Showing papers by "Bethlehem Steel published in 1989"

Crystallography of YBa 2 Cu 3 O 6+ x thin film-substrate interfaces

Abstract: The epitactic nature of the growth of YBa2Cu3O6+x (YBCO) superconducting thin films on ceramic substrates has been studied using high-resolution electron microscopy (HREM) and selected-area diffraction (SAD) of cross-sectional specimens. The films were grown in situ on (001)-oriented MgO and (001)-oriented Y2O3-stabilized cubic ZrO2 (YSZ) single-crystal substrates by electron beam evaporation. Both of these materials have large lattice misfits with respect to YBCO. Different orientation relationships were observed for films grown on the two types of substrates. These orientation relationships are shown to provide the best matching of the oxygen sublattices across the substrate-film interfaces. A crystalline intermediate layer, 6 nm thick, between the YBCO film and YSZ substrate was observed by HREM and shown by EDS to be a Ba-enriched phase, possibly barium zirconate formed by a reaction. In contrast, the YBCO–MgO interface was found to be sharp and free of any intermediate layers.

Spinodal decomposition during aging of Fe-Ni-C martensites

Abstract: A collaborative study of the aging of virgin Fe-Ni-C martensites has combined the techniques of transmission electron microscopy (TEM), atom-probe field-ion microscopy (APFIM), and electrical resistometry. Aging at room temperature leads to the rapid development of a finescale structural modulation along 〈203 〉 lattice directions. Atom-probe analysis of Fe-15Ni-lC martensite reveals the formation of carbon-rich regions whose carbon concentration increases with time and approaches 11 at. pct C on prolonged aging. The early stage kinetics of this process are composition-dependent and are consistent with carbon-diffusion control. The morphological features of the aging reaction are explained by elastic strain-energy considerations. In accordance with previous thermodynamic models, it is concluded that virgin Fe-C martensites are unstable and that phase separation occurs by a spinodal mechanism. The martensitic substructure does not appear to exert any substantial influence on this decomposition behavior.

Carbide precipitation during stage I tempering of Fe-Ni-C martensites

Abstract: Microstructural changes which accompany the first stage of tempering have been studied by transmission electron microscopy (TEM) and electrical resistometry in two Fe-Ni-C alloys that form platelike martensite. The e-carbide transition phase in these alloys adopts a platelike shape with a habit plane near {012=α. Electron diffraction data indicate that the carbide may be partially ordered, resulting in orthorhombic symmetry, and therefore, this phase is designated as e′- carbide. The carbide particles contain a fine internal substructure which appears to represent an internal accommodation deformation (faulting) on the carbide basal plane. Detailed analysis of the kinematics of carbide precipitation suggests that the observed habit plane and accommodation deformation permit an invariant-plane strain transformation which minimizes elastic strain energy. The apparent selection of only a limited number of possible orientation variants is explained in terms of the symmetry of the parent martensitic phase, which is known to undergo spinodal decomposition prior to the nucleation of the transition carbide. The martensitic substructure is not found to exert any significant influence on this overall precipitation behavior.

Austenite recrystallization and carbonitride precipitation in niobium microalloyed steels

Abstract: The response of austenite to thermomechanical treatment is investigated in two series of niobium microalloyed steels. Optical and electron metallographic techniques were used to follow the austenite recrystallization and carbonitride precipitation reactions in these steels. The first series of steels contained a constant level of 0.05Nb, with carbon levels varying from 0.008 to 0.25 pct. It was found that a lower carbon concentration results in faster austenite recrystallization, due to a smaller carbonitride supersaturation, which leads to a reduced precipitate nucleation rate. The second series of steels was designed with a constant carbonitride supersaturation, by simultaneously varying the Nb and C concentrations while maintaining a constant solubility product. In these steels, the recrystallization kinetics increase as the volume fraction of Nb(C, N) is reduced and/or as the precipitate coarsening rate is increased. The volume fraction of carbonitrides increases as the Nb: (C+12/14 N) ratio approaches the stoichiometric ratio of approximately 8:1. The precipitate coarsening rate was shown to increase with increasing amounts of niobium remaining in solution in the austenite (i. e., “excess” Nb after precipitation). As expected, recrystallization proceeds more slowly at lower temperatures and after a reduced amount of deformation. An experiment to determine whether Nb atoms dissolved in the austenite could exert a significant solute-drag effect on the recrystallization reaction indicated that 0.20Nb in solution could reduce the rate of recrystallization compared to a Nb-free C-Mn steel. However, this solute effect was smaller than the retarding effect which 0.01Nb can have when it is precipitated in the form of carbonitrides on the austenite substructure after rolling.

