What is electric resistance welded tube?

Electric resistance welding (ERW) is a highly efficient and environmentally friendly steel pipe manufacturing process that joins metal components by applying an electric current. The ERW manufacturing process involves multiple steps, such as uncoiling, flattening, forming, welding, sizing, and cutting, to ensure the production of high-quality steel pipes that meet industry standards. ERW pipes are divided into low-frequency and high-frequency welding, offering advantages in cost-effectiveness, production speed, and versatility, and can be applied in various industries such as oil and gas, agriculture, and automotive.

What is Electric Resistance Welding (ERW)

Electric resistance welding (ERW) is a special welding process that uses the heat generated by an electric current to join metal components. This technology is particularly suitable for steel pipe manufacturing because it can precisely and efficiently join metal surfaces.

Depending on the specific application requirements, this process can employ low-frequency or high-frequency electric resistance welding. ERW is known for its high efficiency and low environmental impact, making it a highly attractive option in today's sustainable world. Electric resistance welded tubes are a prime example of the advantages of this process.

The core principle of ERW is to use an electric current to heat metal components, melting the contact surfaces and forming a strong weld. This method is particularly suitable for thinner materials, but can also weld components of varying thicknesses.

High-frequency welding (HFW) is a branch of ERW that introduces resistance heat through contact and induction, thereby improving production efficiency. Various factors, such as workpiece size, metal coating, electrode material, and welding parameters, affect the heat generated during ERW welding, ensuring customized solutions for different applications.

ERW Manufacturing Process

The manufacture of ERW steel pipes begins with the cold forming of flat steel strips into round tubes. This manufacturing process is renowned for its efficiency and cost-effectiveness, making it the preferred choice for steel pipe production. The process involves several key steps, each crucial to the quality and performance of the final product.

1. Uncoiling and Flattening

The manufacturing process of ERW (Electric Resistance Welded) pipes begins with the uncoiling and flattening of the steel strip. The steel coil needs to be uncoiled and cut before processing and welding, marking the beginning of the transformation from raw material to finished product. Uncoiling is a crucial step that ensures uniform thickness by flattening the steel strip, thus preparing it for subsequent processing. The flattening process is achieved by passing the steel strip through rollers, eliminating coil deformation and forming a flat steel strip, ready for subsequent processes.

Steel strip flattening ensures consistency and quality throughout the manufacturing process. Uniform thickness guarantees that subsequent forming and welding processes will not encounter problems due to material inhomogeneity. This initial step lays the foundation for producing high-quality ERW tubing, enabling it to be formed and welded into its final shape.

2. Forming and Welding

After the steel strip is uncoiled and flattened, the forming stage begins. This stage uses a series of rollers to gradually bend the flat steel strip into a cylindrical shape, ultimately forming a steel tube. The ends of the steel coil are butt-welded together to form a continuous steel strip ready for further processing. The forming process shapes the steel into a tube, preparing it for welding.

During welding, a high-frequency induced current generates a strong weld, tightly connecting the edges of the steel coil. This high-frequency current has skin and proximity effects, concentrating on adjacent surfaces, enhancing the strength and integrity of the weld. The heated edges of the steel are butt-welded to ensure a strong and durable weld.

3. Dimensioning and Cutting

After welding, the ERW steel pipe undergoes dimensional adjustment and straightening to meet specific customer requirements. This step ensures the pipe has the required outer diameter, wall thickness, and length. Dimensioning is crucial for producing steel pipes that meet precise specifications, whether for industrial or structural applications.

The final step in the manufacturing process is cutting the steel pipe to the required length. A flying saw is used for cutting, enabling continuous production without stopping the production line. This efficient cutting process allows for smooth delivery and installation of pipes to meet the precise needs of a variety of applications.

Types of Electric Resistance Welded Tubes

Electric resistance welded tubes, including electric resistance welded (ERW) tubes and high-frequency welded (HFW) tubes, can be classified into different types based on the welding method and the pressure applied during production. Understanding these classifications is essential for selecting the appropriate steel pipe for a specific application. They are mainly divided into two types: low-frequency electric resistance welded tubes and high-frequency electric resistance welded tubes, each with its unique characteristics and uses.

1. Low-Frequency Electric Resistance Welded Tubes

Low-frequency electric resistance welded tubes use a lower current frequency during the welding process, typically below 100 kHz. Compared to high-frequency ERW pipes, low-frequency ERW pipes typically have larger diameters and thicker walls, making them suitable for a variety of heavy-duty applications such as structural supports, oil and gas pipelines, and large-diameter water pipelines.

A key advantage of low-frequency ERW pipes is their ability to use thicker steel plates for welding, resulting in higher strength and durability. Furthermore, these pipes are typically manufactured using stainless steel and conform to standards such as ASTM A269 and A312.

Additionally, low-frequency ERW pipes exhibit less thermal deformation during welding, resulting in greater product stability. This stability makes them highly favored in industries requiring high-pressure applications, such as construction projects and manufacturing processes demanding robust and durable pipes.

2. High-Frequency Electric Resistance Welded Tubes

Compared to low-frequency ERW pipes, high-frequency ERW pipes are characterized by faster production speeds and higher weld quality. The high-frequency current during the welding process enables precise and efficient welding, making these pipes ideal for applications requiring high strength and precision.

Common applications for high-frequency ERW (Electrical Resistance Welded) pipes include those with extremely high dimensional and strength requirements, with nominal sizes typically ranging from 1/8 inch to 4 inches.

The high-frequency welding process ensures that the produced pipes meet stringent quality standards, making them suitable for high-pressure and high-stress applications. These pipes are commonly used in industries such as automotive, where precision and reliability are paramount.

Comparison of Electric Resistance Welded Tubes with Other Pipes

Comparing different types of steel pipes, such as electric resistance welded (ERW), electrofusion welded (EFW), and seamless steel pipes, reveals several key differences and advantages.

Electric resistance welded pipes utilize cold-formed steel sheets and are welded using high-frequency current, simplifying the production process and reducing costs.

In contrast, electrofusion welded pipes use fusion welding, making them more suitable for high-pressure and corrosive environments.

Seamless steel pipes are generally preferred in high-stress environments such as oil and gas due to their excellent resistance to high temperatures and pressures. However, electric resistance welded pipes have a wide range of applications, including water supply and drainage, HVAC, and structural framing.

Advances in electric resistance welded pipe manufacturing technology have also reduced the risk of manufacturing defects, thereby improving reliability.

FAQ

1. What are the main advantages of ERW pipe?

The main advantages of ERW steel pipe are its high cost-effectiveness, ease of installation, ample supply, and wide range of applications, making it suitable for numerous industries.

2. In which fields are ERW steel pipes used?

ERW steel pipes are widely used in oil and gas, agriculture, automotive, thermal power plants, and engineering fields such as fencing and scaffolding. Its versatility makes it an indispensable material in various industrial applications.

Summary

In conclusion, electric resistance welded tubes (ERW), with its advantages of high strength, high efficiency, and cost-effectiveness, has become an important component of various industries. Manufacturing processes, including uncoiling, flattening, forming, welding, sizing, and cutting, ensure that these pipes meet stringent quality standards. ERW pipes have a wide range of applications, divided into low-frequency and high-frequency types, suitable for many fields from oil and gas transportation to structural support.

Read more: ERW Pipe Specifications and Models or The Basic Principle of Welding ERW Pipe