1970 Volume 56 Issue 2 Pages 311-330
As the pipe materials for nuclear fuel cover in fast reactor, type 304, 347 and 316 austenitic stainless steels are used. In future plutonium carbide for nuclear fuel and liquidus sodium for coolant would be used. As the result pipe materials for nuclear fuel cover are carburized, and it would become a problem whether high temperature properties are affected.
From this standpoint, in this paper we investigated the effect of carbon on high temperature properties of type 304 and 316 austenitic steels.
Results obtained are as follows:
When these alloys are solution treated at 1150°C, (1) solution hardness:(2) deformation resistance at 900°C, 1000°C and 1100°C:(3) tensile strength and yield strength at room temperature, 600°C, 700°C and 800°C tend to increase nearly in proportion to carbon content, but (a) recrystallization temperature:(b) 10000 hr creep rupture strength at 600°C, 700°C and 800°C show maximum at about 0.2% carbon content.
It is believed that such behaviour of (a) and (b) are due to excellent solution hardening and precipitation hardening, because residual carbide particles in the alloy containing carbon more than 0.2% cause precipitates to form around it in heating at high temperature, and cause solution strengthening and precipitation strengthening to lower.
But, when solution temperature is 1200°C, the maximum of creep strength is obtained at a higher amount of carbon than 0.3%, and the effect for improvement of strength is a little, further the ductility lowers.
Therefore, the upper limits of carbon content and solution temperature are considered to be about 0.2% and 1150°C respectively.