The effect of chromium on the microstructure/toughness relationship of C–Mn weld metal deposits

Submerged-arc single-pass welds were prepared with varying chromium content in the range of 0–3.8%. Two carbon contents were obtained by dilution using different welding procedures. The variation in the chromium content was obtained by the addition of different amounts of chromium powder to the weld groove. The relationship between microstructure and toughness of weld deposits was studied by means of hardness, Charpy-V notch and metallographic tests in specimens cut transversely to the weld beads. Qualitative and quantitative analyses of microstructural constituents and fine phases were made by light optical and scanning electron microscopy, respectively. In this investigation, a selective etching method was employed in order to distinguish the martensite–austenite (M/A) “microphase” constituent from carbides. The results show that chromium impairs impact toughness, although it promotes an increase in the percentage of acicular ferrite (AF). In addition, it was observed that an increase in carbon content promoted a further decrease in impact toughness due to the higher volume fraction of the M/A constituent.