CAN/CGSB-48.5-95 Part III:Chapter 9

9.1 Introduction It has been well known in the field that industrial radiographers are called upon to interpret radiographic images of components, subassemblies and structures either at the time of manufacture or during service. This may include a variety of specialized welding techniques. Consequently, radiographers become not only associated with welding techniques but also benefit by the association, as the knowledge gained will assist them in the interpretation of weld radiographs. It can be appreciated that a wide variety of specialized welding processes is being used in industry. Techniques and metallurgical details are numerous; however, an attempt will be made to briefly summarize the essentials of some of the processes that are commonly encountered. Nonetheless, the industrial radiographer is encouraged to refer to some of the publications of the professional societies whose names appear in par. 9.9. It is hoped, however, that the information covered in this chapter will enable industrial radiographers to become aware of the problems associated with the welding process and its effect on interpretation of weld radiographs. A "weld" is considered to be an intimate and homogeneous union between pieces of metal at interfaces rendered pasty or molten by heat or pressure or both. a filler metal whose chemical composition and melting temperature are similar to that of the parent metal may or may not be required depending upon the type of process used. "Welding" is a metal-joining process involving several metallurgical principles. Welded joints are expected to be as strong as the parent metal. Modern welding processes sometimes produce joints which are stronger than the parent material. The term "welding technique" is generally used to describe the preparation of metal joints and the control of factors such as heat, pressure, speed of deposition and other variables which directly influence the strength of the joint. The term "weldment" describes a unit or a structure formed by welding together an assembly of pieces.