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The difference between seamless steel pipe and welded steel pipe

Oct. 14, 2019

1. Different production processes

The welded steel pipes is welded by strip steel; the seamless pipe is perforated with a steel billet and there is no welded joint on the pipe. A welded steel pipe is a steel pipe which is welded and formed by a steel strip or a steel plate and deformed into a circular shape or a square shape, and has a joint on the surface. The blank used for welded steel pipes is steel or strip. The seamless tube is a long strip of steel with a hollow section and no seams around it.

2. Different capacity

The production capacity of seamless steel pipe is low; the production capacity of welded pipes is high. Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welded joints has been continuously improved, the variety specifications of welded steel pipes have been increasing, and more and more fields have replaced Seam steel pipe. Welded steel pipes are more efficient than seamless steel pipes.

3. Different price

Seamless tubes are more expensive; welded tubes are cheaper. Welded steel pipes are less expensive than seamless steel pipes. According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency electric resistance welded pipe, gas welded pipe, furnace welded pipe and so on.

1) According to the application: the seamless pipe is used for the flow pipe and pressure parts above 0.8MRa; the welded pipe can only be used for the flow pipe and structural pipe below 0.8MRa.

2) According to the source: the seamless pipe is made by punching and extruding the steel billet; the welded pipe is welded by strip steel.

3) According to the value: seamless pipe height; low welded pipe, seamless pipe than welded pipe is higher than 1500--2000 yuan / ton.

4) According to the naming: the seamless pipe is directly marked, such as Φ32X2.5 indicating a diameter of 32 and a wall thickness of 2.5; the welded pipe is marked with a nominal diameter (nominal size) "DNXX", such as DN32 indicating a diameter of 42.4, wall thickness, 2.75- -3.94.

The difference between seamless steel pipe and welded steel pipe

Thick Wall Seamless Steel Pipe

Selection of seamless tube welding methods

The choice of seamless steel pipe welding method should be selected according to the material and wall thickness of the seamless pipe. Different welding methods have different characteristics because of different welding methods with different arc heat and arc forces. For example, tungsten arc welding is characterized by low current density, stable arc combustion, good weld formation, especially suitable for thin plate welding, and thick plate welding is not an option; plasma arc is characterized by high arc column temperature and high energy density. The plasma arc has good straightness, and has a wide adjustment range of rigidity and flexibility, and the work is stable, but the operation is complicated; the submerged arc welding has the characteristics of deep penetration capability and high welding wire deposition efficiency, and thus the welding speed It can be greatly improved, the welding cost is low, but the working conditions and environment are relatively poor. It can be seen that different welding methods have different capabilities and different operating costs. According to the material and wall thickness of the seamless pipe, the reasonable selection of the welding method is a very important task to ensure the welding quality, increase the productivity and reduce the cost.

In addition, the same welding method, the type and size of the welding current, the arc voltage, the welding speed, and the welding materials used have a great influence on the arc heat and the arc force. Therefore, different welding methods can only be applied to welding of different materials and thicknesses.

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