Abstract

In this paper the author discusses the occurrence, origin, andremedy of flakes. He gives the results of a series of experiments as follows:-
(1) The cause of flakes is chiefly due to the grain size of primary crystals formed on the solidification of an ingot.
When the casting temperature is high, the primary crystals become coarse and the inner pertion of the in got will solidify much more slowly than the outer. if the temperature be high, the stress jnduced in the ingot during solidification should be great and weak parts should be produced around the coarse grain boundaries of the primary crystals.
(2) These weak parts will develope to hair crack called flakes by tensile stress in duced on cooling stage during annealing or on quenching operation.
(3) Flakes will be avoided with slow cooling after forging in case of thin material but this remedy is rot satisfactory, because it is impossible to avoid this defect completaly in case of thick material.
(4) If an ingot be cast in too low temperature, the crack like flakes will also occur and this defect will generally start from the minute non-metallic inclusions in the ingot.
(5) The reasonable casting process requesting high temperature melting and moderately low temperature terming is strongly recommended by the anthor to avoid both dirt and flakes.