An ERW pipe mill line is composed of various pieces of equipment, each playing a crucial role in the pipe manufacturing process. These machines are responsible for uncoiling, leveling, cutting, welding, and sizing steel strips to produce high-quality welded pipes. Below is an overview of the key equipment used in an ERW pipe mill line.
Uncoiler
The uncoiler disassembles the hot-rolled steel coil and sends it to the leveling machine. It operates in two ways: upper unwinding and lower unwinding.
Steel Strip Leveling Machine
The leveling machine ensures the strip is leveled before forming. Typically composed of upper and lower machine bases and a transmission device, it features five or seven rollers. In welded pipe production lines, pinch rollers are often installed before the leveler.
Head Cutting and Butt Welding Machine
To maintain continuous production, the head and tail of the steel strips must be trimmed neatly using a shear butt welder. This device welds the trimmed strips together, enabling uninterrupted production.
Storage Looper
A storage looper is installed to store the strip steel, allowing continuous production even while the head and tail of the strips are cut and welded. It keeps the production line running without interruption.
Horizontal Looper
The horizontal spiral looper is suitable for strip steel thicknesses of 0.4–16mm, accommodating pipe specifications from 14–610mm. It consists of various guiding and roller systems, offering benefits such as minimal deformation of the strip and easy maintenance.
Disc Shears
Disc shears trim both sides of the strip to meet the width and straightness requirements for the forming machine. Key components include cutting edges, width adjustment mechanisms, and guide rollers.
Edge Milling Machine
For strips thicker than 10mm, edge milling ensures proper welding quality by shaping the strip edges for optimal welding conditions. The equipment consists of milling cutters, a control system, and a transmission system.
Forming Machine
The forming machine is responsible for shaping the steel strip into a pipe form before welding, using straight seam resistance roll forming.
Rollers
Rollers are essential in shaping high-frequency welded pipes. They are divided into cast and forged types based on their manufacturing method. The quality of the rollers significantly impacts product quality and production costs.
High-Frequency Welding Device
Using the skin and proximity effects of high-frequency current, this device rapidly heats the metal to a molten state for welding. It typically operates within a frequency range of 300–450 kHz and a power range of 100–1000 kW.
Sizing Machine
The sizing machine consists of horizontal and vertical roll racks that ensure the accuracy of the pipe's outer diameter and cross-sectional shape, improving stress concentration and reducing residual stress.
Internal Burr Removal
This device removes weld burrs from the pipe. A two-way hydraulic internal burr removal system is commonly used, with a ring knife preferred for cutting.
Weld Heat Treatment
To normalize the weld and heat-affected zone, intermediate frequency heat treatment machines are used. This process eliminates welding stress and improves the mechanical properties of the weld.
Length Cutting Machine
The cut-to-length machine allows for high-precision cutting of pipes and profiles. The cutting can be done using sawing, rotary cutting, or punching, with servo drive systems controlling the length.
Steel Pipe Straightening Machine
After sizing, the pipe may still have some curvature. A roller straightening machine is typically used to straighten the pipe by repeatedly bending it through straightening rollers.
Pipe End Flat Head Chamfering Machine
This machine trims the burrs and imperfections left on the pipe ends after cutting. It mills the ends of the pipe to create a flat, chamfered surface suitable for subsequent processes.
Hydraulic Testing Machine
The hydraulic testing machine is essential in welded pipe production. Its basic operation includes feeding, clamping, filling, pressurizing, holding pressure, releasing, and discharging. Modern machines are PLC-controlled, automating each step and recording test results. Hydraulic testing machines can have two types of seals: radial and end face. Radial seals use a pressure-expanded sealing ring for reliable clamping and minimal axial force but are more complex. End face seals are simpler and more versatile but demand higher sealing material performance and precise control.
Ultrasonic Flaw Detection
This non-destructive method detects internal material defects by using ultrasonic waves, which diffract when encountering interfaces of varying density.
Eddy Current Testing
Eddy current testing is mainly used for small-diameter ERW pipes, offering high-speed, non-contact flaw detection. It excels at detecting surface defects but is less effective for internal or layered defects. Impedance plane technology can also analyze defect depth and location.
By integrating these machines into the production line, ERW pipe mills ensure efficient, continuous production of high-quality welded steel pipes.
United Steel Industry As the most important steel pipe manufacturer and exporter in China, in the past 20 years, we have completed more than 100 projects, with partners in more than 100 countries, and established relationships with oil and gas and EPC companies in many countries business relationship.
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