The Effect of Ti on High Temperature Properties of Austenitic Steel

Abstract

Following the previous report (Tetsu-to-Hagane 45, 1959, 11, p. 1276), the effect of Ti and C on the mechanical properties (such as creep rupture strength, tensile strength and aging hardness) and the microstructure of 18 Cr-12 Ni austenitic stainless steel containing Ti were studied.
The range of the C contents studied was from 0.06% to 0.49%, and that of the Ti contents was from 0% to 155%.
With these steels, TiC and Cr₂₃C₆ precipitated during aging at 600, 650, 700 and 750°C. The aging hardness increased with increasing C contents and decreased with increasing Ti contents.
When the Ti content was over four times as much as theC content, large granular TiC remained on grain boundaries. It seemed that this structure had a unfavorable effect on the mechanical properties.
Precipitates were examined by the same method as described in the previous report. With the specimens with 0. 06% and 0. 12% of C, X-ray diffraction lines of TiC, TiN, τ phase which seemed Ti sulfide were obtained but with the specimens with higher C contents, TiN and τ phase were not detected.
The tensile strength depended mainly upon the C content dissolved in the matrix.
When the Ti content was about four times as much as the C content, the creep rupture strength was maximum for each C content.