scholarly journals Multiphase Model for the Prediction of Shrinkage Cavity, Inclusion and Macrosegregation in a 36-Ton Steel Ingot

2020 ◽  
Vol 7 ◽  
Author(s):  
Mengye Xie ◽  
Houfa Shen
Keyword(s):  
Liquid Phase ◽  
Thin Layer ◽  
Mold Wall ◽  
Steel Ingot ◽  
Shrinkage Cavity ◽  
Multiphase Model ◽  
Solidification Shrinkage ◽  
Discrete Phase ◽  
Inclusion Distribution ◽  
Equiaxed Grains

A five-phase model consisting of a liquid phase, columnar dendrites, equiaxed grains, air, and inclusion (discrete phase) is developed to predict the shrinkage cavity, inclusion distribution and macrosegregation simultaneously during solidification of a 36-ton steel ingot. The air phase is introduced to feed the shrinkage cavity and no mass or species exchange with other phases occurs. The transport and entrapment of inclusions are simulated using a Lagrangian approach. The predicted results agree well with the experimental results. The characteristics of inclusion distribution are better understood. A thin layer of inclusions tends to form close to the mold wall, and more inclusions reside in the last solidified segregation channels. The inclusion is easy to aggregate near the riser neck, and it is dragged by the solidification shrinkage. The influence of the inclusion on macrosegregation is comparatively small, while the solidification shrinkage affects the formation of macrosegregation significantly and makes the simulation result more accurate.

Synthetic hydroxymethyl-porphyrins for protection of carboxy group

2007 ◽  
Vol 11 (06) ◽  
pp. 434-441 ◽  
Author(s):  
Hitoshi Tamiaki ◽  
Kouji Kumon ◽  
Reiko Shibata
Keyword(s):  
Liquid Phase ◽  
Carboxylic Acid ◽  
Thin Layer ◽  
Peptide Synthesis ◽  
Phenyl Group ◽  
Coupling Reagents ◽  
Protective Groups ◽  
Simple Filtration ◽  
Meso Position ◽  
Layer Chromatography

Hydroxymethyl-porphyrins were prepared by modifying tetraarylporphyrin possessing a p-(methoxycarbonyl)phenyl group at the meso-position and octaethylporphyrin. The synthetic alcohols reacted with carboxylic acids by the use of coupling reagents, to give the corresponding esters quantitatively. Due to the porphyrin dye moiety, the esterification was easily monitored on thin layer chromatography, and the resulting esters were highly soluble in most organic solvents and easily handled. The esters were readily cleaved by the action of an acid to give the original carboxylic acid and hydroxymethyl-porphyrin. Separation of the two species was performed by simple filtration: the carboxylic acid was soluble (filtrate) and the porphyrins were precipitates in methanol. These protective groups for carboxy groups were useful for peptide synthesis in the liquid phase.

scholarly journals Influence of Alloy Elements on Cracking in the Steel Ingot during Its Solidification

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 836 ◽  
Author(s):  
Junli Guo ◽  
Guanghua Wen
Keyword(s):  
Carbon Content ◽  
Cooling Rate ◽  
Steel Ingot ◽  
Solidification Process ◽  
Solidification Shrinkage ◽  
Liquid Feeding ◽  
Peritectic Solidification ◽  
Longitudinal Cracks ◽  
Cracking Tendency ◽  
Solidification Crack

The average steepness of |dT/d(fs)1/2| on the T − (fs)1/2 curve were calculated during peritectic solidification, which was used to investigate the effect of alloying elements on surface longitudinal cracks of peritectic steels in the solidification process. The value of |dT/d(fs)1/2| indicates the liquid feeding capacity between interdendrites during solidification, where cracks can easily occur if there is poor capacity of liquid feeding, as in peritectic solidification shrinkage. The cracking tendency as a function of carbon content was well described by the |dT/d(fs)1/2| at the cooling rates of 0.5, 5, and 10 °C/s, and the influences of other solute elements on |dT/d(fs)1/2| were also calculated. The results indicate that the possibility of crack occurrence increased and the maximum average steepness |dT/d(fs)1/2| changed from 496.75 °C located near 0.09C wt.% to 622.14 °C near 0.11C wt.% with increasing cooling rate. The value of |dT/d(fs)1/2| on the T − (fs)1/2 curve during the peritectic solidification can be used to analyze the solidification crack for peritectic steels.

On Scouring Efficiency of Flush Waves in Sewers: A Numerical and Experimental Study

2019 ◽  
Author(s):  
Maryam Alihosseini ◽  
Paul Uwe Thamsen
Keyword(s):  
Sediment Transport ◽  
Multiphase Model ◽  
Discrete Phase Model ◽  
Sluice Gate ◽  
Ansys Fluent ◽  
Sediment Bed ◽  
Complex Process ◽  
Discrete Phase ◽  
Sand And Gravel ◽  
The Waves

Abstract In sewer sediment management, the removal of depositions using hydraulic flushing gates has recently gotten great attention. Despite numerous investigations, the complex process of sediment transport under flushing waves is not yet well understood. The present work aims to calibrate and validate a coupled computational fluid dynamics and discrete element method (CFD-DEM) to study the fluid-sediment interaction in sewers. The CFD part of the simulation was carried out in the software Ansys Fluent which is two-way coupled to the DEM software EDEM. The multiphase model volume of fluid (VOF) was used to simulate the flushing wave, while the sediments were handled as DEM particles using the discrete phase model (DPM). To validate the 3D model, experimental work has been performed in a circular laboratory pipe with sand and gravel of different size distributions. A construction of a sluice gate was installed to realize the flushing event, which is similar to a dam-break wave. The evolution of the sediment bed and the scouring efficiency of the waves were examined under different flushing conditions. The results showed that the CFD-DEM method could be used to investigate the performance of flushing devices and various features of sediment transport which are not easy to obtain in the laboratory or field.

