Abstract
The effect of phosphorus on properties of 19-9DL type heat-resisting steels with or without addition of boron and rare earth elements was studied. The results obtained were as follows:
(1) The phosphorus increased the maximum hardness obtained by aging after water-quenching from 1150°C, and the addition of phosphorus more than 0·2% accelerated overaging at temperatures higher than 750°C.
(2) The phosphorus greatly improved the rupture strength at 650°C ahd 700°C, but the rupture elongation and impact value was decreased with increasing phosphorus content.
Small addition of rare earth elements improved the ductility of the 19-9DL type heatresisting steel containing 0·15% P, and the stress-rupture values at 650°C or 700°C were equivalent to hot-cold-worked 19-9DL heat-resisting steel.
(3) Small addition of boron improved the rupture life and ductility of the 19-9DL type heat-resisting steel containing 0·15% P with or without addition of rare earth elements.
The new type heat-resisting steel invented by the authors contained 0·3% C, 19% Cr, 9% Ni, 1·5% W, 1·5% Mo, 0·5% Cb, 0·2% Ti, 0·15% P, 0·1% B and 0·3% rare earth elements, and the stress-rupture values at 700°C were higher than those of the LCN-155 Alloy.
