scholarly journals A Kinetic Model for the Modification of Al2O3 Inclusions during Calcium Treatment in High-Carbon Hard Wire Steel

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1305
Author(s):  
Zuobing Xi ◽  
Changrong Li ◽  
Linzhu Wang
Keyword(s):  
Kinetic Model ◽  
Early Stage ◽  
Morphological Evolution ◽  
Product Layer ◽  
Melting Time ◽  
Calcium Treatment ◽  
High Carbon ◽  
Inclusion Modification ◽  
Shrinking Core ◽  
Wire Steel

Laboratory-scale experiments for the modification of Al2O3 inclusions by calcium treatment in high-carbon hard wire steel were performed and the compositions and morphological evolution of inclusions were studied. The kinetics of the modification of Al2O3 inclusions by calcium treatment were studied in high-carbon hard wire steel based on the unreacted shrinking core model, considering the transfer of Ca and Al through the boundary layer and within the product layer, coupled with thermodynamic equilibrium at the interfaces. The diffusion of Al in the inclusion layer was the limiting link in the inclusion modification process. The Ca concentration in molten steel had the greatest influence on the inclusion modification time. The modification time for inclusions tended to be longer in the transformation of higher CaO-containing calcium aluminate. The modification of Al2O3 into CA6 was fastest, while the most time was needed to modify CA into C12A7. It took about six times time longer at the later stage of inclusion modification than at the early stage. The complete modification time for inclusions increased with the square of their radii. The changes of CaO contents with melting time were estimated based on a kinetic model and was consistent with experimental results.

scholarly journals Modification of Type B Inclusions by Calcium Treatment in High-Carbon Hard-Wire Steel

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 676
Author(s):  
Linzhu Wang ◽  
Zuobing Xi ◽  
Changrong Li
Keyword(s):  
Inclusion Size ◽  
Type B ◽  
Calcium Treatment ◽  
High Carbon ◽  
Fine Size ◽  
Dispersed Inclusions ◽  
Wire Steel ◽  
Classical Thermodynamics ◽  
The Relationship

To investigate the modification of type B inclusions in high-carbon hard-wire steel with Ca treatment, Si-Ca alloy was added to high-carbon hard-steel, and the composition, morphology, size, quantity, and distribution of inclusions were observed. The samples were investigated by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The experimental thermal results showed that the modification effect of inclusion was better in high-carbon hard-wire steel with Al of 0.0053% and Ca of 0.0029% than that in steel with Al of 0.011% and Ca of 0.0052%, in which the inclusions were mainly spherical semi-liquid and liquid CA2, CA, and C12A7. The inclusion size decreased from 3.2 μm to 2.1 μm. The degree of inclusions segregation was reduced in high-carbon hard-wire steels after calcium treatment. The results indicate that the modification of inclusions is conducive to obtaining dispersed inclusions with fine size. The ratio of length to width decreased and tended to be 1 with the increase in CaO content in the inclusion. When the content of CaO was higher than 30%, the aspect ratio was in the range of 1 to 1.2. The relationship between the activity of aluminum and calcium and the inclusions type at equilibrium in high-carbon hard-wire steel was estimated using classical thermodynamics. The calculated results were consistent with the experimental results. The thermodynamic software Factsage was used to analyze the effect of aluminum and calcium additions on the type and quality of inclusions in high-carbon hard-wire steels. The modification law and mechanism of type B inclusions in high-carbon hard-wire steels are discussed.

scholarly journals Interfacial Phenomena and Inclusion Formation Behavior at Early Melting Stages of HCFeCr and LCFeCr Alloys in Liquid Iron

2021 ◽  
Author(s):  
Yong Wang ◽  
Andrey Karasev ◽  
Joo Hyun Park ◽  
Wangzhong Mu ◽  
Pär G. Jönsson
Keyword(s):  
Liquid Iron ◽  
Diffusion Zone ◽  
Early Stage ◽  
Interfacial Phenomena ◽  
Solid Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Free Zone ◽  
Formation Behavior ◽  
Predetermined Time

AbstractChromium is normally added to liquid alloy in the form of different grades of ferrochromium (FeCr) alloys for the requirement of different alloy grades, such as stainless steels, high Cr cast iron, etc.. In this work, inclusions in two commercially produced alloys, i.e., high-carbon ferrochromium (HCFeCr) and low-carbon ferrochromium (LCFeCr) alloys, were investigated. The FeCr alloy/liquid iron interactions at an early stage were investigated by inserting solid alloy piece into contact with the liquid iron for a predetermined time using the liquid-metal-suction method. After quenching these samples, a diffusion zone between the alloys and the liquid Fe was studied based on the microstructural characterizations. It was observed that Cr-O-(Fe) inclusions were formed in the diffusion zone, FeOx inclusions were formed in the bulk Fe, and an “inclusion-free” zone was detected between them. Moreover, it was found that the HCFeCr was slowly dissolved, but LCFeCr alloy was rapidly melted during the experiment. The dissolution and melting behaviors of these two FeCr alloys were compared and the mechanism of the early-stage dissolution process of FeCr alloys in the liquid Fe was proposed.

