Ronald O'Malley | Missouri University of Science and Technology (original) (raw)

Papers by Ronald O'Malley

Metals

Iron ore pellet reduction experiments were performed with pure hydrogen (H2) and mixtures with ca... more Iron ore pellet reduction experiments were performed with pure hydrogen (H2) and mixtures with carbon monoxide (CO) at different ratios. For direct reduction processes that switch dynamically between reformed natural gas and hydrogen as the reductant, it is important to understand the effects of the transition on the oxide reduction kinetics to optimize the residence time of iron ore pellets in a shaft reactor. Hence, the reduction rates were studied by varying experimental parameters such as the temperature (800, 850 & 900 °C), reactant gas flow rate (100, 150 & 200 cm3/min), pellet size and composition of the reactant gas mixture. The rate of reduction was observed to increase with an increase in temperature and reactant gas flow rate, but it decreased with an increase in pellet size. SEM greyscale analysis was performed to analyze the porosity and phase composition of partially reduced pellets. The porosity of the pellets was observed to increase from 0.3 for unreacted pellet to ...

Applied Optics

This research reports an advancement in splicing silica glass fiber to sapphire single-crystal op... more This research reports an advancement in splicing silica glass fiber to sapphire single-crystal optical fiber (SCF) using a specialized glass processing device, including data that demonstrate the thermal stability of the splice to 1000°C. A filament heating process was used to produce a robust splice between the dissimilar fibers. A femtosecond laser is used to inscribe a fiber Bragg gratings sensor into the SCF to measure the high-temperature capabilities and signal attenuation characteristics of the splice joint. The experimental results demonstrate that the proposed splicing method produces a splice joint that is robust, stable, repeatable, and withstands temperatures up to 1000°C with a low attenuation of 0.5 dB. The proposed method allows placement of SCF-based sensors in the extreme environments encountered in various engineering fields, such as nuclear, chemical, aviation, and metals manufacturing, to enable improvements in process monitoring, product quality, and production ...

A strip caster (10) for producing a continuous strip (24) includes a tundish (12) for containing ... more A strip caster (10) for producing a continuous strip (24) includes a tundish (12) for containing a melt (14), a pair of horizontally disposed water cooled casting rolls (22) and devices (29) for electrostatically coating the outer peripheral chill surfaces (44) of the casting rolls with a powder flux material (56). The casting rolls are juxtaposed relative to one another

The production of steels with low total oxygen content and preferred oxide morphologies requires ... more The production of steels with low total oxygen content and preferred oxide morphologies requires effective inclusion removal during ladle treatment after deoxidation and control of the evolution of the inclusion population during ladle processing and steel transport. As demands for increased steel cleanliness continue to grow, ongoing research on the behavior of inclusion populations in the ladle during ladle treatment has continued to advance our understanding of the ladle treatment process. This paper provides an introductory overview of inclusion behavior in the ladle along with a review of the some of the ongoing research in the area of ladle treatment and the factors that influence the evolution and removal of inclusions

Iron and Steel Technology, 2013

A new methodology is presented to calibrate the 1D CON1D model with a full 3D finiteelement model... more A new methodology is presented to calibrate the 1D CON1D model with a full 3D finiteelement model of the mold. The thermocouple depth in the 1D model CON1D is “offset” to account for both the 3D geometric effects and for the heat removed along the thermocouple wire by water or air convection. With the offset, this simple 1D model can match closely with the 3D model. Coupled with models of solidification and interfacial phenomena, this modeling tool is applied to gain insights into many aspects of heat transfer in the process. The harsh environment of commercial steel continuous casting processes makes taking measurements difficult, expensive and limited with regard to the information gained. Computational models potentially offer deeper knowledge, but only if they can accurately predict the plant behavior. This requires including and solving the equations which govern all of the important physical phenomena. To achieve reasonable speed while retaining accuracy, computational models ...

$Research paper thumbnail of Mechanism for Carbon Transfer from Magnesia-Graphite Ladle Refractories to Ultralow-Carbon Steel$

Figure 1: First patient's CT image before endoscopic evaluation (Dilatated stomach and phytobesoa... more Figure 1: First patient's CT image before endoscopic evaluation (Dilatated stomach and phytobesoar in gastric antrum) (Phytobezoar was shown with yelow arrow).

