing Standards

Common standards include ASTM A106, ASTM A53, API 5L, EN 10210, and GB/T 8163.

2. Production Process

Hot-rolled seamless pipe: Pierced, rolled, and sized at high temperatures. Suitable for thick-walled or large-diameter pipes.

Cold-drawn seamless pipe: Cold-worked to achieve higher dimensional accuracy and better surface quality, it is commonly used in machining and hydraulic systems.

3. Definition of "Black Steel Pipe"

This refers to ordinary carbon steel pipe without galvanizing or coating, and has a black oxide scale.

Comparing ERW and Seamless Black Steel Pipe

1. Manufacturing Process Comparison

ERW Steel Pipe: Made from steel strips through high-frequency electric resistance welding, with longitudinal welds.

Seamless Black Steel Pipe: Made from a single steel billet through perforation and rolling, with no welds.

2. Dimensional Accuracy Comparison

ERW Steel Pipe: High dimensional accuracy and good roundness.

Seamless Black Steel Pipe: Hot-rolled pipes have lower accuracy, while cold-drawn pipes have higher accuracy.

3. Strength and Performance Comparison

ERW Steel Pipe: Weld strength is slightly lower than the parent material.

Seamless Black Steel Pipe: Uniform overall strength and strong pressure resistance.

4. Pressure Capacity Comparison

ERW Steel Pipe: Suitable for medium and low-pressure fluid transportation (≤7 MPa).

Seamless Black Steel Pipe: Can withstand high-pressure and high-temperature environments.

6. Appearance and Wall Thickness Comparison

ERW Steel Pipe: Uniform wall thickness, smooth appearance.

Seamless Black Steel Pipe: Variable wall thickness, with a high surface scale.

7. Cost Comparison

ERW Steel Pipe: Low cost, high production efficiency.

Seamless Black Steel Pipe: Higher cost, long production cycle.

8. Application Comparison

ERW Steel Pipe: Suitable for water pipes, gas pipes, structural pipes, and automotive pipes.

Seamless Black Steel Pipe: Suitable for boiler pipes, oil pipelines, hydraulic systems, and high-pressure equipment.

ERW Steel Pipe vs. Seamless Black Steel Pipe: How to Choose

When high strength, high temperature and high pressure resistance, or critical process applications are required, seamless black steel pipe is preferred.

When projects prioritize cost-effectiveness and production efficiency, ERW steel pipe is a good choice.

For structural applications (such as steel structures and building supports), ERW steel pipe is an ideal choice.

Summary

Although both ERW steel pipes and seamless black steel pipes play an important role in social construction, ERW steel pipes and seamless black steel pipes have different appearances, uses, and manufacturing processes.

Read more : Seamless vs welded pipe or ERW Pipe Specifications and Models