Relation between Directionality of Quenching-Deformation of Low Alloy Tool Steel and its Structure

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  • Yokoyama Kinji
    Tokyo Institute of Technology, Research Laboratory of Precision Machinery and Electronics
  • Suzuki Tomoo
    Tokyo Institute of Technology, Research Laboratory of Precision Machinery and Electronics
  • Kano Toshio
    Tokyo Institute of Technology, Research Laboratory of Precision Machinery and Electronics
  • Tachi Yasuo
    Tokyo Institute of Technology, Research Laboratory of Precision Machinery and Electronics

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  • 低合金工具鋼の焼入歪の方向性と組織との関連について
  • テイゴウキン コウグ コウ ノ ヤキイレ ワイ ノ ホウコウセイ ト ソシキ ト ノ カンレン ニ ツイテ

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Abstract

To investigate the effect of directionality on the quenching deformation of a low alloy tool steel (JIS SKS 3), the dimentional changes due to quenching and subsequent treatments were measured of the specimens forged at various forging ratios. Further, thermal dilatometric experiments and microscopic observation were carried out. The results are as follows. (1) There is no difference in quenching-deformation of as cast steels by the direction in which the specimens were cut out, but the linear expansion due to quenching was more marked in the transversal specimens of the steel forged at a forging ratio of 1.5 than the longitudinal ones. This shows that a slightly forged steel has directionality on quenching-deformation. (2) When the cylindrical specimens were quenched, they were deformed by the effect of the form of specimens and at the same time by the effect of directionality of the steel. The subsequent tempering or the sub-zero treatment does not change the ratio of length and diameter of the specimens. (3) The Ms point of the longitudinal specimen is 10°C lower than the transversal one. (4) The fibre structure of the steel consists of many fine layers containing alloying elements of different amounts, and the layers have different Ms points. It was concluded that anisotropy of the quenching-deformation of this steel depends on the above feature of the fibre structure.

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