Laser Welding Applications Research Articles

Microstructure Analysis of Laser Bonding Welding on Steel-Aluminum

Laser bonding welding test of the lap joint between steel and Al was conducted. The microstructure analysis is carried out by means of metallographic microscope, which provides an important theoretical and experimental basis for the popularization and application of laser welding of steel / aluminum dissimilar metal structures. The results showed that under the conditions of 1650W laser power, 35m/s welding speed, +3mm defocus amount and 25L/min flow rate of Ar as the protective gas, there are no cracks, pores and inclusions in the weld zone. The fusion line is smooth and smooth. Under the conditions of 1650W laser power, 38m/s welding speed, +3mm defocus amount and 25L/min flow rate of Ar as the protective gas, the overall appearance of the weld zone of the laser welding joint, there are serious cracks, pores and other defects in the weld area. In the P=1680W, V=35mm/s, f=+1mm, q=20L/min, the crystal structure appeared, in the process of cooling, the crack expands and forms a radial shape under the action of internal stress.

Opto-Electron Eng, 2017, 44(10)] Research status and development prospects of laser welding under vacuum

Compared with conventional laser welding, the welding quality was improved significantly while the laser welding was conducted under vacuum. The penetration depth of the weld seam increased sharply. The welding formation was improved and the porosity defects were suppressed effectively. In recent years, numerous researches on the mechanism of welding process, low vacuum and local subatmospheric pressure laser welding equipments have been undertaken. The laser welding under vacuum exhibits the wonderful application prospects to weld the thick plates in the shipbuilding, nuclear instrument and pressure vessel industries. The influences of ambient pressure on the laser welding penetration depth, surface formation and porosity defect were summarized. The domestic and overseas research findings on mechanism of laser welding under vacuum were elaborated from the aspects of plasma plume, keyhole and molten pool behaviors. In addition, the applications of laser welding under vacuum in the industry were introduced. Finally, the problems of reported researches were analyzed and the prospects of the technology were discussed.

Investigation on the Effect of Pulsed Energy on Strength of Fillet Lap Laser Welded AZ31B Magnesium Alloys

AZ31B magnesium alloy have been hugely applied in the aerospace, automotive, and electronic industries. However, welding thin sheet AZ31B was challenging due to its properties which is easily to evaporated especially using conventional fusion welding method such as metal inert gas (MIG). Laser could be applied to weld this metal since it produces lower heat input. The application of fiber laser welding has been widely since this type of laser could produce better welding product especially in the automotive sectors. Low power fiber laser was used to weld this non-ferrous metal where pulse wave (PW) mode was used. Double fillet lap joint was applied to weld as thin as 0.6 mm thick of AZ31B and the effect of pulsed energy on the strength was studied. Bond width, throat length, and penetration depth also was studied related to the pulsed energy which effecting the joint. Higher pulsed energy contributes to the higher fracture load with angle of irradiation lower than 3 °

Fundamental understanding of the interaction of continuous wave laser with aluminium

In welding, the depth of penetration, weld profile and the corresponding thermal cycle are the three basic outcomes that a user wishes to control flexibly. In laser welding applications, controlled application of power and energy density is the key to achieve predictable control of these characteristics. Creation of an analytical model is an important step towards understanding the underpinning science of laser metal interaction in controlling the depth, bead geometry and thereby temperature profile of a weld. The “power factor model”, which correlates the power applied per unit length to the laser metal interaction time, has been originally developed and validated for mild steel, guides a user on the selection laser system parameters, to achieve specific weld profile. This study is performed to extend the power factor–interaction time model to aluminium alloys by understanding the underpinning laser aluminium interaction parameters in terms of power density, interaction time, specific point energy and their correlation with the weld bead profiles. Although the power factor and interaction time showed a rectangular hyperbolic relationship, as observed in low carbon steel, for a specific weld depth and profile, the absolute magnitude and the characteristic profile of the curve is different due to the intrinsic differences in physical and thermal properties of aluminium as compared to steel. It was shown that identical depth of penetration but different weld metal profile can be obtained for a specific beam diameter for a range of power and travel speed by keeping the energy input per unit length constant.

Validation of a spatter detection algorithm for remote laser welding applications

The use of laser scanners in industrial laser welding applications is increasing. Welding spatters are challenging if a high quality is required. A control system for spatters is currently being developed, and this study focuses on the validation of a robust spatter detection algorithm. To validate the detection algorithm, artificial spatter images are created. These images provide the ground truth concerning the number of spatters and can therefore be used to improve the recognition quality of the detection algorithm. As a result, this paper describes a method for validating a spatter detection algorithm, which can recognize spatters with a high accuracy.

