Urgessa, GirumDenes, Andrei2017-12-212018-04-28https://hdl.handle.net/1920/10881This thesis has been embargoed for 1 year. It will not be available until April 2018 at the earliest.This thesis presents an experimental investigation of the Narrow Gap Improved Electroslag (ESW-NG) welding method when applied on HPS 70W high-performance steel and the associated tests required for qualification of the welding method under the American Welding Society D1.5:2010 (AWS) bridge welding code. The welding process is studied in detail through testing of two weld qualification plates and the base metal. Tension testing, toughness testing and hardness testing of specimens with various geometries and orientations within the two plates and the base metal were performed, in addition to the tests required for weld qualification. The testing methods and specimens used are thoroughly described and their significance is explained. The experimental results achieved the objective of determining and characterizing the mechanical properties of HPS 70W high-performance steel when welded with ESW-NG. However, the research revealed that ESW-NG cannot be pre-qualified for HPS 70W per the AWS code at this time due to the failure of the all-weld tension specimens.enESW-NGElectroslagWeldSteelHPSBridgeThesis