Gittikçe büyüyen spor ekonomisi içerisinde önemli yer tutan spor organizasyonlarına ev sahibi ola... more Gittikçe büyüyen spor ekonomisi içerisinde önemli yer tutan spor organizasyonlarına ev sahibi olabilmek için yarışan ülkeler bu organizasyonları düzenlerken sosyo-kültürel, çevresel, politik ve ekonomik beklentiler içerisine girmektedir. Bu çalışmada 17. Akdeniz Oyunları'nın Mersin ilinde yaratması beklenen ekonomik etkiler incelenmekte, ekonomik beklentiler beklenen gelir (ex-ante) yöntemi çerçevesinde referans alınan güvenilir anket çalışmalarının derlenmesiyle oluşturulmakta, ekonomik veriler gerçekleşen getiri (ex-post) yöntemi çerçevesinde istatistiksel olarak analiz edilmekte ve beklentilerle uyumluluğu yorumlanmaktadır. Analiz sonuçlarına göre, 2013 yılında düzenlenen 17. Akdeniz Oyunları Mersin ilinde ekonomik canlanma ve istihdam yaratma, devlet gelirlerini ve fiyatlar genel seviyesini arttırma beklentilerini karşılamamaktadır. Ayrıca, dış ticaret ve turizmde olumlu etkiler görülmekte fakat Rusya ile yaşanan krizin de bu olumlu etkiyi ortadan kaldırdığı düşünülmektedir. Beklenen ekonomik etkilerin gerçekleşmemesinin nedenleri olarak da Ankara ve İstanbul merkezli taşeron firmaların organizasyonda, altyapı ve üstyapı çalışmalarında yer alması, finansman yetersizliği, uluslararası pazarlama ve reklamcılık faaliyetlerinin yetersiz kalması, yayın ve bilet gelirlerinin çok düşük kalması belirlenmektedir.

Automated Feature Analysis (AFA) provides the means to rapidly characterize large inclusion popul... more Automated Feature Analysis (AFA) provides the means to rapidly characterize large inclusion populations. System settings must be optimized to properly detect and interpret the important inclusion characteristics. The effects of sample area and AFA parameter settings (step size, magnification and threshold) on inclusion characterization results has been investigated and optimized. Methodologies for determining average inclusion chemistry, total element concentrations within inclusions, and for using joint ternary diagrams with size visualization to represent inclusion populations are presented. These methodologies were applied to samples collected from industrial steel mill and steel foundries and demonstrated in this study. INTRODUCTION Non-metallic inclusions are an inevitable consequence of steelmaking and are undesirable for the most part. Mechanical properties are largely affected by them and some inclusions promote clogging of submerged entry nozzles (SEN) . Complete removal ho...

With high yield strength, toughness and good weldability, microalloyed steels are widely used in ... more With high yield strength, toughness and good weldability, microalloyed steels are widely used in the automotive, pipeline and transportation industries. An understanding of the thermodynamics and kinetics of microalloy precipitation during casting and cooling can be important to microstructure control. Titanium nitride (TiN) precipitation is considered here, as TiN has high stability and may precipitate at temperatures near the liquidus. Titanium nitride precipitates may remain stable at elevated temperatures during later processing, suppressing grain growth during solid state processing or in weld heat-affected zones. Smaller precipitates have a greater effect on the grain boundary pinning and therefore the TiN size distribution is important.

The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundr... more The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundry. The steel was followed from electric arc furnace melting through ladle refining to final casting. Timed sampling was performed at all stages of the process. Samples were analyzed using an automated SEM/EDS system. The overall evolution of oxide inclusions in terms of nucleation, growth, and flotation during liquid processing was studied using area fraction and average diameter. Chemical composition evolution was observed using a joint ternary plotting tool developed under this program. It was found that the use of zirconium as an addition for nitrogen/oxygen removal leads to a large number of ZrO2 inclusions, which is related to insufficient flotation due to the higher density of zirconia and in turn less effective calcium treatment. In addition, no ZrN formation was observed, likely due to the high FeO acid slag practice used. Argon stirring was found to reduce the flotation problems...

