Showing papers by "Steel Authority of India published in 1994"
TL;DR: In this paper, a microstructural insight into the cause of premature breakage of a second-intermediate Sendzimir mill drive roll used at a stainless steel sheet rolling plant under the Steel Authority of India Limited is provided.
Abstract: Although a precise understanding of roll failure genesis is complex, the microstructure of a broken roll can often unravel intrinsic deficiencies in material quality responsible for its failure. This is especially relevant in circumstances when, even under a similar mill-operating environment, the failure involves a particular roll or a specific batch of rolls. This paper provides a microstructural insight into the cause of premature breakage of a second-intermediate Sendzimir mill drive roll used at a stainless steel sheet rolling plant under the Steel Authority of India Limited. Microstructural issues influencing roll quality, such as characteristics of carbides, tempered martensite, retained austenite, etc., have been extensively studied through optical and scanning electron microscopy, electron-probe microanalysis, image analysis, and x-ray diffractometry. These are discussed to elucidate specific microstructural inadequacies that accentuated the failure. The study reveals that even though retained austenite content is low (6.29 vol%) and martensite is non-acicular, the roll breakage is a consequence of intergranular cracking caused by improper carbide morphology and distribution.
15 citations
TL;DR: In this article, an attempt has been made to design and develop acicular ferritic steels by adopting three-stage controlled rolling, with titanium alone as a microadditive.
Abstract: An attempt has been made to design and develop acicular ferritic steels by adopting three-stage controlled rolling, with titanium alone as microadditive. Process parameters such as finish rolling temperature (FRT), amount of deformation during the last pass and also the cooling rate after finishing have been altered to obtain different microstructural effects. Optical as well as transmission electron microscopy studies indicated that acicular ferritic microstructure can be engendered by applying a minimum deformation of 25 % at the finishing pass followed by water quenching. Decreasing the FRT from 850 °C, for water quenched steels deformed 33 %, resulted in the refinement of polygonal ferrite, whereas the reverse is the case with the aspect ratio of acicular ferrite
9 citations
TL;DR: In this article, a modification of the sintering model proposed by Frenkel and valid for non-crystalline viscous solids has been proposed, in which the viscosity term is presumed to be linearly related to time.
6 citations
TL;DR: In this paper, the solidification structure of undercooled melt of Ag-Cu alloy, entrained in its primary Cu-rich phase, has been investigated, and the microstructure of the under-cooled alloy indicated a complete absence of eutectic reaction on subsequent quenching.
Abstract: The solidification structure of undercooled melt of Ag-Cu alloy, entrained in its primary Cu-rich phase, has been investigated. The undercooling procedure consisted of equilibration of a Cu-13 pct Ag alloy in the two-phase liquid-solid region, followed by repeated thermal cycling of the liquid. Slow cooling of the sample in the present work established the ability to undercool the melt up to 70 K below the eutectic temperature of this alloy. The microstructure of the undercooled alloy indicated a complete absence of eutectic reaction on subsequent quenching of the melt directly from the equilibration temperature. The compositional analysis of the constituent phases by electron probe microanalysis (EPMA) technique provided evidence for the massive diffusionless solidification of the undercooled liquid. The X-ray diffraction study and electron microscopic examination indicated evidence for the spinodal transformation of the metastable solid solution phase. The composition of the phases formed on decomposition matched well with the calculated coherent spinodal boundaries in this system. The evolution of the metastable microstructure in the mushy-state quenching process of this alloy is discussed.
4 citations
TL;DR: In this article, the authors examined the fatigue cracked and fast fractured regions in four-point bend specimens prepared from 25 wt% silicon carbide whisker reinforced alumina composite by scanning electron microscopy and found that the alumina matrix failed mainly in a transgranular mode and the whiskers mainly failed with a flat fracture surface.
Abstract: Fatigue cracked and fast fractured regions in four-point bend specimens prepared from 25 wt% silicon carbide whisker reinforced alumina composite were examined by scanning electron microscopy. This composite was found to be susceptible to a fatigue crack growth phenomenon similar to that in the case of metallic materials, but with a higher crack growth exponent. In the fatigue region, the alumina matrix failed mainly in a transgranular mode and the whiskers mainly failed with a flat fracture surface but without their pullout. On the other hand, in the fast fracture region, the whiskers failed predominantly by pullout and the alumina matrix failed in a mixed mode with about half in transgranular and the other half in intergranular mode. Thus, to improve the fracture toughness of the material, the grain boundary strength of alumina and the matrix whisker interfacial bonding should be improved. To increase the resistance to fatigue, the fracture strength of the alumina grains should be improved by using finer α-alumina particles and the fatigue strength of the whisker have to be increased by improving the uniformity in distribution of β-SiC whiskers during hot pressing.
1 citations
Journal Article•
TL;DR: In this article, the authors studied the decomposition and transferring rate of straw and found that the transfer rate depends mainly on the C/N ratio of straw, which is the ratio between the C and N ratio.
Abstract: To study the decomposition and transferring rate of straw, the ~(14)C traced straw was used in labor and field experiments. The preliminary results are as follows:( 1 ) Decomposition rate of straw depends mainly on the C/N ratio. After straw applied into soil, the population of microorganism increases rapidly, especially bacteria.( 2 ) During its decomposition, the straw changes at first into the non-structure substances. Most of these non-structure substances transfers then into fulvic acfd and afterwards humic acid. The dico-mposed substances can renew soil humus. The procedure takes place at the functional groups of humus surface and the fraction of the molecules. The non-structure substance can cross link with a single humic acid molecule. Under certain conditions the cross-linked molecule can enter into the kernel of humus molecule. The transformation and re-distribution of the single component of humic acid in soil is only close related with exchange reaction of functional groups of humus.( 3 ) Clay minerals can adsorb humic acid selectively. Preference of this selective adsorption is given to the low molecule humic acids.
1 citations
TL;DR: In this article, a better understanding of the mechanisms associated with deformation and restoration of austenite during continuous multipass hot rolling of microalloyed steels is presented.
Abstract: In recent times, efforts have been directed towards a better understanding of the mechanisms associated with deformation and restoration of austenite during continuous multipass hot rolling of microalloyed steels. The correspondence between the condition of austenite before transformation and the resultant microstructure upon cooling holds the key to the attainment of interesting properties.
TL;DR: In this article, the effect of heat treatment of the steels with and without rare-earth metal (RE) treatment on their SSCC resistance was studied, and threshold stress, corrosion rate, and hydrogen content in three steels were determined.
Abstract: Sulphide stress corrosion cracking (SSCC) studies on a set of three steels with different inclusion morphologies were conducted. Effect of heat treatment of the steels with and without rare-earth metal (RE) treatment upon SSCC resistance was studied. Threshold stress, corrosion rate and hydrogen content in the steels were determined. Quenched and tempered structure was found to improve the SSCC resistance only when the steel is RE treated. Corrosion rate and hydrogen content in the steels were found to decrease as the inclusion morphology is changed from elongated stringers to globular shape, which improves the SSCC resistance