Ion And Molecule Coexistence Theory Research Articles

Control of Aluminum and Titanium Contents in the Electroslag Remelting of ATI 718PlusTM Alloy.

The burning loss of Al and Ti elements in superalloys during electroslag remelting has become a prevalent issue. And the existing slag system is not suitable for smelting the ATI 718PlusTM alloy. Therefore, it is imperative to develop a new slag system for smelting the ATI 718PlusTM alloy. To mitigate this issue, a thermodynamic model of the oxidation reaction of Al and Ti at the slag and alloy interface was established based on the ion and molecule coexistence theory (IMCT). The thermodynamic model was used to investigate the correlation between the equilibrium content of Al and Ti, slag composition, smelting temperature, and initial Al and Ti content of the electrode. The results indicate that while increasing the smelting temperature can effectively inhibit the burning loss of Al, it will exacerbate the burning loss of Ti. Increasing CaO and Al2O3 contents can inhibit the Al burning loss, while an increase in the TiO2 content can inhibit the Ti burning loss. Although an increase in the MgO content results in the burning loss of Al, its impact on the Al is minimal. The burning loss of Al and Ti was not affected by the change in the CaF2 content. The high Al content in ATI 718PlusTM makes it prone to burning loss of Al during the electroslag remelting. The combustion loss of Al can be reduced by increasing the Ti content in the electrode or adding a suitable amount of aluminum powder to the slag system. The accuracy of the model had been validated through experimental verification.

A thermodynamic model for predicting Ti and Al element of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag in electroslag remelting process

The control of titanium and aluminium in nickel-base superalloy with high titanium and low aluminium during the electroslag remelting (ESR) process has not been resolved well so far. The loss of titanium (Ti) and aluminium (Al) during the ESR process is critical to improve the high-temperature performance of GH4065A superalloy. A thermodynamic model based on the ion and molecule coexistence theory (IMCT) was developed to calculate the Ti and Al content of SiO2–Al2O3–FeO–TiO2–CaO–MgO–CaF2 slag system during the ESR process of GH4065A superalloy. Results show that the order of the ability of each element in the slag system to weaken the loss of Al content is in the following order Al2O3 > CaO > CaF2, enhance the loss of Al content is SiO2 > FeO > TiO2, CaF2 > MgO and enhance the loss of Ti content is FeO > SiO2 > Al2O3 > CaO. Considering the influence of the slag system on the elements Al and Ti, the optimal ratio of the slag system is CaO = 15 w%∼20 w%, CaF2 ≥ 60 w%, Al2O3 = 18 w%∼25 w%, SiO2 ≤ 0.5 w%, TiO2 = 1 w%+(0.2 w%∼0.6 w%), MgO ≥ 4 w%, FeO ≤0.1 w%.

Effect of Mold Flux Containing Ce2O3 on the Contents of Aluminum, Silicon, and Titanium in Incoloy825 Super Alloy

The effect of mold flux containing Ce2O3 on the contents of aluminum, silicon, and titanium in Incoloy825 super alloy was investigated based on the slag-steel interfacial chemical reaction experiment between mold flux and alloy. Firstly, the activity model of the CaO-SiO2-Al2O3-Na2O-MgO-CaF2-Ce2O3 slag system was established according to the ion and molecule coexistence theory (IMCT), and the calculation results show that with the increase of Ce2O3 content in the mold flux, the activity of Al2O3 decreases significantly and the activity of SiO2 decreases and gradually tends to 0. Secondly, thermodynamic calculations of the slag-steel interfacial chemical reaction revealed that the main chemical reaction in this study system is [Ti] + (SiO2) = [Si] + (TiO2). With the increase of Ce2O3 content in the mold flux, the slag-steel interfacial chemical reaction is weakened and the oxidation of Al and Ti in steel is inhibited. Finally, the results of slag-steel reaction experiment show that the increase rate of Al content increases from 1.03% to 10.31%, the increase rate of Si content decreases from 55.95% to 31.25%, and the oxidation rate of Ti content decreases from 33.27% to 20.00% when Ce2O3 content in the mold flux increases from 0% to 15% and the slag-steel reaction for 40 mins.

