Showing papers by "Steel Authority of India published in 2002"

Weldability and Microstructural Aspects of Shielded Metal Arc Welded HSLA-100 Steel Plates

Abstract: HSLA-100 steel with 14 mm thickness in quenched and tempered condition was shielded metal arc welded (SMAW) with 2 kJ/mm heat input using basic flux coated filler rods without any pre or post welding heat treatments. The steel was found to be welded satisfactorily in this condition without developing any defect. Optical microscopy studies revealed typical cast dendritic structure in the weld metal and coarse bainite in grain-coarsened area of the heat-affected zone (HAZ). Transmission electron microscopy (TEM) study confirmed incidence of mixed structure of martensite laths and bainite in weld metal, while, it was mainly of bainite laths in HAZ with evidence of martensite–austenite (M–A) constituent and massive ferrite. The yield strength (YS), ultimate tensile strength (UTS) and Charpy V-notch (CVN) impact energy of the weld metal (YS-695 MPa, UTS-842 MPa and CVN-105 J at –50°C) and HAZ (YS-790 MPa, UTS-891 MPa and CVN-130 J at –50°C) were found satisfactory although HAZ properties were inferior to the base metal properties. The hardening of HAZ was not very significant in this steel under the present welding condition.

Impact toughness of high strength low alloy TMT reinforcement ribbed bar

Abstract: Charpy V-notch impact toughness of 600 MPa yield stress TMT rebars alloyed with copper, phosphorus, chromium and molybdenum has been evaluated. Subsize Charpy specimens were machined from the rebar keeping the tempered martensite rim intact. The copper-phosphorus rebar showed toughness of 35 J at room temperature. The toughness of copper-molybdenum and copper-chromium rebars was 52 J. The lower toughness of phosphorus steel is attributed to solid solution strengthening and segregation of phosphorus to grain boundaries. Due to superior corrosion resistance, copper-phosphorus TMT rebar is a candidate material in the construction sector.

Weldability characteristics of shielded metal arc welded high strength quenched and tempered plates

Abstract: High strength, quench and tempered (Q&T) plates having yield strength of a minimum of 670 MPa and conforming to SA 517 Gr. F specification were successfully developed at Rourkela Steel Plant in plates up to 40 mm thickness. The plates are used extensively for the fabrication of impellers, penstocks, excavators, dumpers, and raw material handling devices, where welding is an important processing step. SA 517 Gr. F plates, characterized by a relatively high carbon equivalent (CE: ∼0.6) and alloyed with Ni, Cr, Mo, Cu, and V, are susceptible to a crack-sensitive microstructure and cold cracking during welding. In view of the above, the present study investigated the weldability properties of 20 mm thick plates using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were carried out to assess the cold cracking resistance of the weld joint under different welding conditions. Preheat of 100 °C, partial or full rebake, and a heat input of 14.9 to 15.4 KJ/cm resulted in static fatigue limit (SFL) values well in excess of the minimum specified yield strength (MSYS) of 670 MPa and a critical restraint intensity (K cr) value of 34,650 MPa, indicating adequate cold cracking resistance. Lamellar tear tests conducted using full thickness plates at heat input levels ranging from 9.7 to 14.4 KJ/cm and weld restraint loads (WRL) of 510 to 685 MPa showed no incidence of lamellar tear upon visual, ultrasonic, and four-section macroexamination. The weld joint, based on optimized welding parameters, exhibited adequate tensile strength (812.4 MPa) and low temperature impact toughness 88.3 and 63.4 J (9.2 and 6.6 kg-m) at −40 °C for weld metal (WM), and heat-affected zone (HAZ) properties, respectively. The crack tip opening displacement (CTOD) values of WM and HAZ (0.40 and 0.36 mm, respectively) were superior to that of the parent metal (0.29 mm), indicating adequate resistance of weld joint to brittle fracture. It was concluded that the weld joint conforms to the requirements of SA 517 Gr. F specification and ensures a high integrity of the fabricated products.

From Resources to Applications. Designing the Multilingual ISLE Lexical Entry.

