Seamless steel pipe production lines are industrialized facilities specifically designed to manufacture seamless tubular steel products (seamless steel pipes). These products, renowned for their high strength, high-pressure resistance, and corrosion resistance, find extensive applications across industries such as petroleum, natural gas, chemical engineering, power generation, machinery, and aerospace (e.g., oil and gas transmission pipelines, boiler tubes, structural mechanical tubes).
I. Classification and Characteristics of Seamless Steel Pipes
By Application: Includes pipes for fluid conveyance, structural pipes, boiler tubes, high-pressure fertilizer pipes, petroleum cracking pipes, etc. Materials predominantly consist of carbon steel, alloy steel, stainless steel, and others.
II. Hot-Rolled Seamless Steel Pipe Production Line (Mainstream Process)
Hot rolling is the core production method for seamless steel pipes. The process primarily includes: “Billet Preparation - Heating - Piercing - Rolling - Sizing - Cooling - Finishing.” Key equipment and processes are as follows:
1. Billet Preparation
Raw Material: Primarily round billets (continuously cast or forged), with diameters determined by finished pipe specifications (e.g., φ50mm-400mm) and lengths of 3-6 meters.
Pre-treatment: After inspection (surface free of cracks and inclusions), billets undergo end trimming and centering (drilling a center hole at one end to ensure uniform wall thickness during piercing).
2. Heating
The billets are fed into a ring furnace or continuous furnace and heated to 1100-1250°C (adjusted per steel grade) to impart good plasticity and reduce subsequent piercing and rolling resistance.
3. Piercing (Core Process)
The heated billet enters the piercing machine, where the solid billet is pierced into a hollow tube blank (pipe blank). This is the critical step in forming “seamless” tubing.
Common piercing machines: Tilting piercing machines (e.g., Mannesmann piercing machines) employ two inclined rollers to rotate and roll the billet while a mandrel pushes from within, progressively deforming the billet into a hollow tube blank (slightly larger outer diameter than the finished pipe, with thicker walls).
Requirements: The tube blank must ensure uniform wall thickness, minimal ovality, and avoid surface cracks or internal folds.
4. Rolling (Drawing and Wall Reduction)
The blank enters the tube rolling mill for further wall reduction, elongation, and dimensional refinement. Common equipment varies by product specifications:
Multi-Pass Mill (MPM): Continuous rolling across multiple stands offers high efficiency and wall thickness precision, suitable for mass production.
Automatic Tube Mill: Utilizes coordinated roll and mandrel action for medium-sized steel tubes.
Periodic rolling mill: Produces large-diameter thick-walled tubes by achieving significant deformation through periodic rolling.
After rolling, the blank tube becomes a near-finished blank tube.
5. Sizing and Reducing
Sizing mill: Rolls the blank tube to the finished outer diameter using multiple stands, ensuring dimensional accuracy (tolerance up to ±0.1mm).
Reducer: Performs reduction and elongation on steel tubes, enabling a single blank size to be rolled into multiple smaller-diameter tubes for enhanced flexibility.
6. Cooling and Finishing
Cooling: Rolled tubes are cooled to room temperature via water or air cooling, with controlled cooling rates to optimize microstructure properties.
Finishing:
End Trimming: Removes irregularities from both ends of the tube.
Straightening: Eliminates bending through multi-roll straighteners to ensure straightness.
Non-Destructive Testing: Utilizes ultrasonic testing (for internal defects) and eddy current testing (for surface defects).
Hydrostatic Testing: Assesses pressure resistance (e.g., withstanding pressures above 20MPa without leakage).
Surface Treatment: Remove scale, apply paint or zinc coating (for corrosion protection).
7. Inspection and Packaging
Dimensional inspection (OD, wall thickness, length), mechanical property testing (tensile, impact), chemical composition analysis, etc.
Qualified steel pipes are bundled by specification, labeled with steel grade, dimensions, standards, and stored in inventory.
