ERW steel pipes are straight-seam welded pipes formed by high-frequency resistance welding of hot-rolled or cold-rolled steel strips. They feature narrow welds, high dimensional accuracy, and low cost, making them suitable for medium- and low-pressure fluid transportation and general structural applications. LSAW steel pipes, on the other hand, are made from thick steel plates, formed by JCOE or UOE processes and welded using submerged arc welding. They offer a wider range of pipe diameters and wall thicknesses, higher weld quality, and greater pressure resistance, and are primarily used in critical projects such as high-pressure, long-distance oil and gas transportation. Today, let's take a look at the other differences between these two types of steel.
Differences between ERW pipes and LSAW pipes
Straight seam welded steel pipes can be divided into LSAW (straight seam submerged arc welding) steel pipes and ERW (straight seam high frequency resistance welding) steel pipes according to the welding process. Baowi-steel welded steel pipe manufacturer will introduce the differences between ERW and LSAW steel pipes from the following four aspects. Read on to learn more.
1. Raw materials and production capacity
The raw materials of ERW steel pipes are hot-rolled steel coils, while the raw materials of LSAW steel pipes are hot-rolled steel plates. Therefore, ERW steel pipes can achieve continuous operation on the assembly line, with high production efficiency and low production cost; while submerged arc welded steel pipes are made from steel plates, which cannot achieve continuous operation on the assembly line, with low production efficiency and high production cost. ERW steel pipes are limited by the thickness of the steel coils, and the maximum thickness that can be produced is generally 25mm, and the maximum diameter that can be produced is 660mm; while the maximum thickness that can be produced by LSAW steel pipes is 40mm, and the maximum diameter that can be produced is only limited by the width of the steel plate, with a maximum production diameter of 1422mm.
2. Welding
ERW steel pipe welding does not require welding wire; LSAW steel pipes require welding wire.ERW welding relies on high-frequency electrical current, which can be AC or DC depending on pipe size and thickness. High-frequency welding is particularly suitable for thin-wall pipes and smaller diameters. Because no welding wire is used, the weld zone undergoes recrystallization rather than full melting, which helps maintain uniform material properties.
LSAW welding uses submerged arc welding, often with multi-wire configurations such as three-wire or four-wire systems. Although filler metal is used, the heat input is carefully controlled, and the flux shields the weld from atmospheric contamination. Multi-wire welding also helps reduce residual stress and improves weld toughness.
In addition, LSAW forming methods differ:
UOE: U-forming → O-forming → internal & external welding → expansion
JCOE: Incremental pressing → pre-welding → final welding → cold expansion
HME: Mandrel rolling with “C-C-O” forming followed by welding
Each method is selected based on pipe size, grade, and application requirements.
3. Appearance
The inner and outer welds of ERW steel pipes need to be removed, which is beneficial for corrosion prevention; the inner and outer wall welds of LSAW steel pipes have extra height, which is not conducive to corrosion.
4. Procurement cost and difficulty
ERW steel pipe procurement cost is lower, while LSAW steel pipe cost is higher, and the general price difference is 15%-25%.Because of their higher strength and reliability, API standards restrict certain pipeline zones to LSAW pipes only, especially for Class 1 and Class 2 areas such as densely populated cities, mountainous terrain, and coastal regions.ERW welded pipe production benefits from streamlined production lines, thus improving efficiency. ERW welded pipe also has lower raw material procurement and processing costs, and steel coils are easier to handle than steel plates. Furthermore, ERW welded pipe can often be sourced locally, while LSAW welded pipe may require importation.
Conclusion
In short, the main differences between ERW and LSAW steel pipe come down to raw materials, welding technology, size limitations, performance, and cost:
ERW is cost‑effective, fast to produce, and suitable for smaller diameters.LSAW is higher performance, ideal for large diameters and high‑pressure use, but comes with greater cost.Choosing between ERW and LSAW should depend on project specifications, pressure requirements, size needs, and budget considerations.
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