OCT-Einschweißtiefenüberwachung bei Unterdruck/OCT-based weld penetration monitoring at reduced ambient pressure – Influence of reduced ambient pressure on the OCT signal quality in laser deep penetration welding

Die optische Kohärenztomographie (OCT) erlaubt die zerstörungsfreie In-situ-Überwachung der Einschweißtiefe beim Laserstrahlschweißen. Für dieses Verfahren wird hier der Einfluss von verringerten Umgebungsdrücken auf die Messqualität untersucht. Es wird gezeigt, dass sich bei niedrigerem Umgebungsdruck deutlich größere Signalanteile aus dem Bereich des Bodens der Dampfkapillare zurückerhalten lassen. Auf diese Weise steigen die effektive Messfrequenz und die Erkennbarkeit von Änderungen der Einschweißtiefe.   Optical coherence tomography (OCT) enables non-destructive in-situ monitoring of the weld penetration depth during laser beam welding. For this technology, the influence of reduced ambient pressures on the measurement quality is investigated. It is shown that significantly larger signal components are obtained from the bottom of the vapor capillary at lower ambient pressure increasing the applicable measurement frequency and the detectability of changes in the weld penetration depth.

Experimental analysis of key parameters of laser fion welding of honeycomb plate heat exchanger

The combination of laser deep penetration welding and hydraulic bulging is the most advanced production technology of honeycomb plate heat exchanger in the world. The micro-shape and heat transfer effect of the heat exchanger of honeycomb plate are mainly determined by the distribution mode of welding spot, weld shape and welding point arrangement. Therefore, the important principle of the honeycomb plate heat exchanger processing is to improve the pressure as much as possible to form turbulence while ensuring the welding quality. In the present experimental work, the effect of different weld shape and weld distribution of honeycomb plate heat exchanger produced by 06cr19n10 plate using hydraulic bulging and laser deep penetration welding on hydraulic bulging effect was studied carefully. The results showed that the optimal arrangement method is the equilateral triangle. The welding process parameters were optimized to increase the welding strength. The results showed that when the welding power was 2.1 kW, the bonding strength of the weld was the highest, at 52.70 kN. When the welding power was 2.2 kW and the gap between the welding points was 30 mm, the tensile strength of the honeycomb plate was the best, at 19.0 MPa. The results of this paper provide experimental support for industrial production of honeycomb plate heat exchanger.

Microstructure and Mechanical Properties of Aluminum Alloy/High Strength Steel Double Beam Laser Deep Penetration Welded Joint

A new dual beam laser deep penetration welding technology for lap joint of 1.5 mm thick aluminum alloy and high strength steel was explored in this paper, and the effects of three different beam energy ratios (RS=0.25,0.33,0.5) on weld formation, interface microstructure and mechanical properties were studied. The result shows that under certain conditions of other parameters, double beam laser deep penetration welding process can be applied to lap joint of aluminum alloy / high strength steel with good weld shape when RS=0.25,0.33,0.5. As RS increases from 0.25 to 0.5, the penetration of the weld reduces from 575 μm to 424.2μm, the thickness of intermetallic compound (IMC) layer at the interface between aluminum alloy and weld metal reduces from 3.4 μm to 2.5 μm, the average microhardness of the IMC layer decreases from 771.1 HV to 571.9 HV, the mechanical resistance of the joint raises from 95.7N/mm to 115.2N/mm. When RS=0.5, double beam laser deep penetration welding of aluminum alloy / high-strength steel joints has the highest mechanical resistance of joints, because of the relatively good plastic ductility of the joint.