1985 Volume 26 Issue 6 Pages 397-404
The yield stress, tensile strength and ductility of hypo-eutectoid graphitic steels are given as functions of microstructural factors such as the ferritic grain size dF, volume fraction of graphite f, mean graphite nodule diameter dG, and mean ferrite path between graphite nodules λ.
The graphitic steel in which graphite nodules have formed at ferrite grain boundaries exhibits a sharp yield point, and the yield stress can be expressed by a function of two factors dF−1⁄2 and λ−0.22. The steel containing a number of graphite nodules inside the ferrite grains shows no yield point, and the 0.2% proof stress is nearly constant independent of f, dF, dG and λ.
The tensile strength of the graphitic steel increases linearly with dF−1⁄2, but decreases slightly with increasing dG.
The ductile fracture strain is given by a function of lndG and lnλ, or of ln[(1−f)⁄f] according to a multiple regression analysis. It is concluded that the ductility of the graphitic steel depends strongly both on dG and λ, or on the volume fraction of graphite.