While effects of aluminum on the properties of vanadium microalloyed steels have been recognized ... more While effects of aluminum on the properties of vanadium microalloyed steels have been recognized in the past, recent work by Garrison et al. reported an interesting competition between vanadium and aluminum for nitrogen in steels. Aluminum variations were found to influence the mechanical properties of vanadium microalloyed sheet steels in both the hot-rolled condition, as well as after subsequent cold-rolling and annealing (including both batch and continuous annealing processing simulations). Because of the “apparent competition” between aluminum and vanadium for the available nitrogen, a reduced level of aluminum was associated with higher strength levels. Recrystallization during annealing after cold rolling was also suppressed in the low-aluminum steel based on the observed microstructure and property responses to continuous annealing over a range of temperatures. These behaviors were believed to be due to aluminum effects on vanadium carbonitride precipitation strengthening. I...

Metallurgical and Materials Transactions B, 2021

Al is sometimes added to ferritic 430 type stainless steel to improve the surface appearance of c... more Al is sometimes added to ferritic 430 type stainless steel to improve the surface appearance of cold rolled bright annealed products. High-surface quality is required for such applications. However, during continuous casting, slab reheating, and hot rolling, complex oxides can penetrate deep into the matrix and form highly adherent subsurface scale layers that resist removal using high pressure water descaling. Therefore, an understanding of the oxidation phenomena during reheating in the combustion atmosphere of the slab reheating process is critically important for control and elimination of potential scale related surface defects on the product. In this article, the kinetic aspects of oxidation and scale formation on a standard and an Al alloyed 430 ferritic stainless steel were investigated using several experimental and modeling methods. Experiments were performed in a TGA apparatus that replicates the combustion gas atmosphere and temperature in an industrial slab reheat furnace. Oxidized samples were characterized using optical microscopy, scanning electron microscopy (SEM), and Raman spectroscopy to document the specific changes in the scale morphology and microstructure in the base and Al alloyed 430 ferritic stainless steels. Focused ion beam (FIB) sectioning of the scale layer, followed by high resolution transmission electron microscopy (TEM), revealed details of the phase, composition and structure of the oxides formed in the subsurface region of the ferritic matrix. Thermodynamic simulations were used to predict phases in the multilayer scale structure. Differences in oxidation kinetics, phase, composition, topology, and microstructure of the multi-layered scale formed during re-heating of the investigated alloys are discussed.

Metallurgical and Materials Transactions B, 2020

The structure, phase, and composition of scale formed on a continuously cast steel slab during re... more The structure, phase, and composition of scale formed on a continuously cast steel slab during reheating depend on intrinsic factors (steel chemistry, microstructure, and as-cast surface condition) and extrinsic parameters (temperature, time, composition, and velocity of combustion gas atmosphere). The scale that forms on a slab normally has several layers with differing compositions and phases and knowledge of this scale structure is important in subsequent descaling and hot rolling processing steps. Formation of multiphase scale structures on steel during high temperature oxidation in reheat furnace proceeds according to a local thermodynamic equilibrium, while thickness of layers depends on kinetic conditions (mostly by diffusion). In this study, the local thermodynamic equilibrium conditions through the scale layer were simulated using different oxygen/steel ratios, which mimicked the conditions for scale formation at the external, internal, and sublayer oxide region at metal/sc...

Heat Treat 2021: Extended Abstracts from the 31st Heat Treating Society Conference and Exposition, 2021

Instrumented methods for measuring the coefficient of heat transfer are difficult to implement in... more Instrumented methods for measuring the coefficient of heat transfer are difficult to implement in industrial quench systems. In 1985 Roy Kern presented a simple empirical method for calculating the quench severity of commercial quench systems using measured Jominy hardenability and a mid-radius (r/R=0.5) hardness of a 3-inch diameter 8640 or 4140 steel bar. A more general approach using the Kern methodology is presented here with hardness profile matching to determine the quench severity. Experiments were performed using 2-inch diameter bars of 8620 with a length to diameter ratio of 4. Test bars and Jominy bars were heat-treated following ASTM A255. Test bars were quenched using an experimental draft tube with a water velocity of 6 ft/s. An excel workbook was programmed to calculate the quenched hardness profile as a function of quench severity using prior austenite grain size and steel chemistry. Measured Jominy hardness and calculated hardenability were in good agreement provided...

