Real-time Process Monitoring of Laser Welding by Infrared Camera and Image Processing

2020 ◽  
Vol 856 ◽  
pp. 160-168
Author(s):  
Boonrit Kaewprachum ◽  
Pornsak Srisungsitthisunti
Keyword(s):  
Laser Welding ◽  
Real Time ◽  
Welding Speed ◽  
Molten Pool ◽  
Laser Power ◽  
Rapid Heating ◽  
Welding Process ◽  
Infrared Camera ◽  
Low Carbon ◽  
Welding Processes

Understanding and predicting relationships between laser welding process parameters, such as laser power and welding speed, and molten pool have been studied widely in order to critically control and improve laser welding. The laser welding processes are difficult to monitor in real time because of high temperature and rapid heating characteristics. In this study, infrared camera was set to collect data and provide real time monitoring system to determine the molten pool characteristics and weld quality. This study carried out a laser welding of SS400 low carbon steel and analyzed real-time image of the welding process to determine the average temperature of molten pool and calculate the size of molten pool. By varying the laser power and the welding speed, the infrared camera and imaging processing technique can monitor change of molten pool temperature in a range of 1000 C to 15000 C with about 1% temperature fluctuation. In addition, the size of molten pool can be calculated from the temperature profile of the welding zone. The calculated molten pool size was about 95% accurate compared to the measured size from microscope imaging.

Residual Stress Analysis and Weld Bead Shape Study in Laser Welding of High Strength Steel

2013 ◽  
Author(s):  
Wei Liu ◽  
Fanrong Kong ◽  
Radovan Kovacevic
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Laser Welding ◽  
Welding Speed ◽  
High Strength Steel ◽  
Laser Power ◽  
Measurement Data ◽  
Welding Process ◽  
High Strength ◽  
Weld Bead

The X-ray diffraction (XRD) technique is employed to measure residual stress induced by the laser welding of 6.7 mm thick ASTM A514 high strength steel plates. The distribution of residual stress in the weld bead is investigated. The results indicate that the fusion zone (FZ) has the maximum tensile stress, the transition from tensile to compressive stress tends to appear in the heat affected zone (HAZ), and the initial stress far from the weld center are not influenced by the welding process. Based on the measurement data, the influence of the laser power and the welding speed on residual stress is obtained. The magnitude of residual stress near the weld bead increases with an increase in laser power or a decrease in welding speed. The welds with incomplete penetration have a considerably lower magnitude of residual stress in FZ than ones with full penetration. Post-weld heat treatment is utilized to relieve residual stress in the weld bead. Although residual stress is not completely relieved after the heat treatment, a dramatically reduced magnitude and much more uniform distribution are achieved. In addition, the effects of the laser power, the welding speed, the laser spot diameter, and the gap between two plates on the weld shape are also studied.

scholarly journals Experimental Study of Thermomechanical Processes: Laser Welding and Melting of a Powder Bed

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 246
Author(s):  
Yassine Saadlaoui ◽  
Julien Sijobert ◽  
Maria Doubenskaia ◽  
Philippe Bertrand ◽  
Eric Feulvarch ◽  
...  
Keyword(s):  
Laser Welding ◽  
Molten Pool ◽  
High Speed ◽  
Experimental Approach ◽  
Welding Process ◽  
Infrared Camera ◽  
Powder Bed ◽  
Thermomechanical Processes ◽  
And Behavior ◽  
Physical Quantities

In this study, an experimental approach was developed to analyze and better understand the laser welding and melting of a powder bed process. Different optical diagnostics tools (high-speed camera, infrared camera, pyrometer, etc.) were applied to measure different physical quantities (molten pool morphology, temperature field, residual stresses, and distortions). As a result, measurements during the laser welding process facilitated the building of a database of experimental results (experimental benchmarks). The study of the melting of a powder bed enabled a better understanding of the physics related to the formation and behavior of the molten pool. These results can be used by researchers to improve and validate numerical simulations of these processes.

Effect of Laser Welding on the Mechanical Properties AISI 1018 Steel

MRS Advances ◽  
2017 ◽  
Vol 2 (64) ◽  
pp. 4031-4039 ◽  
Author(s):  
M. A. Carrizalez-Vazquez ◽  
M. Alvarez-Vera ◽  
A. Hernández-Rodríguez ◽  
J. M. Orona-Hinojos ◽  
Gabriel Sandoval-Vázquez ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Fusion Zone ◽  
Heat Affected Zone ◽  
Welding Speed ◽  
Laser Power ◽  
Steel Plates ◽  
Welding Joints ◽  
Welding Processes

AbstractLaser welding processes offer significant advantages such as high welding speed, narrow heat affected zone and quality of the welding joint. In this study, the process parameters of laser power and welding speed were modified for AISI 1018 steel plates of 8 mm thickness and compared using finite element method. The results of cross-section microstructure, heat affected zone and fusion zone were characterized. The grain refinement was affected as the parameters were modified. Tensile and microhardness tests were performed to determine the mechanical properties of the welding joints. Microhardness increased in fusion zone and decreased in heat affected zone. Tensile test showed ductile fracture in heat affected zone of the welding joints. The simulated profiles were compared with the experimental observations showing a reasonable agreement.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

Microstructure and mechanical property improvement of dissimilar metal joints for TC4 Ti alloy to Nitinol NiTi alloy by laser welding

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yan Zhang ◽  
DeShui Yu ◽  
JianPing Zhou ◽  
DaQian Sun ◽  
HongMei Li
Keyword(s):  
Tensile Strength ◽  
Laser Welding ◽  
Mechanical Performance ◽  
Niti Alloy ◽  
Welding Process ◽  
Ti Alloy ◽  
The One ◽  
Fusion Weld ◽  
Welding Processes ◽  
Cu Interlayer

Abstract To avoid the formation of Ti-Ni intermetallics in a joint, three laser welding processes for Ti alloy–NiTi alloy joints were introduced. Sample A was formed while a laser acted at the Ti alloy–NiTi alloy interface, and the joint fractured along the weld centre line immediately after welding without filler metal. Sample B was formed while the laser acted on a Cu interlayer. The average tensile strength of sample B was 216 MPa. Sample C was formed while the laser acted 1.2 mm on the Ti alloy side. The one-pass welding process involved the creation of a joint with one fusion weld and one diffusion weld separated by the remaining unmelted Ti alloy. The mechanical performance of sample C was determined by the diffusion weld formed at the Ti alloy–NiTi alloy interface with a tensile strength of 256 MPa.

