Seamless Steel Pipe vs. Welded Pipe: What Are the Differences?
Last Updated: March 16, 2021
With the ever-evolving industrial applications, piping systems and products have become widely used in numerous construction sectors. Manufacturers have doubled their production rate over the past decade to keep up with the market demands.
Pipe molding can only follow two specific techniques that result in either seamless steel or welded pipe. Crude raw material such as ore or scrap metal cast into ingots is the first step. The last step of the fabrication process is to shape the pipes by extending the seamless tube.
There is a thin line between seamless steel and welded pipes. This article will provide a detailed overview of each, the advantages and disadvantages, their differences, application, and when to use them.
Seamless Steel Overview
A seamless steel pipe is made of a single piece of metal, and it does not have a jointed steel pipe on the surface. As its name suggests, seamless steel pipe does not have a seam (crease) or a welded joint.
Seamless steel pipes are characterized by a perfect finishing that is flawless and desirable, resulting in higher demand. They are manufactured in circular, rectangular, or square shapes, and the pipes are tubular (hollow) since most of them carry flowing substances such as gases, liquid, slurries, and powders.
Seamless steel is strong and durable because it does not weld, neither does it have joints; this implies that the pipe has a uniform structure that ensures even distribution of strength.
Seamless steel pipes use specific applications because of their unique properties such as uniform strength distribution, non-welded joints, and their ability to withstand high temperatures, pressure capacity, high quality, better weight limit, and many more.
How is a Seamless Steel Pipe Made?
Seamless steel pipe manufacture is from a round and robust piece of steel known as a billet. The billet has to be heated first, then stretched and finally pushed or rolled over a frame or form until the pipe is hollow.
Seamless steel pipes (ASTM and API 5L) adopt their shape by passing through a perforated tube.
A hot rolled seamless steel pipe manufacture is from forging billet, perforating, rolling, and shaping. The tubing is manufactured through an industrial extrusion process and is used to manufacture thick-walled seamless steel pipes and large diameter pipes.
On the other hand, cold drawn seamless steel pipes use the cold-drawn technology, which is suitable for pipes that are of small diameter and thin-walled since they have a lower material strength. It is also useful when the goal is to manufacture a stunning pipe with a smooth internal surface. During the extrusion process, the seamless steel pipes can only roll using a low alloy structure, carbon structural steel, or an alloy structure.
Some seamless steel pipes often harden during the manufacturing process; in such cases, the manufacturer will not use heat treatment methods.
Welded Pipe Overview
Welding steel pipes is a multi-million dollar industry. It is growing every day to cater to the endless demand for the welded tubings. Luckily, today several sectors are involved in the mass production of welded steel pipes.
Welded steel pipes are always available in plenty because of their lower production cost and raw materials availability. It is, therefore, one of the most widely used metals in the world. Its application in different industries and the manufacture of numerous products. Examples of ASTM or API 5L welded steel pipes include SSAW pipe, ERW steel pipe, and LSAW pipe.
Many people confuse the ERW pipe with seamless steel because it does not use fusion metals, the weld seam is not always visible, and you cannot feel it. On the contrary, a Double Submerged Arc Weld (DSAW) leaves evident traces of weld beads, which can be eliminated using different processes depending on the application method.
Welded steel pipes are widely used in several industries because they are cost-effective. They can also be manufactured in different lengths and welded from different tubing shapes. Application is entirely dependent on the use and other related factors.
How is a Welded Steel Pipe Made?
Most welded steel pipes are from steel plates and steel strips. These strips and plates are made by moving steel loops and coils with a proper thickness gauge to form a leveled material. The flat leveled material is then measured and cut to the desired lengths.
The process starts with bending the steel plate, and then it is welded to the desired shapes, be it a circle, rectangle, square, and many more using a progression of bending machines or rollers. The metallic pipe weld using a powerful energy source. Some pipes can also be welded together with filler material. Most welded steel pipes must pass through the heat treatment process.
The weakest piece of a welded steel pipe is always the joints. The weld joint’s quality determines the quality of a welded pipe—welding with a robot mostly in automated production lines such as in the automobile industry. Alternatively, for stronger steel pipe welds, human labor has proven to be perfect; for example, in aerospace construction.
Seamless Steel vs. Welded Pipes
The seamless steel and welded pipes manufacturing process are different, and both have got other properties. Study the table below to determine which steel pipe you will choose to help you get the desired outcome.
|Seamless Steel Pipe||Welded Steel Pipe|
|Length||Shorter because of manufacturing difficulties||Can be manufactured in various sizes and lengths|
|Pipe Surface||Rough surface as a result of the extrusion process||Smoother surfaces|
|Production Process||Complex with longer manufacturing and procurement time||Simpler with a short manufacturing and procurement time|
|Application||High temperature, high pressure, sensitive units, and corrosive environment||Low pressure, less corrosive environment, lower budgets|
|Tests||No tests required||Must be tested before use|
|Shape||Better ovality, round||Poor ovality|
|Diameter||Thicker diameter||Thinner diameter|
|Strength||Capable of withstanding very high pressure||Can only withstand 20% less stress because of the welds|
|Size||Nominal size of 24 inches or less||No size restrictions|
|Availability||Less available because of limited raw materials||Readily available because of availability of raw materials|
|Internal Surface Check||Internal surface checking is impossible||Internal surface check before the manufacturing process|
|Molding Process||Can be manufactured one time in the rolling process||Manufactured with steel strips and plates that weld after bending|
|Preferred Field of Application||High-pressure equipment manufacture, industrial boilers,||Aerospace, automobile, electric, the construction industry|
|Welds||No welds||ERW, SSAW, LSAW, DSAW|
Cost of Seamless Steel vs. Welded Pipe
Strength and durability are some of the factors that determine the cost of both welded and seamless tubing. Seamless steel is stronger than welded pipes, making it more expensive because of the higher production cost.
On the other hand, welded steel pipes are easier to manufacture due to the cheaper cost of production and raw material availability. Also, the production process of seamless steel is complicated and time-consuming. Since each of the tubings has its unique features, advantages, and disadvantages, there is need to learn about acceptable purchasing practices to develop a reasonable budget.
Healthy Purchasing Practices for Seamless Steel and Welded Pipes
Good purchasing habits go a long way in cutting on material costs by minimizing any metal pipe waste. It also ensures that the best material completes the job.
How to Choose Pipes, Seamless or Welded?
With the insight provided here, you now have the relevant knowledge to help you settle for the right pipe. It is also imperative to remember that quality overrides quantity, so plan and purchase seamless steel pipe if required and consider welded pipes if all factors favor it. In a nutshell, environmental factors and the intended use determine the best pipe.
After the delivery, you might be interested in doing some welds; here are some welding tips that will help you keep safe.
Other comparison articles you may be interested in:
- Auto-Darkening vs. Passive Welding Helmet: Which Is Better?
- Welding Goggles vs Helmet: Which to Choose?
Featured image credit: Martinelle, Pixabay
- Seamless Steel Overview
- How is a Seamless Steel Pipe Made?
- Welded Pipe Overview
- How is a Welded Steel Pipe Made?
- Seamless Steel vs. Welded Pipes
- Cost of Seamless Steel vs. Welded Pipe
- Healthy Purchasing Practices for Seamless Steel and Welded Pipes
- How to Choose Pipes, Seamless or Welded?