Analysis of Characteristic of Metal Vapor Plume during High-Power Disc Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 1126-1129
Author(s):  
Qian Wen ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
High Speed ◽  
Welding Process ◽  
Metal Vapor ◽  
Welding Quality ◽  
Absolute Value ◽  
Coordinate Difference ◽  
Vapor Plume ◽  
The Absolute

Metal vapor plume which induced during high power disc laser welding contains lots of information that related to the welding quality. Stainless steel 304 was taken as the experiment object for the high power disc laser welding experiment. A high-speed camera was used to capture the ultraviolet band and visible light band metal vapor plume images in the laser welding process. Image processing techniques such as median filtering, Wiener filtering, gray level threshold and image binarization were applied to get the images that only metal vapor plume was included. The ratio of the absolute value of coordinate difference between the centroid of plume and welding point was taken as the characteristic parameter. Welding experimental results and analysis of the changing of the ratio of the absolute value of coordinate difference between the centroid of plume and welding point confirmed that the welding quality could be monitored by the metal vapor plume during high power disc laser welding.

Analysis of Image Characteristics of Plume and Spatter of High Power Disk Laser Welding Based on K-L Transform

2012 ◽  
Vol 532-533 ◽  
pp. 330-334
Author(s):  
Qian Wen ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
High Speed ◽  
Metal Vapor ◽  
Mean Value ◽  
Gray Level ◽  
Characteristic Parameters ◽  
Transform Method ◽  
Disk Laser ◽  
Vapor Plume

Metal vapor plume and spatters are the important phenomena in the process of high power disk laser welding, and there exists a close relationship with the welding stability. The images of metal vapor plume and spatters which captured by a high speed camera during high power disk laser welding were analyzed in this experiment. Image processing techniques such as median filtering, Wiener filtering, gray level threshold and lightness transform were used to process the images so that the image characteristic parameters such as the area and number of spatters in an image, the average gray, mean value, variance and entropy of a spatter gray level image and the coordinate ratio of the centriod of plume and the welding point can be extracted. To reflect the actual welding results obviously by those characteristic parameters, K-L transform method was used to get a new set of characteristic parameters. Experimental results showed that this new set of characteristic parameters could reflect the actual welding effectively.

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.

Investigation of Image Characteristics of Plume and Spatters during High-Power Disk Laser Welding

2013 ◽  
Vol 709 ◽  
pp. 301-304 ◽  
Author(s):  
Gui Qian Liu ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
Laser Power ◽  
High Speed ◽  
Continuous Wave ◽  
Welding Process ◽  
Metal Vapor ◽  
High Speed Photography ◽  
Monitoring And Control ◽  
Disk Laser

During high-power laser welding process, the workpiece produces metal vapor because of the laser irradiation. The characteristics of metal vapor are related to the quality and stability of welding and the utilization of the laser power. An approach of analyzing the characteristics of metal vapor was researched during high-power disk laser bead-on-plate welding of Type 304 austenitic stainless steel plates at a continuous wave laser power of 10 kW. A high-speed photography was used to capture metal vapor dynamic images. Metal vapor area, beam path, swing angle are calculated by image processing, which is the foundation for monitoring and control of welding quality in real time.

Classification of Plume Image and Analysis of Welding Stability during High Power Disc Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 1139-1142 ◽  
Author(s):  
Qian Wen ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
Nearest Neighbor ◽  
Welding Process ◽  
Welding Quality ◽  
K Nearest Neighbor ◽  
Dimension Vector ◽  
Absolute Value ◽  
Neighbor Classification

Plume images which captured during the high power disc laser welding contain lots of information that related to the welding quality and stability. The classification of plume images is an important foundation for online monitoring during welding process. Stainless steel 304 was taken as the experiment object for the high power disc laser welding experiments. A high-speed camera was used to capture the ultraviolet band and visible light band plume images in the laser welding process. Image processing techniques were applied to get the characteristic parameters such as the ratio of the absolute value of coordinate difference between the centriod of plume and the welding point, the number of spatter, the average gray level and entropy of a spatter image, and formed a four dimension vector. Then K-nearest neighbor classification method was used to separate the poor welding quality images out from good ones. Welding experimental results confirmed that using K- nearest neighbor classification method to classify the four dimension vector samples which formed by the ratio of absolute value of coordinate difference between the centriod of plume and welding point, number of spatters, average gray level and entropy could obtain a recognition rate that close to the actual welding results.

Segmentation of Molten Pool Infrared Images Using Morphology during High Power Disk Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 91-94
Author(s):  
Yan Xi Zhang ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
Molten Pool ◽  
Welding Process ◽  
Histogram Equalization ◽  
Welding Quality ◽  
Infrared Images ◽  
Traditional Methods ◽  
Disk Laser ◽  
Laser Welding Process

Configuration of a molten pool is related to the laser welding quality. Analyzing the configuration of a molten pool is important to monitor the laser welding process. This paper proposes a method of segmentation of a molten pool and its shadow during high power disk laser welding, consequently provides the groundwork for reconstruction of the molten pool and analysis of welding quality. Subsection linear stretching histogram equalization was applied to enhance the contrast of the original images firstly, and then edge detection was used to highlight the edges. After that we used the morphology filtering method to produce the segmentation mask, and then combined the mask with the original images to get the final segmentation results. Also, the proposed method was compared with other traditional methods. The experimental results showed that our method not only could give better segmentation results and process large quantities images automatically, but also overcame the less-segmentation problems of traditional methods.

Study of Plume Behavior during High-Power Disk Laser Welding

2012 ◽  
Vol 201-202 ◽  
pp. 1076-1079
Author(s):  
De Yong You ◽  
Xiang Dong Gao
Keyword(s):  
Laser Welding ◽  
High Power ◽  
High Speed ◽  
Welding Process ◽  
Image Sequences ◽  
Process Conditions ◽  
High Speed Photography ◽  
Disk Laser ◽  
Industrial Manufacturing ◽  
Laser Welding Process

Laser welding process has been widely used in industrial manufacturing. The purpose of this paper is to explore the inter-relation between laser welding results and the laser-induced plume behavior. High-power disk laser welding of stainless steel type304 was performed at different welding speeds. Combing the high speed camera and ultraviolet sensing filter, the plume image sequences of laser welding process have been obtained. Plume features including plume volume and plume flowing direction have been extracted by using high-speed photography and image processing technology. The dynamic behavior of laser-induced plume was investigated. The results showed that the laser-induced plume feature, especially the plume volume, was closely related to laser welding process conditions.

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.

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.

Color Image Segmentation of Plume for Monitoring Disk Laser Welding Process

2012 ◽  
Vol 201-202 ◽  
pp. 166-169
Author(s):  
Teng Wang ◽  
Xiang Dong Gao
Keyword(s):  
Image Segmentation ◽  
Laser Welding ◽  
High Speed ◽  
Clustering Algorithm ◽  
Color Image ◽  
Color Space ◽  
Welding Process ◽  
Metal Vapor ◽  
Color Image Segmentation ◽  
Deep Penetration

During deep penetration laser welding, changes in the metal vapor plume contain information about the stability of welding process. A high-speed camera was used to online monitor the welding process in order to detect the laser welding defects. A color segmentation clustering algorithm based on HSI color space was proposed for processing the recorded welding sequences. The effectiveness of algorithms based on different model is discussed, welding experimental results showed that the proposed algorithm could achieve better image segmentation, and it highlighted the edge of the metal vapor details in the image.

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