Analytic temperature field solution of dual laser welding heat sources and application in static recrystallization

The explicit temperature function of dual laser welding was presented, and the effect of welding pass distance and heat source distance on the thermal history was analyzed. There was excellent correlation between analytically solved and finite element method (FEM)-predicted dual laser welding temperature field. The analytical temperature function is applied to study the static recrystallization kinetics upon dual laser welding of nanobainite steel. By calculation, the optimal welding process parameters can be obtained when the static recrystallization fraction takes the maximum value. The corresponding temperature is above the martensite transus temperature and is appropriate to produce sufficient plastic strain in the austenite grains.

Benefits And Prospects Of Laser Welding Application In Vacuum

<p>In the recent years laser beam welding has been more and more broadly used in the industry for the production of details of significant appointment. One of the perspective directions of laser technologies for the production of significant products of big thickness is the welding by the concentrated laser beam in vacuum that allows producing faultless welded seams with the high relation of seam depth to its width. The conducted researches confirm results of theoretical modeling of processes at laser beam welding.</p>

Trend and innovations in laser beam welding of wrought aluminum alloys

The drive toward fulfilling weight reduction obligation, superior weld quality requirement, and industrial manufacturing rationale has sprung up considerable interest in applying laser welding technology on aluminum alloys. Nevertheless, porosity, solidification cracking, and surface reflectivity have been the major banes of laser welding of aluminum alloys. However, literature has shown that positive efforts have been accomplished in reducing these fundamental concerns by adopting careful selection of welding procedure, modification of pure laser welding techniques, and the use of appropriate filler metal. Albeit, there is still upbeat progression on the application and improvement of laser welding of aluminum alloys. At present, laser welding technology has the potential of fulfilling industrial requirements in joining lightweight aluminum alloys because of its capacity for automation and intrinsic flexibility, precision and repeatability, low general heat input, high welding speed, and low weld distortion. As a result, this report examines the available and current status of laser technologies in welding aluminum alloys. It further categorizes the laser technologies of aluminum alloys into four assemblages, namely, pure or single-beam laser welding, laser-arc hybrid welding, tailored heat source laser welding, and other innovative laser welding technologies, respectively. Mechanical, corrosion, and microstructural behaviors of laser welded aluminum alloys are also studied. Conversely, some of the research areas that need further investigations are proposed. Corrosion behavioral properties, influence of micropores on fatigue and quasi-static tensile strength, and toughness characterization of laser welded aluminum alloys are insufficient in literature.

Flexible System Solutions for Innovative Laser Welding Processes

AbstractThe new platform WeldMaster by Precitec provides a large toolset for modern laser welding applications. Sensors and actuators for the pre‐, in‐ and post‐process monitoring and control are implemented, offering the most advanced all‐in‐one system‐solution for laser welding tasks. The customer's benefits are especially valuable in automotive applications, where robustness, efficiency and reliability are highly demanded. The combination with an intelligent welding head allows to improve known applications and to develop trend‐setting joining processes.

Fusion weldability studies in aerospace AA7075-T651 using high-power continuous wave laser beam techniques

Abstract The weldability of AA7075-T651 during keyhole laser and laser–arc hybrid welding was studied using microstructural and X-ray radiography techniques. The results showed that the application of cold wire laser welding reduced macroporosity, while the problem of heat-affected zone (HAZ) cracking was appreciably minimized by modifying the amount of heat in the HAZ. It was also found that the welding condition that minimized macroporosity was found unfavorable for resistance to HAZ cracking and vice versa. A compromise between these competing weld discontinuities was realized by a combination of localized modification of the strength of the HAZ and the application of cold wire laser welding. Also, differences were observed in the extent of porosity for Ar-shielded and He-shielded laser welds, where Ar shielding appeared to be more effective in minimizing porosity. In addition, the ability of AA7075-T651 to recover mechanical strength by post-weld natural aging will be useful when post-weld heat treatment is not practicable.

Numerical sensitivity analysis of single pulse laser welding with a C-shaped beam

Even though Gaussian and top-hat beam profiles are suitable for most laser welding applications, for certain cases other beam distributions can be favored in terms of weld quality or performance. One promising method to generate a tailored beam shape is diffractive optical elements. A numerical model on the temperature field generated by specific beam shapes is therefore under development to iteratively identify desired beam shapes for specific applications. The present study is based on two thin steel sheets that are conduction welded in a lap joint mode by a C-shaped single laser pulse. The main aim is to ensure a specified weld width along the C-weld shape at the overlap interface between the two sheets in a robust manner. The sensitivity of main criteria like the interface weld width and phase changes at the workpiece top and bottom is studied and discussed in a systematic manner by applying a numerical heat transfer model for various parameters and conditions.

