High-frequency welded pipe production line configuration

The configuration of the high-frequency welded pipe production line needs to comprehensively consider equipment selection, process parameters, and automatic control. The following are the key configuration points:
1. Core equipment selection
Forming unit
Cr12MoV alloy steel roller molds can be used, with surface hardness of HRC 58-62, forming speed of 15-25m/min, suitable for pipe materials with outer diameters of Φ8-76mm and wall thicknesses of 0.3-3mm.
Four-roll flat roller structure requires 12 progressive bends, and the maintenance gap of the rollers should be ground to 0.45mm based on the original gap of 0.3mm.
High-frequency welding system
IGBT inverter technology welding machines can be selected, with frequency adjustment range of 300-450kHz, welding speed error of ±0.5%, equipped with argon gas protection device (suitable for stainless steel material)‌.
Solid-state high-frequency welders need to integrate switch rectifier cabinets and inverter output cabinets, and use MOSFET bridge circuit to achieve 98% energy conversion.
Diameter control and straightening equipment
Adjustable four-roll diameter control machine can control the outer diameter tolerance of ±0.15%, equipped with laser diameter measuring instrument (sampling rate of 2000 times/second)‌.
Straightening machine needs to achieve ±0.02mm positioning accuracy, and the hydraulic quick-change system can increase the changeover efficiency by 3 times‌.
2. Process parameter configuration
Welding parameters
High-frequency current frequency of 30-80kHz, welding time of 0.08-0.15 seconds, melting temperature of 1250-1450℃, weld seam strength of over 95% of the base material.
The error of the induction coil and the extrusion roller distance should be controlled within 3cm to ensure the weld seam strength of 520MPa.
Forming parameters
Opening angle controlled within 2-6°, the deviation of the strip is compensated by the guide ring, and the stable forming speed is 20m/min.
Cold rolling process requires a hydraulic AGC system, wall thickness tolerance of ±0.03mm, and the surface roughness of the roller should be ≤0.4μm.
3. Automation and quality control
Control system
The Siemens S7-1500 PLC integrated with WinCC system can be selected to achieve the linkage of forming, welding, and cold rolling processes.
The servo shearing system realizes ±1mm fixed-length cutting through PID algorithm, and is equipped with an inertia compensation module.
Quality inspection
Four-level inspection nodes: laser diameter measurement at the forming section, infrared temperature measurement at the weld area (±5℃), diameter control by eddy current testing (detection rate ≥ 99.6%), final inspection water pressure test (2.5 times pressure holding)‌.
OPC protocol realizes full-process quality traceability, with a scrap rate controlled below 0.3%.
4. Auxiliary system configuration
Energy and cooling
The total installed capacity of the line is 680kW. The water consumption for high-frequency welding is 30-50 tons/hour (cycled use), and the water hardness should be ≤0.017/ liter.
The cooling fluid consumption is 25-30 tons/hour, and the compressed air demand is 6m³/min (pressure 0.4-0.6MPa).