A thermodynamic model of the titanium distribution behaviour between slag and molten steel during LF refining process: description and application

ABSTRACT Titanium distribution ratio is a key parameter which directly reflect the ability to remove titanium in the LF refining process. A thermodynamic model for calculating the titanium distribution ratio (LTi) between ladle furnace (LF) refining slags, i.e., CaO–SiO2–MgO–FeO–(CaF2)–MnO–Al2O3–TiO2 slags, and molten steel has been developed by coupling with the ion and molecule coexistence theory (IMCT) and slag–metal equilibrium theory. The reliability of the model was verified by comparing it with industrial data. Using this model, the effects of Al, Si content in steel and CaO, MgO and TiO2 in slag on the L Ti were investigated. Meanwhile, the optimal equilibrium slag composition of GCr15SiMn bearing steel was predicted. On this basis, five groups of industrial tests were carried out, and the results indicated that the optimized practice had achieved remarkable results in limiting titanium content compared with the routine process.

Oxidation behavior of boron in 9CrMoCoB steel by CaF2–CaO–Al2O3–SiO2–B2O3 electroslag remelting (ESR) type slag

The laboratory-scale experiments between the CaF2–CaO–Al2O3–SiO2–B2O3 slag and 9CrMoCoB steel were carried out in alumina and magnesia crucibles at 1823 K to investigate the oxidation behavior of boron (B) during the electroslag remelting (ESR) process. The activities of SiO2 and B2O3 in the slag and the activities of Si and B in the molten steel were calculated by the ion and molecule coexistence theory (IMCT) and the Wagner formalism, respectively. The results showed that both SiO2 and B2O3 have a significant influence on the equilibrium B content. The calculated content of B was in good agreement with the experimental value when the SiO2+B2O3 content in the slag is more than 3.3 wt%. The temperature had little influence on the equilibrium B content when the SiO2, B2O3 and CaO content were in the ranges of 3–5 wt%, 0–1 wt%, and 20–30 wt%, respectively. However, the Si is more prone to oxidation than is B as the temperature increases, indicating that more SiO2 should be added in the slag to reduce the oxidation of Si. From the 80 tonnes industrial tests, the distribution of B and Si content along with the radial direction of the remelted ingot was almost uniform, which is in line with the calculated B content (approx. 30 ppm) under conditions of the Si content in the liquid steel and the (%B2O3)/(%SiO2) ratio are 0.07% and 0.05, respectively, at 1973 K.

The Establishment of Thermodynamic Model for Ti Bearing Steel-Slag Reaction and Discuss

A thermodynamic model for seven CaO-MgO-BaO-CaF2-SiO2-Al2O3-TiO2 ladle slags based on the Ion and Molecule Coexistence theory (IMCT) is establishment and validated by the experiment results at 1873K. The calculated activity of SiO2, Al2O3 and TiO2 in the slag can be approved by the experiment results and the IMCT model used in this study is reasonable. Then the influence factors such as the mass ratio of CaO to SiO2 (C/S ratio) ranging from 1 to 10, the mass ratio of CaO to Al2O3 (C/A ratio) ranging from 1 to 2.5, TiO2 content (wt pct) ranging from 0 to 30, BaO content (wt pct) ranging from 0 to 30 are investigated based on the thermodynamic calculating results. The raise of C/S ratio, TiO2 content and BaO content in the slag can increase the molar Gibbs energy change (ΔG) of Ti reacted with SiO2 and Al2O3 or Al reacted with SiO2. The effect of C/A ratio on the molar Gibbs energy change (ΔG) of Ti reacted with SiO2 and Al2O3 or Al reacted with SiO2 was less. Finally, the slag with higher C/S ratio and TiO2 content and appropriate BaO content can weaken the reaction between Ti and SiO2 or Al2O3 in the slag.

Innovative separation model for boron removal from silicon during slag refining based on ion and molecule coexistence theory

How to reduce boron concentration to an extremely low level has become a major obstacle during silicon waste recycling. As a simple and efficient method of removing impurities, slag refining plays an increasingly important role for industrial silicon waste recovery. The deboration ability of slag is usually evaluated by boron distribution ratio LB. However, the development of a separation prediction model is challenged by the limitations on the recognition of impurity structure in slag and complexity of slag-silicon reactions. Herein, a novel thermodynamic model for predicting boron distribution ratio between CaO-SiO2 based slags and molten silicon has been developed based on ion and molecule coexistence theory (IMCT), i.e., IMCT-LB model. The reaction abilities of structural units are represented by the calculated mass action concentration. The predictive boron distribution ratio between CaO-SiO2, CaO-Al2O3-SiO2, CaF2-CaO-SiO2 slags and silicon correspond well with experimental data, reflecting the reasonability of IMCT-LB model. According to IMCT, deboration reactions between slags and silicon can be represented by ion couples (Ca2+ + O2–), simple molecule Al2O3 with SiO2 to form eight deboration products as B2O3, 3CaO · B2O3, 2CaO · B2O3, CaO · B2O3, CaO · 2B2O3, 2Al2O3 · B2O3, 9Al2O3 · B2O3, CaO · 2SiO2 · B2O3. With the developed IMCT-LB model, the respective boron distribution ratio LB,i of the eight deboration products can be determined quantitatively. Furthermore, the effect of temperature, mass ratio of CaO to SiO2 (%CaO/%SiO2), Al2O3 and CaF2 content of CaO-SiO2 based slags on LB are fully discussed.

