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 48 All articles Published: 2 January 2023 Article ID 0009
Formability behaviour of ferritic and austenitic rolled Nb–Ti stabilized IF grade steel
D SATISH KUMAR S MANJINI K UDAYA BHAT
Recently, soft hot strip and hard hot strip produced through ferritic rolling are projected as a direct replacement to austenitic cold-rolled sheets for many forming applications. However, industrial hot-rolling mills, with final rolling thickness limitations cannot produce these thinner products and have to be subsequently cold-rolled to the desired application thickness and further annealed. Under ferritic rolling conditions, the hotrolling temperature of these coils governs the final properties. The temperature difference in hot-rolled sheetsgenerates the difference in the microstructure and texture of these coils after cold-rolling and annealing and variation in their formability behaviour. In the present work, an Nb–Ti stabilized IF grade steel was hot-rolled at two different temperatures in the ferritic regime and subsequently cold-rolled and annealed for structureproperty comparison. As formability is an application-specific requirement, the annealed sheets were tested for different formability characteristics. Industrially rolled samples were tested for fracture criterion, stretchflangeability, deep drawability and stretch formability through the formability limit diagram, hole expansion ratio, earing test and Erichsen cupping test respectively. These parameters were compared with those of the austenitic regime rolled sheets. High temperature ferritic rolled sheets show improved formability in all tests due to better r, higher n-value, low Δr and stronger gamma fibre maxima at 111<121>. Low temperature ferritic rolled sheets show the lowest Δr and improved n-value, but has reduced r and higher alpha fibre texture. High temperature ferritic rolled sheets show higher formability limits in uniaxial tension and low temperature ferritic rolled sheets in biaxial tension of the FLD curve. Various tests established that high temperature ferritic rolled sheets are best suited for deep drawing and stretching applications whereas low temperature ferritic rolled sheets should be preferred for stretch forming applications.
Volume 48, 2023
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