Stainless steels compose one of the main groups of structural steels that we use to date. In cost, corrosion resistance, and weldability they are one of the most suitable steels for most of today's applications. Understanding how these grades of steel are affected by welding should be considered necessary knowledge for all welding engineers. In this study, I tried to discover how improper welding practices can adversely affect the weld content and microstructure, by using visual inspection and a microscope.
Background.
Stainless steels are widely used in various industries where corrosion is concern. The welding of stainless steels, especially the austenitic grades, is particularly important in energy-related systems. 304 stainless steel is classified as austenitic grade stainless steel. Austenitic grades contain 15% to 26% chromium and 6% to 22% nickel content required to maintain a stable austenitic structure, over the temperature range of 1100C to room temperature, without the formation of martensite. The formation of martensite is detrimental to the structure of austenitic stainless steels. It has adverse affects on the strength and toughness of this classification of steels.
Objectives.
The objectives of this study were simple. Complete three welds with varying degrees of contamination, and then analyze the fusion and HAZ zones for micro structural changes. Second, obtain a better understanding of what happens to austenitic stainless steels, then try to explain the findings in a report format. While seemingly basic, these objectives actually turned out to be quite challenging. The main set back was figuring out what was going on in the zones of study.
Methodology.
The first thing done was to acquire and prepare the 304 stainless steel samples. After an adequate amount of 304 steel was acquired, it was prepared into 2" X 3" inch samples. One set of the samples were cleaned, and the other two were not.