Classification and application of welded steel pipe

Types of Welded Steel Pipes:

Welded steel pipe also called welded pipe, is a steel pipe in which the edges of steel plates or strip coils are welded into a cylindrical shape. According to the welding method and shape, welded steel pipes can be divided into the following categories:

Longitudinal welded steel pipe (LSAW/ERW): It is divided into two types: LSAW and ERW pipes according to different production processes. Longitudinal welded steel pipe is a steel pipe in which the edges of steel plates or strip coils are butted and then welded in a straight line. This kind of steel pipe has good strength and low production cost, but its strength is slightly lower than that of the spiral welded steel pipe of the same specification.

a. LSAW steel pipe (Longitudinal submerged arc steel pipe) is a steel pipe with a weld seam parallel to the longitudinal direction of the steel pipe. It is made of hot-rolled or cold-rolled steel plates or steel strips that are curled and welded. The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. Straight seam steel pipes are widely used in water supply projects, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction.

b. ERW steel pipe (Electric resistance welded steel pipe) uses the skin effect and proximity effect of high-frequency current to heat and melt the edge of the pipe blank after the hot rolled coil is formed by a forming machine, and presses it under the action of a squeeze roller Welding to achieve production. ERW has the characteristics of high efficiency,low cost,material saving and easy automation,it is widely used in aviation, aerospace, energy, electronics, automotive, light industry and other industrial sectors, is an important link in the welding process.

Spiral Welded Steel Pipe (SSAW): Spiral welded steel pipe is a steel pipe in which strip steel is rolled into a cylinder and welded in a helical direction. This kind of steel pipe has higher strength, but the production cost is slightly higher.

The main uses of welded steel pipes are as follows:

1. Conveying pipelines: Welded steel pipes are widely used to transport oil, natural gas, gas, water and other fluids, especially in urban gas and water supply systems.
2. Structural pipe: Welded steel pipes are used in engineering fields such as building structures, bridges, steel frames, and supports. They have good bearing capacity and shock resistance.
3. Machinery manufacturing: Welded steel pipes can be used to manufacture various mechanical parts, such as shafts, brackets, conveyor rollers, etc.

4. Oil and gas drilling: Welded steel pipes can be used in the manufacture of oil and gas drilling and oil production equipment, such as drill pipes, casings, etc.

5. Tower Fabrication: Welded steel pipes are used in the fabrication of broadcasting and communication towers.
6. Greenhouses: Welded steel pipes are often used in the manufacture of supports for greenhouses due to their lower cost and better strength.
7. Bicycle and motorcycle manufacturing: Welded steel pipes are used to make the frames of bicycles and motorcycles.
8. Furniture manufacturing: Welded steel pipes can be used to produce various furniture such as bed frames, bookshelves, chairs, etc.

In short, welded steel pipes have a wide range of applications, and their uses depend on the type, specification and material of the steel pipe. When selecting welded steel pipes, the appropriate steel pipe type should be determined according to actual needs and engineering environment. At the same time, the installation, use and maintenance of steel pipes are also key factors affecting their performance and service life, and relevant specifications and standards need to be strictly followed.

Welded Steel Pipe VS Seamless Steel Pipe

Method for identification of seamless and welded steel pipes:
 
Common steel pipe mainly has two forms of seamless steel pipe and welded steel pipe. In the process of engineering construction, appropriate steel pipes will be selected according to the specific construction situation, and the cost will be the primary factor.
 

1) Manufacturing process
Seamless steel pipe is mainly a solid tube billet or steel ingot for perforation, made of wool tube, and through hot rolling, cold rolling, cold drawing and other processing, and then formed seamless steel pipe. Since seamless steel tubes contain a members section, this hollow section can be used as a conduit for transporting fluids.
 
 A Welded steel pipe is generally a steel strip or steel plate under the action of external force, make it into a round or square, and then weld the surface joints, thus forming a welded steel pipe. The commonly used processes are arc welding, high or low frequency, cold rolling and so on, but the use of these processes for welding will lead to welded steel pipes. At present, according to the shape of welding seam can be divided into straight seam and spiral welded steel pipe, but the two use different technology. The spiral steel pipe is welded by submerged arc welding, which has the advantages of high welding efficiency and less dust. For high frequency or low frequency welding, mainly based on the principle of electromagnetic induction, due to the ac charge in the conductor will occur adjacent and turbine heat effect, can achieve the welding edge of steel to melt state, the final completion of welding.
 

2) Appearance difference
In appearance, the difference between seamless steel pipe and welded steel pipe is that the inner wall of the welded pipe has welding ribs, while seamless steel pipe does not. Seamless steel pipe pressure is higher, welded pipe is generally about 10 MPa. Seamless steel tube is formed once in rolling. Welded steel pipes need to be rolled and welded, generally spiral welding and direct welding. Performance seamless tube is better. Of course, the price is higher.

3) Wall thickness
The precision of seamless steel pipes is low and the wall thickness is relatively thick. The steel pipe of welded steel pipe has high precision and the wall thickness is usually thin.

4) Price
Seamless steel pipes are more expensive than welded steel pipes because the production process of seamless steel pipes is more complex and their costs are higher.

5) Performance characteristics
Seamless steel pipe: Because there are no welded joints, seamless steel pipe generally performs better in high temperature, high pressure, and corrosive environments. They are suitable for applications requiring high strength and high corrosion resistance, such as oil and gas transmission, chemical industry and high-pressure boilers. 

Welded steel pipe: The performance of welded steel pipe often depends on the quality of the weld. Although they can be used in many applications, welded joints can become a potential source of corrosion and weakness. However, with proper welding techniques and corrosion protection, the risk of these problems can be reduced. In terms of corrosion resistance, pressure bearing, high temperature resistance and other properties, seamless steel pipes are better than welded steel pipes.

6) Applicable fields
Seamless steel pipe: Due to their high-performance characteristics, seamless steel pipes are often used in applications that require a high degree of reliability and safety, such as nuclear power plants, high-temperature and high-pressure vessels, and chemical equipment.
Welded steel pipe: Welded steel pipe is suitable for some general engineering and low pressure applications such as building structures, hydraulic transmission and general piping systems. They are usually more affordable.

Seamless steel pipes and welded steel pipes each have advantages in different application areas. When selecting pipe materials, engineering needs, performance requirements, and cost factors need to be considered to determine which type of steel pipe is more suitable for a specific project.

Go here to learn more about: Welded steel pipe production process