Lower acicular ferrite

An experiment has been designed to confirm that the mechanism of growth of acicular ferrite in steel welds is similar to that of bainite in ordinary steels. On the hypothesis that the growth mechanisms are identical, it was expected that if the carbon concentration of a weld is increased sufficiently, then for similar welding conditions, the microstructure should undergo a transition from acicular ferrite tolower acicular ferrite, in which the plates of acicular ferrite should contain cementite particles of the sort normally associated with lower bainite in wrought steels. An experimental weld of unusually high carbon concentration was prepared, and metallography confirmed the existence of lower acicular ferrite, supporting the conclusion that acicular ferrite is simply an intragranularly nucleated bainite.