A SULPHIDE CAPACITY PREDICTION MODEL OF BLAST FURNACE SLAG

A sulphide capacity prediction model of CaO-SiO2-MgO-Al2O3 slags has been developed based on the ion and molecule coexistence theory(IMCT). Sulphide capacity(Cs) of slag for blast furnace (BF) with high Al2O3 in the CaO-SiO2-MgO-Al2O3 system at 1773K were measured by applying slag-metal equilibrium method. The feasibility of the developed IMCT model is verified by the sulphide capacity measured in the experiment. Effects of R(w(CaO)/w(SiO2)), w(MgO)/w(Al2O3) and w(Al2O3) on sulphide capacity were discussed. There is a good linear relationship between the experimental value and the predicted value. Therefore, the theoretical model of ion and molecule coexistence can be used to calculate the sulphide capacity of CaO-SiO2-MgO-Al2O3 quaternary slag system. When w(Al2O3)=20% and w(MgO)/w(Al2O3)=0.5, the sulphide capacity of slag increased with the increase of R. When w(Al2O3)=20% and R=1.30, the sulphide capacity of slag increased with the increase of w(MgO)/w(Al2O3). When R=1.30 and w(MgO)/w(Al2O3)=0.4, the sulphide capacity of slag decreased with the increase of w(Al2O3).

Effect of various components on the distribution of phosphorus in CaO–FeO–MgO–SiO2–MnO–TiO2–V2O5–P2O5 slag based on IMCT

ABSTRACT A thermodynamic calculation model of phosphorus distribution ratio between CaO–FeO–MgO–SiO2–MnO–TiO2–V2O5–P2O5 slags and molten metal has been developed based on the ion and molecule coexistence theory (IMCT). The calculated phosphorus distribution ratio shows a good agreement with the measured ones by the data of industrial trial, which proves the reliability of this model. Therefore, the model is used to study the effects of TiO2, V2O5, slag basicity, FeO, MgO and MnO on phosphorus distribution. The results illustrate that the effects on phosphorus distribution from V2O5 and TiO2 are non-negligible and they are almost the same, slag basicity and FeO have the most significant effects on phosphorus distribution, while MgO and MnO have the least.

A Further Evaluation of the Coupling Relationship between Dephosphorization and Desulfurization Abilities or Potentials for CaO-based Slags: Influence of Slag Chemical Composition

The coupling relationships between dephosphorization and desulfurization abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags over a large variation range of slag oxidization ability during the secondary refining process of molten steel have been proposed by the present authors as log L P + 5 log L S or log C PO 4 3 − + log C S 2 − in the reducing zone and as log L P + log L S − 5 log N Fe t O or log C PO 4 3 − + log C S 2 − − log N FeO in the oxidizing zone based on the ion and molecule coexistence theory (IMCT). In order to further verify the validation and feasibility of the proposed coupling relationships, the effects of chemical composition of the CaO-based slags are provided. The chemical composition of slags was described by three group parameters including reaction abilities of components represented by the mass action concentrations N i , two kinds of slag basicity as simplified complex basicity ( % CaO ) / [ ( % P 2 O 5 ) + ( % Al 2 O 3 ) ] and optical basicity Λ , and the comprehensive effect of iron oxides FetO and basic oxide CaO. Comparing with the strong effects of chemical composition of the CaO-based slags on dephosphorization and desulfurization abilities or potentials, the proposed coupling relationships have been confirmed to not only be independent of slag oxidization ability as expected but also irrelevant to the aforementioned three groups of parameters for representing the chemical composition of the CaO-based slags. Increasing temperature from 1811 to 1927 K (1538 to 1654 °C) can result in a decreasing tendency of the proposed coupling relationships. In terms of the proposed coupling relationships, chemical composition of slags or fluxes with assigned dephosphorization ability or potential can be theoretically designed or optimized from its desulfurization ability or potential, and vice versa. Considering the large difference of magnitude between phosphate capacity C PO 4 3 − and sulfide capacity C S 2 − , the proposed coupling relationships between dephosphorization and desulfurization abilities for CaO-based slags are recommended to design or optimize chemical composition of slags.

