Seamless pipe – hot rolling and cold drawing process

What is Seamless Pipe?

Seamless pipe is a metal pipe that is formed in one go through a whole round steel or steel ingot by perforating, rolling or extruding using a cold rolling or cold drawing process. It is a steel pipe without welds and has a stronger pressure-bearing capacity than welded pipes.

Seamless Steel Pipe Production process

The first step is to prepare the tube blank. Take the blank or round bar, and accurately control the carbon content between 0.1% and 0.25%. In order to avoid rolling cracks, the surface defect depth needs to be less than 0.5mm. Heating at extremely high temperatures makes it soft and elastic.
The second step is perforation. The blank has been heated to a soft texture and can be molded into any shape. The blank is perforated with a mandrel to make it look like a tube.
Seamless pipes are not welded pipes, so how to increase their size? Then the stretching process is used to stretch the tube blank.

Two processes for seamless pipes

Hot rolled seamless pipe

The hot rolled process is the most common type of seamless pipe, which is first hot rolled at 1000 degrees Fahrenheit and then straightened. The manufacturing process of hot rolled seamless steel pipe is similar to the above method, requiring the use of billets heated at extremely high temperatures.

Advantages

Hot rolling has fewer steps, faster production, higher efficiency, and cheaper pipes.
Hot-rolled seamless steel pipes have good mechanical properties, including tensile strength, compressive strength, and bending strength.
This grain structure gives the pipes ultra-high strength and ultra-long life, and a full range of specifications to meet the needs of different working conditions. Whether you need a small-size pipe section or a large-diameter pipe, you can quickly match the corresponding specifications.
The wall thickness of the hot-rolled steel pipe is uniform, and the tolerance is only within ±0.8% to ensure stable delivery of fluid/gas driven by circumferential pressure.

Disadvantages

The surface of the hot-rolled seamless steel pipe may be rough and uneven.
And there will be oxide scale, which looks not so beautiful, and the oxide scale treatment process is required.
The precision of the hot-rolled seamless pipe is slightly lower than that of other seamless pipes.

Cold rolled seamless pipe

First, the steel billet is hot rolled. Then, it is pickled to remove the scale and impurities, and then cold rolled to finally make a seamless pipe.
The cold rolling process compresses the material to make it hard and smooth. The cold rolling process is time-consuming and labor-intensive. Finally, annealing and surface treatment are required. These two processes make the material durable and beautiful.

Advantages

The dimensions of cold-rolled seamless pipes are very strict and the precision is very high.
The pipes are very clean and the surface treatment is very good.
High strength, uniform structure, suitable for use in high temperature and high pressure environments
The cold rolling process is famous for its excellent corrosion resistance and good corrosion resistance.

Disadvantages.

Because there are more steps, the cost is also a little higher, and the overall price is higher than similar products.
It is not suitable for welding and connection, so the scope of application of cold rolling is not as wide as that of hot rolling.

FAQs

1.seamless vs welded pipe？

The pressure bearing capacity and strength of seamless steel pipe are higher than those of ERW welded steel pipe. The weld of welded steel pipe is its weak link, and its quality will affect the overall performance.

2.‌What are the main application areas of seamless steel pipes?

Widely used in petroleum, chemical industry, machinery manufacturing, aerospace and other fields, especially suitable for high pressure and high temperature environments.

3.How to choose high-quality seamless steel pipes?

Check the surface for cracks, folds and other defects
Measure whether the dimensional tolerance meets the standards
Ask the supplier to provide material reports and test certificates

aiden.z

June 9, 2025

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