Prediction of microstructure and mechanical properties of multipass SAW

A detailed study on the microstructure, phase analysis and mechanical properties, HAZ width of SA weld metal multipass joint and heat-affected zone of 16 mm thick mild steel plate was carried out using trinacular metallurgical microscopy, with Onix Vision Video Microscope Projection System including mega pixel camera and image analysis software. The bulk hardness, impact energy and microhardness of a multipass welded joint were tested by Rockwell hardness testing machine, Charpy V Notch test and Vickers microhardness test. The various sub-zones in the microstructure were observed in the HAZ of SA weld are spheroidized, partially transformed, grain refined and grain coarsened. The variation in hardness of weld metal, fractured surface and base metal were compared with the microstructure, to get a defect free weld, and also it was correlated with the microstructure of weld metal and heat-affected zone. The main purpose of present work is to investigate and correlate the relationship between the various parameters; mechanical properties and microstructure of single “V” butt joint of mild steel plate, and also to perform the phase analysis of the multipass welded joint to get defect free welded structures.