Paul Kah

The effect of the relative location of laser beam with arc in different hybrid welding processes

Hybrid welding requires that several parameters are properly adjusted in order to reach high weld quality. One of the main setup parameters of hybrid welding is the order of the different power sources. The selection partly depends on the results desired for welding whether it is gap bridging, penetration depth, welding speed, melting efficiency, process stability, control of weld width, porosity reduction or weld appearance. In this paper we have studied how the placement of the different sources in laser hybrid welding influences the overall weld quality. The paper is based on an analysis of the results of various studies carried out by different research groups. The process is analyzed with regard to process parameters, the type and thickness of the base material, power and beam quality together with the optical parameters of the laser system applied.Hybrid welding requires that several parameters are properly adjusted in order to reach high weld quality. One of the main setup parameters of hybrid welding is the order of the different power sources. The selection partly depends on the results desired for welding whether it is gap bridging, penetration depth, welding speed, melting efficiency, process stability, control of weld width, porosity reduction or weld appearance. In this paper we have studied how the placement of the different sources in laser hybrid welding influences the overall weld quality. The paper is based on an analysis of the results of various studies carried out by different research groups. The process is analyzed with regard to process parameters, the type and thickness of the base material, power and beam quality together with the optical parameters of the laser system applied.

Aluminium alloys welding processes: Challenges, joint types and process selection

Aluminium and its alloys have gained increasing importance in structural engineering due to advantageous properties such as light weight, ease of machining and corrosion resistance. This article presents surface-related challenges facing aluminium welding, specifically weld process limitations and joint limitations. The methodological approach is a critical review of published literature and results based on eight industrial welding processes for aluminium and six joint types. It is shown that challenges such as heat input control, hot cracking, porosity and weldable thickness vary with the process used and that there is no optimal general weld process for all aluminium alloys and thicknesses. A selection table is presented to assist in selection of the optimal process for specific applications. This study illustrates that knowledge of weld limitations is valuable in selection of appropriate weld processes.

Trends in Joining Dissimilar Metals by Welding

The welding of dissimilar materials finds a wide variety of applications in the fields of industrial construction and manufacturing, where the characteristic features of the different materials are optimized for the desired application to result in cost effectiveness and value addition. Non-fusion welding methods such as solid state welding and high energy beam welding are more popular for welding dissimilar metal combinations, due to fewer complications, than fusion welding, which melts the base metal and forms brittle intermetallic compounds (IMCs) that may lead to failure. Various factors have to be considered when assessing the feasibility of welding dissimilar metals and producing a sound weld joint. This paper presents a broad classification of the most commonly used welding processes for dissimilar materials, discusses some of the commonly used welding processes with examples of some common material combinations, critical factors for good welding, and practical difficulties arising from the physical and chemical properties of materials. From the findings, it can be inferred that continuous improvement and research is still required in the field of dissimilar metal welding, particularly in the light of increasing demand for tailored material for modern engineering and industrial applications.

State-of-the-art of advanced gas metal arc welding processes: Dissimilar metal welding:

The manufacturing industry has for many years shown interest in opportunities offered by the welding of dissimilar metals, for example, in transportation to reduce vehicles weight and in power plants, to fit heterogeneous working conditions. Early gas metal arc welding (GMAW) processes had limited control of heat input, but advanced GMAW processes of the last decades offer new perspectives for welding dissimilar metals. The study review briefly dissimilar metal welding (DMW) and investigates advanced GMAW processes with emphasis on their general operating principles and arc control. Experiments performed on dissimilar metals using GMAW processes are then reviewed, highlighting those made using advanced gas metal arc welding processes. The study collates data from scientific literature on fusion dissimilar metal welding, advanced gas metal arc welding processes and experiments conducted with conventional GMAW. The study shows that the welding procedure specification is an important factor in dissimilar metal welding. Advanced GMAW processes have significant potential in fusion welding of dissimilar metals in the case of ferrous metals, ferrous and non-ferrous metal combinations and non-ferrous metals of different grades. Accurate control of heat input allows more effective prediction of intermetallics and better control of post heat treatments. Increased understanding of advanced processes will permit development of more suitable specifications of gas metal arc welding procedures for dissimilar metal welding. Process flexibility and adaptability to robotic mass production will allow for wider application of this process and the avoidance of costly alternative methods.

Real Time Non-Destructive Testing Methods of Welding

This work presents a review of the three most efficient non-destructive testing methods. The methods are radiography, eddy current and ultrasonic inspection. These particular techniques were chosen because they are able to cover most of the industrial needs for welding joint inspection. The aim of this work is to present the physical background of operation for the given methods, discuss their benefits, limitations, and typical areas of application, and compare them with each other. In the first part of this work, all three methods and their variations are described in detail with schemes and figures which represent their working principles. It appears that, although all the given methods can detect all types of flaws in welded joints, they have their specific limitations. For example, ultrasonic testing is able to detect defects only in certain directions. The eddy current technique is also sensitive to defect direction, but it can be applied for inspecting conductive materials only. The main flaw of radiography is the resolution: it is not usable for very fine defects. The second part of the work is for comparing the testing methods and for drawing the conclusions. The methods are compared according to the possible materials, defect types and their position, as well as the possible areas of application. This part gives the background for choosing a proper welding joint testing method for certain applications in the welding industry.

