In submerged-arc welding, flux is produced through bonding so that alloying element can be added to Weld Metal. In this method, mineral ingredients and alloying elements are milled and mixed with glue in appropriate proportions. Once the drying of the pellets is complete in air, they are baked at 350 degree centigrade and broken up by using a sieve to attain the desired particle size (0.3-1 mm). The various content of Cr, Mo and Cr-Mo was added to bonded flux. Addition of alloying elements was done through flux and slag-weld metal reactions. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The addition of 0.4 wt. % Mo increased the volume fraction of Acicular Ferrite (AF) to 87%. The Ultimate Tensile Strength (UTS) increased by 20% and Impact Toughness (IT) decreased by 25%. Cr affected AF content less than Mo. The addition of 0.4 wt. % Cr increased the volume fraction of AF to 57%. The UTS almost did not change and IT decreased by 35%. Further increase in Cr content led to increase of Ferrite with Second Alloyed phase that strongly impaired IT (60%). The highest proportion of AF (95%) obtained in 0.28 wt. %Cr and 0.35 wt. % Mo. In this specimen UTS increased by 20% (100 Mpa) and Impact Toughness was decreased by 15% (20 j).

Keywords: Submerged Arc Welding, Bonded Flux, Acicular Ferrite, Alloying elements, Inclusion

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