Improvement of Impact Toughness of API-X70 Steel Weld metals With Electromagnetic Vibration

The effect of electromagnetic vibration on the microstructure and impact toughness of API-X70 steel weld metal was investigated. The welding was carried out by gas tungsten arc welding process and using filler metals including ER80S-G and ER309L. Electromagnetic vibration under voltages 0- 30 volts concurrent with welding was applied. The microstructure of the base and weld metals using optical microscope and SEM was studied. The impact energy of weld metals at TR, 0°C and -20℃ using charpy impact test was measured. Microstructural investigations revealed that applying electromagnetic vibration have caused the finer and more uniform of Martensitic-Austenitic (MA) islands in the ER80S-G weld metal . The results showed that, due to electromagnetic vibration, the microstructure became finer and the average size of dendrites in the ER309L weld metal decreased from 18.19 to 8.01 μm.. The impact test result, illustrated that the applied vibration cause improvement of impact energy of weld metals at different temperature (TR, 0°C and -20℃). It was found that with vibration under 30V, impact energy of ER80S-D weld metal in TR, 0°C and - 20℃ was increased equal to 53, 29 and 36 percents, respectively. Besides for ER309L weld metal, the impact energy in TR and -20℃ was increased equal to 18 and 5 percents, respectively. (TR= Room Temperature).