Monitoring of high-speed laser welding process based on vapor plume

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.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.201-202.388 ◽

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.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.201-202.1126 ◽

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.

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

Metals ◽

10.3390/met8080625 ◽

2018 ◽

Vol 8 (8) ◽

pp. 625 ◽

Cited By ~ 3

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.

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