INFLUENCE OF ALLOYING ELEMENTS ON THE AS-CAST STRUCTURE OF 17-PERCENT CHROMIUM STAINLESS-STEELS

Ti-additions together with boron had the most significant influence on the length and thickness of columnar crystals and on the size of the equiaxed zone. Microprobe analysis has shown segregation of titanium, zirconium and sulphur. Microscopical examination of alloys containing titanium has shown the presence of sulphur-titanium eutectic in the interdendritic space. Precipitation conditions are discussed in relation to calculated activities of titanium and sulphur in liquid steel. Electron microscopical investigation has shown existence of boron-containing eutectic in interdritic space and boron-rich phase along grain boundaries. Examination of mechanical properties has pointed out deleterious effect of yttrium on toughness. Yttrium addition increased both ductility and tensile strength of alloys containing up to 1 wt. % Ti.