ORIGINATION OF TITANIUM NITRIDE IN A LOW-CARBON STEEL
Abstract
In this work an investigation into conditions of origination of the titanium nitride and its effect on initiation of cracks in low-carbon steels with titanium is presented. Various sorts of titanium oxides and titanium nitride are originating after deoxidation of iron by titanium in relation with the degree of chemical oversaturation of the melt, whereby the oversaturation is necessary for origination of such inclusions. For a homogeneous nucleation of titanium dioxide there has been determined the degree of chemical oversaturation of ?TiO2 = 102, while for the titanium nitride of ?TiN = 108. The high degree of chemical oversaturation for the homogeneous nucleation of titanium nitride is not attained in an iron melt and thus, the titanium nitride is nucleating in a heterogeneous way at the oxides with a degree of chemical oversaturation of approx. 102.
The origination of cracks is dealt here with on the basis of oxidation of titanium nitride (and/or carbonnitride) that is associated with a transformation of the inclusions of TiN ? TiO and with enlargement its molar volume by approx. 10 % and thus, stress is originating in the metallic matrix.
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