scholarly journals Research on hydrogen generation from rapid hydrolysis of aluminum in sodium fluoride solution

2019 ◽  
Vol 118 ◽  
pp. 03048
Author(s):  
Changchun Li ◽  
Yuxin Wu
Keyword(s):  
Hydrogen Production ◽  
Kinetic Model ◽  
Sodium Fluoride ◽  
Hydrogen Generation ◽  
Hydrogen Yield ◽  
Shrinking Core Model ◽  
Fluoride Solution ◽  
Shrinking Core ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

Hydrogen generation from rapid hydrolysis of aluminum in sodium fluoride solution was investigated through a hydrolysis experiment. Rapid and instant hydrogen yield were observed using sodium fluoride as additive. The experimental results demonstrate that the increase of temperature and the amount of additives in a certain range will boost the hydrogen production. The amount of additives outside the range only has an effect on the rapid hydrolysis of the aluminum during the initial stage, but the total amount of hydrogen produced doesn’t increased significantly. Theoretical analysis of the effects of the mixing ratio and the temperature on the hydrogen production rates were performed using the shrinking core model and the kinetic model. The shrinking core model parameter a and k indicate the film change degree of porosity and thickness and the effect of time on the diffusion coefficient. the kinetic model is verified and the activation energy confirming hydrogen yield control by a molecular diffusion process. Correspondingly, mechanisms of Al corrosion in NaF solutions under low and high alkalinity were proposed, respectively.

Theory and Experimental Research on Inclusion Modification in Improved Carbon Structural Steel

2010 ◽  
Vol 146-147 ◽  
pp. 1659-1666
Author(s):  
Cai Jun Zhang ◽  
Li Guang Zhu ◽  
Dong Mei Tu ◽  
Shuo Ming Wang ◽  
Hui Ding
Keyword(s):  
Carbon Steel ◽  
Experimental Research ◽  
Calcium Treatment ◽  
Sulfur Activity ◽  
High Quality ◽  
Steel Temperature ◽  
Aluminum Activity ◽  
Molten Steel Temperature ◽  
Inclusion Modification ◽  
Carbon Structural Steel

By means of the thermodynamics analysis of inclusion modification in the process of calcium treatment, and the advantage area chart of calcium, aluminum, sulfur, oxygen activity in inclusion midification, this paper analyzes the effects of molten steel temperature, aluminum activity, sulfur activity and other factors on inclusion modification. After calcium treatment, inclusions in high-quality carbon steel S48 will become massive or globular calcium aluminate, MnS inclusion and the composite inclusions of MgO·Al2O3 in kernel and CaO·Al2O3 in shell.

scholarly journals Long-term molecular evolutionary rate determines intraspecific genetic diversity

2019 ◽  
Author(s):  
Jiaqi Wu ◽  
Takahiro Yonezawa ◽  
Hirohisa Kishino
Keyword(s):  
Genetic Diversity ◽  
De Novo ◽  
Early Stage ◽  
Morphological Evolution ◽  
Biological Traits ◽  
Gene Trees ◽  
Intraspecific Genetic Diversity ◽  
Molecular Evolutionary Rates ◽  
Species Specific

AbstractWhat determines genetic diversity and how it connects to the various biological traits is unknown. In this work, we offer answers to these questions. By comparing genetic variation of 14,671 mammalian gene trees with thousands of individual genomes of human, chimpanzee, gorilla, mouse and dog/wolf, we found that intraspecific genetic diversity is determined by long-term molecular evolutionary rates, rather than de novo mutation rates. This relationship was established during the early stage of mammalian evolution. Expanding this new finding, we developed a method to detect fluctuations of species-specific selection on genes as the deviations of intra-species genetic diversity predicted from long-term rates. We show that the evolution of epithelial cells, rather than of connective tissue, mainly contributes to morphological evolution of different species. For humans, evolution of the immune system and selective sweeps subjected by infectious diseases are most representative of adaptive evolution.

scholarly journals Kinetic Studies on Gas-Based Reduction of Vanadium Titano-Magnetite Pellet

2018 ◽  
Author(s):  
Junwei Chen ◽  
Liang Mi ◽  
Yang Jiao ◽  
Xidong Wang
Keyword(s):  
Early Stage ◽  
Reduction Process ◽  
Kinetic Studies ◽  
Product Layer ◽  
Diffusion Control ◽  
Reduction Degree ◽  
Reduction Temperature ◽  
Pellet Size ◽  
Reduction Time ◽  
Time Reduction

