1. Precise Control of Equipment Core Parameters
1.1 Dynamic Matching of Power and Energy
Set the power according to the material thickness: 1000-1500W for 1mm stainless steel, and increase to over 2000W for aluminum parts thicker than 2mm. Inadequate power easily leads to insufficient penetration, while excessive power may burn through the material.
Ensure the energy output fluctuation is ≤±3% through a laser power supply voltage stabilizer to avoid inconsistent welding strength caused by grid voltage fluctuations.
1.2 Collaborative Control of Welding Speed and Heat Input
The speed must match the power: when welding aluminum with 3000W, the recommended speed is 0.5-1.2m/min. Excessive speed may result in incomplete molten pool formation, while too slow speed expands the heat-affected zone. Optimize parameters through trial welding (refer to the formula: heat input = power/speed).
Adjust the pulse frequency: use high-frequency pulses (50-100Hz) for thin parts (<0.5mm) to reduce thermal deformation, and low-frequency pulses (10-20Hz) for thick parts (>2mm) to ensure penetration.
1.3 Calibration of Focus Position and Spot Quality
Precisely locate the focus using a focal spot tester: the focus for stainless steel welding is typically 0.2mm below the material surface, while that for aluminum parts needs to be raised by 0.1mm. Focus offset will cause the spot energy density to drop by over 30%.
Regularly maintain the optical system: wipe the focusing lens and reflecting mirror with anhydrous ethanol weekly to prevent spot distortion and affect welding accuracy due to dust.
2. Strengthening Material Pretreatment and Assembly Process
2.1 Surface Cleaning and Precision Control
Remove surface impurities: use acetone to wipe oil stains on stainless steel, and aluminum parts require additional removal of the oxide film by sandpaper grinding or chemical degreasing. Impurities will cause pores or spatter during welding.
Control the butt joint accuracy: the butt joint gap should be ≤0.1mm (for thin parts) or ≤0.3mm (for thick parts), and the offset should be ≤10% of the plate thickness; otherwise, incomplete fusion defects are prone to occur.
2.2 Design of Workholding Fixtures and Auxiliary Gases
Use pneumatic fixtures or magnetic platforms to rigidly fix workpieces, especially for materials with high thermal expansion coefficients such as aluminum alloys. The fixture positioning accuracy should be ≤0.05mm to reduce thermal deformation.
Use high-purity argon (purity ≥99.99%) as the shielding gas. The flow rate is 10-15L/min for stainless steel and 15-20L/min for aluminum. The gas flow direction should be perpendicular to the weld to prevent oxidation.
3. Standardizing Operation Procedures and Personnel Skills
3.1 Machine Preheating and Equipment Calibration
Preheat the laser generator for 15-30 minutes after startup (extend in winter) to stabilize the resonator temperature and avoid power fluctuations during cold start.
Check the laser beam offset with the crosswire method daily, and readjust the mirror angle if the offset exceeds 0.1mm.
3.2 Professional Requirements for Operators
Operators must pass laser safety training (such as FDA or CE certification training) and master the parameter adjustment logic for different materials: for example, increasing the pulse width during aluminum welding to compensate for its high thermal conductivity.
Observe the molten pool status in real time during welding: the molten pool of stainless steel is bright white, and that of aluminum is mirror-like. Stop the machine immediately for inspection if abnormal spatter or excessive smoke is found.
4. Equipment Maintenance and Condition Monitoring
4.1 Key Component Maintenance
Cooling system control: maintain the water temperature at 22-25℃, and replace the deionized water every 3 months to avoid scale deposition causing overheating of the laser head (temperature exceeding 35℃ will lead to power attenuation).
Laser generator inspection: check the loss of the laser rod/optical fiber every 1000 hours, and replace it promptly if the loss exceeds 20% to prevent energy output decline.
4.2 Application of Online Monitoring Technology
Infrared temperature measurement: monitor the temperature of the welding area in real time through a sensor (melting point of stainless steel is 1450℃, and that of aluminum is 660℃), and automatically adjust the power if the temperature deviation exceeds ±50℃.
Visual inspection: install a CCD camera to capture the weld formation in real time, and use an AI system to identify defects such as undercut and pores (detection accuracy ≤0.02mm).
5. Welding Quality Inspection and Traceability
5.1 Routine Quality Inspection
Visually observe the weld surface: the roughness should be ≤Ra1.6μm, and the stainless steel weld should be silver white. If yellow or blue oxidation occurs, adjust the shielding gas parameters.
Destructive testing: sample for tensile testing (tensile strength should reach over 85% of the base metal) or bending testing (no cracking after 90° bending).
5.2 Non-Destructive Testing Technology
X-ray testing: for key welds such as pressure vessels, detect internal pores (qualified if the diameter ≤0.5mm and the spacing ≥5mm).
Ultrasonic testing: suitable for welds of thick plates (>5mm), detect incomplete fusion defects (sensitivity should reach Φ1mm flat-bottomed hole equivalent).
6. Key Points for Welding Special Materials
6.1 Stainless Steel Welding
Avoid carbon contamination: use ceramic or titanium alloy fixtures to prevent iron ion penetration into the weld, causing intergranular corrosion.
Control the cooling rate: fast cooling can reduce chromium carbide precipitation and lower the risk of stress corrosion.
6.2 Aluminum Alloy Welding
Remove the oxide film: adopt laser cleaning or chemical etching to remove the Al₂O₃ layer before welding.
Adjust the wavelength matching: select green light (532nm) or blue light (450nm) laser. Compared with 1064nm fiber laser (aluminum absorption rate is only 3%), the blue light absorption rate can reach 60%, significantly improving welding efficiency.
7. Environmental and Process Document Management
Workshop environment control: temperature 15-30℃, humidity ≤60%, away from electromagnetic interference sources (such as welding machines), and vibration amplitude ≤50μm.
Establish a standardized process database: record the optimal power-speed combination for different plate thicknesses and materials, and retain parameter logs for each welding to facilitate quality traceability.