Abstract
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°C) 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 (650 to 750°C) for longer times. The effect of V is considered to be mainly due to solutionhardening, and the element rather accelerates the coalescence of carbide at high temperatures. The effect of B is considered to be depressing the precipita;ion and especially the coalescence of carbide.
These steels have to be improved further for practical applications, i. e. both steels have considerable amount of delta ferrite resulting in poor hot workability, especially this is further pronounced in the boron bearing steel due to the existence of boride within the composition range of this work.
The resistance to high-temperature oxidation was also investigated for those steels in air and in gasturbine atmosphere with blast furnace gas as fuel.