Abstract: The ISLE Computational Lexicon Working Group is committed to the consensual definition of a standardized infrastructure to develop multilingual resources for HLT applications. In particular, the ISLE-CLWG pursues this goal by designing MILE (Multilingual ISLE Lexical Entry), a general schema for the encoding of multil ingual lexical information. This has to be intended as a meta-entry, acting as a common representational layer for multil ingual lexical resources. We present the general architecture and features of MILE, as well as the methodology adopted for its definition. In particular, we focus on two essential ingredients for the MILE specification: the selection of the types of lexical information most relevant to establish multili ngual correspondences, and the specification of a data structure which will provide the formal backbone of the MILE as a general representation language to develop multili ngual resources. The ISLE recommendations wil l also consist of a first repository of shared lexical objects, including main syntactic constructions, basic operations and conditions to establish multilingual l inks, macro-semantic objects, etc., for the encoding of lexical units at a higher level of abstraction, as a step in the direction of simplifying and improving the usability of the MILE recommendations. We are also developing the ISLE Lexicographic tool.

Utilization of mixed pond ash in integrated steel plant for manufacturing superior quality bricks

Abstract: Fly ash (FA) poses serious problems to the industries. Integrated steel plants generate huge quantity of FA from their captive power plants and other furnaces. This ash is generally disposed off in the ash ponds along with other sludges and residues of steel making operations. This changes the constitution of FA and makes the brick manufacturing difficult. This paper has attempted to devise the ways for the use of this mixed ash for manufacturing mixed ash clay bricks successfully. The bricks thus made are superior in structural and aesthetic qualities and portents huge saving in the manufacturing costs with better consumer response.

Process technology for the continuous hot band annealing of 17%Cr ferritic stainless steel

Abstract: As an alternative to time- and energy-consuming batch annealing, process technology for the continuous hot band annealing of 17%Cr ferritic stainless steel has been established. Process parameters (i.e., temperature and time) for the hot band annealing were optimized in the laboratory and, subsequently, plant trials were conducted. The impact toughness value of the annealed hot band was found to be the most crucial parameter to assess the cold rollability in the commercial run. When the hot bands were continuously annealed at 900 °C, the improved impact toughness values resulted in successful cold rolling to the desired thickness. The impact toughness value and subsequent cold rollability were found to be related to the formation of martensite volume%. Annealing the hot band in the lower temperature range of the two-phase (α+r) region (i.e., 900 °C) yielded the best result. Improvement in roping index has been reported as a result of the weakening of the texture of the continuous-annealed hot band.

Weldability characteristics of torr and corrosion-resistant TMT bars using SMAW process

Abstract: Torr steel rebars, also known as cold twisted deformed (CTD) rebars, are used extensively for the construction of reinforced cement concrete (RCC) structures. These steels, which are characterized by a high carbon content and are subjected to a cold twisting operation to attain the desired strength level and bond strength, suffer from low ductility and poor bendability properties. Furthermore, these rebars are not suitable for coastal, humid, and industrial conditions where corrosion rates are very high. To combat these problems, recent efforts at the Steel Authority of India Limited (SAIL) have led to the successful development of corrosion-resistant thermomechanically treated (TMT) rebars with a minimum yield strength of 500 MPa. These rebars are characterized by a low carbon content, exhibit excellent strength-ductility-corrosion properties, and are rapidly replacing traditional torr rebars in corrosion-prone areas for a wide range of applications, namely, concrete reinforcement structures, bridges, flyovers on dams, etc. A comprehensive evaluation of the weldability properties of corrosion-resistant Cu-TMT rebars was carried out, and they were compared with those made of torr steel in order to assess their suitability for various structural applications. Implant and restraint cracking (RC) tests were carried out to assess the cold-cracking resistance of the weld joint under different welding conditions. The static fatigue limit (SFL) values were found to be similar, namely, 640 MPa (torr steel) and 625 MPa (Cu-TMT steel) under condition of no preheating and no rebaking using a heat input of 7.5 KJ/cm, indicating adequate cold-cracking resistance for both the steels. Restraint cracking tests yielded critical restraint intensities (Kcr) in excess of 16,800 MPa for both of the steels. Based on the weldability tests, the optimized conditions for welding were formulated and extensive tests were carried out on the welded joints. Both of the steels exhibited adequate strength levels (tensile strength (TS): torr rebars, 524 Mpa; Cu-TMT rebars, 630 MPa) and adequate low-temperature impact toughness properties, ensuring a high integrity of the fabricated products.

