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A steel pipe manufacturing machine, more accurately referred to as a pipe mill or tube mill, is an integrated production line that transforms raw steel into finished pipes through a continuous, highly automated process. These machines, such as those built by Shijiazhuang Faith Machinery Co., Ltd., systematically perform a sequence of operations to ensure dimensional accuracy and material integrity in the final product.
The production process begins with material preparation. A large coil of steel strip, which is the raw material, is loaded onto a decoiler. The leading end of the strip is fed into the mill line, often passing through a cropping shear that squares off the end to ensure a clean entry into the next stage. The strip then travels through a precision leveling machine. This unit is equipped with multiple small-diameter rolls that flex the steel back and forth beyond its yield point, effectively removing any coil memory, curls, or crossbow. A flat, stress-free strip is essential for consistent forming and high-quality welding.
The next critical phase is the forming section. Here, the flat strip passes through a series of tandem stands, each containing specifically contoured rolls. These rolls are arranged in a cascading fashion, and each set incrementally bends the edges of the strip upward. The progression is carefully calculated to shape the metal gradually without over-straining it. The final stands in this section close the strip into a cylindrical profile with the two edges meeting neatly at the top, ready for welding.
The welding station is where the open-seamed tube becomes a closed pipe. In a common High-Frequency ERW mill, the edges are forced together under pressure from squeeze rolls. Simultaneously, a high-frequency electrical current is applied to the edges. The resistance to this current generates intense heat, bringing the steel to a plastic state. The pressure from the rolls then forges the heated edges together, creating a solid-state bond. This welding method is efficient and does not require filler metal.
Following the weld, the pipe undergoes several post-weld operations. It immediately passes through a scarfing unit, where tungsten carbide cutters trim off the internal and external weld flash, creating a smooth surface. The pipe then enters a cooling section, which may use air or water mist to normalize the weld area. After cooling, the pipe proceeds to the sizing section. This part of the machine uses another set of stands with calibrated rolls to impart the final exact diameter and to perfect the roundness of the pipe.
Finally, a flying cutoff saw cuts the continuously moving pipe to the required length. This saw is mounted on a carriage that moves synchronously with the pipe during the cut, ensuring a clean, square cut without interrupting the forward motion of the production line. The finished pipes are then conveyed to a run-out table where they may be straightened, inspected, and bundled for shipment. This comprehensive process, orchestrated by a central control system, allows Shijiazhuang Faith Machinery Co., Ltd.'s equipment to produce large volumes of finished steel pipe efficiently and with consistent quality.
