Refining Slag Composition Research Articles

Effect of Refining Slag Composition on the Cleanliness of Oriented Silicon Steel

To improve the cleanliness of oriented silicon steel, industrial experiments are performed under different refining slag composition conditions. The results show that the use of medium‐basicity refining slag (w(CaO)/w(SiO2) = 2.3–2.6, w(CaO)/w(Al2O3) = 2.3–2.6) results in higher steel cleanliness with lower Al2O3 volume fraction, and smaller inclusions. In addition, the thermodynamic equilibrium between the oriented silicon steel slag and the molten steel is investigated at a temperature of 1873 K (1600 °C) to understand the effect of different slag compositions on the oxygen content and Al2O3 absorption capacity. Furthermore, a mathematical model is introduced to describe the behavior of inclusions at the steel–slag interface as well as to predict the removal of oxide inclusions during the slag‐refining process. The experimental and predicted results for inclusion removal after slag refining are in good agreement.

Microstructure, thermal stability and soft magnetic properties of Fe81B10P8Cu1 amorphous/nanocrystalline alloy refined by slags with low basicity

The amorphous/nanocrystalline duplex structure is stable and exhibits excellent soft magnetic properties. However, the presence of impurities inevitably impacts the performance of the products. In this work, the impact of refining slags with various basicities (R=1, 0.66, 0.5, 0.4) on the microstructure, thermal stability, and soft magnetic properties of Fe81B10P8Cu1 alloy was investigated by varying the composition ratio x:1:1 (x = 2, 3, 4, & 5) of B2O3:MnO:MgO. The utilization of refining slag with low basicity is beneficial for removing impurity, enhancing magnetic exchange interactions and reducing magnetic anisotropy in amorphous alloy, thereby improving its soft magnetic properties. Notably, when the refining slag composition of B2O3:MnO:MgO is 4:1:1, the Fe81B10P8Cu1 nanocrystalline alloy exhibits exceptional soft magnetic properties and the smallest grain size, with a Bs of 1.717 T, Hc of 3.85 A/m and an average grain size of 23.84 nm. These findings are significant for enhancing the performance of Fe-based nanocrystalline alloys.

Optimal Alkalinity Model of Ladle Furnace Slag for Bearing Steel Production Based on Ion–Molecule Coexistence Theory

The fatigue life of bearing steel is closely related to the total oxygen content (T(O)) of the liquid steel. In order to stably and effectively control the T(O) during the ladle furnace (LF) refining process, we established a calculation model of optimal alkalinity for the refining slag CaO–SiO2–Al2O3–MgO–FeO–CaF2 at 1853 K based on ion–molecule coexistence theory (IMCT). Here, the influencing factors are discussed. The results show that the maximum value of NFeO occurred when the optimal alkalinity was around five at varied FeO contents, and that the optimal alkalinity basically remained the same with changes in FeO content. With the increase of MgO content, the optimal alkalinity decreased. However, the change in the value of NFeO against the higher alkalinity was not obvious at a given MgO content. The effect of Al2O3 content on the optimal alkalinity was opposite to that of MgO. With the increasing Al2O3 content, the optimal alkalinity obviously increased, while the maximum value of NFeO occurred when the Al2O3 content varied from 35 wt% to 45 wt% at higher alkalinity. The higher w(CaO)/w(Al2O3) mass ratio had a distinct effect on the value of NFeO against alkalinity, while the effect of alkalinity on the value of NFeO was not obvious at a fixed CaF2 level. This optimal alkalinity model based on IMCT can provide a certain guiding role in the process of refining slag composition optimization and is conducive to effectively controlling total oxygen content in the refining process.

Evolution of inclusions in the whole process of GCr15 bearing steel

Inclusions have an important effect on the fatigue performance of bearing steels. Therefore, the study of the evolution of inclusions in the whole process and the reasonable control of inclusions (quantity, type, size, etc.) in steel can improve the production stability and fatigue performance of bearing steel. In this study, with the help of thermodynamic calculations and experimental studies, the evolution of the whole-process refining slag, oxygen and nitrogen content, and inclusions in bearing steel produced in a plant is systematically investigated. Overall, the refining slag composition of the refining process fluctuates less, and the oxygen content during LF refining and RH refining has been trending down, with an oxygen content of 5.7 × 10‒6 in the bearing steel billets. Although the cleanliness level is good for bearing steels, there is still room for improvement in refining slag composition, refining time, protected casting, and cut waste length.

