High speed video analysis of melt flow inside fiber laser welding keyholes

2011 ◽  
Author(s):  
Ingemar Eriksson ◽  
John Powell ◽  
Alexander F. H. Kaplan
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
Video Analysis ◽  
High Speed ◽  
Melt Flow ◽  
Fiber Laser Welding ◽  
High Speed Video

Extraction of Weld Pool Width Feature Based on Visual Sensing during High-Power Fiber Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 388-391
Author(s):  
Zi Qin Chen ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
Weld Pool ◽  
High Power ◽  
High Speed ◽  
Welding Process ◽  
304 Stainless Steel ◽  
Fiber Laser Welding ◽  
Weld Pool Width ◽  
Laser Welding Process

In a high-power fiber laser welding process, the thermal radiation of a weld pool contains plenty of information for welding quality, in which the pool width can reflect the welding stability. Thus, extracting the welding pool width of high-power fiber laser welding based on infrared thermal imaging is an important method for monitoring the weld seam quality. In this paper, we studied the 304 stainless steel welded by a 10kW high-power fiber laser continuously. A near-infrared high-speed sensing camera was used to capture the weld pool images. Image algorithms such as median filtering, gray scale stretching, cutting, dynamic threshold mathematical morphology were applied to extract the weld pool image edge, analyze and detect the weld pool width. Welding experimental results showed that the proposed methods could extract the weld pool width, which could reflect the stability status of high-power fiber laser welding process accurately.

scholarly journals High-Speed Observation and Spectroscopic Analysis of Laser-Induced Plume in High-Power Fiber Laser Welding of Stainless Steel

2007 ◽  
Vol 25 (3) ◽  
pp. 455-460 ◽  
Author(s):  
Yousuke KAWAHITO ◽  
Keisuke KINOSHITA ◽  
Naoyuki MATSUMOTO ◽  
Masami MIZUTANI ◽  
Seiji KATAYAMA
Keyword(s):  
Stainless Steel ◽  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
High Speed ◽  
Spectroscopic Analysis ◽  
Fiber Laser Welding

scholarly journals Mechanisms for Improvement of Weld Appearance in Autogenous Fiber Laser Welding of Thick Stainless Steels

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 625 ◽  
Author(s):  
Mingjun Zhang ◽  
Shun Chen ◽  
Yingzhe Zhang ◽  
Genyu Chen ◽  
Zhuming Bi
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
High Speed ◽  
Imaging System ◽  
Metal Flow ◽  
Welding Process ◽  
Back Surface ◽  
Fiber Laser Welding ◽  
Vapor Plume

High-power fiber laser welding is an efficient and effective way to produce heavy section structures. However, there is a significant challenge in producing the welds with free of imperfections such as nail-head-shaped welds, spatters, and root sagging. This is partially due to a lack of understanding of the welding mechanism of high-power fiber laser. In this paper, we were especially interested in the mechanism to improve the appearance of welds, and we focused on the autogenous laser welding on thick stainless steel plates by a 10 kW fiber laser. To look into the relations of process parameters and the quality of welds, a high-speed imaging system was applied to observe the molten pool flow and vapor plume during the welding process. The appearances of welds subjected to different welding conditions were analyzed. The results showed that (1) nail-head-shaped welds were suppressed by using a gas jet during laser welding process. (2) In the forward welding, a gentle upwelling molten metal flow on the rear keyhole wall, a deeper weld pool and a weaker vapor plume resulted in no spatter. (3) The gravity affected the formation of underfills and root sagging significantly during autogenous laser welding of thick plates. (4) When the workpiece was placed vertically in the transverse position, the welding process was stable without an aggregation of molten melt at the back surface. Moreover, the mechanisms of forming root sagging and humps were different at the top surface.

scholarly journals A Study on Lap Joint Welding of Thin Plate ASTM F1684 Using Fiber Laser Welding

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 428
Author(s):  
Jaewoong Kim ◽  
Younghyun Kim ◽  
Jisun Kim ◽  
Yongtai Kim ◽  
Dongwoo Kim ◽  
...  
Keyword(s):  
Shear Strength ◽  
Laser Welding ◽  
Fiber Laser ◽  
High Speed ◽  
Coefficient Of Thermal Expansion ◽  
Lap Joint ◽  
Fiber Laser Welding ◽  
Cross Sectional ◽  
Shear Strength Test ◽  
Welding Part

