Abstract
By the author’s previous research,it has been found that the parts of fiber structure corresponding to the boundaries of primary crystals give aid to formation and propagation of heat-checks. As these fiber structures are affected by the forging ratio, their effect on heat-checking was studied in the same method as in the previous report, and the results obtained are as follows: (1) In proportion to the increase of the forging ratio, the total number(n) and the total depth (L) of the checks decrease, but the max.depth (lmax) and the mean depth (L⁄n) change scarcely. In the present case, n,L and their decreasing rate corresponding to the forging ratio are larger when the checks appear in parallel to the direction of the fibres than when perpendicular. (2) The influence of the forging ratio on heat-checking is found similarly also on the specimen sampled from the core part of billets, but their properties is somewhat inferior to the outside part, as far as heat-checking concerns. (3) Homogenized and upset specimens have little directional properties on heat-checking and have better properties than that of ordinary forged one in the case of the same real forging ratio. (4) The above mentioned results could interpreted by the microstructure of the specimen.