Optimization of Refining Slag Composition and the Deoxidation Practice of Liquid Steel in BOF–CAS–CC Process

The cleanliness level in the slabs of micro-alloy structure steel produced in the BOF–CAS–CC process was studied by optimizing the compositions of molten steel and refining slag in trial heats. When the slag composition was controlled in the range of CaO = 45–53 wt%, Al2O3 = 28–32 wt%, SiO2 = 6–11 wt% and MgO = 5–10 wt% in CAS, the steel composition should be in the range of [Als] = 0.025–0.035 wt% and a[O] = 0.8–1.5 ppm. After CAS treatment without feeding calcium, the results showed that the removal ratio of total oxygen content increased to 61% and the nitrogen content decreased from 34 to 13 ppm in the improved process. The residual micro-inclusions in slabs mainly consisted of SiO2–Al2O3–TiO2 and sulfides, and the particle size was predominately below 5 μm.

Effect on cleanliness of molten steel with different refining slag systems for low alloy ship plate

To study the effect of refining slag on the compositions of molten steel and inclusions, the reaction between ship plate steel and different slag systems (slag A-CaO/Al2O3: 1.0, SiO2: 5 mass-% and slag B-CaO/Al2O3: 1.5, SiO2: 9 mass-%) was investigated by laboratory-scale high-temperature equilibrium experiments. Results showed that the desulphurisation capacity of the two slags was very similar, and the average sulphur content for both was 0.002 mass-% in steel, but the deoxidation capacity of slag B was slightly higher than slag A. The amount of inclusions <5 μm was more in steel balanced with slag B than in that balanced with slag A. To generate inclusions smaller than 5 μm, and spherical liquid CaO–MgO–Al2O3–SiO2 inclusions, and to decrease the T[O] (total oxygen) content in steel, refining slag composition should be: CaO/Al2O3 ∼ 1.5, and SiO2 ∼ 9 mass-%. Slag system optimisation can reduce or even eliminate calcium treatment during production. T[O] content in the slab could be controlled to 15–21 ppm, with typical micro-inclusions of ≤10 μm, and CaO–Al2O3–MgO and CaO–Al2O3–CaS systems in molten steel.

Optimization of Calcium Addition to High-strength Low-alloy Steels

Nozzle blockage is a common problem during continuous casting of Al-killed steel, and calcium treatment is widely used to resolve it. In consideration of the production costs, the technology of nonmetallic inclusion control was studied to optimize the Ca consumption. The proposed process of slag washing was employed, and the refining slag composition, deoxidation conditions and alloying systems were optimized. Using these measures, the steel cleanliness before Ca addition was improved significantly, and the corresponding Ca consumption was reduced. Moreover, the continuous casting could be conducted smoothly.

Improvement in castability of Al containing resulphurised free machining steel

During the continuous casting (CC) of Al containing resulphurised steel, the submerged entry nozzle is often clogged by high melting point inclusions such as MgO.Al2O3 spinel and CaS. Casting extended for only one to two heats before optimisation. The main objective of the present study is to improve the castability of this steel. A suitable refining slag composition was sought and designed thermodynamically, and a soft blowing system was improved for reducing the dynamics of steel–slag desulphurisation. An optimisation plant trial was conducted on a sequence with four heats. By adopting the optimised refining slag and improved soft stirring operation, the steel castability was improved and the number of CC heats of a single tundish was increased from 1–2 to more than 4.

Effect of slag composition on desulfurization and inclusion modification during ladle furnace refining

The influence of LF refining slag composition on desulfurization and inclusion modification was investigated through industrial experiments and thermodynamic analysis. The results show that the sulfide capacity decreases with the decrease in (%CaO)/(%SiO2) and (%CaO)/(%Al2O3) of the slag. The theoretical sulfur distributions agree well with the analysis results when the sulfide capacity is calculated by Zhang's model, but the theoret- ical sulfur distributions are higher than the analysis results when the sulfide capacity is calculated by the KTH model. During the LF refining process, inclusions are transformed from Al2O3 inclusions into CaO-MgO-Al2O3 system inclusions. Higher slag basicity results in higher CaO and MgO and lower Al2O3 content inclusions in molten steel at the end of the LF process.