Thermodynamic analysis for the oxidation behaviour of manganese in iron-based melts during demanganisation processes

ABSTRACTIn this study, the influences of the solid oxidants and pure oxygen on oxidation behaviour of manganese in hot metal are investigated. The results indicate that the content of manganese in liquid iron decreases faster by using of iron ore fines than that by using of pure oxygen in the first 10 min. Manganese reversion could be happened by using solid oxidant Fe2O3, whereas it did not occurr under condition of oxygen blowing within 40 min. Meanwhile, the thermodynamic behaviour of manganese between CaO–SiO2–MgO–FeO–Fe2O3–MnO–Al2O3–P2O5 slag and molten steel has also been studied by means of IMCT-LMn model based on the ion and molecule coexistence theory (IMCT). With the aid of the current model, the effects of basicity on activity coefficient of MnO are investigated, which demonstrate that shows a negative correlation with mass percent of FetO in the range of 18.06–36.52%, indicating that the slag can hold more manganese oxide.

Clarification of the Dissolution of Solid CaO and the Phosphorus‐Enrichment Capability of Calcium Silicates in the Multiphase Slag Based on the Ion and Molecule Coexistence Theory

Recently, a new refining method of using a solid/liquid coexistence multiphase slag for dephosphorization of hot metal was proposed, with the aim to improve the utilization efficiency of CaO and the degree of dephosphorization. Based on this method, an ion and molecule coexistence theory (IMCT) based the thermodynamic model has been developed to clarify the behavior of solid CaO dissolution and the phosphorus‐enrichment capability of calcium silicates in the multi‐phase slag in this article. According to the calculated mass action concentration of the related structural units, the reaction mechanism between solid CaO and the liquid slag in the multi‐phase slag is explained. Meanwhile, the phosphorus‐enrichment capability of calcium silicates is probed. The results show that the dissolution of solid CaO into the multi‐phase slag will be enhanced with the addition of the temperature or the increase of the FeO content, the mass percent ratio of FeO to Fe2O3 (m(FeO)/m(Fe2O3)), and the P2O5 content, while the high basicity (CaO/SiO2) will restrict the dissolution of solid CaO. Besides with the increase of basicity and m(FeO)/m(Fe2O3), the phosphorus‐enrichment contribution ratio of 2CaO · SiO2 displays an exponential growth tendency, while it exhibits an asymmetric parabolic relationship with the increase of FeO, and it slightly decreases with the increase of P2O5 and unchanged with the temperature. Those results obtained can provide a fundamental guidance for the dephosphorization by using the CaO‐based solid/liquid coexistence multiphase slag for hot metal treatment.

A Thermodynamic Model to Design the Equilibrium Slag Compositions during Electroslag Remelting Process: Description and Verification

Based on the ion and molecule coexistence theory (IMCT) and slag-metal equilibrium theory, a thermodynamic model to design the slag compositions balanced with the consumable electrode of G20CrNi2Mo bearing steel during electroslag remelting (ESR) process was developed. With this model, an equilibrium slag system of Al2O3, SiO2, MnO and FeO can be obtained quantitatively, which is favorable to decrease the extent of steel constituents oxidized by the molten slag. In order to validate the reasonability of this model, an industrial experimental with four types of slag systems was carried out in a special steel plant of China. The composition variation of Al, Si, Mn and oxygen corresponds well with deviation of Al2O3, SiO2, MnO and FeO from equilibrium, reflecting the reasonability of this model. This model could also provide some guidance for deoxidation practice during industrial ESR process. It is concluded that large deviation of measured FeO from equilibrium is a key factor leading to the Al-oxidation and oxygen increase. In order to improve the cleanliness of refined ingot, under the premise of one slag system with relatively low CaO content, a feasible means is to strengthen the protecting atmosphere or add strong oxidizer into the slag pool to suppress the FeO-activity to a minimum level, particularly during the last stage of remelting.

