The Difference Between Precision Steel Pipe and Seamless Steel Pipe

In mechanical processing, hydraulic, and pressure service piping projects, there is an increasing demand for high-precision pipes, which has now become a procurement challenge.  Even when the correct pipes are ordered, there are often discrepancies in the precision grade.

The key point is this:

lSeamless steel pipes have no welds and are manufactured by stamping/rolling from round steel bars.

lPrecision steel tubes require strict control over outer diameter/tolerance and surface quality, and are typically manufactured using cold drawing or cold rolling processes.

Comparison Table

Definitions of Precision Steel Pipe and Seamless Pipe

What is a Precision Steel Pipe?

Precision steel tubes have strict dimensional control, including outer diameter, inner diameter, wall thickness, straightness, and ovality, and some even require specific surface finishes.  Commonly used EN standards include seamless cold-drawn tubes (EN 10305-1) and welded cold-drawn tubes (EN 10305-2).

What is a Seamless Steel Pipe?

Seamless steel pipes refer to steel pipes without any welds. They are typically made by inserting a round steel bar into a piercing machine for perforation, and are also known as hot-rolled steel pipes, reaching their final dimensions through this process.

Key Differences Between Precision Steel Pipe and Seamless Steel Pipe

Manufacturing Process

We'll use a case we encountered to explain this problem: why do size/surface issues still occur even though I specifically requested seamless steel pipes?

lThe traditional seamless steel pipe production process involves heating the round steel, then piercing, rolling, sizing, straightening, inspection, and finishing. This process results in a strong structure, but the dimensions and surface finish largely depend on whether hot rolling or cold rolling is used.

lThe manufacturing process for precision steel tubes involves hot piercing, followed by cold drawing, then heat treatment (+C +LC +SR +A +N), and finally straightening, cutting, and inspection to meet stricter tolerance requirements.

If your project has strict requirements for inner and outer diameter tolerances, seamless precision steel tubes are more suitable, as you can specify the required precision standards and tolerance levels.

Surface Quality

We will continue to explain with examples: our pipes are experiencing leakage, poor plating adhesion, and inconsistent friction.

Typically, after seamless steel pipes arrive, their surface may meet pressure requirements, but the pipe's sealing performance is not optimized, which is critical in hydraulic systems. Hydraulic systems are highly sensitive to the outer diameter accuracy, roundness, and surface defects of the pipe material when using compression/flared/compression-type fittings:

lOversized/undersized outer diameter, large ovality → Unstable ferrule engagement, uneven flaring fit → Prone to leakage even after tightening on-site.

lSurface scratches/pitting, eccentric wall thickness → More likely to cause cracking at the flared end or incomplete sealing surface.

Precision steel tubes are subject to strict standards. Hydraulics is a field where precision steel tubes are frequently used.  For this reason, EN has specifically created the EN 10305-4 standard for hydraulic system tubing. Taking the 37° flare fitting as an example, this standard emphasizes that these fittings provide a metal-to-metal seal in hydraulic systems and are performance-verified according to pressure ratings.

Mechanical Properties

Let's continue with the example: the steel pipe passed the tensile test, but it cracked during the forming process.

The steel pipe passed the tensile test, but cracked during bending or flaring. The main reasons are likely low elongation, high residual stress caused by cold working, and surface defects.

So why don't precision steel tubes have this problem? Because EN 10305-1 clearly specifies the delivery conditions and mechanical property requirements to address these risks. +SR indicates stress relief, +A indicates annealing, and +N indicates normalizing, which can generally increase ductility.

In addition to these aspects, EN 10305-1 also strengthens the control over surfaces and defects, classifying defects exceeding the minimum wall thickness as non-conforming products, thus significantly reducing the risk of cracking during use.

Therefore, if your project involves bending, flaring, or fatigue-sensitive conditions, please specify your delivery conditions and testing standards, referring to EN 10204 3.1.

Applications of Precision Steel Tube and Seamless Pipe

Uses of Precision Steel Pipe and Tube

Seamless precision steel tubes are commonly used in automotive, machinery, and hydraulic transmission systems, such as in automotive shock absorber tubes and chassis components, as well as hydraulic/pneumatic components.

Uses of Seamless Steel Pipe

Seamless pipes are used in applications such as oil and natural gas transportation, and as supports for high-end furniture.

Choosing Between Precision Steel Pipe and Seamless Pipe

If you're having trouble deciding, TORICH Group can recommend pipes that meet your project requirements, including (precision tubes and standard seamless tubes, as well as suitable delivery terms), and provide a quotation with clear inspection document requirements, ensuring that the materials you receive meet your production needs. Contact us today!