The piping products and systems have had to keep up with the changes and evolution in industrial applications as they’ve become more complicated.
Although there are a variety of pipe manufacturing technologies, the most common debate in the industry pits Welded steel pipe with seamless steel pipe (SMLS). For decades, both production technologies electric resistance welded steel pipe and seamless steel pipe have been used in the industry. Over the years, their process of development has advanced.
As it is understood by the name itself, the differences between the seamless and welded pipes lie majorly in their basic production procedure.
Formation of Seamless Steel Pipe
A seamless steel pipe is a type of steel pipe formed of a single piece of metal with no jointed steel pipe on the surface. The hot rolled tube, the cold rolled tube, the cold drawn tube, the extruded tube, the top tube, and the like are all differentiated according to the production technique.
Seamless steel tubes are split into two groups based on their cross-sectional shape: round and irregular, and special-shaped tubes come in a variety of complicated shapes such as square, oval, triangular, hexagonal, melon-shaped, star-shaped, and finned tubes.
Formation of Welded Steel Pipe
Welded pipe begins as a skelp, a long coiled ribbon of steel. The skelp is cut into a flat rectangular sheet of the desired length. The outer circumference of the pipe will be determined by the width of the sheet’s shorter ends, a value that may be used to compute the pipe’s eventual outside diameter.
Manufacturing techniques for welded pipes have developed over time. The move to high-frequency electric currents for welding is perhaps the most significant advancement. Low-frequency current was employed prior to the 1970s. Low-frequency ERW weld seams were more susceptible to corrosion and seam failure. But with advancements, these are giving a tough competition to seamless pipes.
Seamless vs welded steel pipe differences
- Length: Due to manufacturing challenges, seamless pipes are generally shorter in length whereas welded pipes manufacturing can be done in long continuous lengths.
- Corrosion: Corrosion resistance, whether good or poor, is also dependent on the alloy composition. Welded Pipe corrosion resistance and fully heat-treated seamless pipe have the same chemical makeup. A seamless steel pipe does not show signs of corrosion until it is exposed to a highly corrosive environment, but the weld area in welded tubes is far more susceptible to corrosion attacks.
- Appearance: Steel billet is the raw material for a seamless steel pipe. The hot rolling method cannot remove the outer surface defects of the billet. It is only polished once the product gets completed. These defects can be partially eliminated in the wall reduction process.
Welded steel pipe is formed from the hot-rolled coil as raw material, and the surface quality of the coil is identical to that of the pipe, making it simple to manage. As a result, the surface quality of welded steel pipe is far superior to that of seamless steel pipe.
- Molding Process: In the rolling process, seamless steel pipes can be manufactured once.
Steel strip or steel plate is bent along with several other welding processes to create welded steel pipe.
- Performance: Seamless steel pipes are widely used in high-pressure equipment, and thermal boiler industries as they have better pressure capacity and strength whereas
Welded steel pipes can withstand 20% less pressure than seamless steel pipes. Welded pipes are favored in the aviation, automobile, and electronics industries, where work pressure on the pipes is relatively low.
- Diameter and Thickness: The majority of Chinese seamless steel pipe manufacturers provide original seamless pipe sizes with a maximum OD of 20 inch and a maximum diameter of 508 mm. Because of equipment usually being smaller than 16 inch, 406.4 mm. If the client wants to buy more seamless steel pipe than the above diameters, hot expanding machining will be used. However, the quality of this type of hot expanded seamless steel pipe is usually inferior to that of the original seamless steel pipe.
Welded steel pipe, on the other hand, has no such constraints, with sizes ranging from 1-1/2 inch 48.3mm to 100 inch 2540 mm.
- Cost and Prices: Because of the raw material, production equipment, and processes, seamless steel pipes are usually more expensive than welded steel pipes. However, the welded pipe is occasionally more expensive due to market pressure, so if you find yourself in this position, don’t hesitate to purchase a seamless steel pipe of the same size.
Conclusion: Which one is better to buy?
A seamless tube is made from a billet that has been extruded and drawn, whereas a welded tube is made from a strip that has been roll-shaped and welded into a tube. Welded tube is far less expensive than the seamless tube, and it comes in long continuous lengths. The moulding processes for seamless steel pipe and welded steel pipe are primarily different. Welded steel pipe, such as water pipes, is often welded through the flat plate after bending up, and you can see a seam in the above; the diameter spiral weld is generally thicker. The seamless steel pipe is made by stretching molten steel through the annular slit of the backlog before treatment processes like moulding, so there are no seams. It is frequently used for high voltage devices due to its superior performance, particularly due to its bearing capacity, when compared to regular steel. Hydraulic equipment and piping connections, for example. Weld quality affects the entire performance of the main variables, and the weld area of welded steel pipe is its weak link.
Despite the fact that improved production technologies have recently made welded pipes equivalent to seamless pipes, seamless pipes are still preferable in the vast majority of cases. Welded pipes are chosen for large pipeline applications (>24 inch NPS) because they are less expensive. For pipe selection, numerous other parameters like as diameter to thickness ratio, availability, corrosion resistance, and so on are taken into account in addition to cost.