Coupling relationship between dephosphorisation and desulphurisation abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags over a large variation range of slag oxidisation ability during secondary refining process of molten steel

The coupling relationships between dephosphorisation and desulphurisation abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags during secondary refining process of molten steel have been proposed as or in reducing zone at oxygen potential less than 2.27 × 10−6 Pa as well as or in oxidising zone at oxygen potential greater than 2.27 × 10−6 Pa through deleting slag oxidisation ability expressed by the comprehensive mass action concentration of iron oxides based on the ion and molecule coexistence theory (IMCT). The proposed coupling relationships between dephosphorisation and desulphurisation abilities or potentials of the slags have been verified to be valid using reported data of oxygen, phosphorus and sulphur distribution equilibria between the slags and liquid iron over a temperature range from 1811 to 1927 K (1538–1654 °C) and predicted results of dephosphorisation and desulphurisation abilities or potentials. Not only the proposed coupling relationships between dephosphorisation and desulphurisation potentials but also the correlated coupling relationships between dephosphorisation and desulphurisation abilities for the slags in reducing and oxidising zones have been verified to be indeed independent of slag oxidisation ability.

A thermodynamic model for predicting phosphate capacity of CaO-based slags during hot metal dephosphorisation pretreatment process

A thermodynamic model for predicting phosphate capacity of the CaO-based slags over a temperature range from 1750 to 1793 K (1477–1520°C) during dephosphorisation pretreatment of hot metal has been developed based on the ion and molecule coexistence theory (IMCT), i.e. the IMCT– model. The developed IMCT– model has been verified to be valid through comparing with the measured and the predicted ones by four reported models from the literature. Besides the total phosphate capacity , the respective phosphate capacity of nine dephosphorisation products as P2O5, 3FeO·P2O5, 4FeO·P2O5, 2CaO·P2O5, 3CaO·P2O5, 4CaO·P2O5, 2MgO·P2O5, 3MgO·P2O5 and 3MnO·P2O5 can also be accurately predicted by the developed IMCT– model. The formed 3CaO·P2O5 accounts for 99.20% of dephosphorisation products comparing with the generated 4CaO·P2O5 for 0.80%. The results also revealed that the effects of slag chemical composition including slag oxidisation ability, slag basicity and the comprehensive influence of iron oxides FetO and basic oxide CaO on phosphate capacity were largely different with those on phosphorus partition between the CaO-based slags and hot metal. Although and are both distinct thermodynamic quantities and related to each others provided that the entire slag system is correctly defined, phosphorus partition has much guide meaning on dephosphorisation operation than phosphate capacity . The main interest of measuring phosphate capacity from laboratory experiments can be attributed to obtain phosphorus partition through relationship between and .

Critical Assessment of P2O5 Activity Coefficients in CaO-based Slags during Dephosphorization Process of Iron-based Melts

According to the experimental results of hot metal dephosphorization by CaO-based slags at a commercial-scale hot metal pretreatment station, activity $$ a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} $$ of P2O5 in the CaO-based slags has been determined using the calculated comprehensive mass action concentration $$ N_{{{\text{Fe}}_{t} {\text{O}}}}^{{}} $$ of iron oxides by the ion and molecule coexistence theory (IMCT) for representing the reaction ability of Fe t O, i.e., activity of $$ a_{{{\text{Fe}}_{t} {\text{O}}}}^{{}} $$ . The collected ten models from the literature for predicting activity coefficient $$ \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} $$ of P2O5 in CaO-based slags have been evaluated based on the determined activity $$ a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} $$ of P2O5 by the IMCT as the criterion. The collected ten models of activity coefficient $$ \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} $$ of P2O5 in CaO-based slags can be described in the form of a linear function as $$ \log \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \equiv y = c_{0} + c_{1} x $$ , in which independent variable $$ x $$ represents the chemical composition of slags, intercept $$ c_{0} $$ including the constant term depicts temperature effect and other unmentioned or acquiescent thermodynamic factors, and slope $$ c_{1} $$ is regressed by the experimental results. Thus, a general approach for obtaining good prediction results of activity $$ a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} $$ of P2O5 in CaO-based slags is proposed by revising the constant term in intercept $$ c_{0} $$ for the collected ten models. The better models with an ideal revising possibility or flexibility in the collected ten models have been selected and recommended.

