Abstract
In view of obtaining the basic data for manufacture of precision tools and gauges, the authors measured the longitudinal change due to the subzero-temperature treatment after quenching with 3 kinds of self-hardening tool steels and an 1.1% C tool steel. The result of measurement was compared with that of the hardness, the intensity of magnetization and electric resistivity; and the cause of the change was studied. Then the longitudinal change of these steels due to aging at room temperature was measured and its stability was examined. The experimental result was summarized as follows: (1) In any steel tested, the degree of increase in the hardness and the ratio of longitudinal change due to the subzero-temperature treatment became larger with rise of the quenching temperature. (2) In each steel tested, the length at room temperature after the subzero-temperature treatment was reduced with the lapse of aging days, and the degree of contraction was the more marked for the steel quenched from the higher temperature. In every steel tested, the degree of contraction due to room-temperature aging was more pronounced in the steel subzero-cooled after quenching than in quenched simply steel. (3) The longitudinal change of the high-C high-Cr steel subzero-treated after quenching due to room-temperature aging was less remarkable than in other kinds of steels tested. (4) In the special tool steel subzero-treated after oil-quenching, the longitudinal change due to room-temperature aging became small by tempering at 150°.