Effects of Mn, Si, and purity on the design of 3.5NiCrMoV, 1CrMoV, and 2.25Cr-1Mo bainitic alloy steels

Abstract: Three high-temperature bainitic alloy steels were evaluated in the laboratory to determine the effects of Mn, Si, and impurities (i.e., S, P, Sn, As, and Sb) on microstructure and mechanical properties. The alloy steels were 3.5NiCrMoV and CrMoV, which are used for turbine rotors, and 2.25Cr-1Mo, which is used in pressure vessel applications. The important effects of Mn, Si, and impurities, which should control the design of these high-temperature bainitic steels, are presented. Key results are used to illustrate the influence of these variables on cleanliness, overheating, austenitizing, hardenability, tempering, ductility, toughness, temper embrittlement, creep rupture, and low-cycle fatigue. Low levels of Mn, Si, and impurities not only result in improved temper embrittlement resistance in these steels but also lead to an improvement in creep rupture properties (i.e., improved strength and ductility). These results have produced some general guidelines for the design of high-temperature bainitic steels. Examples illustrating the implementation of the results and the effectiveness of the design guidelines are provided. Largely based on the benefits shown by this work, a high-purity 3.5NiCrMoV steel, which is essentially free of Mn, Si, and impurities, has been developed and is already being used commercially.

Process for chemical stabilization of heavy metal bearing dusts and sludges

Abstract: A calcium-alumino-silicate composition comprising the reaction product of electric arc furnace dust and/or an aqueous chemical waste sludge including a source of ferrous ions and selective additive materials, the additive materials are selected so that the total composition of the additive ingredients and said sludge includes fly ash, electric arc furnace dust, lime kiln dust, ferrous sulfate, hydrated lime to provide an alkalinity of about 9 to 9.5% and water, the composition contains at least 0.2% by weight of ferrous ions and is hardenable through chemical reactions, the product of which includes calcium-alumino-silicates.

Mechanisms of Cosmetic Corrosion in Painted Zinc and Zinc-Alloy-Coated Sheet Steels

Abstract: A major consideration in autobody application of coated sheets is paint performance on electrogalvanized coatings. This paper describes a study in which a number of electrogalvanized coatings, including Zn, 9%Ni-Zn, 13%Ni-Zn, and 18%Fe-Zn, were characterized for composition, structure, and phosphatability and compared for paint performance in accelerated corrosion tests. Metallographic examination and microanalysis of scribe cross sections were conducted to understand the mechanisms of cosmetic corrosion. Results indicate that paint creep-back is determined by two interrelated factors, namely, (1) anodic dissolution of the coating and (2) metal coating/e-coat interfacial failure. The relative importance of these factors in relation to test conditions and the coating characteristics is examined, and approaches to improve cosmetic corrosion performance of electrogalvanized coatings are discussed.

Plasma arc process systems, reactors, and applications

Abstract: Thermal plasma arc systems are being applied to a wide variety of high-temperature applications. The use of electricity is proving to be a cost-effective alternative for the treatment of industrial wastes, recycling of scrap, upgrading of existing metallurgical processes, and new methods for the production of materials. Thermal plasma arc reactors are classified according to; (1) the mode of arc attachment, as nontransferred and transferred: and (2) the site for energy and/or mass transfer, as dispersed phase or condensed phase (bulk, film and packed bed). Unique features in the design of plasma reactor systems and applications in waste treatment and metals production are discussed.

Method and apparatus for controlling the thickness of metal strip cast in a twin roll continuous casting machine

Abstract: A method and apparatus for controlling the thickness of a metal strip cast by pouring molten metal between a pair of closely spaced, water-cooled rotating rolls. The temperature of at least one of the rolls is measured at a fixed position relative to the roll bite before and during the cast. The rotational speed of the rolls is adjusted in proportion to a measured roll separation or roll separating force corrected by the roll temperature measured during the cast such that a predetermined and substantially uniform thickness of the metal strip is produced.