ISIJ International, 2017

Solidification macrostructure is of great importance for the properties and the quality of castin... more Solidification macrostructure is of great importance for the properties and the quality of castings made from austenitic grade stainless steels (ASS) because there are limited options to change as-cast macrostructure in the solid condition. A typical cast macrostructure of ASS has a fine surface chilled zone followed by an elongated dendrite zone, columnar to equiaxed transition (CET) zone, and centrally located equiaxed crystals. Several castings from ASS were produced to determine the effects of casting geometry, chilling, and grain refinement on CET. The transient thermal field in solidified heavy castings was simulated and used to determine an isotherm velocity (V) and the thermal gradient (G) in mushy zone at 50% solid fraction. The critical value of the parameter G n /V was determined from the macrostructure of the cylindrical casting. Using this value, the location of CET was predicted in the heavy rectangular casting and this prediction was in agreement with experimental macrostructure. Two methods of controlling casting macrostructure by using a chilled mold to stimulate extensive columnar zone and by using melt grain refinement to produce fine equiaxed crystals were experimentally verified and simulated.

Journal of Materials Science, 2016

Accuracy and reliability of numerical simulation of hot rolling processes are dependent on a suit... more Accuracy and reliability of numerical simulation of hot rolling processes are dependent on a suitable material model, which describes metal flow behavior. In the present study, Gleeble hot compression tests were carried out at high temperatures up to 1300°C and varying strain rates for a medium carbon microalloyed steel. Based on experimental results, a Johnson-Cook model (JC) and a Zerilli-Armstrong (ZA) model were developed and exhibited limitation in characterizing complex viscoplastic behavior. A combined JC and ZA model was introduced and calibrated through investigation of strain hardening, and the coupled effect of temperature and strain rate. Results showed that the combined JC and ZA model demonstrated better agreement with experimental data. An explicit subroutine of the proposed material model was coded and implemented into a finite element model simulating the industrial hot rolling. The simulated rolling torque was in good agreement with experimental data. Plastic strain and stress distributions were recorded to investigate nonlinear mass flow behavior of the steel bar. Results showed that the maximum equivalent plastic strain occurred at 45°and 135°areas of the cross section. Stress increased with decreasing temperature, and the corresponding rolling torque was also increased. Due to the extent of plastic deformation, rolling speed had limited influence on the internal stress of the bar, but the relative rolling torque was increased due to strain rate hardening.

Metallurgical and Materials Transactions B, 2016

Refinement of the as-cast grain structure of austenitic steels requires the presence of active so... more Refinement of the as-cast grain structure of austenitic steels requires the presence of active solid nuclei during solidification. These nuclei can be formed in situ in the liquid alloy by promoting reactions between transition metals (Ti, Zr, Nb, and Hf) and metalloid elements (C, S, O, and N) dissolved in the melt. Using thermodynamic simulations, experiments were designed to evaluate the effectiveness of a predicted sequence of reactions targeted to form precipitates that could act as active nuclei for grain refinement in austenitic steel castings. Melt additions performed to promote the sequential precipitation of titanium nitride (TiN) onto previously formed spinel (Al 2 MgO 4) inclusions in the melt resulted in a significant refinement of the as-cast grain structure in heavy section Cr-Ni-Mo stainless steel castings. A refined as-cast structure consisting of an inner fine-equiaxed grain structure and outer columnar dendrite zone structure of limited length was achieved in experimental castings. The sequential of precipitation of TiN onto Al 2 MgO 4 was confirmed using automated SEM/EDX and TEM analyses.

Advances in Molten Slags, Fluxes, and Salts, 2016

Mold fluxes are used in continuous casting of steel to control heat transfer from the steel shell... more Mold fluxes are used in continuous casting of steel to control heat transfer from the steel shell to the copper mold based on their structure and properties. Structures observed in mold flux film samples extracted from conventional and thin slab continuous casters at the end of a cast were examined using cathodoluminescence (CL) imaging in conjunction with XRD and SEM/EDS analysis. Glassy and crystalline structures in the flux films varied greatly depending on sampling location in the mold, distance from the mold wall and the mold flux being examined. Temperature data collected from thermocouple arrays in a thin slab funnel mold indicated sawtooth temperature fluctuations in the lower area of the funnel region, presumably due to cyclic fracture and regrowth of the mold flux crystalline layer in that region of the mold. The temperature observations correlate well with the structures observed in the flux film samples from the region. CL microscopy clearly distinguishes glassy regions from regions with devitrified and dendritic crystal growth, as well as continuous and fractured crystallite layers and cuspidine and nepheline phases that are present. The technique also highlights small variations in Mn oxide content in the glassy region of the flux that results from exchange reactions with the steel, making flow lines in the previously liquid portion of the flux film clearly visible. The benefits of applying cathodoluminescence imaging to the analysis of mold flux films in continuous casting are discussed.