SAIKAT DE - Academia.edu (original) (raw)

Papers by SAIKAT DE

International journal of metallurgical engineering, 2016

Steel Authority of India Limited (SAIL) has developed a number of economical, value added hot and... more Steel Authority of India Limited (SAIL) has developed a number of economical, value added hot and cold rolled steels which has satisfied the material requirements for a variety of critical applications. Keeping in view the development in infrastructure, automobile, transport and power sector in India there is huge potential for increase in per capita consumption of steel from the present level of 60kg. Construction and infrastructure will continue to be the dominant steel consuming segment. To meet the requirement of corrosion resistant property for the steels to be used in these two segments, SAIL has successfully developed a number of special quality steel grades with copper such as SAILCOR for Railways and BHEL, HCR variety TMT rebars, IS 2062 Cu bearing structural & plates and copper containing Stainless Steel. Further, a lot of application engineering efforts have been put in to establish these grades in the market by improving product quality, suiting the process at the customers' end and thus ensuring greater acceptability of products. These grades possess superior corrosion resistance and high strength combined with good workability, excellent welding properties and other superior mechanical properties. Such characteristics make these steels a natural candidate for use in a number of segments like transport, construction, power and other engineering sector, agriculture and mining.

In this paper, efforts made at BSL, SAIL towards developmental of API X70 grade HR coils intended... more In this paper, efforts made at BSL, SAIL towards developmental of API X70 grade HR coils intended for SW pipes, have been presented. Two trial heats with Nb-Cr-V and Nb-Cr-V-Mo based chemistry aiming (a) ferrite-pearlite and (b) ferrite-pearlite-bainite microstructures respectively were made and cast into 1400 x 210 mm slabs. These trial slabs were processed under suitably designed process variables. Acicular ferrite microstructure engineered through Nb-V-Cr-Mo alloy design has been found more suitable to achieve requisite strength level (in 45° direction) and impact toughness properties consistently in API X70 HR coils. All the properties requirements like, Yield Strength (YS): 515-536 MPa, Ultimate Tensile Strength (UTS): 590-610 MPa, Percentage elongation (%El) in 50mm GL: 25-35%, YS/UTS: 0.86-0.88, Hardness: 184-218 HV10 and Impact toughness (at -5°C): 305-328 J were successfully achieved in HR coils of Nb-V-Cr-Mo heat. Performance trial for three number of coils of Nb-V-Cr-Mo h...

For supply of API 5L Grade X70 (PSL 2) 1610 mm wide hot rolled (HR) coils of 10.4, 11.2 and 12.8 ... more For supply of API 5L Grade X70 (PSL 2) 1610 mm wide hot rolled (HR) coils of 10.4, 11.2 and 12.8 mm thickness, trial ro lling was undertaken at Bo karo Steel Limited (BSL). Two heats were made and cast into 200 x 1630 mm section slabs with designed alloy chemistry. Rolling parameters of exit roughing (R5) temperature, fin ish rolling temperature (FRT), and coiling temperature (CT) were kept in the range of 1080 - 1100 ° C, 860 - 890° C, and 600 - 630 ° C respectively. Coiling of high strength 10.4, 11.2 and 12.8 mm thick co ils of 1610 mm width at such low temperature was carried out for the first time in SAIL. M icrostructure of hot rolled coils co mpris ed ferrite and pearlite. Average grain size for ferrite varied between 6.3 - 9.2 micron. Microstructure of Centreline segregated zone of cast slab showed presence of primary carb ides of microalloying elements. Optical micrograph clearly shows formation of coarse primary carbides at inter dendritic region. SEM and EDAX examinations...

Materials Science and Technology, 2008

Boron exerts a large influence on mechanical properties of steel through microstructural control.... more Boron exerts a large influence on mechanical properties of steel through microstructural control. It increases the hardenability of steel by retard ing the heterogeneous nucleation of ferrite at the austenite grain surfaces and the decomposition kinetics of austenite to ferrite t ransformat ion are governed by its location and chemical state. To understand the effect of boron (~ 25 pp m) on microstructural evolution and change in continuous cooling transformat ion (CCT) diagram , a systematic study has been carried out using Gleeble thermo-mechanical simulator in unalloyed (C: 0.05 wt%; Mn : 0.2 wt%) and low alloyed (C: 0.2 wt%; Mn : 1.2 wt%: Cr: 0.15 wt%) steels. CCT diagrams, plotted for the onset and end of pearlit ic, bainitic and martensitic reactions, consisted essentially of two C-curves and a remarkable d ifference was observed on comparing the results for both steels. It is interesting to note that bainite and martensite are co mpletely absent even at higher cooling rate o f 70°C/sec in the unalloyed steel with boron addition. In contrast, the addition of boron was observed to promote significant bainite format ion even at a slower cooling rate of only 20°C/sec in the low alloyed steel. These contradicting effects on hardenability can be explained by the effect of boron in shifting only the upper C curve to the right for reconstructive transformation.

Materials and Manufacturing Processes, 2010

Microstructural control through thermo-mechanical simulation has been attempted in aluminum-kille... more Microstructural control through thermo-mechanical simulation has been attempted in aluminum-killed low carbon-manganese boron containing steel. The results from dilatometric studies were used to explain austenite decomposition characteristics under different ...

Journal of Materials Engineering and Performance, 2008

Addition of boron in low carbon (0.06% max) hot rolled steel has improved its formability. A uniq... more Addition of boron in low carbon (0.06% max) hot rolled steel has improved its formability. A unique combination of properties with low strain hardening exponent (n) and high total elongation has resulted into higher percentage of cold reducibility of hot rolled coils.

Materials and Manufacturing Processes, 2011