Nickel-containing superalloy laser weld qualities and properties

Hot section jet engine and elevated temperature corrosion-resistant applications can both require high integrity welding of nickel-containing superalloy components, both in original fabrication and subsequent repair operations. However, it is recognized that there can be a number of difficulties when welding these alloys, including the introduction of cracks, pores, distortion, and/or the degradation of mechanical properties. Laser welding, being a low heat input process, has potential for low distortion fabrication. However, concerns remain around the weld qualities that can be achieved in these materials [Khan et al., “Meeting weld quality criteria when laser welding Ni-based alloy 718,” in ICALEO, Anaheim, USA (2012), Paper No. 1707], and the effect laser welding could have on material properties. In this work, TWI and NLR have examined the development and application of fiber laser welding for a number of superalloys, of different grades and thicknesses. The weld qualities and microstructures were evaluated (e.g., using X-ray radiography, metallographic sectioning, and microscopic examination). Selected static and dynamic mechanical properties were also measured, both at room temperature and at elevated temperatures, more representative of service conditions. In this way, the relative qualities, tensile strengths, ductility, and low cycle fatigue behaviors of a range of different laser welds have been compared.

Strength characterization of assemblies of polymers, made by laser welding

We experimentally establish a plastic and breaking intrinsic stress criterion for welded joints made by laser radiation using the TWISTr configuration. This welding is used in junction of two plastics materials, one laser transparent, one no laser transparent as control panels. Two types of plastic materials have been studied, ABS and PA66 polymers. The yield surface which characterize the limit of elasticity and the rupture surface have been described by a modified Drucker-Prager criterion identified in the case of complex mixed modes state of stresses coupling tensile and shear stresses. The conclusion is that ABS is a good candidate for laser welding application, whereas PA66 presents lower mechanical properties in the welding area. For design purpose of welded zones, the proposed Drucker-Prager criterion has been used for the calculation and the simulation of breaking welded ABS plates and welded PA66 step plates. The comparison between experimental and numerical simulation values shows a relatively good agreement.

초고장력 강판을 적용한 Cowl Cross Member의 레이저 용접 적용에 관한 연구

A cowl cross is a part of the car's instrument panel used to maintain the rigidity of the vehicle body side. The application of laser welding has the benefits of speed and thermal deformation compared to arc welding. An ultra-high strength steel sheet is used to reduce the weight of the vehicle body parts. Generally, formability of such a steel sheet is poor because its elongation is very low. For this reason, a method for cold forming of an ultra-high strength steel sheet is required. This paper describes how to improve the formability and weldability of the ultra-high strength steel sheet. Mechanical tests of this material were also performed to evaluate the welding properties of <TEX>$CO_2$</TEX> (GMAW) and those of laser welding.

Fiber Laser Seam Stepper Replacing Resistance Spot‐Welding

AbstractResistance spot welding is known in high‐volume production environment in the automotive industry since many years. The laser welding technology is also established in this application for more than 20 years, however it could still not capture the majority of the market even the modern laser welding application offers the following advantages:

Prediction of pore size in high power density beam welding

This study is to investigate parameters responsible for the final pore size during high power density laser and electron beam welding processes. Dimensionless parameters include the surface tension parameter, Mach number and liquid pressure at the keyhole base, friction factor, melting temperature, ratio of specific heats at constant pressure and volume, and loss coefficient. The friction factor can also be treated as a combination of viscous shear stress and thermocapillary force. Although the formation of macro-porosity is recognized as an important problem that limits the widespread industrial application of laser and electron beam welding, the physics of the macroporosity formation is not well understood. In order to solve this problem, both the states at the times when the keyhole is about to be enclosed and the pore is completely formed are considered to be governed by the equation of state. The pore shape thus can be determined by the Young–Laplace equation. The gas pressure is determined by calculating a compressible flow of the two-phase, vapor–liquid dispersion in a vertical keyhole of varying cross-section, paying particular attention to transition between the annular and slug flows. It shows that regardless of a supersonic or subsonic flow at the base, the final pore size decreases as the dimensionless surface tension parameter, liquid pressure at the keyhole base, and melting temperature decrease. The pore size also decreases with increasing friction factor subject to a supersonic flow at the base. The effects of the ratio of specific heats at constant pressure and volume, friction factor and loss coefficient on the final pore size are insignificant for a subsonic mixture. This work provides a systematical understanding of the factors affecting the final pore size during keyhole mode welding.

