In this study, pot sinter tests were carried out to study the sintering properties of iron ores of different alumina (2-4-6%) level. It was observed that the 6% alumina level ores have a higher RDI values and decreased tumbler index (TI) compared to its other two counterparts. It was observed that an increase in composite fracture toughness (CFT) of sinter improves the Tumbler as well as RDI of the sinter. Beyond 4 CFT there is remarkable improvement in TI, RDI and RI values. The mechanical strength parameters of sinter phases were further correlated and analysed with respect to the chemistry of sinter and mineralogy of sinter phases. There is strong evidence which suggests that the Al 2 O 3 deteriorates the strength of the phases by making them hard and thus generating cracks in them. Unlike alumina, CaO and SiO 2 tend to stabilise and improve the strength of the phase.

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The nature of microstructures in the subzones of the HAZ greatly influence weld metal toughness and strength BY A. JOARDER, S. C. SAHA AND A. K. GHOSE ABSTRACT. A detailed study on the microstructure of submerged arc (SA) weld metal and the heat-affected zone of a 1.2-cm (0.5-in.) thick plain carbon steel plate was carried out using transmission electron microscopy. The various subzone microstructures observed in the HAZ of a SA weld are spheroidized, partially transformed, grain-refined and graincoarsened. The grain-coarsened area exhibits predominantly Widmanstatten ferrite with pearlite, while the other subzones of HAZ reveal polygonal ferrite and pearlite. Depending on the number, size and distribution of inclusions, the weld metal microstructure varies. With a larger number of inclusions, grain boundary ferrite and, in absence of inclusion, either side plate with pearlite or cementite along the boundaries of side plates are observed. It is noticed that a limited number of larger size inclusions favor the formation of acicular ferrite. Because of the prevalence of varying cooling rates in weld metal, a wide range of microstructures, such as periodic pearlite, grain boundary ferrite with pearlite, and side plate with cementite along the side plate boundaries, are observed.

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