Extraction of Characteristic Parameters of Keyhole during High Power Fiber Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 352-355
Author(s):  
Yong Hua Liu ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Continuous Wave ◽  
Welding Process ◽  
Detection Methods ◽  
Deep Penetration ◽  
Welding Quality ◽  
Characteristic Parameters ◽  
Fiber Laser Welding

During deep penetration laser welding, a keyhole is formed in the molten pool. The characteristics of keyhole are related to the welding quality and stability. Analyzing the characteristic parameters of a keyhole during high power fiber laser welding is one of effective measures to control the welding quality and improve the welding stability. This paper studies a fiber laser butt-joint welding of Type 304 austenitic stainless steel plate with a high power 10 kW continuous wave fiber laser, and an infrared sensitive high-speed video camera was used to capture the dynamic images of the molten pools. A combination filtering system with a filter length of 960-990nm in front of the vision sensor was used to obtain the near infrared image and eliminate other light disturbances. The width, the area, the leftmost point, the rightmost point, the upmost point and the bottommost point of a keyhole were defined as the keyhole characteristic parameters. By using the image preprocessing method, such as median filtering, Wiener filtering, threshold segmentation and Canny edge detection methods, the characteristic parameters of a keyhole were obtained. By analyzing the change of the keyhole characteristic parameters during welding process, it was found that these parameters could reflect the quality and stability of laser welding effectively.

Elucidation of Welding Stability Based on Keyhole Configuration during High-Power Fiber Laser Welding

2011 ◽  
Vol 314-316 ◽  
pp. 941-944 ◽  
Author(s):  
Xiang Dong Gao ◽  
Qian Wen ◽  
Seiji Katayama
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Continuous Wave ◽  
High Energy ◽  
High Energy Density ◽  
Deep Penetration ◽  
Characteristic Parameters ◽  
Fiber Laser Welding ◽  
Welding Stability

During deep penetration laser welding, a keyhole is formed in the molten pool due to the intense recoil pressure of evaporation. The formation of the keyhole leads to a deep penetration weld with a high aspect ratio and this is the most advantageous feature of welding by high-energy-density beams. The configuration and characteristics of a keyhole are related to the welding stability. In a fiber laser butt-joint welding of Type 304 austenitic stainless steel plate with a high power 10 kW continuous wave fiber laser, an infrared sensitive high-speed video camera was used to capture the dynamic images of the molten pools. The configurations of a keyhole were analyzed through image processing techniques such as median filtering, wiener filtering and gray level threshold segmentation to obtain the edge of a keyhole. The width and the area of a keyhole were defined as the keyhole characteristic parameters, and the deviation between the laser beam and weld center as a parameter reflecting the welding stability. By analyzing the change of the keyhole characteristic parameters during welding process, it was found that these parameters were related to the welding stability. Welding experimental results and analysis of the keyhole characteristic parameters confirmed that the welding stability could be monitored and distinguished by a keyhole configuration during high-power fiber laser welding.

Detection of Seam Offset Based on Molten Pool Characteristics during High-Power Fiber Laser Welding

2012 ◽  
Vol 549 ◽  
pp. 1064-1068
Author(s):  
Jian Bin Liang ◽  
Xiang Dong Gao ◽  
De Yong You ◽  
Zhen Shi Li ◽  
Wei Ping Ruan
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Molten Pool ◽  
High Energy ◽  
High Energy Density ◽  
Deep Penetration ◽  
Characteristic Parameters ◽  
Fiber Laser Welding ◽  
Deep Penetration Welding

