Articles written in Sadhana
Volume 47 All articles Published: 23 January 2022 Article ID 0025
Precipitation of titanium nitride inclusions during continuous casting of high carbon wire rod grade steel SWRH 72A
P MALLIKARJUNA RAO D SATISH KUMAR S MANJINI G BALACHANDRAN
The precipitation and growth behavior of titanium nitride (TiN) inclusions during the continuous casting of high carbon wire rod grade steel SWRH 72A was investigated based on the thermodynamic calculations. Titanium is a tramp element in this grade and its pick up in liquid steel mainly takes place from the ladle alloy additions. Titanium in liquid steel is the limiting factor for the growth of TiN inclusions as it diffuses slowly in steel than nitrogen and enriches in interdendritic liquid regions creating favorable conditions for TiN precipitation. It was also observed from this study that the temperature for the formation of TiN inclusion decreased with decrease in titanium for a fixed nitrogen. Titanium nitride inclusions precipitate in steel during solidification even with low titanium and nitrogen content due to the effect of elemental segregation. Solidificationsegregation of both titanium and nitrogen increased with increase in cooling rate and their segregation tendency increased rapidly with increasing solidification fraction. The effect of titanium, nitrogen and cooling rate on the growth radius of titanium nitride inclusion was studied and validated with actual inclusion measurement.
Volume 47 All articles Published: 23 June 2022 Article ID 0122
Effect of composition and inter-critical annealing parameters on microstructure and mechanical properties of DP steel
PRABHAT K RAI D SATISH KUMAR G BALACHANDRAN
The present study aims at to study the effect of chemical composition, intercritical annealing parameters (temperature and holding time) on microstructure and mechanical properties of dual phase steels. Three normalized steels (A, B and C) with different compositions were subjected to inter-critical annealing at 760°C and 810°C for different holding times (3, 6 and 9 min). The microstructural characterization was carried out using a scanning electron microscope (SEM) and mechanical properties were evaluated using microhardness measurements and tensile tests. The strength has been found to increase from 500 MPa (steel A) to >1200 MPa (steel C) at the cost of a decrease in elongation from 25% (steel A) to 7.5% (steel C). Results havebeen analysed and discussed.
Volume 47 All articles Published: 15 October 2022 Article ID 0206
Development of ultra high strength 27MnSiVS6 micro-alloyed steel by austempering and forced cooling conditions
G RAMA RAO K K RAKESHA T SUMAN BABU K S ADARSH M VIDHYASAGAR D SATISH KUMAR G BALACHANDRAN
Strips of micro-alloyed steel grade 27MnSiVS6 was subjected to austenitization, followed by forced air cooling and austempering conditions. The forced air cooled condition resulted in a tensile strength of 1345 MPa and 13.5% elongation with an yield ratio of 0.41, with a microstructure consisting of ferrite, bainite with blocky martensite/austenite (M/A) constituent. The same steel was subjected to austenitization at 950 °C for 10 min followed by austempering in a salt bath at 450 °C for 5 min, showed a fully bainitic ferrite microstructure with very fine M/A constituents, where a tensile strength of 969 MPa and an elongation of 16.8% and an yield ratio of 0.82 were noticed. During austempering, the holding time at the austenitization temperature and isothermal temperature were varied which resulted in a moderate influence on the strength and the ductility. The work hardening behavior of the steel was examined using the Hollomon equation and modified C–J (Cussard–Jeoul) analysis. The work hardening initially takes place in the softer ferrite phase, which is beyond acritical strain, changes over to harder tempered martensite phases followed by void nucleation and failure. The study establishes a new range of mechanical properties in the micro-alloyed steel that can be used in flat products.
Volume 48, 2023
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