Papers by Author: K. Saravanan

Abstract: 0.3C-CrMoV(ESR) steel is an ultra-high strength low alloy steel indigenously developed by ISRO for space applications. The steel is used in the form of rings of 2.8 m diameter also. In this paper, the effect of tempering temperature on ring rolled steel for the best combination of fracture toughness and strength properties is studied. The tensile properties and fracture toughness of the steel were evaluated in the as quenched and tempered conditions through the specimens drawn in radial direction of the ring segment. Five tempering temperatures were used in the study: 200, 450, 475, 500 and 510°C. Tensile strength of the steel showed continuous decrease with increasing tempering temperature, but yield strength increased reaching maximum when tempered at 450°C and further decreased with increasing tempering temperature. The elongation was higher for higher tempering temperature. The strain hardening exponent decreased with increasing tempering temperature. The fracture toughness test results showed that tempering between 475 and 510°C exhibited better combination of fracture toughness and strength.

Abstract: The weld portion will have different mechanical properties in weld bead, HAZ and fusion boundary due to variation in the microstructure, chemistry and internal stresses that arise in the welding process. Inconel 718 TIG welded samples are tested to study the deformation behavior of the weld constituents with the help of non contact laser extensometer. Stress-strain curves for the individual constituents of weld, parent, fusion boundary and HAZ are evaluated at room temperature and at 550°C. Test results show that the welded samples exhibited 50% lower tensile properties compared to the parent material. Parent metal remains elastic through out the test. The proof stress of the weld alone is 100 MPa lower than the average proof stress of the welded sample when considered standard gauge length.