Multiphase modeling study for storm water solids treatment in experimental storm water settling chamber

2011 ◽  
Vol 63 (12) ◽  
pp. 3020-3026 ◽  
Author(s):  
Jungseok Ho
Keyword(s):  
Reference Frame ◽  
Particle Motion ◽  
Coupled Model ◽  
Storm Water ◽  
Computational Time ◽  
Settling Chamber ◽  
Multiphase Model ◽  
Coupled Models ◽  
Eulerian Model ◽  
Discrete Phase

This study tests four different types of multiphase models to determine the most appropriate model for predicting the behaviors of various types of storm water solids in a settling chamber. The Lagrangian reference frame discrete phase models of uncoupled and coupled models based on the interaction between the discrete phase and the continuous phase were tested. The rigid moving objects model providing six degrees of freedom particle motion was also tested to model non-spherical particle motion. The fourth model was a sediment transport model using the Eulerian reference frame model. This study tested five different storm water solids consisting of bulk, gross, coarse, sediment and fine which are classified by particle size and settling characteristics. Particle settling efficiency and computational time were considered in determining the most appropriate multiphase model. The coupled model provided better solid settling than the uncoupled model, but required 8.2% more computational time in this study. The Eulerian model matched settling efficiency for the high density finer solids. Although the Eulerian model showed reliable settling prediction, the Lagrangian coupled model can be an effective alternative requiring significantly reduced computational time.

Effects of High Density Ultrasonic Field Coupling on the Microstructures and Properties of Al-Si Alloy

2011 ◽  
Vol 291-294 ◽  
pp. 1981-1988 ◽  
Author(s):  
Ying Long Li ◽  
Hua Ding ◽  
Fu Rong Cao
Keyword(s):  
Liquid Phase ◽  
Acoustic Streaming ◽  
Sound Intensity ◽  
Large Degree ◽  
Ultrasonic Field ◽  
High Density ◽  
Field Coupling ◽  
Cavitation Effect ◽  
Eutectic Si ◽  
Equiaxed Grains

The effects of high density ultrasonic field coupling on the microstructures and properties of Al-12Si alloy were investigated. It is shown that when the melt undergoes ultrasonic coupling processing prior to solidification, the nucleation rate of liquid phase can be raised to make α(Al) dendrite transform towards near equiaxed grains, the growth of Si phase is restrained and eutectic Si microstructure is refined due to acoustic streaming effect and thermal mechanism; When the melt undergoes ultrasonic coupling processing during the melt solidification, large degree of supercooling is produced in the liquid phase in the solidification interface front edge to reduce the critical radius of crystal nucleus and critical work of nucleation and break up, rupture by melting and refine the Si phase to improve obviously the strength of Al-12Si alloy due to its cavitation effect, acoustic streaming action and heat undulation; The crushing effect of ultrasonic coupling on Si phase occurs mainly during the crystallizing solidification and threshold sound intensity exists.

Formation of in situ Reinforced Microstructures in α-sialon Ceramics: Part II. In the Presence of a Liquid Phase

2002 ◽  
Vol 17 (5) ◽  
pp. 1136-1142 ◽  
Author(s):  
Hong Peng ◽  
Zhijian Shen ◽  
Mats Nygren
Keyword(s):  
Fracture Toughness ◽  
Liquid Phase ◽  
Sintering Temperature ◽  
Crystalline Modification ◽  
Fine Grained ◽  
Low Sintering Temperature ◽  
Precursor Powders ◽  
Equiaxed Grains ◽  
Sialon Composition

In situ reinforced microstructures with well-dispersed elongated grains, up to 10 μm in length, embedded in matrices consisting of submicron equiaxed grains, were developed by hot pressing Y-, Yb-, and (Y + Yb)-doped a-sialon ceramics containing approximately 3 vol% extra liquid phase at a comparatively low sintering temperature, 1800 °C. The liquid phase, thermodynamically compatible with a-sialon, was introduced by raising the oxygen content of an already oxygen-rich α-sialon composition, e.g., by increasing the O/N ratio in RExSi12-(3x+n) Al3x+nOnN16−n. Two different α–Si3N4 precursor powders, one fine-grained and one coarse, and one coarse β–Si3N4 powder were used, and the influence of particle size and crystalline modification of the precursor Si3N4 powder on the formation of elongated a-sialon grains was investigated. The formation of elongated α-sialon grains was promoted by introducing an extra liquid phase and by using a fine-grained α–Si3N4 powder, whereas the coarse β–Si3N4 powder did not yield any elongated grains at all. The obtained in situ reinforced α-sialon ceramics were both hard and tough, with a Vickers hardness and a fracture toughness of 21 GPa and approximately 5 MPa m1/2, respectively.

Thin-layer GaInSbAsPBi/GaSb heterostructures obtained from liquid phase in a temperature-gradient field

2017 ◽  
Vol 62 (1) ◽  
pp. 139-143 ◽  
Author(s):  
D. L. Alfimova ◽  
L. S. Lunin ◽  
M. L. Lunina ◽  
A. S. Pashchenko ◽  
S. N. Chebotarev
Keyword(s):  
Liquid Phase ◽  
Temperature Gradient ◽  
Thin Layer ◽  
Gradient Field
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