Extended range electric vehicle

Abstract: An extended range E-V uses a compressed energy system to power a flywheel having an internal battery with a ball-mounted axle, for recharging of the main battery, by driving a generator. The flywheel coupled within the vehicle uses the leverage end of the axle, a bearing coaxially surmounted by an elastic medium, actuators, and a pivotally coupled sub-carriage for stability. The flywheel comprises a power take off gearing means within the ball to drive a generator for supplementing the electrical power in the batteries. A catch releases compressed energy to initiate motion of the flywheel that allows the E-V battery to be recharged while the E-V is in operation. A retractable sliding contact provides the path for the compressed energy absorber to receive energy from an advocated bus in the roadway, to be rapidly charged while stopped at a station, or while E-V is moving slowly.

Improvement in the surface quality of ball bearing steel rounds at Bar Mill

Abstract: The rejection of ball bearing steel rounds had increased at Bar Mill due to surface defects following an increase in the demand for a better surface quality. The genesis of surface defects in ball bearing steel rounds is attributed to steel-making and rolling processes. The steel-making defects are exogenous in nature with the presence of non-metallic inclusions in steel. The rolling defects are generated due to poor quality of the input billets, improper thermal regime of reheating, incorrect setting of entry and exit guides, misaligned roll pass line and inappropriate rolling schedule. This paper discusses the generation of surface defects and the formulation of a strategy to reduce these defects at Bar Mill. The improvement in the surface condition of the input billets, correct entry/exit guide setting and modification in roll pass design have reduced the rejection rate by 34.6%.

An investigation into the failure of API 5L X-46 grade ERW linepipes

Abstract: The genesis of failure of 6.1 mm thick electric resistance welded (ERW) API 5L X-46 pipes during pretesting at a pressure equivalent to 90% of specified minimum yield strength (SMYS) was investigated. Cracks were found to initiate on the outer surface of the pipes in the fusion zone and propagate along the through-thickness direction. The presence of extensive decarburization and formation of a soft ferrite band within the fusion zone may have contributed to the nucleation of the cracks. Crack propagation was aided by the presence of exogenous inclusions entrapped within the fusion zone. Analysis of these inclusions confirmed the presence of Fe, Si, Ca, and O, indicating slag entrapment to be the most probable culprit.

Process for thermorming a three-dimensionally curved panel

Abstract: A device for making panels with three-dimensional curvature from a sheet material, includes a forming impression ( 5 ) defined by a membrane ( 6 ) including an elastically stretchable skin ( 11 ), preferably in combination with a skeleton formed by a grid pattern of flexurally elastic battens ( 10 ) which are mobile in longitudinal translation relative to the skin, and a set of elements for selectively deforming the impression acting on the battens ( 10 ) of the membrane to impart thereto an adaptable three-dimensional curvature. The invention is particularly useful for making sails.

Thinning as a failure criterion during sheet metal forming

Abstract: Thinning during forming is often considered a failure criterion in the metal forming industry. It is believed that a critical amount of thinning takes place in a sheet metal before failure. In this study, varying widths of low-carbon steel sheets were punch stretched under laboratory conditions. Thinning during punch stretching was measured at various locations along the steel sheets. These measurements demonstrated that thinning during forming is not constant, but that it is a function of the strain path followed by the sheet. Hence, thinning should not be used as a failure criterion during forming of sheet metals.

Prediction of mechanical properties of multiphase steels containing retained austenite

Abstract: A theoretical model has been developed for predicting the flow behavior of dual-phase steels containing retained austenite. A good agreement between theoretical predictions and experimental values is obtained by optimizing the value of load-transfer factor and by using an additional term considered to account for the geometrically required dislocations around the hard particles.

Influence of Metallurgical Factors on the Performance of IS:7887 Gr. 3 Billets for Fastener Applications

Abstract: The quality advantages of continuous casting (concast) have enabled the production of a wide range of billets for various end applications, including IS:7887 Gr. 3 billets for the fastener industry. This paper discusses the influence of the internal quality of these concast billets on the processing of a wide range of products for the fastener industry. Internal soundness, inclusion volume fraction, and cleanliness were found to have a strong influence on the cracking susceptibility of self-tapping screws and nuts. A high incidence of hairline cracks on nut surfaces was found to be due to a combination of a high volume fraction of inclusions (0.54%) and the presence of complex manganese (Mn) (aluminate-silicate)-type inclusions.