Introduction

Knowledge of welding metallurgy can be beneficial to almost every aspect of fabrication, inspection, and failure analysis. Too often, problems occur re- peatedly because the metallurgical aspects are not sufficiently understood (note Figure l), and as the old saying goes, ”When you continue the exact same practices, why should you expect different results?”

While the subject of metallurgy, and its subset welding metallurgy, encompasses a very large technical base, there are several basic issues that can be studied and implemented to aid in avoiding problems associated with fabrication and repair welding. These basic issues will be discussed in simple terms and hopefully with an approach that will enable a non-metallurgist to grasp and apply them in order to avoid common welding problems.

Since carbon and low-alloy steels are used predominantly in many industries, these alloys form the basis for much of this metallurgical review. An understanding of the steel basics can then lead to other alloy groups including austenitic stainless steels, copper and aluminum alloys, and the high alloys that include the nickel alloy groups. These families of alloys will also be discussed, but to a much lesser degree.