9 - Narrow-gap welding techniques

Abstract

This chapter discusses the principles and features of narrow-gap welding, narrow-gap welding processes, developments in narrow-gap gas metal arc welding (GMAW), and uses of narrow-gap welding. Welding process economics may be improved by better control of the process to give reductions in post-weld inspection and repair or by decreasing the joint completion time. The aim of many process developments has been to decrease the time taken to complete the joint (so reducing labor costs) by increasing metal deposition rates and using automation. An alternative approach is to reduce the weld size or joint volume. In fillet welds, the possibility of a reduction in weld size will depend on design constraints and the achievement of smaller weld volume is easily controlled by the operating parameters of the process. In butt welds, significant changes in weld metal volume may require modification of the joint configuration, a change of process, or both. The term “narrow-gap” welding is used to describe a group of process developments that have been specifically designed to reduce weld metal volume in butt welds. Most of the development and the application of the processes described in the chapter relates to plain carbon and low-alloy steels.