Effects of alloying elements on the microstructure and inclusion formation in HSLA multipass welds

The effects of Ti, Ni, Mo and Cr on microstructural development, and the chemical composition of the non-metallic inclusions, in high strength low alloy multipass (HSLA) weld metal have been considered. Increasing titanium content, in the range of 50 to 400 ppm, has not caused any major effects on microstructural development. With a further increase in the hardenability, by Ni, Mo and Cr additions, the microstructure has changed from a mixture of allotriomorphic ferrite, Widmanstätten ferrite, acicular ferrite and microphases to a mixture of acicular ferrite, bainite, low carbon martensite and microphases. In weld metals with low titanium content, manganese and silicon were the main chemical elements present in inclusions. Increasing the titanium content in the weld metal leads to an increase in the titanium content of the inclusions. For a very high titanium content, ≈ 700 ppm, the amount of titanium in the inclusions varies in the range of 60 to 70 wt.%.