Composition: Carbon steel (0.35%C, hypoeutectoid).

Processing: Hot-rolled. Annealing (870ºC - 1h), Water quenching and Tempering (660ºC - 4d).

Etching: 10-15 s immersion in 2% nital.

This steel has the same composition as X27. However, in this case, tempering was performed at a higher temperature (660ºC). This increase in temperature produces significant changes in the size of cementite particles and ferrite. Cementite globules are more visible and the ferrite phase acquires an equiaxial shape with better defined grain boundaries. 

Fe-Fe₃C diagram

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