The International Maritime Organization (IMO) has developed stricter regulations on emission standards for sulfur oxides, etc., and the demand for Liquefied Natural Gas (LNG) is increasing as an alternative to satisfy these standards. This study relates to fiber laser welding, an approach which offers high-speed welding and low welding deformation for ASTM F1684, which has a low coefficient of thermal expansion (CTE) even in a cryogenic environment. In this study, through three preliminary experiments using 0.25 mm thick Invar, the conditions required to secure sufficient penetration depth and back bead were identified. Through the cross-sectional observation analysis, the welding conditions without defects were identified and the trend of penetration shape according to increasing welding speed was identified. Following a lap joint laser welding experiment under the secured conditions, the mechanical properties were evaluated through the shear strength test and the heat influence range of a fiber laser was identified through the temperature measurement of a welding part. As a result, it was confirmed that the shear strength of the lap joint laser welding part was 86.8% that of the base metal.

scholarly journals Numerical And Experimental Analysis of Temperature Distribution And Melt Flow In Fiber Laser Welding of Inconel 625

2021 ◽  
Author(s):  
Iskander Tlili ◽  
Dumitru Baleanu ◽  
S. Mohammad Sajadi ◽  
Ferial Ghaemi
Keyword(s):  
Temperature Distribution ◽  
Laser Welding ◽  
Fiber Laser ◽  
Experimental Results ◽  
Coarse Grained ◽  
Inconel 625 ◽  
Welding Parameters ◽  
Melt Flow ◽  
Fiber Laser Welding ◽  
Speed Accuracy

Abstract In these days, laser is a useful and valuable tool. Low input heat, speed, accuracy, and high controllability of laser welding have led to widespread use in various industries. Nickel-based superalloys are creep-resistant materials used in high-temperature conditions. Also, these alloys have high strength, fatigue, and suitable corrosion resistance. Inconel 625 is a material that is strengthened by a complex deposition mechanism. Therefore, the parameters related to laser welding affect the microstructure and mechanical properties. Therefore, in this study, the effect of fiber laser welding parameters on temperature distribution, weld bead dimensions, melt flow velocity, and microstructure was investigated by finite volume and experimental methods. In order to detect the temperature history during continuous laser welding, two thermocouples were considered at a distance of 2 mm from the welding line. The heat energy from the laser beam was modeled as surface and volumetric heat flux. The results of numerical simulation showed that Marangoni stress and buoyancy force are the most important factors in the formation of the flow of liquid metal. Enhancing the laser power to 400 W led to the expansion of the width of the molten pool by 1.44 mm, which was in good agreement with the experimental results. Experimental results also showed that increasing the temperature from 500 °C around the molten pond leads to the formation of a coarse-grained austenitic structure.

Seam Tracking Monitoring Based on Keyhole Features during High-Power Fiber Laser Welding

2011 ◽  
Vol 314-316 ◽  
pp. 932-936
Author(s):  
Xiang Dong Gao ◽  
Ling Mo ◽  
Seiji Katayama
Keyword(s):  
Laser Beam ◽  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
High Speed ◽  
Continuous Wave ◽  
Welding Process ◽  
Seam Tracking ◽  
Fiber Laser Welding ◽  
Welding Seam

Seam tracking is an important field to obtain good welding quality. During the high-power fiber laser welding, the laser beam focus must be controlled to track the welding seam accurately. A method of detecting the offset between the laser beam focus and the welding seam based on analyzing the keyhole features was researched during high-power fiber laser butt-joint welding of Type 304 austenitic stainless steel plates at a continuous wave fiber laser power of 10 kW. The joint gap width was less than 0.1mm. An infrared sensitive high speed camera was used to capture the thermal images of a molten pool in welding process. Two parameters called the keyhole centroid and keyhole shape were defined as the eigenvalues of seam tracking offset to determine the offset between the laser beam focus and the desired welding seam. The welding experiments confirmed that the offset between the laser beam focus and the welding seam could be monitored and estimated by the keyhole centroid and keyhole shape parameters effectively.

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