Seamless vs welded pipe

Pipes made from seamless steel are made from solid round steel billets that are heated and pressed into hollow tubes using a form. A variety of sizes and schedules are available for seamless pipes. In spite of this, manufacturers are limited when it comes to manufacturing pipes with large diameters. In the manufacturing of pipe fittings, such as bends, elbows, and tees, seamless pipes are frequently used. Seamless pipes have no seams, so the entire diameter of the pipe can withstand high pressure no matter what. The welding line is usually the weakest part of the pipe.

Seamless steel pipe is ideally a solid metal tube with each end attached to another tube without any welding joints. There are two different types of threaded pipes: those with threads on one end and those with threads on both ends. In spite of this, the seamless pipe can carry its own weight as well as the heavy weight of the loaded pipe and still maintain its original structure due to the lack of a welding line. The unique strength and anti-bending feature of seamless pipes make them suitable for a wide range of commercial applications, including oil fields, offshore rigs, pressure vessels, shipbuilding, manufacturing, and chemical industries.

Stainless Steel Pipes are available in a variety of grades. The most commonly used stainless steel grades in the industry are stainless steel 304 pipes and stainless steel 316 pipes. Besides seamless steel pipes, these pipes are also available as welded steel pipes. A wide range of industries require high corrosion resistance in their pipes, and stainless steel 304 pipes are widely used for those applications. Pipes made of stainless steel 316 are mainly used in the marine industry.

In Industrial pipe and steel, HR coils are necessary for the fabrication of welded / ERW (electronic resistance welded pipe) steel pipes. Steel coils are cold formed into round cylindrical pipes by welding them together. As part of a continuous phase, the first plate or coil is rolled in a circular section with the help of a plate bending machine or roller. The pipe can be welded with or without filler material once the circular segment is rolled from the plate. It is possible to produce welded pipes in larger sizes without exceeding the upper limit. For the production of long-radius bends and elbows, welded pipe with filler material can be used. Despite being cheaper than seam pipes, welded pipes are also weak since they are welded together. In addition to transporting liquids, such as fuel and gas, ERW pipes play a crucial role in the world’s line pipe industry. When it comes to ERW pipe, one of the benefits is that only the tube billet ends are heated during manufacturing, so the whole piece stays clean and only the welding component needs cleaning. By reducing the post-welding cleaning process, the quality of the work is greatly improved, resulting in significant cost savings. Further, since ERW pipes have a nearly smooth and clean surface, coatings are simple to apply to them.

Seamless Pipe Manufacturing

The difference between welded and seamless tubing can also help determine which is the most suitable choice for a given application. Manufacturing methods for welded and seamless tubing are evident from their names alone. The definition of a seamless tube is that it does not have a welded seam. By extruding stainless steel billets into hollow tubes, the tubing is made from a solid billet of stainless steel. An oblong circular mold is formed from the billets, which are then hollowed in a piercing mill. An elongation rod is used to draw the molds through a mandrel rod while they are hot. Molds are enlarged by twenty times during the mandrel milling process to form seamless tubes. Pilger, cold rolling, or cold drawing are additional methods of shaping tubing.

Welded Pipe Manufacturing

In order to fabricate a welded stainless steel tube, strips or sheets of stainless steel must be formed into a tube shape and the seam must be welded longitudinally. Cold forming and hot forming are two methods of fabricating welded tubing. Compared to hot forming, cold forming produces a smoother finish with tighter tolerances. Regardless of the method, steel tubes made by either method are durable, strong, and corrosion-resistant. Cold rolling and forging can be used to further work the seam, or the seam can be left beaded. To produce a finer weld seam with tighter tolerances and better surface finishes, welded tubes can also be drawn similarly to seamless tubing.

Differences in Seamless & Welded Stainless Steel Pipe

Length: The length of seamless steel pipes is quite short, while the length of welded tubes can be extended for long periods of time.

Corrosion: There is usually no corrosion on seamless steel pipes until and unless they are exposed to highly corrosive environments, whereas the welding area of welded pipes is much more vulnerable to corrosion. Welded areas are known for their inhomogeneity, exhibiting greater dimensional variability, less corrosion resistance, and varying malleability. The corrosion resistance of seamless steel pipes is high because they prevent all these problems.

Cost: Raw materials, production equipment, and processes have generally raised the cost of seamless steel pipes over welded steel pipes. There are times, however, when market pressure makes welded pipes more expensive, so if you’re in a similar situation, don’t hesitate to choose a seamless steel pipe that is of the same size.

Appearance: There is a difference in appearance between seamless steel pipe and steel billet. In the hot rolling process, it is not possible to remove exterior surface defects of the billet, they are only removed after the billet is polished. It is only possible to partially remove the defect in the process of reducing the wall.
In the case of welded steel pipe made of the hot-rolled coil as raw material, the surface quality of the coil is the same as that of the pipe, so it is easy to manage. It has a superior surface quality due to its hot-rolled process. As a result, the surface consistency of welded steel pipes is a lot higher than that of seamless steel pipes.

Methods of molding: seamless steel pipes and stainless steel welded pipe have primarily different processes of molding. In the rolling process, seamless steel pipes can be formed in one step. Welded steel pipes are formed with steel strips or steel plates by bending and welding.

Performance: Seamless steel pipe can handle higher pressures than ERW welded steel pipe, and its strength is greater than that of welded steel pipe. Due to this, it is widely used in high-pressure equipment, as well as thermal equipment and boilers. There is generally a weak point in the welding seam of welded steel pipes, the quality of which has an impact on the overall performance. The working pressure of welded steel pipes is generally 20% lower than that of seamless steel pipes. The reliability of seamless steel pipes is the primary reason people choose them.

Usage: Pipelines in industrial settings are generally made from seamless pipes since they are subjected to extreme thermal, chemical, and mechanical loads. There are many industries that use welded pipes, including aerospace, automobiles, and electronics. These industries have comparatively low budgets and comparatively low workloads.

Welding performance: There is a difference in the chemical composition of seamless steel pipes and welded steel pipes when it comes to welding. I.e. ASTM defines only the basic requirements for the manufacture of seamless steel components.

Wall thickness and diameter: Thin-walled pipe with a smaller diameter and thickness, best produced by welding. It is better to manufacture a large thick-walled pipe by means of seamless fabrication.