Takayuki Shinoda

Effects of some carbide stabilizing elements on creep-rupture strength and microstructural changes of 18-10 austenitic steel

The creep rupture test has been carried out for 18Cr-10Ni-0.1 wt pct C stainless steels bearing individually Ti, Nb(Cb), and V, followed by the microstructural study. The highest value of 700°C-104 h rupture strength in a titanium and niobium series (the steel containing various amounts of titanium and niobium, respectively) has been obtained at Ti/C and Nb/C atomic ratio of 0.8 and 0.2 to 0.4, respectively. On the other hand, in a vanadium series, the creep rupture strength of the steel showed its maximum at V/C atomic ratio of about unity in the testing at the temperature of 700° and 800°C, but at 600°C, the strength increases monotonically with vanadium content up to 1.53 wt pct. Such high strength in the steels con-taining proper amount of Ti, Nb, and V is related mainly with the fine distribution of M23C6 precipitates which is caused by the acceleration of nucleation due to the foregoing precipi-tation of a MC type carbide within the austenite grains. And it has been deduced that the solid solution strengthening effect of the vanadium contributes also to the remarkable in-crease in the rupture strength of the vanadium steel at 600°C.

Manufacture of heat-resisting steel ontaining high concentration of nitrogen and its high temperature properties

To utilize nitrogen as an alloying element in heat-resisting steels, an experimental study was made on the fundamental phenomena occurring in melting and casting of various high-chromium steels under high-pressure nitrogen atmosphere. By this technique, sound ingots containing high concentration of nitrogen could practically be obtained, and the new high strength heat-resisting steel could be developed, some of which have the creep-rupture strength at 700°C --IO3 hr far exceed 20 kg/mm2 with an excellent high-temperature ductility.

Effect of Additions of Ti, Nb, V and Ti, Nb, B on Creep-Rupture Strength of High-Mn Austenitic Steel

Synopsis: The effects of further addition of V or B to 18% Cr-6%Ni-8% Mn steel with small amounts of Ti and Nb, which has been found to have high creep-rupture strength and to be very economical, on creep-rupture strength are investigated. As a result, it was found that the addition of V in the range of 0.3 to 0.5% is effective to raise the creep-rupture strength at relatively low temperatures(600 to 650•Ž) for shorter times and the addi. tion of B up to 0.05% is effective to raise the creep-rupture strength at relatively high temperatures