Sensing in Aluminum Alloy Welding

With the emerging trends of automation of welding technology for high volume manufacturing and use of aluminum for lightweight construction, continuous efforts have been undertaken to improve sensing and data acquisition for automated welding of aluminum and its alloys. This work aims to present and compare various sensing methods i.e. touch sensing, through-arc seam tracking (TAST), vision and composite sensing for automated fusion welding of aluminum alloys. Sensing technologies used for sensing of the seam and weld process are analyzed with focus on difficulties specific to aluminum alloy welding. It is found that the automated welding of aluminum is a well-established subject and that solutions for most industrial automated aluminum welding needs can be developed by integrating ongoing advancement in the field of sensor technology.

Welding of Ultra High Strength Steels

The ongoing need to reduce the weight of products while increasing strength has resulted in new generation steel manufacturing using special heat treatments to produce High Strength Steels (HSS) and Ultra High Strength Steels (UHSS) with up to 1700 MPa tensile strength. The high strength level of these steels makes it possible to produce structures with a considerable weight and cost reduction, and such steels have been adopted in the automotive industry and for mobile heavy equipment. Welding of UHSS is, however, not without its complications and welding processes for these steels need careful attention. For instance, their high susceptibility to cracking and Heat Affected Zone (HAZ) softening are risks that need to be borne in mind when choosing welding parameters. This research work discusses the difficulties and challenges of successful welding of UHSS. Common welding methods used in welding of UHSS are briefly reviewed to gain a better understanding of the effects of different welding parameters and methods. The paper finds that UHSS can be satisfactorily welded with laser welding, electron beam welding, resistance welding, and conventional arc welding methods, but the quality of the weld is dependent on appropriate control of several parameters and variables of the welding processes.

Advanced submerged arc welding processes for Arctic structures and ice-going vessels

The Arctic region is expected to play an extremely prominent role in the future of the oil and gas industry as growing demand for natural resources leads to greater exploitation of a region that holds about 25% of the world’s oil and gas reserves. It has become clear that ensuring the necessary reliability of Arctic industrial structures is highly dependent on the welding processes used and the materials employed. The main challenge for welding in Arctic conditions is prevention of the formation of brittle fractures in the weld and base material. One mitigating solution to obtain sufficiently low-transition temperatures of the weld is use of a suitable welding process with properly selected parameters. This work provides a comprehensive review with experimental study of modified submerged arc welding processes used for Arctic applications, such as narrow gap welding, multi-wire welding, and welding with metal powder additions. Case studies covered in this article describe welding of Arctic steels such as X70 12.7-mm plate by multi-wire welding technique. Advanced submerged arc welding processes are compared in terms of deposition rate and welding process operational parameters, and the advantages and disadvantages of each process with respect to low-temperature environment applications are listed. This article contributes to the field by presenting a comprehensive state-of-the-art review and case studies of the most common submerged arc welding high deposition modifications. Each modification is reviewed in detail, facilitating understanding and assisting in correct selection of appropriate welding processes and process parameters.

Improvement of strength and toughness: The effect on the weldability of high-strength steels used in offshore structures

The effect of strength and toughness on the weldability of high-strength steels is very vital consideration in the offshore oil and gas industries. Improved impact toughness of high-strength steels in offshore structures enables viable exploitation of hydrocarbons in technologically challenging conditions. This article reviews improvements in the weldability and impact toughness of high-strength steels. Steels with high strength are associated with high carbon content and addition of alloying elements as they induce hardness which leads to a higher risk of brittle fracture and hydrogen-induced cracking needs. The combination of high strength with high toughness was studied by examining the toughening mechanism of thermomechanical-controlled processing steels, which have higher strength than conventional steel plates but meet the conflicting requirements of strength, toughness and weldability. The thermomechanical-controlled processing production process entails controlled rolling process combined with accelerated cooling or direct quenching to ensure stable mechanical properties of thermomechanical-controlled processing products in welded constructions. It is concluded that due to their very fine grain size and refined heat-affected zone structure, thermomechanical-controlled processing steels can be an effective cost-saving means for fabrication of offshore structures, particularly in shipbuilding, offshore platforms and pipelines for high-operating pressures.

A New Approach to Manage Welding Quality in Supply Chain Networks: A Supplier Network Complaints Perspective

This study presents a five-step method for analysis of supply chain networks from the perspective of the welding quality of manufactured products. The presented approach gives tools to take care of welding quality assessment in supply chain networks. The study uses data based analysis of complaints data and survey results to provide information that may assist managerial decision-making and supplier-related marketing activities. The results reflect the importance of information sharing as a means to reduce the number of complaints and show that combining production data and information about the production offers potential for manufacturing quality development in the supply chain network. The study uses applied RACI matrix and the case of a welding supply chain network to establish the findings. The case example discusses the observations dealing with GMAW process.