Engineering Commons^™

Alloy Dissolution In Argon Stirred Steel, Darryl S. Webber

Doctoral Dissertations

"Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I …

Effect Of Nickel On Castability Of Chromium Molybdenum Steel & The Dynamic Fracture Toughness Of Hy-130, Abhilash Dash

Masters Theses

"The fill lengths of Ni alloyed Cr-Mo steels obtained from fluidity studies (Paper 1) varied linearly with superheat. A 5% Ni steel showed a maximum fill length compared to other steels tested. Ni decreased the liquidus, solidus, and dendritic coherency temperature, but it did not have any significant effect on volume fraction (0.27-0.31) of the solid phase at the dendrite coherency point. The filling time obtained experimentally at 150 C⁰ superheat for 5% Ni steel (HY 130) was close to 1.4 s. For similar conditions, the predicted fill time using a Magmasoft model was close to 1.9 s. Modeling results …

Thermo-Physical Properties Measurement And Steel - Ceramic Shell Interactions In Investment Casting, Chirag Mahimkar

Masters Theses

"Investment casting is a process in which a ceramic shell is prepared on a wax or foam pattern. The wax is melted out or the foam is burnt out and the shell is sintered to have sufficient strength to withstand casting conditions. The investment casting process is very important as it produces near net shape castings which reduce the need for subsequent operations of castings like machining etc. Investment casting shells are subjected to a number of heating cycles during pattern removal, firing, preheating before pouring and finally during solidification. The thermo-physical properties of the shell play an important role …

Processing And Characterization Of Boron Carbide-Hafnium Diboride Ceramics, Harlan J. Brown-Shaklee

Doctoral Dissertations

"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, …

Two-Point Bend Studies Of Glass Fibers, Zhongzhi Tang

Doctoral Dissertations

"The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of …

Additivity Of Strengthening Mechanisms In Ultrafine Grained Aluminum Alloy, Nilesh Kumar

Doctoral Dissertations

"Friction stir processing (FSP) has been used in the present work to obtain ultrafine grained (UFG) microstructure in a twin-roll cast (TRC) Al-Mg-Sc alloy. An attempt has been made to establish a correlation between processing, microstructure, and properties (mechanical) in UFG regime for this alloy system.

The effect of initial microstructural conditions and processing parameters (tool rotation rate) were shown to have a profound impact on the development of UFG microstructure. FSP led to a microstructure consisting of grains with an average grain size as small as 390 nm, having high angle grain boundaries and a completely random texture. The …

Calcium Wire Ladle Treatment To Improve Cleanliness Of Centrifugal Cast Steel, Edith Yolanda Martinez Silva

Masters Theses

"Centrifugal casting provides the opportunity of combining large centrifugal forces and directional solidification to reduce non-metallic inclusions in the cast steel product. Calcium treatment in the ladle has the potential of reducing and modifying non-metallic inclusions to achieve better machinability and mechanical properties. The objective of this research is to analyze the combined effects of calcium wire ladle treatment and centrifugal casting on the number, size, composition and morphology of non-metallic inclusions in centrifugally cast steel products.

All experiments were completed at an industrial foundry. The experiments involved feeding calcium wire into the ladle after argon oxygen decarburization (AOD) and …

Crack Formation In Investment Casting Ceramic Shells, W. A. Everhart

Masters Theses

"This thesis is a collection of papers that discuss shell cracking in investment casting during pattern removal. The application of rigid polymeric foam for large investment casting patterns with complex geometries can improve the dimensional tolerances and the surface quality of the casting. However, these pattern materials have a tendency to promote crack formation in investment casting shells during pattern removal by firing.

The first two papers discuss the factors affecting shell cracking and methods to prevent it. Experimental methods were combined with finite element modeling to predict stress in the shell. A 3D nonlinear finite element model was developed …

Stress Measurement And Development Of Zirconium Diboride-Silicon Carbide Ceramics, Jeremy Lee Watts

Doctoral Dissertations

"Research presented in this dissertation focused on the production of ZrB₂-SiC composites and their characterization; in particular their mechanical properties and thermally generated residual stresses. Thermally generated stresses were measured using Raman spectroscopy as well as both neutron and x-ray diffraction. For 70 vol% ZrB₂ - 30 vol% SiC composites neutron diffraction revealed that the SiC phase was under ~880 MPa compressive stress and the ZrB₂ phase was under ~450 MPa tension at room temperature. It was also discovered that stresses began to accumulate at ~1400 ⁰C upon cooling from the processing temperature (1900 ⁰C -2000 ⁰C). Raman spectroscopy and …