CaO In Slag Research Articles

Thermodyanmics of CaO in Slag Reduced by Carbon during VD Process of Hollow Steel 95CrMo and its Effect on Inclusions

With the help of thermodynamics calculation and kinetic model, the generation mechanism of calcium aluminate inclusions in hollow steel 95CrMo was analyzed. The steel was produced in a certain steelmaking factory whose smelting process is EAF-LF-VD-CC and the micreostructure of the hollow steel 95CrMo samples have been investigated by SEM and EDS. Based on Lumsden’s regular solution model to molten slags, the possibility of CaO in slags reduced by carbon during hollow steel refining in VD furnace was calculated. The influence of furnace vacuum, slag basicity and liquid steel temperature on the reduction of CaO in slag by carbon was discussed. It was showed that the carbon dissolving in liquid steel might reduce CaO in slags to dissolved calcium which could also react with Al2O3 and turn into dot calcium-aluminate inclusions in the steel. The calcium-aluminate existing in the hollow steel easily turned into dot inclusions, which would decrease the fatigue life of the hollow steel. According to the thermodynamic conditions of dot calcium-aluminate inclusions, the influence of slag basicity, temperature of liquid steel, vacuum degree and the Ca treatment process on the quantity of dot inclusions in hollow steel 95CrMo was analyzed.

Effect of B2O3 addition on viscosity of mould slag containing low silica content

The viscosity of SiO2–30Al2O3–B2O3–12Na2O–CaO slag system (CaO/SiO2 = 2·68–7·35, B2O3 = 0–9 wt-%) was investigated in the present study. The objective is to study the influence of B2O3 on the viscosity and structure of mould slags containing low silica content. The research of the low silica slag system is meaningful because of it is less reactive with Al during continuous casting of steels containing high amounts of dissolved aluminium, such as transformation induced plasticity assisted steels. The viscosities of these quinternary slags decreased slightly with an increase in the content of additive B2O3 above the break temperature. The apparent activation energy of viscous flow was found to decrease with increasing B2O3 content. The break temperature also decreased with increasing B2O3 content. Based on the experimental data, the decrease in break temperature per mol.-% B2O3 ΔTbr is 15·23 K. An empirical model was then established to predict the break temperature of mould slags containing B2O3, and the deviation is between −25 and +25 K. Based on the viscosity and Fourier transform infrared analysis, it is proposed that the three-coordinated boron is dominated in these slags over the entire compositional range, and the borosilicate networks are loosened with increasing B2O3 content in the present study. The Riboud model was modified empirically based on the present experimental data, and the mean deviation is ∼13%.

The Wear Mechanism Comparison between MgO-Based Chrome-Free Brick and MgO-Cr<sub>2</sub>O<sub>3</sub> Brick in the Lower Part of RH Vacuum Degasser

The damage and improvement mechanism of rebonded MgO-Cr2O3 brick and MgO-ZrO2 brick used in the lower part of RH vacuum degasser were studied. The results show that the main damage of rebonded MgO-Cr2O3 brick is structure spalling because of the penetration of slag. MgO-ZrO2 brick has characteristics of high direct-bonding degree, small air permeability and making the viscosity of penetrated slag increased by means of ZrO2 absorbing CaO in slag to form CaZrO3 or ZrO2 solid solution, which make the degree of slag penetration decrease and improve the structure spalling resistance. MgO-ZrO2 brick has the defect of poor thermal shock resistance in use, the incorporation of MgO-rich spinel into MgO-ZrO2 brick significantly improved both thermal shock resistance and hot modulus of rupture because of the formation of eutectoid structure of grain-refining spinel and zirconia, which also improved structure spalling resistance because air permeability was decreased to 5% of MgO-ZrO2 brick

A Sulfur Diffusion Investigation in Metal and Oxide Phases

The purpose of the present work is to investigate the mutual interaction between the melted metal and oxide phases with a small amount of sulfur. In this research, the following phases took part: metallic phase of Fe – C – S and slag CaO–Al2O3 –MgO–S. The mathematical model of sulfur diffusion in the metal and oxide is employed. The experiment was carried out at the temperature of 1773K. The result of the calculation is in qualitative agreement with the experiment. The proposed approach can be applied to the investigations of diffusion processes in molten metal and slag phases.

Tin solubility in CaO‐bearing slags

A series of laboratory experiments were undertaken to study the tin (Sn) solubility in lime (CaO) bearing slags. The equilibrium Sn solubility at 1873K was investigated using a gas‐slag‐metal equilibrium technique. Sn solubilities from the high CaO slags are discussed as a function of slag composition and oxygen potential.

Software package for determination of surface tension of liquid metals

The problems of the development of algorithms to process experimental results obtained by the sessile drop method are discussed. Algotithms are based on the numerical solution of the Young-Laplace equation and the regularization method for Dorsey formula. A software package for IBM PC AT has been developed. The results of calculations for droplets formed in a cup (liquid Fe) and on a plate (slag CaOB 2O 3) are given.