Method and system for dimensional and weight measurements of articles of manufacture by computerized tomography

Abstract: Tomographic imaging of an inanimate object in which a fan-shaped beam of radiation is generated and divided into fan ray elements which are directed through a planar section of the object and detected by a set of detectors. Each detector produces a signal representative of the intensity of the radiation of a detected fan ray element and selected coordinates defining a cross-sectional image of the object are determined from the intensity signals of the detectors. The coordinates are stored and displayed on a display device. The detectors include a scintillation crystal which is provided with a half-solid cylinder of lead disposed on a side of the crystal.

{011} Twinning in Fe-Ni-C martensites

Abstract: The substructures of two Fe-Ni-C alloys that form platelike martensite have been studied by transmission electron microscopy (TEM). Planar features with a {011 } habit are observed, in addition to the usual {112 } transformation twins and arrays of screw dislocations. The results of diffraction-contrast experiments are consistent with these {011 } defects being fine twins within which the carbon atoms occupy a different octahedral interstitial sublattice from the surrounding matrix. In any given martensitic plate, this twinning appears to occur preferentially on the {011 } plane containing the same {111 } direction as the operative {112 } transformation-twinning variant. The possibility that {011 } twinning occurs during the martensitic transformation and/or when virgin martensite is heated from subambient temperatures is discussed in relation to crystallographic observables such as the martensitic habit plane and axial ratios.

Microalloyed steel and process for preparing a railroad joint bar

Abstract: A microalloyed, fully killed steel has a composition, in weight percent, of from about 0.20 to about 0.45 percent carbon, from about 0.90 to about 1.70 percent manganese, from about 0.10 to about 0.35 percent silicon, from about 0.01 to about 0.04 percent aluminum, from about 0.05 to about 0.20 percent vanadium, from about 0.008 to about 0.024 percent nitrogen, balance iron. The steel is particularly useful when hot rolled to a railway joint bar section, and air cooled. The resulting joint bar meets AREA specifications in the as-rolled condition, without the need for a reheat and oil quench heat treatment after rolling.

Process for improving wear on conductor rolls in electroplating of steel surfaces

Abstract: In the electroplating of strip steel (11) with zinc or zinc alloys in a strip electroplating line the steel strip (11) coated with zinc or zinc alloy exits the system via a metal conductor roll (20). Metal tends to deposit on the conductor roll. To remove such metal the conductor roll (20) is normally partially immersed in an acid bath (21) containing, for example, sulfuric acid. A problem is corrosion of the conductor roll (21) by the acid. This corrosion of the conductor roll (21) is considerably slowed by adding an oxidizing agent such as hydrogen peroxide, sodium peroxydisulfate or potassium peroxydisulfate to the acid bath in accord with the present invention.

Curtain door for metal reheating furnace

Abstract: A curtain door for use at the charge or discharge openings of a metal reheating furnace the curtain door comprising a horizontal support bar extending across the furnace opening, a horizontal curtain hanger member removably attached to the horizontal support bar and supporting at least two spaced apart metal mesh curtains of unequal length, an insulation means depending from the horizontal support bar adjacent the furnace side of the metal mesh curtain nearest the furnace opening and means to vertically raise or lower the horizontal support bar.

Method for retaining slag during the discharge of molten metal from a vessel

Abstract: A method for retaining slag in a ladle or similar vessel containing molten metal such as used in the steel industry. Lumps of a highly refractory material having a density between the density of the molten metal and the density of the slag are added to the vessel. As the molten metal is drained from the vessel, the lumps agglomerate around the drain orifice and block the discharge of the slag from the vessel.

Method for the controlled cooling of hot rolled steel samples

Abstract: A method for cooling samples of hot rolled steel sections. A programmable controller directs a predetermined sequence of air and cooling water sprays against the sample while held in a closed container. The controlled cooling of the sample prevents dimensional distortion of the sample so that accurate measurements of the finished hot rolled steel section can be determined.