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.

Fiber Laser Welding of Noncombustible Magnesium Alloy

2008 ◽  
Vol 580-582 ◽  
pp. 479-482 ◽  
Author(s):  
Yuji Sakai ◽  
Kazuhiro Nakata ◽  
Takuya Tsumura ◽  
Mitsuji Ueda ◽  
Tomoyuki Ueyama ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Magnesium Alloy ◽  
Laser Welding ◽  
Fiber Laser ◽  
Vickers Hardness ◽  
Laser Power ◽  
Welded Joint ◽  
Welding Process ◽  
Fiber Laser Welding ◽  
Laser Welding Process

Noncombustible magnesium alloy AMC602 (Mg-6mass%Al-2mass%Ca) extruded sheet of 2.0mm thickness was successfully welded using a fiber laser welding process at welding speed of 10m/min at 3kW laser power. Tensile strength of the welded joint was about 82 to 88% of that of the base metal. Vickers hardness, tensile strength and micro structural properties are also discussed.

scholarly journals Numerical Simulation Mode of Spot Contact Welding Processes

2021 ◽  
pp. 85-91
Author(s):  
А.С. Угловский ◽  
И.М. Соцкая ◽  
Е.В. Шешунова
Keyword(s):  
Spot Welding ◽  
Low Carbon Steel ◽  
Welding Process ◽  
Welding Parameters ◽  
Low Carbon ◽  
Detailed Data ◽  
Welding Quality ◽  
Welding Processes ◽  
Contact Welding

Цель рассмотрения численного метода заключалась в получении подробных данных, позволяющих оценить проведение сварочного процесса: изменение объёма сварного шва, радиуса сварного шва, радиуса зоны термического влияния. При проведении моделирования авторами выведены зависимости параметров точечной сварки низкоуглеродистой стали толщиной до 3,2 мм. Данные зависимости будут определять качество сварных швов. Соответствующее сочетание параметров точечной сварки обеспечит прочное соединение и хорошее качество сварки. The purpose of the numerical method consideration was to obtain detailed data allowing evaluating the performance of the welding process: changing the volume of the weld, the radius of the weld, the radius of the weld-affected zone. During the simulation the authors have derived dependencies of the parameters of spot welding of low-carbon steel up to 3.2 mm thick. These dependencies will determine the quality of the welds. The correct combination of spot welding parameters will ensure a firm joint and good welding quality.

Numerical Analysis of Solidification Behavior during Laser Welding Nickel-Based Single-Crystal Superalloy Part: II Crystallography-Dependent Supersaturation of Liquid Aluminum

2021 ◽  
Vol 1018 ◽  
pp. 13-22
Author(s):  
Zhi Guo Gao
Keyword(s):  
Laser Welding ◽  
Single Crystal ◽  
Weld Pool ◽  
Welding Speed ◽  
Heat Input ◽  
Laser Power ◽  
Liquid Aluminum ◽  
Dendrite Growth ◽  
Solidification Cracking ◽  
Solid Liquid Interface

The thermal metallurgical modeling of liquid aluminum supersaturation was further developed through couple of heat transfer model, dendrite selection model, multicomponent dendrite growth model and nonequilibrium solidification model during three-dimensional nickel-based single-crystal superalloy weld pool solidification. The welding configuration plays more important role in supersaturation of liquid aluminum, morphology instability and nonequilibrium partition behavior. The bimodal distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically symmetrical about the weld pool centerline in (001) and [100] welding configuration. The distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically asymmetrical throughout the weld pool in (001) and [110] welding configuration. Optimum low heat input (low laser power and high welding speed) with (001) and [100] welding configuration is more favored to predominantly promote epitaxial [001] dendrite growth to reduce the metallurgical factors for solidification cracking than that of high heat input (high laser power and slow welding speed) with (001) and [110] welding configuration. The lower the heat input is used, the lower supersaturation of liquid aluminum is imposed, and the smaller size of vulnerable [100] dendrite growth region is incurred to ameliorate solidification cracking susceptibility and vice versa. The overall supersaturation of liquid aluminum in (001) and [100] welding configuration is beneficially smaller than that of (001) and [110] welding configuration regardless of heat input, and is not thermodynamically relieved by gamma prime γˊ phase. (001) and [110] welding configuration is detrimental to weldability and deteriorates the solidification cracking susceptibility because of unfavorable crystallographic orientations and alloying aluminum enrichment. The mechanism of asymmetrical solidification cracking because of crystallography-dependent supersaturation of liquid aluminum is proposed. The eligible solidification cracking location is particularly confined in [100] dendrite growth region. Moreover, the theoretical predictions agree well with the experiment results. The useful modeling is also applicable to other single-crystal superalloys with similar metallurgical properties for laser welding or laser cladding. The thorough numerical analyses facilitate the understanding of weld pool solidification behavior, microstructure development and solidification cracking phenomena in the primary γ phase, and thereby optimize the welding conditions (laser power, welding speed and welding configuration) for successful crack-free laser welding.

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