Showing papers by "Bethlehem Steel published in 1987"

Carbonitride precipitation in niobium/vanadium microalloyed steels

Abstract: A detailed study of carbonitride precipitation in niobium/vanadium microalloyed steels is presented. A thermodynamic model is developed to predict the austenite/carbonitride equilibrium in the Fe−Nb-V-C-N system, using published solubility data and the Hillert/Staffansson model for stoichiometric phases. The model can be used to estimate equilibrium austenite and carbonitride compositions, and the amounts of each phase, as a function of steel composition and temperature. The model also provides a method to estimate the carbonitride solution temperatures for different steel compositions. Actual carbonitride precipitation behavior in austenite is then examined in two experimental 0.03Nb steels containing 0.05V and 0.20V, respectively. Samples were solution treated, rolled at 954°C (20 pct or 50 pct), held isothermally for times up to 10,000 seconds at 843°C, 954°C, or 1066°C, and brine quenched. The process of carbonitride precipitation in deformed austenite is followed by analytical electron microscopy (AEM) of carbon extraction replicas. Precipitates are observed at prior-austenite grain boundaries, and also within the grains (presumably at substructure introduced by the rolling deformation). Analysis of the grain-boundary and matrix precipitate compositions by AEM indicates that the grain-boundary precipitates are consistently richer in vanadium than the matrix precipitates, although compositional trends with holding time and temperature are similar for the two types of precipitates. The compositions of both the grain-boundary and matrix precipitates are not significantly influenced by the rolling reduction or the holding time at temperature. As predicted by the thermodynamic model, the precipitates become more vanadium-rich as the vanadium level in the steel is increased and as the temperature is reduced. The agreement between the measured and predicted precipitate compositions is quite good for the grain-boundary precipitates, although the matrix precipitates are consistently more niobium-rich than predicted by the model.

Optimal Selection of Ingot Sizes Via Set Covering

Abstract: In 1984, Bethlehem Steel Corporation installed a new ingot mold stripping facility at its Bethlehem Plant that is capable of handling taller ingots. In order to take maximum advantage of this new facility, we developed a two-phase, computer-based procedure for selecting optimal ingot and internal ingot mold dimensions. Phase I of this procedure generates feasible ingot and internal ingot mold dimensions consistent with both the new stripper's capability and with mill constraints. Phase II then uses a set covering approach to select the optimal ingot and internal ingot mold sizes from among the feasible sizes generated. After analyzing the model, we recommended six new rectangular mold sizes to replace seven existing sizes. To date, implementation of these new ingot and mold sizes is proceeding smoothly and realizing the projected cost reduction benefits.

A consistent definition of probe size and spatial resolution in the analytical electron microscope

Abstract: A technique for measuring the extremely small (<2 nm) probe sizes generated in a field emission gun analytical electron microscope is described. The technique involves scanning the fine probe across the edge of small oriented MgO cubes. A mathematical description of the intensity profiles is developed and it is shown how this relates to various definitions of the probe size. The experimentally measured probe sizes are then combined in a consistent manner with both beam broadening calculations and experimental measurements. This approach results in the first self-consistent definition of the spatial resolution of X-ray microanalysis in thin foils.

Group mean hearing threshold changes in a noise-exposed industrial population using personal hearing protectors.

Abstract: The audiometric test data of 265 employees in one facility were studied to determine group mean hearing threshold changes. The data covered seven to thirteen years. During this time the population was exposed to workplace noise (OSHA) exposures of 86 to 103 dBA. Personal hearing protection was used. Essentially no change in the mean threshold hearing level was found. Certain other hearing conservation program effectiveness indicators also were used to evaluate this population. The results of these indicators were used to evaluate this population also. The results of these indicators generally follow the trends for effective programs.

Continuous caster tundish having wall dams

Abstract: A continuous caster tundish having refractory wall dams formed as part of a portion of the lining of the interior of the side walls, where each refractory wall dam is characterized by a flange projecting substantially horizontally inwardly to prevent turbulent surface flow as molten metal is poured into the tundish.

Drain hole design for ladle

Abstract: This invention is directed to a system for reducing the yield loss from a metallurgical vessel, such as a ladle holding liquid metal having a slag layer thereon, by delaying the onset of slag entrapment in the metal stream during the tapping thereof. More particularly, such system includes a modification to the drain hole and/or bottom of such vessel.

The effect of processing parameters on the propensity for central fracturing in piercing

Abstract: Successful competition in the seamless tubular products market demands improvements in surface and dimensional quality in products from seamless pipe mills. It is reported that pass design, piercer setup and operating parameters have critical effects on both dimensional and surface quality. Defects which form during the piercing process are the result of these mechanical parameters (which control the localized stress states) in combination with metallurgical factors (which determine the material’s resistance to fracture by aggravating stresses). Understanding the detrimental effects of inclusions led to the development of cleaner materials, but economically feasible operations in this direction have been exhausted. Because of this, attention is directed to improvement of deformation limits by control of mechanical processing factors, such as piercer setup and point/pass design. Control of these parameters leads to an optimum pass design that produces conditions favorable not only for enhanced deformation before fracture, but also for energy and power requirements.

Austenite recrystallization in Nb/V microalloyed steels

Abstract: Two Nb microalloyed steels containing 0.05 and 0.20 wt pct V were used in this study. The chemistries of these steels are shown in Table 1. The steels were vacuum induction melted as 136 kg ingots and hot rolled to a thickness of 1.0 cm. Specimens 2.5 cm x 7.6 cm were cut from the plates, retaining the original rolling direction, and thermocouple holes were drilled into the longitudinal faces of these specimens at mid-thickness. The specimens were reheated for 1 hour in an endothermic atmosphere at 1288/sup 0/C. Upon removal of the specimens from the reheat furnace, a sheathed thermocouple was inserted into the drilled hole. The temperature of the specimens was then monitored during air cooling until the desired rolling temperature of 954/sup 0/C was reached, at which time the specimens were deformed 50 pct in a rolling mill at an average strain rate of 10.2 s/sup -1/. Immediately after rolling, the specimens were transferred to a molten chloride salt bath and held for 10, 100, 1000, or 10,000 seconds at 843/sup 0/C, 954/sup 0/C, or 1066/sup 0/C, followed by brine quenching.

Operator's Perspective on Gulf of Mexico Jackup MODU Designs

Abstract: The purpose of this paper is to present some of the observations made as a result of this general operating experience and these detailed engineering studies. It is hoped that by promoting more discussion on GOM jack-up designs that the industry (rig designers and builders, drilling contractors, and petroleum operators) will begin design work toward the next generation GOM jack-up.

Effect of bentonite on the low temperature reducibility of fired iron oxide compacts

Abstract: Our findings show that the presence of any significant amount of bentonite in an iron oxide compact, over a total concentrate impurity range from tenths of a percent to the amounts present in typical production concentrates, is deleterious to reduction behavior, and that the inhibiting effect of bentonite level is far greater than that of equivalent amounts of pure SiO2 or much larger amounts of normal pellet gangue constituents.

Distributor for continuous casting machine

Abstract: A distributor for introducing molten metal into a continuous casting machine. The molten metal is allowed to flow through two interconnected compartments before it is introduced into the continuous casting machine.