Microstructure and properties of ferritic steel welds containing Al and Ti

The combined effect of Al and Ti, in the range 5 to 500 ppm, on the microstructure and properties of C-Mn shielded metal arc welds has been studied. It was found that Ti, in contrast to Al, dramatically enhanced the formation of acicular ferrite and improved notch toughness. A strong interactive effect was encountered, with Al at low concentrations tending to diminish the influence of Ti. Unless a critical balance is achieved, with regard to oxygen content, it is concluded that Ti be optimized at 30 to 40 ppm and that Al be kept as low as possible.