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High-frequency welded (HFW) pipe machines are designed to transform flat strip into longitudinally welded pipes using electromagnetic induction heating. At Shijiazhuang Faith Machinery Co., Ltd., HFW lines begin with coil loading units that feed strip through a series of forming rollers. These rollers progressively shape the strip into a “U” or “O” profile before edges approach the induction coil. The coil generates an alternating magnetic field at frequencies typically between 100 kHz and 500 kHz, inducing eddy currents in the strip edges. These currents produce localized heat sufficient to soften the steel before mechanical forging by weld rolls.
The coil’s design is critical: its turn count, cross-section, and cooling circuit dimensions determine heating efficiency and temperature uniformity. Shijiazhuang Faith’s engineering team uses computational electromagnetic simulations to optimize coil geometry for various strip widths and thicknesses. After induction heating, a forged roll immediately applies pressure to form a bond. The machine’s forge stand integrates precise roll gap control and synchronized speed matching to prevent edge misalignment. Following welding, aging and sizing stands refine tube roundness and wall consistency.
Pipe mills include multiple auxiliary stations: scarfing units to remove weld flashes; hydrostatic testing sections for strength verification; and hydraulic swaging or reducing units for diameter adjustment. Control systems synchronize all stations via a master speed encoder, maintaining a constant line speed. Human-machine interfaces display real-time process metrics—coil tension, weld bead temperature, weld roll pressure, and tube dimensions—enabling operators to make informed adjustments.
Modular design allows customization: for large-diameter pipes, additional forming stands improve edge alignment; for small-diameter or thin-wall tubes, higher-frequency coils provide rapid heating. Cooling systems, employing deionized water, maintain coil temperature and prevent oxidation. Data acquisition modules capture process parameters for traceability, while optional offline bending or threading units can be integrated into the line.
With robust electromagnetic design, precise mechanical forging, and flexible line configurations, Shijiazhuang Faith’s high-frequency welded pipe machines cater to diverse industrial needs, from structural to fluid-transport applications.
