What is the Advantage and Disadvantage of Welded Steel Pipes

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.

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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.

When comparing different types of stainless steel tubing, there are a few factors that should be taken into account. Today, we are going to address one of these factors to help you understand the difference between welded and seamless tubing. Just like many other metal products, the forming method changes the properties of the finished products in distinct ways. From strength and corrosion resistance to speed and cost of manufacturing, welded and seamless are uniquely suited for specific tasks.

Welded Stainless Tubing

Welded tubing is produced by rolling strips of stainless steel into a tube and then welding along its full length. After welding, the weld seam, or bead, can be refined by cold rolling and forging methods or left as is.

Cold forming results in smoother finishes and tighter tolerances. Welded tubing can even be drawn like seamless tubing to offer a better weld seam, and surface finish. Welded tubing can also be produced with thinner walls on larger diameter tubes, compared to seamless tubing. Because welded tubing requires less processing, it is typically quicker to produce as well as lower in cost than seamless tubing.

The down side of welded tubing comes in the form of high pressure and heavy wall applications. The long welded seam causes a stress concentration point, reducing pressure ratings to 80% of comparable seamless tubing. Also, the stainless material used to create welded tubing must be thin enough to roll effectively. Therefore, heavy wall tubing is less feasible as welded tubing.

Upside

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• Better lead times
• Tighter tolerances
• Lower cost
• Thinner wall, large diameter applications
• Available in longer lengths
• More consistent concentricity

Downside

• Heavy wall applications
• Slight impurities
• Less corrosion resistant
• Stress concentration

Seamless Stainless Tubing

         To make seamless tubing, the first step is to form a seamless pipe known as a hollow/mother tube. Starting with solid round stock, the billet is first drilled through then heated and forced through a narrow die. The center of the hollow tube is supported during this process by a long rod known as a mandrel. Next, the mother tube is put through a pilger mill.  This machine uses a pair of rolling dies and a second mandrel to elongate and reduce the tube to size.

This process can quickly reduce the tube cross section by as much as 90% in a single run. However, pilgering is not well suited for smaller diameter tubing.

For small diameter tubing, drawing is a better option. In this process, the mother tube is crimped for grasping on one end, then pulled through a narrowing die. By doing so, the tube is narrowed and elongated.

This process may need to be repeated several times to achieve the size reduction needed.

Seamless tubing can contain higher pressure because it does not have the large stress concentration point that welded tubing has. Additionally, seamless tubing often has a cleaner surface finish meaning it is less susceptible to pitting and corrosion. However, there are many more steps needed to manufacture seamless tubing. Because of this, seamless takes much more time to produce and can be more expensive than its welded counterpart.

Upside

• Superior corrosion resistance
• Higher pressure rating
• Durability
• Higher Purity
• No additional testing
• Ideal for critical applications

Downside

• Higher costs
• Not ideal for thin wall large diameter tubes
• Higher difficulty to manufacture
• Longer lead times

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