A Multiple-criteria Approach to Dynamic Cold-ingot Substitution

Abstract: Bethlehem Steel's plant at Bethlehem, Pennsylvania uses a computer-based mill-providing procedure to plan ingot requirements for the production of structural shapes and pilings. When not enough hot steel is available to meet all the ingot requirements, cold steel ingots from inventory must be substituted in order to meet the production plan. A computer system was developed that dynamically selects cold ingots to use when hot steel is not available. This system selects cold ingots based first on ingot-selection priorities, and secondly, within priorities, on several criteria. An approach was developed that assigns a penalty to each feasible cold ingot such that the priorities and multiple criteria are addressed by simply ranking the ingots based on their penalty values. Ingots are selected from the top of the ranked list, and the results are consistently acceptable to the steel-providers at the Bethlehem plant. The system improves yield and reduces material-handling costs.

Improving the Toughness of 3-1/2NiCrMoV Steam Turbine Disk Forgings

Abstract: Due to the in-service stress corrosion cracking of some 3-1/2NiCrMoV steam turbine disks, the Charpy V-notch toughness requirements for replacement forgings have dramatically increased in recent years. In response to the new requirements, several avenues for improving the toughness of 3-1/2NiCrMoV steel have been explored and are discussed in this paper. Improvements in forging practice, preliminary heat treatment, final heat treatment and composition are recommended which allow the new requirements to be met.

Roll change assembly for a continuous caster

Abstract: An apparatus for exchanging guide rollers in a continuous caster has a frame with two laterally spaced sides extending generally transverse to a support. First, second, third and fourth arms are provided, and the first and second arms are operably associated with a first one of the sides and extend in opposite directions and are pivotal about a first axis. Third and fourth arms are operably associated with the other of the sides and extend in opposite directions, and are pivotal about a second axis coaxial with the first axis. Roll engaging elements are associated with a second end portion of each arm, and the second end portion of each arm is remote from the associated axis. First and second double acting cylinder and piston assemblies are provided. Each of the cylinder and piston assemblies is associated with one of the sides, and the pistons of each cylinder and piston assembly are operably associated with the associated arms for causing pivoting thereof about the associated axis.

In-Plant Demonstration of High-Temperature Emat System on Continuous Caster Strand

Abstract: The Pacific Northwest Laboratory (PNL) has been working with the Office of Industrial Programs of DOE and the American Iron and Steel Institute (AISI) since 1983 to develop a sensor that can determine the internal temperature of hot steel bodies. Research projects utilizing the relationship between acoustic velocity and temperature have been the primary technique investigated. The techniques most recently used have been laser-generated stress waves and EMAT systems [1,2,3]. Development of an ultrasonic sensor that can measure the acoustic velocity at high temperatures has been the major effort over the past few years. The internal temperature of steel bodies can be determined by measuring the time-of-flight through a known distance to calculate the velocity, and from the relationship between temperature and velocity, the average internal temperature can be determined [4,5].

Vibrating mold assembly

Abstract: A continuous caster vibrating mold assembly having lever arms each with a pivot pin including a hollow tubular sleeve having open ends for encircling a removable load cell having strain gauges attached thereto for measuring loads on a pivot joint. When loads are placed on a pivot joint the load cell will deflect and its deflections are detected by a strain gauge which measures the axial deflection of the load cell.

Ultrasonic measurements in hot as-cast billets: field testing of an emat - emat approach to sensing internal temperatures

Abstract: ABSTACT This paper will comment on the field testing of a prototype sensing system for monitoring internal temperatures in solid and solidifying materials. The system was developed as part of an ongoing collaboration among AISI member companies, the U. S. National Bureau of Standards and Battelle's Pacific Northwest Laboratories. The approach uses “non-contacting” electromagnetic acoustic transducers (EMATs) in a transmitter and receiver combination to monitor ultrasonic times-of-flight (TOF). That data can be related to the internal temperature distributions in ascast materials. The field testing demonstrated the viability of the EMAT approach: the device survived difficult mill conditions and successfully acquired data from moving, as-received strand cast materials with surface temperatures in excess of 1130 Celsius.

Improved consumable injection lance

Abstract: A consumable lance (10) for injecting oxygen and other gases such as argon below the surface of a molten metal bath the lance comprising an upper manifold portion (12), a lower nozzle end portion (14), and a plurality of gas conveying conduits (16) attached to a structural support assembly (15) and encased within a protective refractory covering (17).