1988 Volume 74 Issue 1 Pages 107-114
The effects of titanium on metallurgical and mechanical properties of controlled rolled steels areinvestigated and compared with those of niobium. Large TiN particles, existing in high titanium content steels, have little ability to control austenite grain growth in slab reheating. In steels with micro amounts of titanium, finer austenite grain size is observed in slab reheating at high temperatures of above 1 200°C. Controlled rolled titanium steels have high strength and excellent toughness, because titanium, similarly to niobium, strongly retards recrystallization of austenite, and strengthens steel by precipitation of TiC. TiN with very low solubility hardly dissolves at all in slab reheating, and resultantly does not contribute to the strength of the steel. Therefore, an effective titanium content, which is defined by (Total Ti-3.4N), is useful for designing steels. Strengthening by 3 kgf/mm2 in tensile strength per 0.01% effective titanium was observed. Strengthening due to grain refinement and that by precipitation of TiC are almost equal in a 0.1% titanium steel. The value of vEs of 0.003%S-Ti steel with 60 kgf/mm2 in the tensile strength is higher than that of Nb-V steel by about 2 kgf-m, due to sulfide shape control effect by titanium.