石炭高温ガス化炉から排出される石灰石添加スラグのセメント混和材利用に関する基礎研究

Characterization on two sorts of coal gasification slag, Blair Athol and Taiheiyo, with limestone additive was performed in order to obtain the relation between character of glass phase and pozzolanic reactivity of blending component. The content of CaO in slag was varied from 0 to 40wt%.The pozzolanic reactivity of the slag is enhanced with increasing of basicity, content of acid soluble SiO2, Al2O3, and CaO content in slag, and decreasing of degree of condensation of silicate ion in the glass phase.Hydrated products from the slag cement are not basically different from those from blastfurnace slag cement.The compressive strenght of high calcium slag cement is almost equal to that of blastfurnace slag and ordinary portland cement.

Distribution Equilibria of Selenium between Liquid Copper and Na<SUB>2</SUB>O–B<SUB>2</SUB>O<SUB>3</SUB>–CaO Slags

Effect of slag basicity on selenium distribution between slag and metal phase was studied at 1473 K under reducing conditions by equilibrating sodium-borate slags of different Na 2 O/B 2 O 3 ratios (0.527 to 0.864) with Cu-Se alloys containing different initial selenium amounts. Results show that there is an improvement in Se transfer from metal phase to slag with the increase in slag basicity. The Se distribution pattern at equilibrium between slag and metal follows a quantitative relationship In (%Se)/[%Se]=4b-2.76 where b is the slag basicity

還元雰囲気下1600℃におけるMgO-Al<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB>-CaO系スラグ中へのMgO・Cr<SUB>2</SUB>O<SUB>3</SUB>の溶解度

還元雰囲気下1600℃におけるMgO-Al<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB>-CaO系スラグ中へのMgO・Cr<SUB>2</SUB>O<SUB>3</SUB>の溶解度

Some observations on current transfer at iron/calcium fluoride electrodes – Model experiments for current transfer in the ESR process

Measurement of current density‐potential curves with direct and alternating current at iron electrodes immersed into CaF2 or CaF2/10wt.% CaO slag. Theoretical interpretation of overpotentials in low current range. Dependence of overpotential on FeO content of slag.

CaO surface segregation as an emission-loss mechanism

The formation of high work function patches on a cathode surface can lead to cathode failures in certain applications even though the cathode as a whole may show adequate overall emission properties. This type of failure was found for an oxide cathode used in a Vidicon tube wherein the beam current originated from a small portion of the cathode surface. Surface analytical techniques such as AES, used in conjuction with SLEEP, showed that the high work function areas could be correlated with high surface calcium concentration and low surface barium concentration. Auger sputter profiling also revealed that these calcium-rich regions (high work function patches) are actually thin surface layers with a thickness the order of 100 Å while the bulk cathode composition appears to be uniform. A possible explanation for these patches is the formation of a CaO slag on the surface caused by BaO/BaCO 3 eutectic melting during the conversion process.

Electrode polarization in the DC electroslag melting of pure iron

It is evident from the known ionic properties of the slags used in electroslag melting, that the dc melting process must be accompanied by Faradaic reactions on the slag/ingot and slag/electrode interfaces. The present work has determined the magnitude of the overpotentials resulting from concentration polarization at these interfaces, in the case of pure iron/CaF2+Al2O3, CaF2+CaO slags using a galvanostatic pulsing technique in an electrolytic cell. The polarization overpotential existing on an electrode in an operating ESR unit has been measured by the same technique. It is found that the potentials observed on the ESR electrode agree well with the results from the electrolytic cell. The primary anodic process is postulated to be the corrosion of iron, leading to an Fe2+-saturated layer on the anode surface at sufficiently high current densities. The cathodic process is suggested to be the Faradaic reduction of Al3+ or Ca2+, to give a concentration of [Al]Fe or (Ca)slag in the cathode interface region. This observation is supported by the fact that the cathodic potentials with respect to a C/CO reference electrode are close to those predicted from the reactions: (Al2O3)+3C=3CO(g)+2Al(l) or (CaO)+C=CO(g)+Ca(g) At very high current densities both the anodic and cathodic processes may convert to arcs, leading to process instability. The chemical and thermal effects of the overpotentials are briefly discussed and compared with the present results on ESR ingots of pure iron.

Activities of Fe, FeO, Fe203, and CaO in Simple Slags

The data previously reported for the quantity j = Fe+++/(Fe+++Fe+++) as a function of oxygen pressure at 1550°C have been used to compute the activities of Fe, FeO, Fe2O3, and CaO in slags of the ternary system. Activities of the first three have been obtained also for two quasi-ternaries involving fixed CaO:SiO2 ratios.