Seamless Steel Pipe vs. Welded Pipe: What Are the Differences?

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seamless steel pipe vs welded pipe

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

Stainless_Steel_Seamless_Pipe_and_Tube-commons-wikimedia

Credit: Jatinsanghvi, Common Wikimedia

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.

Applications

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.

The following are some areas of application that use specifically seamless steel pipes:
  • Chemical processing plants
  • Manufacturing oil and gas lines
  • Manufacturing medical equipment
  • Hydraulics
  • Nuclear power plants
  • Water purification plants
  • High temperature and pressure units
  • Sensitive measuring units

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.

At this point, the seamless steel pipe forms through the following process:
  • Hot rolled
  • Cold rolled
  • Cold draw

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.

Pros
  • Heavy and thick-walled
  • Has no welds
  • Corrosion resistance
  • Better ovality (roundness)
  • Durable
  • Better pressure capacity
  • No fusion metals used
  • No tests required for weld integrity
Cons
  • Shorter in length because of manufacturing difficulties
  • Size restriction with a nominal size of 24 inches or less
  • Costly
  • The extrusion process makes it rough
  • Inconsistent wall thickness

Welded Pipe Overview

welded pipe-pixabay

Credit: bbeavis, Pixabay

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.

Applications

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.

The following are some of the areas of application:
  • Architecture
  • Food and beverage processing industries
  • Automotive industry
  • Aerospace construction
  • Pharmaceuticals
  • Marine and fishing
  • Construction and mining
  • Pipelines

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.

Pros
  • It can be manufactured in longer lengths
  • Less costly
  • No size restriction
  • Smoother surfaces
  • Readily available
  • Shorter delivery time
  • Thinner walls
  • Lighter in weight
  • Tighter tolerance
  • Consistency in wall thickness
Cons
  • Welds are prone to corrosion
  • It can only withstand 20% less weight
  • Must be tested before use
  • Poor ovality

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
Economy Costly More economic
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.

Here are some tips to remember in your next order:
  1. Understand your environment – The environment that the metal pipe will be exposed to should determine which metal tubing you will purchase. If it is in a less corrosive climate, you can go for welded steel, but if it is in a highly corrosive environment, spending lots of money on seamless steel will be worth it because it will last longer.
  2. Plan ahead – Having an excellent work plan is key to saving you thousands of dollars. A simple technique will help you understand the exact quantity of metal pipes with all their intended dimensions. It, therefore, makes it easier to do procurement and place orders on time.
  3. Contact an expert – Whether you are sure of what you want or not, always seek a professional opinion just to be sure. Someone who has been in this field for decades has the kind of experience you will need to budget and buy the right thing. Contact our offices to learn about welded pipes and seamless steel
  4. Place your order on time – Placing orders earlier allows you to plan on your finances and enable you to purchase the right pipes. Placing an order is as simple as sending the pipe specs, getting your quotation, and within no time, you will receive your consignment.

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:


Featured image credit: Martinelle, Pixabay

Cameron Dekker
 

Cameron grew up in Allentown, Pennsylvania, a once-proud steel town on the Lehigh River, where he got a taste of TIG welding in his high school shop class. He holds certificates for Certified WeldingEducator (CWE) and Certified Resistance Welding Technician (CRWT) from the American Welding Institute. His interests include scuba diving, sculpture, and kayaking.