抄録
The author has investigated the ferrite banding of free cutting steel, and arrived at the following results.
(1) The ferrite banding of hypo-eutectoid steel disappears by rapid cooling, whereas it appears by slow cooling. (2) As the cooling velocity changes from slow to rapid, the bandei structure changes into granurous structure, and "the cooling velocity" which is required for getting boundary structure is defined by the author as" Critical cooling velocity of ferrite banding". (3) The critical cooling velocity of ferrite banding goes downwards by the influence of heating temperature and time. (4) The existence of the banded structure of hypoeutectoid steel, does not affect its mechanical properties.
