Hot Piercing Mills

Stainless Steel Seamless Pipe Mother Tube Production Process
    1.Hot Rolled Bars
    •The process begins with hot rolled stainless steel bars, produced through continuous casting and hot rolling.
    •These bars are selected according to the required grade and dimensional specifications for seamless pipe production.
    2.Cutting to Fixed Length
    •The hot rolled bars are cut into fixed lengths, usually according to the piercing mill requirements.
    •Accurate cutting ensures consistent heating, piercing efficiency, and stable product quality.
    3.Peeling (Surface Conditioning)
    •The cut bars undergo peeling (also called bar peeling or turning), in which the surface layer is mechanically removed.
    •This process eliminates surface defects such as scales, cracks, or decarburized layers, ensuring a smooth and clean surface for further processing.
    •Peeling improves dimensional accuracy and prevents defects from propagating during piercing.
    4.Heating
    •The peeled bar billets are heated in a rotary hearth furnace or induction furnace to the required piercing temperature, typically around 1150–1250 °C.
    •Uniform heating ensures good plasticity, reduces piercing resistance, and prevents cracking during deformation.
    5.Piercing into Hollow Shells (Mother Pipes)
    •The heated billets are transferred to a piercing mill (such as a Mannesmann cross-roll piercing mill).
    •Under the action of skewed rollers and a piercing plug, the solid bar is pierced longitudinally into a hollow shell, also known as the mother pipe.
    •This mother pipe will then be elongated and rolled in subsequent processes (such as plug mill, mandrel mill, or extrusion) to produce seamless stainless steel pipes of the desired dimensions.