Investigation on Thermal Conductivity and Solidification Process of Molten Slags by Using Copper Finger Dip Test

2019 ◽  
Vol 72 (12) ◽  
pp. 3139-3151
Author(s):  
Shaopeng Gu ◽  
Guanghua Wen ◽  
Changlin Yang ◽  
Junli Guo ◽  
Ping Tang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Solidification Process ◽  
Dip Test

Effective Thermal Conductivity of the Mushy Region During Solidification of Aqueous Solutions of Ammonium Chloride

1999 ◽  
Author(s):  
Marcus V. A. Bianchi ◽  
Raymond Viskanta
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Ammonium Chloride ◽  
Solidification Process ◽  
Mushy Region ◽  
Diffusion Controlled ◽  
Model Predictions ◽  
Fundamental Understanding ◽  
Two Phases ◽  
Simple Average

Abstract A theoretical and experimental study of the diffusion-controlled solidification process of an aqueous solution of ammonium chloride has been performed to obtain fundamental understanding relevant to metal casting, solidification of alloys, and freezing of biological materials. The effective thermal conductivity of the solidifying system is calculated using different models and the model predictions are compared. The model is validated by comparing the predictions with experimental data. It was found that, for the conditions considered in the present study, the parallel model, which is a simple average of the thermal conductivities of the two phases, leads to acceptable results. The reasons for this are related to the size of the mushy region and the morphology of the crystals during the solidification process.

A New Numerical Simulation Model for Shrinkage Defect during Squeeze Casting Solidification Process

2013 ◽  
Vol 641-642 ◽  
pp. 309-314
Author(s):  
Hua Hou ◽  
Hong Hao Ge ◽  
Yu Hong Zhao ◽  
Wei Ming Yang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Molten Pool ◽  
Squeeze Casting ◽  
Liquid Surface ◽  
Solidification Process ◽  
Calculation Model ◽  
Shrinkage Defect ◽  
Field Dynamic

In this paper, according to the characteristics of squeeze casting solidification process, the calculation model (FDM format) of the partial differential equations with high thermal conductivity is used to the numerical simulation of temperature field. Dynamic isolated multi-molten pool judgment method is used to determine the position of the pool and FEM is used to calculate the pressure of pool center. If the pressure of molten pool center has been down to 0, the liquid metal closed in the scale will be solidification under the condition of no pressure, and will shrinkage based on the way of gravity shrinkage. The equivalent liquid surface descending method of isolated molten pool is used to predict the formation of shrinkage defect; the simulation result is coinciding with experimental data.

scholarly journals Influence of Crucible Thermal Conductivity on Crystal Growth in an Industrial Directional Solidification Process for Silicon Ingots

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Zaoyang Li ◽  
Lijun Liu ◽  
Yunfeng Zhang ◽  
Genshu Zhou
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Crystal Growth ◽  
Directional Solidification ◽  
Silicon Crystal ◽  
Solidification Process ◽  
Interface Shape ◽  
Directional Solidification Process ◽  
Reasonable Range ◽  
Crystal Interface

We carried out transient global simulations of heating, melting, growing, annealing, and cooling stages for an industrial directional solidification (DS) process for silicon ingots. The crucible thermal conductivity is varied in a reasonable range to investigate its influence on the global heat transfer and silicon crystal growth. It is found that the crucible plays an important role in heat transfer, and therefore its thermal conductivity can influence the crystal growth significantly in the entire DS process. Increasing the crucible thermal conductivity can shorten the time for melting of silicon feedstock and growing of silicon crystal significantly, and therefore large thermal conductivity is helpful in saving both production time and power energy. However, the high temperature gradient in the silicon ingots and the locally concave melt-crystal interface shape for large crucible thermal conductivity indicate that high thermal stress and dislocation propagation are likely to occur during both growing and annealing stages. Based on the numerical simulations, some discussions on designing and choosing the crucible thermal conductivity are presented.

Simulation of Temperature Field in the Solidification Process of Cast

2015 ◽  
Vol 1088 ◽  
pp. 834-837
Author(s):  
Xun Feng Yuan ◽  
Rui Xia Hu ◽  
Ying Li ◽  
Ying Zhou ◽  
Lei Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Temperature Field ◽  
Thermal Resistance ◽  
Heat Conduction Equation ◽  
Solidification Rate ◽  
Solidification Process ◽  
Corner Region ◽  
Actual Design ◽  
The Right

The direct difference method is used for solving the heat conduction equation, and simulate the solidification process of T-type cast. The effect of the thermal resistance at cast/mold on distribution of temperature and the solidification rate of corner region is studied. The results show that during the solidification process of T-type, the riser region first solidified, followed by the right half, finally the solidified part was around the corner. With the decrease of the thermal resistance at cast/mold, the temperature of the corner area decreased more quickly and the solidification rate increased. In the actual design process, the material with the good thermal conductivity should be selected for the cast mold to accelerate the solidification rate of the corner region, so the solidification rate of the corner and riser region tend towards harmony, which reducing the formation of various types of defects, and the quality and mechanical properties of the casts were improved.