Vanadium titano-magnetite is a significant resource in China, and in this study, we characterize its isothermal reduction mechanisms in the mixture of H2, CO, and N2 where the variables considered here include reduction time, reduction temperature, gas composition, and pellet size. The kinetics of the reduction process are mainly studied, which follows a shrinking core model. The results indicate that the reduction degree of oxidized VTM pellets increases with the increase of reduction time, reduction temperature but decreases with the increase of pellet size. Moreover, we found that an increase of H2/(H2+CO) ratio induces an increase of the reduction degree. Then the transformation of main Ti-bearing mineral phases is discussed, and the most probable reaction mechanism is revealed. In the whole reduction process, the kinetic results confirm the existence of an early stage and a latter stage, which are controlled by interface chemical reaction and diffusion, respectively. Furthermore, the results show that the diffusion-control step can be observably shortened with the decrease of pellet size because a thinner product layer is formed during the reduction process. Our study thus provides a valuable technical basis on the VTM industrial application.

scholarly journals Application of the Shrinking-Core Models for Determination of Dissolution Kinetics of Mn and Zn from Spent Zinc–Carbon Battery Powder in Organic Acid Solution

2019 ◽  
Vol 27 (1) ◽  
pp. 99-109 ◽  
Author(s):  
Tevfik Agacayak ◽  
Hasan Ali Taner
Keyword(s):  
Acetic Acid ◽  
Acid Solution ◽  
Acetic Acid Solution ◽  
Dissolution Kinetics ◽  
Kinetic Studies ◽  
Product Layer ◽  
Different Temperatures ◽  
Shrinking Core ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Abstract In this study, dissolution kinetics of manganese and zinc from spent zinc–carbon batteries in acetic acid solution was investigated. To determine the kinetics of dissolution of manganese and zinc, shrinking core model was applied to dissolution recoveries obtained at different temperatures. As a result of kinetic studies, it was determined that manganese and zinc were dissolved in acetic acid solution by diffusion from product layer and then activation energies (Ea) were calculated.

Kinetics of limestone decomposition in hot metal

2018 ◽  
Vol 115 (6) ◽  
pp. 611 ◽  
Author(s):  
Biao Tang ◽  
Qifu Xiang ◽  
Jing Wang ◽  
Yunlong Zhang ◽  
Xingyi Li ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat Conduction ◽  
Cross Section ◽  
Gas Flow ◽  
Kinetic Equations ◽  
Product Layer ◽  
Hot Metal ◽  
Shrinking Core ◽  
Kinetics Of ◽  
Limestone Calcination

Compared with the traditional limestone calcination, this paper focuses on the conditions and temperature in hot metal where limestone calcines in converter steelmaking process. Considering heat transfer, mass transfer driven by concentration gradient and mass transfer (CO2 gas flow) driven by pressure gradient, macro kinetic models are established to describe limestone decomposition rate respectively. The method of rotating cylinder sample is used in the experiment of limestone decomposition in hot metal. The image processing software Image-Pro Plus is used to analyze the cross section of limestone calcined to get the unreacted core radius of cross section of cylindrical limestone. The results show that the decomposition mechanism of limestone follows the unreacted shrinking core model, the heat conduction of lime layer is the controlling step, the heat conduction and CO2 migration through the product layer determine the rate of limestone decomposition, and the corresponding kinetic equations are established.

scholarly journals Shrinking core model of demineralization of chitin isolation from shrimp shell

2018 ◽  
Vol 154 ◽  
pp. 01014
Author(s):  
Ahmad Fadli ◽  
Subkhan Maulana ◽  
Drastinawati
Keyword(s):  
Hydrochloric Acid ◽  
Kinetic Model ◽  
Acid Concentration ◽  
Calcium Content ◽  
Core Model ◽  
Percentage Error ◽  
Hydrochloric Acid Concentration ◽  
Shrinking Core Model ◽  
Shrimp Shell ◽  
Shrinking Core

Chitin is a naturally abundant polymer and most of it was used as a surfactant and cosmetic raw materials. Chitin be able to derive from natural sources like shrimp shell waste. The aim of this research was to study the kinetic model of chitin demineralization with approach to shrinking core model (SCM) with variation of hydrochloric acid concentration. There models were used: Fluid Film Layer Diffusion, Ash Layer Diffusion and Chemical Reaction. It was began with deproteination at first with NaOH 3,5 % and continued with demineralization using hydrochloric acid at concentration 0,3 N; 0,6 N; 0,9 N and 1,2 N with variation of reaction time at 15, 30 and 15 minute. The calcium content in the product was analyzed after it was dried in the air oven. The results showed calcium concentration decrease along with increasing of hydrochloric acid concentration. It get kinetic model at concentration 0,3 N of hydrochloric acid usage with form: [see formula in PDF] with the highest value of R2 is 0,9555 and the smallest percentage error is 5,92%. Meanwhile with usage of hydrochloric acid at concentration 0,6 N; 0,9 N and 1,2 N were get kinetic model with form: [see formula in PDF] with the highest value of R2 is 0,9794.

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