STUDY ON THE TOUGHNESS IMPROVEMENT BY ADDITION OF THE SMALL AMOUNT OF FERRO-TITANIUM IN STRUCTURAL STEEL (I)

Abstract

Titanium added in steels easily combines with sulphur and forms the stable TiS in steels. On the one hand, sulphur in alloy steels has been considered a harmful element and we have made efforts to control sulphur in steels as low as possible in steel-making process. To prevent toughness decrease caused by much sulphur in alloy steels, the auther planed to utilize small amount addition of ferro-Ti in alloy steels. Then effects of small amount addition of ferro-Ti in various kinds of structural alloy steels were examined, with both experimental small ingots and practical ingots. The following conclusions were obtained:
1. As for the alloy element that increases toughness, titanium is more effective than molybdenum and vanadium in alloy steel.
2. It seems especially effective to decrease brittleness in manganese-containing steel by titanium addition.
3. Effect of a little addition of ferro-Ti in alloy steels are not so effective in steels that contains such elements, as Cr, Mo, V, etc which forms carbides easily in steels, while especially effective in steels that contains such elements, as Ni, Mn, etc which are soluble into ferrite in steels,
4. Any steels added with small amount of ferro-Ti has very fine anstenite grains.
5. This treatments are not effective for plain carbon steels but extremely effective for Ni-Cr-Mo structural steels.