Belinga Mvola

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.