Observation of Dynamic Behavior in Primer-Coated Steel Welding by CO2 Laser

2007 ◽  
Vol 124-126 ◽  
pp. 1425-1428
Author(s):  
Jong Do Kim ◽  
Hyun Joon Park ◽  
Mun Yong Lee
Keyword(s):  
Laser Welding ◽  
Weld Metal ◽  
Dynamic Behavior ◽  
Coated Steel ◽  
Porosity Formation ◽  
Laser Induced Plasma ◽  
Weld Defect ◽  
Inner Surface ◽  
Coated Plate ◽  
Keyhole Behavior

This study examines for keyhole behavior by observing the laser-induced plasma and investigates the relation between keyhole behavior and formation of weld defect. Laser-induced plasma has been accompanied with the vaporizing pressure of zinc ejecting from keyhole to surface of primer coated plate. This dynamic behavior of plasma was very unstable and it was closely related to the unstable motion of keyhole during laser welding. As a result of observing the composition of porosity, much of Zn element was found from inner surface of it. But Zn was not found from the dimple structure fractured at the weld metal. therefore we can prove that the major cause of porosity is the vaporization of primer in lap position. Mechanism of porosity-formation is that the primer vaporized from the lap position accelerates dynamic behavior of the key hole and the bubble separated from the key hole is trapped in the solidification boundary and remains as porosity.

Diagnostics of Laser-Induced Plasma in Welding of Aluminum Alloy

2004 ◽  
Vol 261-263 ◽  
pp. 1671-1676 ◽  
Author(s):  
J.D. Kim ◽  
Yun Hae Kim ◽  
Jin Seok Oh
Keyword(s):  
Laser Welding ◽  
Power Density ◽  
High Speed ◽  
Mg Alloys ◽  
Optical Systems ◽  
Irradiation Condition ◽  
Band Spectrum ◽  
Laser Induced Plasma ◽  
Keyhole Behavior ◽  
Al Mg Alloys

The authors have observed directly and simultaneously the laser-induced plasma and keyhole behavior by high speed frame/streak camera using a special optical systems during the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. The dynamic behavior of Al-Mg alloys plasma was very unstable and this instability fluctuation period was about 440µs. After laser termination, abrupt collapse of keyhole within 600µs was observed and it was related to the formation of porosity. The authors also performed the spectroscopic analysis of laser-induced plasma, and clarified the structure and composition of evaporated particles during pulsed laser welding of Al-Mg alloys. In the air environment, the intensities of molecular spectrum of AlO and MgO were different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectrum was predominant in intensity, while the AlO spectrum became much stronger in higher power density. The same result was revealed in analyzing the composition of evaporated particles. These results were attributed to evaporation phenomena of metals with different boiling points and latent heats of vaporization.

Dynamic behavior of plasma and molten pool of pure titanium during hyperbaric laser welding

2021 ◽  
Vol 115 ◽  
pp. 103686
Author(s):  
Jian Long ◽  
Lin-Jie Zhang ◽  
Jie Ning ◽  
Suck-Joo Na
Keyword(s):  
Laser Welding ◽  
Dynamic Behavior ◽  
Molten Pool ◽  
Pure Titanium

Dynamic keyhole behavior and keyhole instability in high power fiber laser welding of stainless steel

2019 ◽  
Vol 114 ◽  
pp. 1-9 ◽  
Author(s):  
Dabin Zhang ◽  
Meng Wang ◽  
Chengsong Shu ◽  
Yunfei Zhang ◽  
Dongsheng Wu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Fiber Laser Welding ◽  
Keyhole Behavior

scholarly journals Depth Dependence and Keyhole Stability at Threshold, for Different Laser Welding Regimes

2020 ◽  
Vol 10 (4) ◽  
pp. 1487 ◽  
Author(s):  
Remy Fabbro
Keyword(s):  
Aspect Ratio ◽  
Laser Welding ◽  
Scaling Laws ◽  
Weld Seam ◽  
Operating Parameters ◽  
Cylindrical Shape ◽  
Aspect Ratios ◽  
Stability Issues ◽  
Keyhole Behavior ◽  
Ratio Range

Depending of the laser operating parameters, several characteristic regimes of laser welding can be observed. At low welding speeds, the aspect ratio of the keyhole can be rather large with a rather vertical cylindrical shape, whereas at high welding speeds, low aspect ratios result, where only the keyhole front is mainly irradiated. For these different regimes, the dependence of the keyhole (KH) depth or the keyhole threshold, as a function of the operating parameters and material properties, is derived and their resulting scaling laws are surprisingly very similar. This approach allows us to analyze the keyhole behavior for these welding regimes, around their keyhole generation thresholds. Specific experiments confirm the occurrence and the behavior of these unstable keyholes for these conditions. Furthermore, recent experimental results can be analyzed using these approaches. Finally, this analysis allows us to define the aspect ratio range for the occurrence of this unstable behavior and to highlight the importance of laser absorptivity for this mechanism. Consequently, the use of a short wavelength laser for the reduction of these keyhole stability issues and the corresponding improvement of weld seam quality is emphasized.

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