Steel Authority of India

About: Steel Authority of India is a based out in . It is known for research contribution in the topics: Microstructure & Ultimate tensile strength. The organization has 797 authors who have published 661 publications receiving 9958 citations. The organization is also known as: SAIL.

Influence of thermomechanical treatments on the microstructure and mechanical properties of HSLA-100 steel plates

Abstract: The influence of thermomechanical treatment (TMT), i.e., controlled rolling and direct quenching, as a function of rolling temperature and deformation on the microstructure and mechanical properties of HSLA-100 steel have been studied. The optical microstructure of the direct quenched (DQ) and tempered steel rooled at lower temperatures (800 °C and 900 °C) showed elongated and deformed grains, whereas complete equiaxed grains were visible after rolling at 1000 °C. The transmission electron microscope (TEM) microstructure of the 800 °C rooled DQ steel showed shorter, irregular, and closer martensite laths with extremely fine Cu and Nb(C,N) precipitates after tempering at 450 °C. The precipitates coarsened somewhat after tempering at 650 °C; the degree of coarsening was, however, less compared to that of the reheat-quenched (RQ) and tempered steel, indicating that the DQ steel was slightly more resistant to tempering. Similar to the RQ steel, at a 450 °C tempering condition, the DQ steel exhibited peak strength with extremely poor impact toughness. After tempering at 650 °C, the toughness of the DQ steel improved significantly, but at the expense of its strength. In general, the strength of the DQ and tempered steel was good and comparable to that of the RQ and tempered steel, although, its impact toughness was marginally less than the latter. The optimum combination of strength and toughness in the DQ steels was achieved after 900 °C rolling with 50 pct deformation, followed by direct quenching and tempering at 650 °C (yield strength (YS)=903 MPa, ultimate tensile strength (UTS)=928 MPa, and Charpy V-notch (CVN) strength=143 J at −85 °C).

Analysis of the temperature dependence of strain-hardening behavior in high- strength steel

Abstract: The stress-strain data of a high-strength low-alloy (HSLA) steel were measured at different temperatures and analyzed in terms of strain-hardening laws proposed by Hollomon,[1] Ludwik,[2] Swift,[3] and Voce.[4] Four methods of analysis, as suggested by Kleemola and Nieminen (K-N),[7] Crussard and Jaoul (C-J),[16] Ramani and Rodriguez (R-R),[11] and Guimaraes (G),[15] have been employed. The C-J analysis has been extended to the Voce equation for the first time. The results have been discussed in terms of the linear correlation coefficient and error in the estimation of uniform strain. The Voce equation has been found to describe the flow be-havior most accurately. The observed increase in flow stress in the dynamic strain aging (DSA) range has been explained in terms of temperature-dependent strain-hardening parameters. It has been established that with increase in the value of the Voce strain component, nv, the magnitude of the saturation stress approaches that of the ultimate tensile stress. A linear relationship has been established between ultimate tensile stress and saturation stress.

Solidification control in continuous casting of steel

Abstract: An integrated understanding of heat transfer during solidification, friction/lubrication at solid-liquid interface, high temperature properties of the solidifying shell etc. is necessary to control the continuous casting process. The present paper elaborates upon the knowledge developed in the areas of initial shell formation, mode of mould oscillation, and lubrication mechanism. The effect of these issues on the caster productivity and the quality of the product has been discussed. The influence of steel chemistry on solidification dynamics, particularly with respect to mode of solidification and its consequence on strength and ductility of the solidifying shell, has been dealt with in detail. The application of these basic principles for casting of stainless steel slabs and processing to obtain good quality products have been covered.

Influence of nonmetallic inclusion characteristics on the mechanical properties of rail steel

Abstract: An extensive investigation has been carried out on six commercial heats of pearlitic rail steel to study the influence of nonmetallic inclusion characteristics on the tensile, fatigue, and fracture toughness properties. The steels investigated were made through the basic oxygen furnace (BOF)-continuous casting route and rolled in the rail and structural mill into 90 kg/mm2 ultimate tensile strength (UTS) grade rails. While tensile properties (yield strength [YS], UTS, and elongation) of the rail steels investigated were found to be insensitive to inclusion type and volume fraction at their present level (0.23 to 0.45%), the fracture toughness and high-cycle fatigue properties were found to be inclusion sensitive. The fracture toughness values of the steels were found to range between 42.33 and 49.88 MPa √m; higher values, in general, were obtained in heats exhibiting lower volume fractions (0.15 to 0.19%) of sulfide inclusions. The high-cycle fatigue limit, i.e., stress corresponding to 107 cycles, was found to be higher in cleaner steels, particularly in those with lower volume fractions of oxide inclusions. This phenomenon was corroborated by scanning electron microscopy (SEM) observations of fracture surfaces, where oxide inclusions in particular were found to be instrumental in crack initiation. Although fatigue life did not show any direct correlation with the volume fraction of sulfides, elongated MnS inclusions were sometimes observed at crack initiation sites of fatigue-tested specimens.