Welded VS. Seamless Steel Pipes: 5 Key Differences
What are the differences between welded VS. seamless steel pipes?
- Applications
- Manufacturing
- Pros
- Cons
- Cost
As industrial and construction applications continue to develop, so do the materials they use. Piping products and systems that are crucial in these applications have evolved and grown more complex, resulting in a variety of pipe manufacturing methods.
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Of all the types of pipes that exist, the most common and widely used products are welded and seamless steel pipes. Often, people wonder which is better for their application — which is why in this post, we discuss the differences between welded vs seamless steel pipes, and how to choose the best option.
Applications
Pipes are widely used in several industries today because they are highly functional and cost-effective products. They can be manufactured in different lengths and shapes, which allows them to be used in a variety of applications.
For welded steel pipes, the misconception is that they are much weaker as weld seams are perceived as a structural flaw. While it’s true that welds are a strength concern, welded pipes go through several quality assurance regimens to ensure that the welded pipe will perform as desired when its tolerances aren’t exceeded.
As a result, welded pipes are recommended for many different industries. Some of them are:
- Food and beverage manufacturing
- Pharmaceutical manufacturing
- Automotive industry
- Construction and mining industry
- Architectural design
- Pipelines
Seamless steel pipes offer unique mechanical properties — such as non-welded joints, uniform strength distribution, and increased pressure capacity — that allow them to perform reliably. They may be able to withstand more pressure, higher temperatures, and heavier weights than welded pipes.
As a result, seamless steel pipes are recommended in situations where environments may be more demanding, such as:
- Chemical processing
- Medical equipment manufacturing
- Oil and gas lines
- Hydraulic systems
- High temperature and pressure systems
- Nuclear power plants
- Water purification plants
Manufacturing
Welded steel pipes start as steel plates and steel strips, called skelp. These pieces are bent and formed using a bending machine and rollers. When it reaches the proper thickness gauge, it is cut to the desired length and formed into a flat rectangular sheet. The width of the sheet’s shorter ends is the pipe’s outside circumference. This measurement is then used to estimate the pipe’s eventual outside diameter.
The pipe pieces are then welded together — sometimes using filler material. Most welded steel pipes are also put through a heat-treatment process. Depending on the application, the pipe may be welded using automated methods, or through human labor. The method used determines the quality of the weld and the welded pipe as a whole.
Seamless steel pipes start as a round piece of steel called a billet. The billet is heated until pliant, then stretched, rolled, and pushed using a frame until the billet forms a hollow shape. Another method for making seamless steel pipes is by pushing the billet through a perforated tube.
From there, a seamless steel pipe may be formed using hot-rolling, cold-rolling, or cold-drawn processes. A hot-rolled seamless pipe goes from forging the billet, to perforating, to rolling, to shaping. This method is used to make thick and large diameter seamless pipes. Cold-drawn seamless pipes are used to create products that are smaller in diameter or have thinner walls. It may also be used to create pipes with smoother internal surfaces.
Pros
There are many advantages to using a welded steel pipe for your application, such as:
- Can be made in longer lengths — no sizing restrictions.
- Manufacturing is cost- and time-efficient.
- Generally has smoother surfaces.
- Products are easier to make, so they’re readily available.
- Shorter delivery time
- Has thinner and more consistent wall thickness.
- Is lighter in weight.
- Possesses tighter tolerances.
Likewise, seamless steel pipes offer their own unique advantages that may put them above welded pipes, depending on the application. These advantages are:
- Has thicker walls.
- Has heavier weight.
- Needs no welding. Thus, no additional metals or materials are needed.
- No tests are required for weld integrity
- Improved corrosion resistance and durability.
- Improved “ovality” — a.k.a. “Roundness,”
- Can withstand more pressure.
Cons
As with every metal product, welded steel pipes have their fair share of disadvantages, which are:
- Welds are more prone to corrosion.
- Must be tested extensively before use.
- Reduced ovality due to welding and manufacturing processes.
- Can’t withstand heavier weights or pressure.
Seamless steel pipes also have a few disadvantages that may make them unsuitable for your application, like:
- Restricted lengths and sizes due to manufacturing difficulties — nominal size is 24 inches or less.
- Manufacturing is costly.
- Seamless pipes may be more difficult to procure.
- The extrusion process creates a rough surface.
- Inconsistent wall thickness.
Cost
The cost of steel pipes heavily relies on raw material availability, the amount of labor needed for production, and the complexity of the manufacturing process. The mechanical properties of steel pipes also influence the product price. Altogether, seamless steel pipes are more expensive than welded steel pipes due to their improved strength, scarcity of raw materials, and labor-intensive manufacturing process.
However, pricing may also vary throughout the year due to market pressure. There will be times when welded pipes will go up in price and become more expensive than seamless pipes. In these cases, it may be appropriate to purchase seamless steel pipe in the same dimensions instead, if budget is a concern.
Key Takeaway
Now that we’ve evaluated welded vs seamless steel pipes, you may have enough information on their key differences to choose the right pipe for your application. If you have questions, message Supreme Pipe today. We are the leading manufacturer and supplier of steel pipes in the Philippines, and we can help you pick out the best products for your project.
