Copper Pipe Induction Brazing System is a highly efficient and precise joining process widely used in refrigeration, HVAC (Heating, Ventilation, and Air Conditioning), and industrial pipeline systems. It achieves rapid brazing or fusion welding of copper pipes and branch connectors through electromagnetic induction heating. The following outlines the core principles and process solutions for this technology:
I. Process Principles and Advantages
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Electromagnetic Induction Heating
- High-frequency alternating current (10–100 kHz) passing through an induction coil generates an alternating magnetic field, inducing eddy currents on the surface of the copper pipe. Resistance heat rapidly raises the temperature to the melting point of the filler metal (e.g., silver-based filler metal: 600–800°C).
- The heating depth is determined by the frequency. Copper pipes (conductivity ≥58 MS/m) are suitable for high frequencies (50–100 kHz) to achieve localized rapid heating.
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Core Advantages
- High Efficiency and Energy Saving: Heating time ≤10 seconds per weld point, with energy consumption only 30–50% of flame welding.
- Precise Temperature Control: Closed-loop infrared temperature control (±5°C) prevents oxidation or overheating of copper pipes.
- Clean and Environmentally Friendly: No open flame, reduced fumes, and optional nitrogen shielding (oxygen content ≤50 ppm) to improve weld surface finish (Ra ≤1.6μm).
- Automation Compatibility: Suitable for integration into assembly lines with high welding consistency (yield ≥99.5%).
II. Equipment Configuration Scheme
| Module | Technical Requirements |
|---|---|
| Induction Power Supply | High-frequency IGBT power supply (20–50 kW, 50–100 kHz) |
| Induction Coil | Custom profile-matched multi-turn coils (made of red copper tubing), designed for branch connector structures (e.g., Y-type, T-type) to cover the welding area with magnetic fields. |
| Filler Metal and Shielding System | Silver-based filler metals (BCuP-5, BAg-8) with melting points of 720–850°C; nitrogen shielding device (flow rate 5–10 L/min). |
| Positioning and Clamping | Pneumatic fixtures + servo positioning (repeatability ±0.1 mm) to ensure a gap ≤0.1 mm between copper pipes and branch connectors. |
| Cooling System | Closed-loop water chiller (water temperature ≤30°C, flow rate ≥20 L/min) to prevent overheating of coils and power supplies. |
| Quality Inspection | Infrared thermal imager (temperature field monitoring), helium mass spectrometer leak detector (leak rate ≤1×10⁻⁶ Pa·m³/s). |
III. Process Parameters and Flow
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Key Parameters
- Frequency: 50–100 kHz (for copper pipe wall thickness 0.5–2 mm);
- Power: 10–30 kW (depending on pipe diameter and filler metal type);
- Heating time: 3–10 seconds (until filler metal wets and flows);
- Holding time: 1–3 seconds (to ensure dense brazing seams).
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Operation Flow
- Preprocessing: Remove oxide layers from copper pipe ends (mechanical grinding/pickling), and pre-place filler metal rings or paste flux.
- Assembly: Position branch connectors and copper pipes, fill gaps with filler metal, and purge the welding area with nitrogen.
- Heating: Surround the weld point with an induction coil and apply high-frequency heating until the filler metal melts (monitored by infrared).
- Cooling: Natural air cooling or forced air cooling to form dense brazing seams.
- Inspection: Visual inspection (full filler metal fillets), pressure testing (1.5× working pressure for 5 minutes).
V. Selection and Maintenance Recommendations
(Note: The original Chinese numbering skips from “III” to “V,” likely a typo. The translation retains the original numbering.)
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Equipment Selection
- Small pipe diameter (Φ≤15 mm): 20–30 kW high-frequency power supply with multi-turn close-wound coils.
- Large pipe diameter (Φ>15 mm): 50 kW medium-high frequency power supply with U-shaped openable coils.
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Maintenance Key Points
- Regularly clean coil oxide layers (soak in citric acid + soft brush) and inspect insulation (withstand voltage ≥2 kV).
- Calibrate the temperature measurement system quarterly and replace aged capacitor banks (capacitance deviation ≤±5%).
VI. Economic Analysis
| Project | Induction Welding | Flame Welding |
|---|---|---|
| Single-Point Cost | ¥0.5–1.0 (filler + power) | ¥1.5–2.5 (gas + filler) |
| Efficiency | 600–800 points/shift | 200–300 points/shift |
| Pass Rate | ≥99.5% | 95–98% |
Conclusion
Induction welding of copper pipes for branch connectors has become the preferred process in the refrigeration and pipeline industries due to its high efficiency, cleanliness, and consistency. A recommended solution is a 30 kW high-frequency power supply + custom coil + nitrogen shielding, with an initial investment of ¥200,000–500,000 and a payback period of <1 year (based on 500,000 weld points annually). For high-requirement scenarios (e.g., medical gas pipelines), upgrading to a vacuum brazing system can completely eliminate oxidation.
