Ensuring Weld Seam Quality in ERW Pipe Production

Shijiazhuang Faith Machinery Co., Ltd utilizes integrated technological systems to maintain consistent weld quality in ERW pipe production. The methodology encompasses material preparation, controlled forming, precision welding, and systematic verification.

Material Selection and Edge Preparation
The process begins with qualified steel coils meeting chemical composition requirements. Coil edges are milled to achieve precise 90-degree angles, ensuring uniform contact during welding. This edge preparation removes oxidized material and creates consistent geometry for stable current transfer.

Controlled Forming Process
Progressive roll forming shapes the material through sequential stands with decreasing roll gaps. Each station contributes to the gradual curvature while maintaining uniform pressure distribution. Tension control systems prevent stretching or compression along the strip edges, preserving material integrity before welding.

Welding Parameter Optimization
High-frequency current (100-400 kHz) generates localized heat through the skin effect. Parameters are calibrated based on material grade and thickness:

• Power input: 60-800 kW (scalable)

• Vee length: 20-30 times material thickness

• Welding speed: 20-60 m/min
  Contact shoes maintain consistent current transfer while cooling systems manage electrode temperature.

Post-Weld Treatment
Immediate seam normalization through induction heating restores microstructure. Temperature profiles are controlled between 850-920°C for carbon steels, followed by controlled cooling. This process eliminates hardness concentrations and improves ductility.

Quality Verification Systems
In-line nondestructive testing includes:

• Eddy current testing for surface defects

• Ultrasonic immersion testing for volumetric flaws

• Real-time weld zone thermography
  Destructive testing protocols involve:

• Transverse weld section macroetching

• Guided bend testing per API 5L standards

• Tensile testing across weld zones

Process Monitoring
Automated systems track:

• Weld power stability (±1.5%)

• Strip edge alignment (±0.1mm)

• Squeeze roll pressure (3-6 kN)
  Data historians record all parameters for traceability and trend analysis.