What is the working process of a steel pipe making machine?

The working process of a steel pipe making machine is a coordinated sequence of mechanical operations that convert coiled steel strip into finished pipes. This process is designed for continuity and efficiency, ensuring a consistent output. Manufacturers like Shijiazhuang Faith Machinery Co., Ltd. engineer these mills to perform the following stages in a seamless, integrated manner.

Stage 1: Uncoiling and Entry
The process initiates with a decoiler, which holds the master steel coil. As the coil unwinds, the strip is fed into the mill line. An entry bench, often equipped with pinch rolls, guides the strip forward. A key component at this stage is the leveling machine. Its purpose is to eliminate any curvature or irregularities imparted from the coiling process, ensuring the strip is perfectly flat before it undergoes forming.

Stage 2: Forming the Tube
The leveled strip then enters the forming section. This section consists of multiple stands, each with a set of rolls that have progressively changing profiles. The initial stands begin to give the strip a slight U-shape. Subsequent stands continue to form the edges upward until the strip takes on a rounded O-shape. The precision of the roll design and alignment in this section is critical, as it dictates the final geometry of the pipe and ensures the edges are presented correctly for welding.

Stage 3: Welding the Seam
Once the strip is fully formed into a cylindrical shape with its edges meeting, it arrives at the welding station. For ERW mills, this involves applying high-frequency electrical current to the edges. The resistance generates heat, and the simultaneous pressure from squeeze rolls forges the heated edges together to form a metallurgical bond. This creates a continuous, longitudinal weld seam along the length of the pipe.

Stage 4: Flash Removal and Weld Treatment
The newly formed weld contains excess material, known as flash, on both the inside and outside of the pipe. The pipe immediately passes through a scarfing unit where dedicated tools scrape or cut this flash away. This results in a smooth weld contour. Following this, the weld zone may be heat-treated using an induction heater and then cooled in a controlled manner. This normalization process refines the grain structure of the weld, improving its mechanical properties and making it comparable to the parent metal.

Stage 5: Sizing and Calibration
After welding and treatment, the pipe enters the sizing section. Here, a series of stands with closely toleranced rolls work the pipe to achieve its final, precise outer diameter. This step is essential for ensuring the pipe meets strict dimensional specifications and improves its roundness. The number of sizing stands depends on the required accuracy and the size range of the mill.

Stage 6: Cutting to Length
The now-complete pipe, which is moving continuously, is cut to specific lengths by a flying cutoff saw. This saw is mounted on a track and accelerates to match the pipe's speed before making the cut, then returns to its start position. This allows for production to continue uninterrupted.

Stage 7: Output and Handling
The cut pipes exit the mill onto a run-out table. They may pass through a straightening machine to correct any minor curvature before being automatically stacked or bundled for easy handling and shipment. The entire working process, from uncoiling to cutting, is a testament to the integrated engineering of machines from Shijiazhuang Faith Machinery Co., Ltd., designed for reliable and repeatable pipe production.