What is a Seamless Pipe?

Seamless pipes don’t have welding joints. They are made without a welding process. Because they don’t have welds, they are spotless, strong, and durable. Their production process is also different from that of welded pipes.

Understanding seamless pipes is a must. That is why I will write a wholly dedicated article on this topic. You’ll learn everything about these seamless pipes, from production to types. A lot of information is coming your way!

Seamless Pipe Manufacturing Process

Seamless pipes made with different materials are available in the markets. Common materials used in their making are stainless steel, carbon steel, and tungsten. These seamless pipes can also be made with some other alloys. Let’s discuss their production process.

  1. First, the billet or round bar is taken. For example, if we use stainless steel, the billet will be made from this material. This billet undergoes extreme heating at high temperatures. This makes it soft and flexible.
  2. Due to its softness, the billet can be transformed into any shape. So, heat is followed by piercing. In this process, the billet is pierced with a mandrel. The mandrel tools create holes in the cylindrical billet. This makes the billets like pipes.
  3. As you know, seamless pipes are not welded. So, to increase their size, elongation comes in handy. The manufacturer elongates the billet (changing it into a hollow tube) through stretching. Due to elongation, the length of seamless pipes increased.
  4. Keep in mind that no welding is involved in their production. Once the elongation process is completed, the pipes are cut into the required sizes. Every cut piece undergoes surface finishing and becomes ready to use.

Characteristics of Seamless Steel Pipe

Seamless pipes serve their purpose, no matter the material they are made from. They are considered superior options to the welded pipes. Let’s down and discuss the characteristics of seamless pipes:

  • These pipes are solid because they don’t consist of welds. No joints mean that the whole pipe remains safe when stress is applied to it.
  • The seamless pipes have exceptional rust resistance. Even if they stay used for years, they won’t get rusty. On the other hand, the welded pipes quickly get rusty from joints.
  • They have a more uniform structure both from inside and outside. This means that the flow of water and other fluids will be smooth. There won’t be pressure at a single point; instead, it will be divided equally throughout the pipes.
  • These pipes won’t have unequal thicknesses. The thickness and material quality will be the same on all sides, interior and exterior.
  • Due to their better strength, these pipes can easily bear high stress and pressure. No matter how fast fluids flow, they will always be in good condition.
  • Above all, these seamless pipes undergo a unique finishing process. So they look cleaner and more aesthetically pleasing. You won’t see any rough surfaces on their bodies.

Hot-Rolled Seamless Pipe

These seamless steel pipes are made through hot rolling at high temperatures.  They are considered the most common type of seamless pipe used in industries. The hot-rolled seamless steel pipe undergoes heat treatment and then straightening.

Accurately, the hot rolling of steel pipe is done at 1,000F or 538°C). The process for making hot-rolled seamless pipes is similar to the one stated above. They require a billet that undergoes heating at a very high temperature.


  • It is a cost-effective process for producing seamless pipes. The reason is that it requires fewer steps than other methods. Due to this, these pipes are also inexpensive.
  • This method manufactures very solid and durable pipes. This is due to the high-temperature graining of the material’s structure, which is perfect.
  • Such graining makes pipes super solid and durable.
    These pipes are available in various sizes to suit different people’s needs. Whether you need smaller pieces or bigger pipes, you’ll quickly find them.
  • The process of hot-rolling gives the pipes a uniform thickness. So, the fluid, gasses, etc., will follow by putting pressure on all sides of the pipes.


  • These pipes do not come with excellent surface finishing.
  • Hot rolling produces many scales on the surface of the pipes, making them look ugly. Therefore, they require a descaling process.
  • The hot-rolled seamless pipes are not precise. Their dimensional precision is significantly lower than all other types of seamless pipes.

Cold Rolled Seamless Pipes

The production of these cold-rolled seamless pipes is more complex. It requires multiple steps. In cold rolling, the pipe is treated at room temperature. Remember that this method also requires hot rolling of the billet.

First, the billet undergoes hot rolling. Then, it is subjected to a pickling process to remove its scaling and impurities. Once it is cleaned, it undergoes cold rolling, which forms it into seamless pipes.

This cold rolling step compresses the material, making it hard and smooth. The cold rolling process requires more time and energy. In the end, annealing and surface process fishing are conducted. These two processes make the material solid and pleasing in appearance.


  • These seamless pipes have tight dimensional tolerances. The hot rolled pipes lag in this aspect.
  • As I said, the material undergoes pickling to remove impurities. So, after the cold rolling, your pipes are very clean. Their surface finishing is second to none.
  • Cold-rolled seamless pipes are great for high-pressure and high-temperature applications. This is because they have excellent strength and a uniform structure.
  • Cold-rolled pipes are also known for their superior corrosion resistance. Both cold-rolled and hot-rolled seamless pipes offer excellent rust resistance.


  • The production of cold-rolled seamless pipes is costly. Due to this, the overall prices of these pipes are higher than those of their counterparts.
  • Their production process requires more energy, which is a big drawback.  It consumes more electricity than hot rolled pipes.
  • Cold-rolled seamless pipes are not suitable for welding or joining. This makes them less versatile compared to hot rolled pipes.
  • The production process of cold-rolled seamless pipes requires both cold and hot rolling. Moreover, it also involves annealing and pickling, making it less manufacturer-friendly.

Frequently Asked Questions

Q1: What is a seamless pipe used for?

They convey fluids and gasses under high pressure and temperature conditions. Their usage is extensive in the oil and gas industry.  This is not the end. These pipes serve many other sectors as well. Those include refineries, petrochemical plants, and power generation.

Q2: What does seamless mean in piping?

Seamless pipes mean that they don’t have any welds or joints. They don’t use any welding process during their manufacturing.

Q3: What is the difference between a seamless pipe and a regular pipe?

Seamless pipes are manufactured without any welding or joints. The “normal” or welded pipes are made by welding rolled steel sheets or plates. The seamless pipes are considered superior due to their better strength.

Q4: Is seamless pipe stronger than welding?

Yes, the seamless pipes are more robust. They have a consistent, homogeneous structure. They don’t have any welds or joints. The presence of those joins would have made them weaker.


It is no mistake that seamless pipes are the backbone of many industries. Unlike regular pipes, they are stronger and perform better under stress. Despite these advantages, many people need help understanding seamless pipes. This guide has everything for someone who wants to understand these pipes.