中炭素鋼に対するウランの添加
鉄鋼におよぼすUの影響に関する研究-II
1964 年 50 巻 1 号 p. 48-56
詳細
1964 年 50 巻 1 号 p. 48-56
In the previous paper, the authors made a study of the influence of uranium addition on low carbon steels, and also suggested:(a) non-metallic inclusions like sulfides and silicates decrease morphologically and also the oxide increases with the addition of uranium;(b) uranium has a solubility in austenite at higher temperature of above 950°and precipitates during tempering at temperature of about 500°C;(c) uranium slightly increases the hardenability of low carbon steels quenched at temperature of above 950°C and (d) corrosion resistance of steel against 5% hydrochloric acid is improved with the increasing content of uranium.
In the present paper, the authors reported on some laboratory tests concerning the inflence of uranium addition up to 0.7% on 0.3-0.4% carbon steels.The results of experiment had been shown as follows:
(1) As far as these small ingots were concerned, no scavenging effect of uranium could be found, but sulfide inclusions decreased, and oxides increased with the addition of uranium.
(2) Uranium refined the austenitic grain size insignificantly as shown in previous works.
(3) Gravitational segregation occurring in a slowly cooled ingot in a melting furnace was revealed through chemical analysis, autoradiograph, β, γ-ray counting and sulfur-print of the longitudinal section.
(4) As-normalized hardness showed an increase through the formation of uranium carbides resulting from uranium addition.
(5) Transformation temperature of steels was not changed by the addition of uranium according to thermal analysis.
(6) Microscopic exermination showed that uranium scavenged the impurities of grain boundary, and the figure of pearlite was changed thereby with a loss of uniformiy. Uranium carbides, UC or UC2, increased with the content of uranium and precipitated at the austenite grain boundaries.
(7) Uranium had no effect on the hardenability of these steels even at the quenching temperature of 1200°C;
(8) No secondary hardening effect was caused even at the quenching temperature of 1200°C and subsequent tempering.From these experiments, it is suggested that uranium carbides were not decomposed and were extremely insoluble to the austenite matrix at higher temperature.
(9) The effect of uranium on the mechanical properties at room temperature was almost negligible, but V-notch Charpy impact strength was reduced with the content of uranium.
(10) The effect of uranium on the corrosion resistance against 5% hydrochloric acid was noticeable, but uranium steel suffered a severe pitting in 5% sulfuric acid. Against 3% nitric acid and 3% sodium chloride aqueous solution, it showed no resistance.
