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A straight seam ERW tube mill is the predominant industrial method for manufacturing tubes with a single, longitudinal weld. Shijiazhuang Faith Machinery Co., Ltd. produces these mills, which are characterized by their ability to create a continuous, straight weld seam parallel to the tube's axis, using the electric resistance welding process.
The fundamental operation of a straight seam mill involves transforming a flat steel coil into a cylindrical form and then welding its edges together. The process begins with the uncoiling and leveling of the strip to ensure a flat, stress-free material enters the forming section. The forming station is comprised of a cascading series of roll stands. Each set of rolls incrementally bends the strip edges upward until the strip takes on a circular cross-section with the two edges meeting at the top, ready for welding.
The welding station is where the straight seam is created. In a high-frequency ERW mill, the open edges of the formed tube are brought together under pressure between two squeeze rolls. Simultaneously, a high-frequency electrical current is directed to the edges, either through contact shoes or an induction coil. The resistance to this current rapidly heats the edges to a forging temperature. The pressure from the squeeze rolls then forges the heated edges together, creating a solid-state weld without the use of filler metal.
Immediately after welding, the tube passes through a scarfing unit that trims off the excess material (flash) from both the inside and outside of the weld. This results in a smooth surface finish. The tube then proceeds to a cooling zone and subsequently to a sizing section. The sizing section, often consisting of several stands of rolls, calibrates the tube to its final diameter and ensures roundness. A flying cutoff saw finally cuts the continuous tube to the required length.
Straight seam ERW tube mills from Shijiazhuang Faith Machinery are utilized for producing a vast range of tubular products, from water and gas pipes to structural hollow sections. The straight seam weld is known for its efficiency and strength, making it a widely adopted solution across the construction and manufacturing sectors.
