A Study on the Effect of the Interpass Temperatures in Properties and Microstructures of the Alloy 625 Dissimilar Fusion Zone

The purpose of this study is to evaluate the effectiveness in the contribution of the interpass welding in the microstructures and properties of the dissimilar fusion zones produced with an alloy 625 and API 5L X65 steel pipes. Three multipass welded joints with v-groove, were made under the same welding parameters, therefore, changing only the interpass temperatures at: 150°C, 250°C and 450°C. The microstructural characterization was performed using the light microscopy and the scanning electron microscopy (SEM). The hardness test, charpy-V impact test and the transverse tensile test were conducted according to specific standards. The results have shown that all ruptures in the tensile tests occurred in the base metal. Both yield strengths and ultimate tensile strengths, have dropped to the 450°C interpass temperature. It was also observed a slight drop in the hardness with increasing interpass temperature. The Charpy-V impact test results showed no significant differences among the interpass temperatures. These said results indicated that the maximum interpass temperature for the alloy 625/X65 steel dissimilar welding is limited by the steel properties.