Welded steel pipe, also called welded pipe, is a steel pipe made of steel plates or steel strips that are welded after being curled and formed. The production process of welded steel pipes is simple, the production efficiency is high, there are many varieties and specifications, and the equipment investment is low, but the general strength is lower than that of seamless steel pipes.
Since the s, with the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has continued to improve, and the varieties and specifications of welded steel pipes have increased day by day, replacing unfinished steel pipes in more and more fields. Sewing steel pipe. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld. Welded steel pipes are widely used in construction, petroleum, chemical industry, light industry, machinery and other fields. The following article will discuss the advantages and disadvantages of welded steel pipes in detail.
Advantages of welded steel pipes:
1. High efficiency and energy saving
The welding process of welded steel pipes uses advanced welding technology and materials, which results in high welding efficiency and low energy consumption. Compared with traditional pipes, it can greatly reduce costs and energy consumption. In addition, the specifications and length of welded steel pipes can be customized as needed, making them more convenient in transportation and installation.
2. Excellent mechanical properties
Welded steel pipes have thicker walls, higher strength and stiffness, and can withstand greater pressure and impact. At the same time, due to its excellent mechanical properties, welded steel pipes can be used in various complex terrains and environments, such as mountains, rivers, bridges, etc.
3. Good corrosion resistance
Welded steel pipes are specially treated and have better corrosion resistance. In corrosive media such as acids, alkalis, and salts, welded steel pipes can operate stably for a long time, ensuring the safety and service life of the pipeline.
4. Good pressure resistance
Another important advantage of welded steel pipe is its excellent pressure resistance. The use of welding technology makes the wall of the steel pipe uniform and dense, which can effectively improve the pressure resistance of the steel pipe and enable it to withstand greater internal pressure. Therefore, welded steel pipe is an indispensable pipeline material in some occasions that require high pressure resistance of pipelines, such as petroleum, natural gas, chemical industry and other fields.
5. High strength
Welded steel pipes use high-temperature fusion welding technology, which can effectively improve the strength and hardness of the pipe. The welded steel pipe not only has excellent strength and stiffness, but also can withstand greater pressure and load. Therefore, welded steel pipes are widely used in some situations that require high strength and stiffness of pipes, such as large machinery manufacturing, shipbuilding, pressure vessels and other fields.
6. Stable quality
Because welded steel pipes adopt a series of precise production processes and quality control measures, their quality is stable and reliable. In particular, the welding process adopts automated production technology, which greatly improves the quality stability of steel pipes, avoids many problems caused by different technical levels of workers or poor welding joint quality in manual welding, and ensures the quality of steel pipes and welding quality.
7. Convenient construction
Another advantage of welded steel pipes is that they are easy to construct and can quickly complete the pipe welding work and improve construction efficiency. Compared with traditional cast pipes, welded steel pipes have a more flexible construction method and can be cut and spliced as needed, making them suitable for various occasions.
8. Environmental protection and health
During the production and use of welded steel pipes, no harmful substances and odors will be produced. At the same time, due to its good corrosion resistance, it can reduce the cleaning and maintenance work of pipelines and reduce the impact on the environment.
9. Reusable
Welded steel pipes have thicker walls and can be reused multiple times after inspection and treatment. This not only reduces costs, but also reduces resource waste and environmental pollution.
10. Wide range of application
Welded steel pipes are suitable for various fields and industries, such as construction, petroleum, chemical industry, light industry, machinery, etc. Its excellent mechanical properties and corrosion resistance enable it to operate stably in a variety of environments.
Disadvantages of welded steel pipe: Seamlsss VS Welded Pipe
1. Welding is not firm
During the welding manufacturing process, if the welding technology is not up to standard, the joints may have problems such as incomplete penetration and unsealed welds, which may lead to water leakage, air leakage, etc. after welded pipe construction.
2. Susceptible to corrosion
Because the surface of the welded pipe does not receive special anti-corrosion treatment, if it encounters high humidity, high oxides and other environments during use, it is easy to cause rust and wear on the surface of the welded pipe. Compared with
seamless steel tubes, the welds of straight seam welded pipes are more susceptible to corrosion by chemical substances. During use, if harmful substances such as strong acids and alkalis are encountered, the metal structure at the weld may be corroded, resulting in pipeline failure, rupture, leakage and other safety issues.
3. Poor surface quality
Since the production process of straight seam welded pipes requires multiple processes such as billet curling, cold bending, and heat straightening, it is difficult to guarantee the surface quality of the pipes. For example, unevenness in the welding joint, residual moisture, grease and other impurities will adversely affect the performance and service life of the pipeline.
4. The pressure resistance is not as good as seamless steel pipe
There is a certain degree of stress concentration in the internal welds of straight seam welded pipes, but seamless steel pipes do not have this defect. This makes the straight seam welded pipe have limited pressure resistance under harsh conditions such as high temperature and high pressure, and is prone to cracks, deformation and other problems.