Uranium Addition to Low Carbon Steels

Influence of uranium addition on iron and steel-I

Abstract

The depleted uranium as a by-product of the enriched uranium manufacturing has been accumulated enormously in these several years, since it is unfit for nuclear uses. For the purpose of utilization of depleted uranium for non-nuclear uses, a large number of studies. concerning the effect of uranium addition on iron and steel have been made in the United States and Canada.
Here, in Japan, in 1961, “The Special Committee for the Study of Uranium Steels”, has; been organized in “The Japan Society for the Promotion of Science” so that industrial and. research fields miy share stuiies systematically from the basic researches to the practical applications.
In this paper, a laboratory study to reveal the principal effects of uranium addition to steel: as an alloying element has been carried out. The aluminum-killed low carbon steels (<0.25. %C) are chosen as the object of study on addition of small amountof uranium (<0.7%U).
The results are as follows:
(1) Recoveries of uranium from steels are 40 to 65% and related, ingeneral, with the: carbon contents as shown in Fig. 1.
(2) Non-metallic inclusions like sulfides and silicates decreased morphologically with uranium addition, but oxide inclusions increased remarkably.
(3) Uranium refined the austenitic grain size of steels slightly.
(4) As-normalized hardness suffered a little effect of uranium addition at a 0.06%C leveL but above a 0.16%C level the effect increased with the content of uranium.
(5) After water-quenching from a solution temperature ranging 950.. to 1250.. in 0.06, %C steels, secondary hardening occurred under the tempering up to 600... Microscopic exa mination showed that uranium caused pseudo-martensitic structure, and it also suggested that uranium had a solubility to austenite matrix to some extent.
(6) After water-quenching from a ferrite region ranging 750 to 800.., no ageing occurred at room temperature and at 150... It was suggested that uranium hadnot the slightest solubility to ferrite matrix.
(7) It appeared from the end-quench tests that the hardenability of steel did not risewith uranium addition from a quenching temperature of up to 900.., butabove 950.., uranium raised the hardenability of steels. So in low carbon steels, uranium formed the _intermetallic compound Fe₂U. And it is considered that Fe₂U decomposed above 950.., uranium had a solubility to austenite and had its hardenability improved, as mentioned above.
(8) Mechanical properties at room temperature were not affected by uranium addition, but impact strength decreased with the content of uranium.
(9) Transformation points of steels rose with uranium addition because of the stabiliza tion of carbon from austenite matrix.
(10) Uranium did not affect the work-hardening effect and since uranium fixed the interstitial atom like carbon and nitrogen, strain-ageing did not occur in silicon-killed uranium steel.
(11) Corrosion resistance against 5% hydrochloric acid improved with an addition of uranium as shown in Canada's report but in 5% sulfuric acid severe pitting occurred, and in 3% nitric acid no beneficial effect was observed.