Seamless Steel Pipe is made of a’ billet’ solid round steel that is heated and pushed or pulled over a form until the steel is molded into a hollow tube. Seamless pipes are produced in a range of sizes and schedules. Nevertheless, the manufacturing of large diameter pipes is limited. Seamless pipes are commonly used in pipe fitting manufacturing, such as bends, elbows, and tees. The welding line is usually the weakest part of the pipes, but a seamless pipe does not have a seam, so that the pipe’s entire diameter can bear high pressure equally.
Ideally, the seamless steel pipe is a solid metal tube with each end attached to another tube, without any welding joint. Such pipes have threads at either one end or can be threaded to both the ends of hollow tube or pipe. However, due to the lack of the welding line, the seamless pipe can bear its own weight and the heavy loaded weight and retain its original structure. Seamless pipe is widely used in a range of commercial applications due to its unique strength and anti-bending feature, not only in oil fields but also in shipbuilding, offshore rigs, pressure vessels, manufacturing, chemical industries and so on.
These Steel Pipes are found in various Stainless Steel Grades. Some of the most used Stainless Steel Grades in the industry are Stainless Steel 304 Pipes and Stainless Steel 316 pipes. These Stainless Steel pipes are available in both, Seamless and welded options. The Stainless Steel 304 Pipes are widely used for applications in industries where they require high resistivity to corrosion. The Stainless Steel 316 Pipes are mostly used in Marine Industries.
HR Coils are needed for the manufacture of Welded / ERW (electronic resistance welded pipe) steel pipes. Welded Pipe is produced by cold forming the steel coil into a round cylindrical pipe. In the case of a continuous phase, the first plate or coil is rolled in the circular section with the aid of a plate bending machine or by a roller to produce a welded pipe. Once the circular segment is rolled from the plate, the pipe may be welded with filler material or without it. Welded pipes can be produced in large sizes without the upper limitations. Welded pipe with filler material may be used to produce long radius bends and elbow. Welded pipes are cheaper than the seamless pipe, and are also weak due to welding. ERW is usually used to transport liquid, such as fuel and gas, and plays an important role in the world line pipe transporting fields. As for the ERW pipe, one of the greatest benefits is that during the manufacturing process only the tube billet ends are heated, so the whole of the ERW pipe stays clean and only the welding component needs to be cleaned. This decreases the post-welding cleaning process, significantly increasing the quality of the work and saving costs. Furthermore, due to the nearly clean and smooth surface, ERW pipes are simple to apply with the coating method.
Differences in Seamless & Welded Stainless Steel Pipes
- Length: The seamless steel pipe is fairly short in length, while the welded tubes can be produced in long continuous lengths.
- Corrosion: The seamless steel pipe usually shows no signs of corrosion until and unless it is exposed to a highly corrosive condition, whereas the welding area of the welded pipe is much more susceptible to corrosion attacks. The welded area is known to be inhomogeneous and thus demonstrates varying malleability and less resistance to corrosion as well as greater dimensional variability. A seamless steel pipe prevents all such problems and thus provides a high resistance to corrosion.
- Costs and prices: The cost of seamless steel pipes is typically higher than the cost of welded steel pipes due to raw materials, production equipment and processes. But sometimes the market pressure makes the welded pipe more costly, so if you’re in a situation like this, don’t hesitate to buy a seamless steel pipe of the same size.
- Difference of appearance: seamless steel pipe uses the steel billet as raw material. The exterior surface defects of the billet cannot be removed by the hot rolling process, it is only polished after the product has been completed. In the course of reducing the wall, the defect can only be partially removed.
Welded steel pipe made of hot-rolled coil as a raw material, the surface quality of the coil is just the surface quality of the pipe and simple to manage. The surface of the hot-rolled coil is of superior quality. Thus welded steel pipe surface consistency is a lot higher than a seamless steel pipe.
- Molding Methods: seamless steel pipe and welded pipe have primarily separate molding methods. A seamless steel pipe can be formed in one time, rolling process. Welded steel pipes are made with steel strip or steel plate by bending and various welding methods.
- Performance: Seamless steel pipe has better pressure capacity, strength is higher than ERW welded steel pipe. So it is widely applied in high-pressure equipment, and thermal, boiler industries. Generally, the welding seam of the welded steel pipe is the weak point, the quality affects overall performance. In general, welded steel pipes can withhold 20% less working pressure than seamless ones. This reliability is the prime factor why people go for a seamless steel pipe.
- Usage: As a matter of fact, all the industrial pipelines are done with seamless pipes only because the pipes undergo extreme thermal, chemical and mechanical workloads. Welded pipes are more preferred in aerospace, automobile and electronics industries where the budget is comparatively low, and so is the work pressure put on the pipes.
- Welding performance: Average Welded Pipe and seamless steel pipe the chemical composition has a certain difference. The production of a seamless steel component is only ASTM the basic requirements.
- Wall thickness and diameter: Small thin-walled pipe preferably by welding production. A large thick-walled pipe is best made with the seamless method.