Technical solution for ensuring weld strength of LPG cylinder longitudinal seam welding machine
Closed-loop control of welding process parameters: The equipment monitors the welding current (fluctuation ≤ ±2%), arc voltage (accuracy ±0.5V) and welding speed (adjustable from 0.5 to 3m/min) in real time through the PLC system. When welding Q345 steel cylinders (wall thickness 4-6mm), the preset current 180-220A, voltage 22-25V parameter combination, with the dynamic matching of wire feeding speed (3-5m/min) and shielding gas flow (15-20L/min), a case shows that this combination makes the weld tensile strength reach 520MPa (standard value of parent material ≥510MPa). The infrared temperature sensor (temperature measurement range 0-800℃) monitors the molten pool temperature in real time. When the local overheating exceeds 900℃, the system automatically reduces the welding speed by 10% and increases the shielding gas flow to prevent the strength from decreasing due to coarse grains.
Pre-weld pretreatment and post-weld inspection system: mechanical grinding (roughness Ra≤12.5μm) and acetone cleaning are used to remove oil stains on the groove, and the V-shaped groove (angle 60±5°) ensures that the penetration depth is ≥85% of the plate thickness; online ultrasonic testing (probe frequency 5MHz) is started immediately after welding, and the weld is 100% scanned. The detection sensitivity is set to Φ1mm flat-bottom hole equivalent. In the inspection of a batch of 2,000 steel cylinders, 3 products with unfused defects are automatically marked and removed, so that the tensile specimen of the qualified weld has an elongation of 21% (standard ≥20%). For high-strength steel cylinders (tensile strength ≥650MPa), stress relief annealing at 200-300℃ (heat preservation for 1 hour) is required after welding to avoid cold cracks by reducing residual stress (≤80MPa) and improve weld toughness (impact energy ≥34J).
Equipment accuracy and stability guarantee: The welding head is driven by a servo motor (positioning accuracy ±0.05mm), and is equipped with a linear guide rail (straightness ≤0.1mm/m) to ensure that the deviation between the welding gun's walking trajectory and the center line of the groove is less than 0.3mm; the rigid welding platform (flatness ≤0.5mm) is equipped with a pneumatic clamp (clamping force 5-10kN) to fix the cylinder to prevent welding deformation (angular deformation ≤1°). A company uses a laser tracking system (sampling frequency 100Hz) to correct the welding gun position in real time. When welding a cylinder with a diameter of 325mm, the weld width fluctuation is controlled within ±0.8mm. After destructive testing, the standard deviation of the weld strength is <15MPa, which meets the requirements of GB 5842-2021.
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