The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ?

Grey iron is extensively used in engineering because of following characteristics.
(a) Cheapness.
(b) Low melting point and high fluidity making it suitable for castings of intricate shape.
(c) Relatively good erosion and corrosion resistance.
(d) High damping capacity, with respect to vibration.
(e) Relatively good mechanical properties under compressive loading.