1.5%C,12%Crダイス鋼の研究
V,Moの影響について
1955 年 41 巻 6 号 p. 613-620
詳細
1955 年 41 巻 6 号 p. 613-620
To investigate the influence of vanadium and molybdenum on the properties of air-hardening die steel containing 1.5%carbon and 12%chromium, the authors measured the critical point, hardenability, quenched and tempered hardness, retained austenite, dimensional change and toughness.
The results obtained were as follows:
(1) The critical point was raised with the vanadium and the molybdenum conten, respectively. The hardenability increased by the addition of molybdenum and ipcreased slightly by vanadium by its addition up to O.8%.
(2) Vanadium addition refined the grain size, and the molybdenum had little effect on the grain size. Full hardness was obtained by quenching from-1000°C to 1O50°C, and as the vanadium contenlt increased, a slightly higher austenitizing temperature was necessary for obtaining the full hardness.
(3) The quantity of retained anstenite measured by the magnetic method decreased with vanadium addition, and themolybdenumhad little effect on the retention of austenite. The authors found more retained austenite in air-hardening than in oil-quenching from the same temperature, and the.amgunt of retaihed atistenite increased as the austenitjzing temperature was raised.
(4) Sub-zero treatment fdllowing.the.original hardehing operationcaused the transformation of large amount of.retained austenite and this breakdown of austenite at-680°C decreased with vanadium addition.
(5) The volume increment. resu1tipg from the air-hardening was less, than oil-quenching from the ordinary temperature. This increment decreased by the addition of vanadium up to O.4%, then increhsed with more vlahadium content. A steel containing 0.45% vanadium showed a dimensionlal change of +0.109% in the direction of hot-working and -0.03% in the transverse direction by air-hardening from 1050°C.
(6) Some of retained austenite in hardened steel decomposed during aging at room temperature and about half of that during the first 24 hts after the uenching. Small amount of reained austenite decomposed on tempering up to 500°C, and all of the retained austenite decomposed at a temperature between 550°C to 600°C the secondary hardness was exhibited at 500°C after quenching from lO50°C and was very marked at 550°C after quenching from 1100°C.
(7) The toughness measured by static bending test.increased with addition of vanadium up to 1%and then decreased with more vanadium content and also O.8-1.0% molybdenunm increased the toughness.