Phosphate enrichment mechanism in CaO–SiO2–FeO–Fe2O3–P2O5 steelmaking slags with lower binary basicity

The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO–SiO2–FeO–Fe2O3–P2O5 slags with a P2O5 content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the (%FetO)/(%CaO) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree \( R_{C_2 S - C_3 P}\) of solid solution 2CaO·SiO2–3CaO·P2O5 (C2S–C3P), where \( R_{C_2 S - C_3 P}\) is a component of the developed ion and molecule coexistence theory (IMCT)–Ni model for calculating the mass action concentrations Ni of structural units in the slags on the basis of the IMCT. The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P2O5 in the C2S–C3P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.

A Thermodynamic Model for Predicting Phosphorus Partition between CaO-based Slags and Hot Metal during Hot Metal Dephosphorization Pretreatment Process Based on the Ion and Molecule Coexistence Theory

A thermodynamic model for predicting phosphorus partition L P between a CaO-based slags and hot metal during hot metal dephosphorization pretreatment process has been developed based on the ion and molecule coexistence theory (IMCT), i.e., the IMCT–L P model. The reaction abilities of structural units or ion couples in the CaO-based slags have been represented by the calculated mass action concentrations N i through the developed IMCT–N i model based on the IMCT. The developed IMCT–L P model has been verified to be valid through comparing with the measured L P as well as the predicted L P by two reported L P models from the literature. Besides the total phosphorus partition L P between the CaO-based slag and hot metal, the respective phosphorus partitions L P,i of nine dephosphorization products as P2O5, 3FeO·P2O5, 4FeO·P2O5, 2CaO·P2O5, 3CaO·P2O5, 4CaO·P2O5, 2MgO·P2O5, 3MgO·P2O5, and 3MnO·P2O5 can also be accurately predicted by the developed IMCT–L P model. The formed 3CaO·P2O5 accounts for 99.20 pct of dephosphorization products comparing with the generated 4CaO·P2O5 for 0.08 pct. The comprehensive effect of CaO+Fe t O, which can be described by the mass percentage ratio (pct Fe t O)/(pct CaO) or the mass action concentration ratio $$ {{N_{{{\text{Fe}}_{t} {\text{O}}}}} \mathord{\left/{\vphantom {{N_{{{\text{Fe}}_{t} {\text{O}}}}} {N_{\text{CaO}}}}} \right. \kern-0pt} {N_{\text{CaO}}}} $$ as well as the mass percentage product (pct Fe t O) × (pct CaO) or the mass action concentration product $$ N_{{{\text{Fe}}_{t} {\text{O}}}}^{5} \times N_{\text{CaO}}^{3} $$ , controls dephosphorization ability of the CaO-based slags. A linear relationship of L P against (pct Fe t O)/(pct CaO) can be correlated compared with a parabolic relationship of L P against $$ {{N_{{{\text{Fe}}_{t} {\text{O}}}}} \mathord{\left/{\vphantom {{N_{{{\text{Fe}}_{t} {\text{O}}}}} {N_{\text{CaO}}}}} \right. \kern-0pt} {N_{\text{CaO}}}} $$ , while the linear relationship of L P against (pct Fe t O) × (pct CaO) or $$ N_{{{\text{Fe}}_{t} {\text{O}}}}^{5} \times N_{\text{CaO}}^{3} $$ can be established. Thus, the mass percentage product (pct Fe t O) × (pct CaO) and the mass action concentration product $$ N_{{{\text{Fe}}_{t} {\text{O}}}}^{5} \times N_{\text{CaO}}^{3} $$ are recommended to represent the comprehensive effect of CaO+Fe t O on dephosphorization ability of the CaO-based slags. Furthermore, a parabolic relationship of L P against binary basicity or complex basicity CB2 and CB3 can be established at binary basicity in 1.8 or at complex basicity CB2 and CB3 in 2.0 corresponding to the maximum of dephosphorization ability of the CaO-based slags. However, the linear relationship between L P and optical basicity can only be correlated with the mathematically regressed $$ \varLambda_{\text{FeO}} $$ = 1.0 and $$ \varLambda_{{{\text{Fe}}_{ 2} {\text{O}}_{ 3}}} $$ =0.75. A great gradient of oxygen potential or oxygen activity a %,O between the dynamically formed metal film beneath slag–metal interface and hot metal bath is the main driving forces of hot metal dephosphorization by the CaO-based slags. The formed metal film with high oxygen content and low carbon content can dynamically be exchanged or replaced by hot metal elements from bath during hot metal dephosphorization process until dephosphorization products mainly as 3CaO·P2O5 are saturated in the CaO-based slags.

