Comprehensive Guide to Checking the Welding Process of Laser Welding Fin Tubes

Ensuring the quality of laser welding fin tubes is crucial for maintaining the efficiency and longevity of heat exchangers and other related equipment. Here is comprehensive guide outlines the essential steps and procedures for checking the welding process of laser-welded fin tubes.

Pre-Welding Preparation

Material Inspection

Before initiating the welding process, it is vital to inspect the materials. Ensure that the fins and tubes are clean and free from contaminants. Check for any defects or irregularities to prevent potential issues during welding.

Equipment Calibration

Proper calibration of the laser welding equipment is essential. Verify that the laser power, welding speed, and focus settings are correctly set according to the material specifications. Regular maintenance of the equipment is also crucial to ensure optimal performance.

Fixture Setup

Securely fix the tubes and fins to prevent movement during welding. Proper alignment is critical for achieving consistent weld quality. Ensure that the fixture setup allows for easy adjustments and stability throughout the welding process.

During Welding

Monitor Parameters

Continuous monitoring of welding parameters such as laser power, welding speed, and gas flow rate is necessary. These parameters should remain consistent to ensure a uniform weld. Any deviations can lead to defects and should be addressed immediately.

Visual Inspection

Perform visual inspections during the welding process. Look for signs of excessive spatter, inconsistent weld beads, or burning. Address any abnormalities promptly to maintain the integrity of the weld.

Real-Time Monitoring

Utilize sensors and cameras for real-time monitoring of the welding process. This technology helps detect any deviations from the desired welding conditions, allowing for immediate corrective actions.

Post-Welding Inspection

Measure Delay Time

Before welding on-site, measure the delay time from the acoustic wave monitor to the receiving system. Calculate the correction value of the delay time to ensure accurate monitoring during the welding process.

Synchronous Probe Movement

When measuring laser-welded finned tubes, ensure that the transmitting and receiving probes rise and fall synchronously at the same elevation or maintain a fixed elevation difference. This ensures accurate and consistent readings.

Measurement Point Distance

Set the standard distance between measurement points on the finned tube to 40 cm. If abnormalities are found, reduce the distance to 20 cm for a more detailed inspection.

Transmission Voltage and Amplifier Gain

Select an appropriate transmission voltage and amplifier gain. Keep these settings unchanged during retests to ensure consistent results.

Real-Time Signal Monitoring and Recording

Ensure the system can display and record the time history curve of the received signal in real-time. This capability allows for immediate detection and analysis of welding defects.

Detection Sections for Multiple Tubes

Combine multiple laser-welded finned tubes into pairs as detection sections. Complete the detection for each section separately to ensure thorough inspection of all welded tubes.

Random Sampling and Statistical Analysis

After testing each group of laser-welded finned tubes, randomly sample 10% of the test points. The relative standard deviation of the delay time should not exceed 5%, and the relative standard deviation of the amplitude should not exceed 10%.

Non-Destructive Testing (NDT) Optional

Ultrasonic Testing (UT)

Use ultrasonic waves to detect internal defects or discontinuities in the weld. This method provides a detailed analysis of the internal structure without damaging the tube.

X-ray Inspection

X-ray imaging can reveal internal defects such as voids, cracks, or inclusions. This technique is essential for ensuring the structural integrity of the weld.

Dye Penetrant Inspection (DPI)

Apply a dye penetrant to the weld surface to detect surface cracks and porosity. This method is effective for identifying surface-level defects.

Magnetic Particle Inspection (MPI)

For ferromagnetic materials, use magnetic particles to detect surface and near-surface defects. This technique helps identify issues that may not be visible to the naked eye.

Laser Welding Fin Tube Mechanical Testing

Tensile Testing

Perform tensile tests to determine the strength and ductility of the weld. This test ensures that the weld can withstand operational stresses.

Hardness Testing

Measure the hardness of the weld to ensure it meets the required specifications. Consistent hardness across the weld indicates uniform quality.

Bend Testing

Bend the welded tube to check for any signs of cracking or failure in the weld area. This test helps assess the flexibility and resilience of the weld.

Documentation and Reporting

Record Keeping

Document all inspection results, including visual inspections, NDT results, and mechanical test data. Maintaining detailed records is essential for quality control and traceability.

Corrective Actions

Address Defects

If any defects are found, determine the root cause and take corrective actions. This may involve adjusting welding parameters, reworking defective welds, or replacing defective components.

Continuous Improvement

Process Review

Regularly review and analyze welding process data to identify areas for improvement. Implement changes to enhance the quality and efficiency of the welding process.

Additional Considerations

Documentation

Keep detailed records of all measurements, settings, and results for quality control and traceability.

Calibration and Maintenance

Regularly calibrate the measuring equipment and maintain it to ensure accuracy and reliability.

Laser welding fin tubes