Oxide inclusions in mild steel weld metal were investigated. Oxide inclusions isolated from mild steel weld metal by ultrasonic agitating dissolution method using I
2-CH
3OH solution were classified according to the size (5 microns over and under) by ultrasonic sieving method, and observed by optical microscope.
Larger inclusion particles over 5 microns were analysed by electron-probe X-ray microanalyzer.
It was found that inclusion particles over 5 microns were spheroidal (MnO·SiO
2, SiO
2, and (Mn, Fe) O), angular (SiO
2), lumpy (SiO
2), platy-shaped (SiO
2), prismatic (Al-silicate), pine needle- or stick-shaped (Ca-silicate), and string-shaped (Ca-phosphate) in shapes (and compostions).
The amount of inclusion particles less than 5 microns was about 90% in oxide inclusions, and the greater portion of these was MnO·SiO
2, the size of which was about 1 micron.
Ti-oxides which were confirmed by X-ray diffraction in inclusion particles less than 5 microns were α-Ti
2O
3, Ti
2O
3, and FeO·TiO
2 when Fe-Ti was added to the flux of low hydrogen type, while TiO
2 (anatase), Ti
2O
3, and FeO·TiO, when TiO
2 (rutile) was added to titania and cellulose type in the compositions.
The mechanism of formation of various oxide inclusion particles in the weld metal was considered.
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