The Influence of Mechanical Mold Vibration on Temperature Distribution and Physical Properties of Al-11.8%Si Matrix Composites

2013 ◽  
Vol 773-774 ◽  
pp. 195-202
Author(s):  
M. Sayuti ◽  
S. Sulaiman ◽  
B.T.H.T. Baharudin ◽  
M.K.A. Ariffin
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Mechanical Vibration ◽  
Solidification Process ◽  
Temperature Inhomogeneity ◽  
Matrix Composites ◽  
Cooling Curves ◽  
Alloy Matrix ◽  
Aluminum Alloy Matrix ◽  
Properties Of Composites

Mechanical vibration was introduced into the Aluminum alloy matrix composite during solidification process. The cooling curves of composite with mechanical vibration were measured and compared without mechanical vibration. The thermal conductivity and thermal diffusivity properties of the Al/TiC composite were investigated. The result indicated that the mechanical vibration reduces the temperature inhomogeneity of melt. The density of the composite with 10.2, 12, 15Hz and 16 Hz of mechanical vibration improved apparently compared with the composite without mechanical vibration. The thermal conductivity and thermal diffusivity properties of composites with mechanical vibration are also both improved significanly.

Numerical Simulation of the Effect of the Size of Suspensions on the Solidification Process of Nanoparticle-Enhanced Phase Change Materials

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Yousef M. F. El Hasadi ◽  
J. M. Khodadadi
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solidification Process ◽  
Liquid Interface ◽  
Local Concentration ◽  
Solutal Convection ◽  
Solid Liquid Interface ◽  
Solid Liquid

Nanostructure-enhanced phase change materials (NePCM) have been widely studied in recent years due to their enhanced thermal conductivity and improved charge/discharge in thermal energy storage applications. In this study, the effect of the size of the nanoparticles on the morphology of the solid–liquid interface and the evolving concentration field during solidification is reported. Combining a one-fluid-mixture approach with the single-domain enthalpy-porosity model for phase change and assuming a linear dependence of the liquidus and solidus temperatures of the mushy zone on the local concentration of the nanoparticles subject to a constant value of the segregation coefficient, thermal-solutal convection as well as the Brownian and thermophoretic effects are taken into account. A square cavity containing a suspension of copper nanoparticles (diameter of 5 and 2 nm) in water was the model NePCM considered. Subject to a 5 °C temperature difference between the hot (top) and cold (bottom) sides and with an initial loading of the nanoparticles equal to 10 wt. % (1.22 vol. %), the colloid was solidified from the bottom. The solid–liquid interface for the case of NePCM with 5 nm particle size was almost planar throughout the solidification process. However, for the case of the NePCM with particle size of 2 nm, the solid–liquid interface evolved from a stable planar shape to an unstable dendritic structure. This transition was attributed to the constitutional supercooling effect, whereby the rejected particles that are pushed away from the interface into the liquid zone form regions of high concentration thus leading to a lower solidus temperature. Moreover, for the smaller particle size of 2 nm, the ensuing solutal convection at the liquid–solid interface due to the concentration gradient is affected by the increased Brownian diffusivity. Due to size-dependent rejection of nanoparticles, the frozen layer that resulted from a dendritic growth contains regions of depleted concentration. Despite the higher thermal conductivity of the colloids, the amount of frozen phase during a fixed time period diminished as the particle size decreased.

The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

1992 ◽  
Vol 50 (2) ◽  
pp. 1696-1697
Author(s):  
H.J. Zuo ◽  
M.W. Price ◽  
R.D. Griffin ◽  
R.A. Andrews ◽  
G.M. Janowski
Keyword(s):  
Directional Solidification ◽  
Space Shuttle ◽  
Solidification Process ◽  
Space Experiment ◽  
Infrared Detection ◽  
Directionally Solidified ◽  
Crystallographic Defects ◽  
Semiconducting Alloys ◽  
Uniform Composition ◽  
Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

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