Workstation Configuration and Process Planning for RLW Operations

The application of Remote Laser Welding (RLW) has become an attractive assembly technology in various branches of industry, as it offers higher efficiency at lower costs compared to traditional Resistance Spot Welding (RSW) when high volumes of sheet metal assemblies are to be produced. However, the introduction of RLW technology raises multiple new issues in designing the configuration, the layout, and the behavior of the assembly system. Since configuring an RLW workstation and planning the welding process are closely interrelated problems, a hierarchical decision process must be applied where configuration and planning go hand in hand. The paper presents a hierarchical workflow for workstation configuration and process planning for RLW operations, and proposes methods for solving the decision problems related to each step of this workflow. A software toolbox is introduced that has been developed to facilitate a semi-automatic, mixed-initiative workstation design and to guide the expert user throughout the configuration, planning, programming, evaluation, and simulation of the RLW workstation. A case study from the automotive industry is presented, where the software tools developed are applied to configuring and planning the behavior of an RLW workstation that replaces RSW technology in assembling a car door.

Microwire Feeder for Laser Applications

This paper focuses on the design and development of a fine microwire feeder for laser applications. The use of metallic wires as a medium of deposition has been popular in aerospace and car manufacturing industries. These micro sized wires are also gaining importance in medical and semi-conductor industries. The use of wire-feeders in laser welding and electrical discharge machining applications has been prominent. There are devices used in laser applications which can handle wires from 0.25mm to 10.0 mm in diameter. The handling of microsized wire in laser application is often considered difficult due to its low buckling strength exposure to harsh environment. The primary function of the microwire feeder described in this paper was to feed wires of varying microdiameters to a desired location with high accuracy and precision to be used in a laser aided manufacturing processes. This can be designed by dividing the microwire feeder into four basic sub-mechanisms: (1) feeding mechanism (2) transfer mechanism (3) precision guidance mechanism (4) adjustment mechanism. These sub-mechanisms are integrated to account for compactness, flexibility and precision. This microwire feeder is capable of handling wires as low as 0.05 mm in diameter. The precision and accuracy of the device was experimentally tested prior to its practical application. A case study on laser deposition was presented; where; a 316 stainless steel microwire of 0.125 mm diameter was fed into a melt pool of 0.2 mm. The wire feed and the traverse speed of the table were varied to achieve a uniformly distributed clad. The effect of wire feed and traverse speed were studied and a deposition process window was developed for future experimentation.

Mechanical properties of thin films of laser-welded titanium and their associated welding defects

The aim of this study was to evaluate the mechanical properties of thin films of laser-welded cast titanium using an interference strain/displacement gauge (ISDG) and to analyze factors that affect laser welding. Dog-bone-shaped small specimens of cast titanium were prepared by wire cutting after they were laser-welded. The specimens were divided into three groups according to the gap distance of the laser weld; the control was non-welded titanium. Small specimens without cast defects detected by X-ray screening were measured by a tensile test machine using ISDG, and stress-strain curves were drawn. Finally, the fracture texture was analyzed. The ultimate tensile strengths (UTSs) of specimens with a gap distance of 0.00, 0.25, and 0.50mm were 492.16 ± 33.19, 488.09 ± 43.18, and 558.45 ± 10.80MPa, respectively. There were no significant differences in UTS between the test groups and the control group (p > 0.05). However, the plastic deformation and the percent elongation increased as the gap distance increased. Incomplete penetration defects appeared in groups that had small gap distances, which may have affected the properties of the laser-welded titanium. However, the welding material was still pure titanium. These results suggest that an appropriate gap distance should be maintained to improve the application of dental laser welding.

LASER PROCESSING ACTIVITIES IN FINLAND – TECHNOLOGICAL AND EDUCATIONAL VIEW

This paper presents the current situation of laser processing technology in Finland; industrial activities, research and development and education. The Finnish laser processing R&amp;D started in 1985 in Lappeenranta University of Technology. The major portion of industrial laser applications are laser cutting and laser welding has a minor role. In the late 1990’s the number of laser welding applications started to grow and many subcontractors established facilities. Research and education on laser materials processing is concentrated in two universities, Lappeenranta and Tampere Universities of Technology. The main research fields are in laser and hybrid welding, surface treatment, laser welding of plastics, micro laser processing and paper processing. In addition, several Applied Universities and schools have started their education and service for the industry in laser and hybrid laser welding and cutting. The postgraduate educational activities in laser processing in Finland are comprehensive in all levels from laser operators to international laser experts. Finland has been the one of the most active countries in the world in organizing continuing education in laser material processing.DOI: http://dx.doi.org/10.5755/j01.mech.18.5.2691