Thermodynamic models for predicting dephosphorisation ability and potential of CaO–FeO–Fe2O3–Al2O3–P2O5 slags during secondary refining process of molten steel based on ion and molecule coexistence theory

Thermodynamic models for predicting phosphorus distribution ratio LP and phosphate capacity of CaO–FeO–Fe2O3–Al2O3–P2O5 slags during secondary refining process of molten steel, according to the ion and molecule coexistence theory (IMCT), i.e. IMCT–LP and IMCT– models, have been developed by coupling with the developed thermodynamic model for calculating the mass action concentrations Ni of structural units or ion couples in the slags, i.e. the IMCT–Ni model, based on the IMCT. The developed IMCT–LP and IMCT– models have been verified with the experimental results from the literature and the predicted results by the summarised five LP models and three models. Besides the total dephosphorisation ability and potential of the slags as LP and , the respective phosphorus distribution ratio LP,i and the respective phosphate capacity of six dephosphorisation products as P2O5, 3FeO·P2O5, 4FeO·P2O5, 2CaO·P2O5, 3CaO·P2O5 and 4CaO·P2O5 can also reliably be predicted by the developed IMCT–LP and IMCT– models. 3CaO·P2O5 accounts for 95.00% of dephosphorisation products com- pared with 5% for 4CaO·P2O5. The comprehensive effect of CaO + FetO, which can be described by the mass action concentration ratio , controls dephosphorisation ability and potential of the slags. An exponentially growing relationship of lg LP against slag oxidisation ability and slag basicity as the simplified complex basicity (%CaO)/[(%P2O5) þ (%Al2O3)] or optical basicity can be established for the slags in a temperature range from 1811 to 1927 K. However, a linearly increasing relationship of lg against slag oxidisation ability and the aforementioned two kinds of slag basicity can be correlated for the slags in the lower temperature range from 1811 to 1828 K and the middle temperature range from 1870 to 1876 K; an inversely asymmetrical U type relationship of lg against the aforementioned parameters can be observed for the slags in the higher temperature range from 1918 to 1927 K. The influences of the aforementioned parameters on dephosphorisation ability are significantly different from those on dephosphorisation potential of the slags.

Thermodynamic models for predicting dephosphorisation ability and potential of CaO–FeO–Fe2O3–Al2O3–P2O5slags during secondary refining process of molten steel based on ion and molecule coexistence theory

Thermodynamic models for predicting phosphorus distribution ratio LP and phosphate capacity of CaO–FeO–Fe2O3–Al2O3–P2O5 slags during secondary refining process of molten steel, according to the ion and molecule coexistence theory (IMCT), i.e. IMCT–LP and IMCT– models, have been developed by coupling with the developed thermodynamic model for calculating the mass action concentrations Ni of structural units or ion couples in the slags, i.e. the IMCT–Ni model, based on the IMCT. The developed IMCT–LP and IMCT– models have been verified with the experimental results from the literature and the predicted results by the summarised five LP models and three models. Besides the total dephosphorisation ability and potential of the slags as LP and , the respective phosphorus distribution ratio LP,i and the respective phosphate capacity of six dephosphorisation products as P2O5, 3FeO·P2O5, 4FeO·P2O5, 2CaO·P2O5, 3CaO·P2O5 and 4CaO·P2O5 can also reliably be predicted by the developed IMCT–LP and IMCT– models. 3CaO·P2O5 accounts for 95.00% of dephosphorisation products com- pared with 5% for 4CaO·P2O5. The comprehensive effect of CaO + FetO, which can be described by the mass action concentration ratio , controls dephosphorisation ability and potential of the slags. An exponentially growing relationship of lg LP against slag oxidisation ability and slag basicity as the simplified complex basicity (%CaO)/[(%P2O5) þ (%Al2O3)] or optical basicity can be established for the slags in a temperature range from 1811 to 1927 K. However, a linearly increasing relationship of lg against slag oxidisation ability and the aforementioned two kinds of slag basicity can be correlated for the slags in the lower temperature range from 1811 to 1828 K and the middle temperature range from 1870 to 1876 K; an inversely asymmetrical U type relationship of lg against the aforementioned parameters can be observed for the slags in the higher temperature range from 1918 to 1927 K. The influences of the aforementioned parameters on dephosphorisation ability are significantly different from those on dephosphorisation potential of the slags.