Laser welding includes the heat conduction welding and the deep penetration welding. Deep penetration welding can not only penetrate the material completely, but also can vaporize the material. An important phenomenon during deep penetration welding is that molten pool in the weldment will appear a keyhole. The formation of the keyhole leads to a deep penetration weld with a high aspect ratio and this is the most advantageous feature of welding by high-energy-density beams. Small focus wandering off weld seam may result in lack of penetration or unacceptable welds, and largely reduce heating efficiency. In a fiber laser butt-joint welding of Type 304 austenitic stainless steel plate with a high power 6kW continuous wave fiber laser, an infrared sensitive high-speed video camera was used to capture the dynamic images of the molten pools. The configurations of molten pools were analyzed through image processing techniques such as median filtering, partial Otsu threshold segmentation and Canny edge to obtain the edge of keyholes and molten pools. The circular degree and the area of keyholes and the width and average gray of molten pools were defined as characteristic parameters to reflect the seam offset between the laser beam and the weld center. By analyzing the change of characteristic parameters during welding process, it was found that these parameters were related to the seam offset. Welding experimental results and analysis of characteristic parameters confirmed that the seam offset could be monitored and distinguished by molten pools configuration during high-power fiber laser welding.

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.

scholarly journals A Study on Determining Weld Joint Hardening and a Quality Evaluation Algorithm for 9% Nickel Weld Joints Using the Dilution Ratio of the Base Material in Fiber Laser Welding

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1308
Author(s):  
Minho Park ◽  
Jisun Kim ◽  
Changmin Pyo ◽  
Jaewoong Kim ◽  
Kwangsan Chun
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
Weld Joint ◽  
Base Material ◽  
Welding Process ◽  
Fuel Oil ◽  
Welding Quality ◽  
Dilution Ratio ◽  
Fiber Laser Welding ◽  
Evaluation Algorithm

The demand for LNG-powered ships and related equipment is rapidly increasing among major domestic and foreign carriers due to the strengthened IMO regulations on the sulfur content of ship fuel oil. LNG operation in a cryogenic environment requires a storage tank and fuel supply system that uses steel with excellent brittleness and fatigue strength. A ship using LNG is very sensitive to explosion and fire. For this reason, 9% Ni is often used, because ships require high quality products with special materials and structural technologies that ensure operability at cryogenic temperatures. However, research to derive uniform welding quality is urgent because the deterioration of weld quality in the 9% Ni steel welding process is caused by high process difficulty and differences in welding quality depending on a welder’s skill set. This study proposes a method to guarantee a uniform quality of 9% Ni steel in a fiber laser welding process by categorizing weld joint hardness according to the dilution ratio of a base material and establishing a standard for quantitative evaluation.

Effect of Laser-Induced Plume on Welding Process During High Power Fiber Laser Welding

2014 ◽  
Vol 41 (6) ◽  
pp. 0603005 ◽  
Author(s):  
邹江林 Zou Jianglin ◽  
李飞 Li Fei ◽  
牛建强 Niu Jianqiang ◽  
孔晓芳 Kong Xiaofang ◽  
马然 Ma Ran ◽  
...  
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Welding Process ◽  
Fiber Laser Welding

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 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.

Keyhole Morphological Characteristics in High-Power Deep Penetration Fiber Laser Welding

2020 ◽  
Vol 47 (11) ◽  
pp. 1102005
Author(s):  
赵乐 Zhao Le ◽  
曹政 Cao Zheng ◽  
邹江林 Zou Jinglin ◽  
韩雪 Han Xue ◽  
肖荣诗 Xiao Rongshi
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Morphological Characteristics ◽  
Deep Penetration ◽  
Fiber Laser Welding

Extraction of Molten Pool and Keyhole Characteristics during High Power Fiber Laser Welding

2012 ◽  
Vol 532-533 ◽  
pp. 344-347
Author(s):  
Ren He Zhen ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
High Power ◽  
Molten Pool ◽  
Critical Role ◽  
Welding Process ◽  
Fiber Laser Welding ◽  
Inspection Method ◽  
Weld Pool Geometry ◽  
Laser Welding Process

It is well known that weld pool geometry plays a critical role in laser welding. In this study, an IPG YLR-10000 device was used to capture a series of molten pool images during high power fiber laser welding process. Then an extraction method of the geometric characteristics of these images was developed. This method could be applied to monitor the configuration of a molten pool and keyhole which was related to welding quality. The experimental results showed that this method was a reliable inspection method for monitoring the configuration of molten pool during high power fiber laser welding.

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