Study of as-rolled carbon steels over ranges of uranium sulphur and carbon contents

Abstract

Certain ad hoc studies of uranium in carbon steels at the Mines Branch have been complemented and clarified by statistically designed and analyzed studies. The results indicate that uranium has a very limited potential usefulness as an alloying element in ferrous metallurgy. Uranium has more potential as a scavenger and sulphide former. A factorial set of as-rolled carbon steels having four uranium levels (nil, 0.15, 0.3 and 0.6%), three sulphur levels (0.006, .0.030 and 0.14%) and two carbon levels (0.14 and 0.34%) was tested to assess the influence of uranium on impact characteristics, active-state corrosion resistance, stress-corrosion resistance, machinability, microstructure, and isothermal transformation of austenite. The sulphur and carbon levels were introduced in anticipation of interaction effects with uranium as well as for hidden replication. Uranium was always detrimental in progressively raising Cv fracture-appearance transition temperatures. However, only uranium contents exceeding 0.15% were inherently detrimental to absorption of impact energy. At the highest sulphur level, and particularly in transverse tests, uranium beneficially raised the curves of Cv impact energy versus temperature. The rates of active corrosion in 5% HG 1 and H2SO4 were significantly but marginally reduced by uranium. Accelerated stresscorrosion results indicate some improvement related to the presence of 0.09% uranium. Uranium in amounts sufficient to globularize sulphides did not significantly affect machinability. Uranium makes possible the production of ultra high sulphur steels having good transverse impact toughness. In carbon steel, uranium refined the as-cast macrostructure, promoted the formation of degenerate pearlite and slightly delayed the transformation of austenite, but had almost no effect on tensile properties. The factorial design of the impact test program permitted quantitative determination of the effects of sulphur and carbon on Cv 15 ft-lb and Cv 50% cleavage transition temperatures.