Assessment of the Possibility of Utilising Waste Materials from the Aluminium Production in the Copper Alloys Refining Processes

Abstract The analysis of possibilities of utilising waste materials as equivalents of substances stimulating in copper alloys refining processes was presented. The results of thermogravimetric investigations determining the refining ability of the slag with the selected waste materials from the aluminium production were discussed. The possibility of optimisation of the refining slag composition on the basis of the Slag- Prop software was indicated.

Study on Refining Technology of Low-Sulfur Steel

In order to bring on the producing of low &amp; ultra-low sulfur steel and optimal control of refining slag composition and property converter tapping, slag oxidability and oxygen activity have been analyzed. In addition, optimal refining slag composition and adding process, adding system of modifying agent and bottom argon-blowing in ladle were researched as well. On this basis, refining process of low-sulfur steel has been optimized. The results show that sulfur content in steel is as low as 6.6×10-6~40×10-6，which achieved the production of low sulfur steel.

Effect of Refining Slag on the Inclusions of Hard Wire Steel during Melting Process

The effect of the refining slag composition on the total oxygen content and inclusions in steel was investigated in 100 t UHP Electric Furnace – LF – Billet CC process. The test steel was 77B hard wire steel and Si-Mn alloy was used as the deoxidizer. Three types slag were used in the industrial tests, which including CaO-CaF2, CaO-CaF2 adding CaC and CaO-Al2O3 refining slag. The results shown that the lowest total oxygen contents of rolled bar can be gained using the CaO-CaF2 refining slag adding CaC, which is 0.0036%, while the total oxygen contents of rolled bar using CaO-Al2O3 refining slag is higher a little than the heats using CaO-CaF2 refining slag. The CaO-SiO2 and CaO-Al2O3-SiO2 compound inclusions with the size of about 5 μm are the main inclusions in the heats refining by the CaO-CaF2 refining slag in the rolled bar, but the pure, indeformable Al2O3 inclusion can also be found with the size of about 10 μm. The CaO-Al2O3-SiO2 and Al2O3-SiO2-MnO compound inclusions are the main inclusions in the heats refining by the CaO-CaF2-CaC refining slag, but most of the inclusion shape is irregular with bigger size of about 10 μm. Similar with the heat using CaO-CaF2 refining slag, the pure Al2O3 inclusion with edge angle can be found in the rolled bar. The inclusions in the rolled bar treated by CaO-Al2O3 refining slag are CaO-Al2O3-SiO2 compound inclusions, most of which are nearly globular shape with the relative small size of about 5 μm. All of the inclusions in rolled bar lie on the low melting zone in the CaO-Al2O3-SiO2 ternary phase diagram in the heats using CaO-Al2O3 refining slag. The similar condition appeared on the most of the inclusions in the heats using CaO-CaF2 and CaO-CaF2 refining slag adding CaC, while part of which are lied on the high melting zone. Therefore, considering of the plastic deformation ability, the CaO-Al2O3 refining slag is the best slag for the melting process of hard wire steel.

Effect of Refining Slag Composition on Inclusions in Molten Steel treated by Barium‐bearing Alloy

AbstractThe effect of the refining slag composition on the inclusions in molten steel was studied in MgO crucible by using MoSi2 furnace. The experimental steel was heavy rail steel and Si‐Ca‐Ba alloy was used as the deoxidizer. The results showed that the total oxygen content of steel, and the total quantities, total areas and average radius of inclusions decreased with the increased basicity of refining slag. The total quantities and total areas of inclusions were the least when Al2O3 content in refining slag was between 13% and 20%, while the proportion of small inclusions increased when Al2O3 content was higher than 20%. The contents of SiO2 and Al2O3 in inclusions were affected directly by the SiO2 and Al2O3 contents in refining slag, and it was very remarkble when the slag composition was CaOAl2O32SiO2. Therefore, it's feasible to control the composition of inclusions by controlling the composition of refining slag.