W pracy tej przedstawiono przemysłowe wyniki oceny efektywności zastosowania żużli syntetycznych podczas obróbki pozapiecowej stali w zakładzie VÍTKOVlCE HEAVY MACHINERY a.s. Celem badań był a ocena ...wpływu brykietówanych i spiekanych żużli syntetycznych opartych na AI2O3 - na przebieg odsiarczania stali i żużla podczas produkcji i obróbki stali 42CrMo4. zgodnie z technologią EAF → LF → VD. Podczas eksperymentów w zakładzie, monitorowano podstawowe parametry wpływające na odsiarczania stali i żużla: stopień odsiarczania, zasadowość, zawartość tlenków łatwo redukowałnych, stosunek CaO/Al2O3 oraz indeks Mannesniann’a. Uzyskane wyniki pozwoliły na porównanie stopnia odsiarczania stali w kontekście zastosowanych żużli. Wykazano, że syntetyczny żużel składający się z brykietowanej mieszaniny wtórnego korundu, może zastąpić syntetyczny żużel otrzymywany ze spieku mieszaniny surowców naturalnych.
The cleanliness of ultrahigh-strength steels (UHSSs) without and with electroslag remelting (ESR) using a slag with the composition of 70% CaF2, 15% Al2O3, and 15% CaO was studied. Three experimental ...heats of UHSSs with different chemical compositions were designed, melted in an induction furnace, and refined using ESR. Cast ingots were forged at temperatures between 1100 and 950?C, air cooled, and their non-metallic inclusions (NMIs) were characterized using field emission scanning electron microscopy and laser scanning confocal microscopy. Thermodynamic calculations for the expected NMIs formed in the investigated steels with and without ESR were performed using FactSage 7.2 software while HSC Chemistry version 9.6.1 was used to calculate the standard Gibbs free energies (?G?). As a result of ESR the total impurity levels (TIL% = O% + N% + S%) and NMI contents decreased by as much as 46 % and 62 %, respectively. The NMIs were classified into four major classes: oxides, sulphides, nitrides, and complex multiphase inclusions. ESR brings about large changes in the area percentages, number densities, maximum equivalent circle diameters, and the chemical composition of the various NMIs. Most MnS inclusions were removed although some were re-precipitated on oxide or nitride inclusions leading to multiphase inclusions with an oxide or nitride core surrounded by sulphide, e.g. (MnS.Al2O3) and (MnS. TiN). Also, some sulphides are modified by Ca forming (CaMn)S and CaS.Al2O3. Some nitrides like TiN and (TiV)N are nucleated and precipitated during the solidification phase. Al2O3 inclusions were formed as a result of the addition of Al as a deoxidant to the ESR slag to prevent penetration of oxygen to the molten steel.
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The influence of boron oxide B
2
O
3
and the basicity of CaO–SiO
2
–B
2
O
3
–Al
2
O
3
slag on the saturation concentration of magnesium oxide MgO is studied by means of simplex experiment-design ...lattices. That permits the formulation of mathematical models describing the dependence of the specific property on the composition in the form of a continuous function. Synthetic slags corresponding in composition to the vertices of the given simplex are produced in graphite crucibles from preroasted analytically pure oxides. The slag compositions corresponding to the other points of the local simplex design are obtained by cross-mixing of the slags at the vertices. The experimental data provide the basis for mathematical models describing the influence of the slag composition on the saturation concentration of magnesium oxide MgO. The results of mathematical modeling are presented as a graph of the slag composition against the saturation concentration of magnesium oxide MgO. By analysis of the results, new information is obtained regarding the influence of the boron oxide and the basicity of CaO–SiO
2
–B
2
O
3
–Al
2
O
3
slag on the saturation concentration of magnesium oxide MgO. It is found that, for slags formed in regions of basicity 2—3 with 1–3% B
2
O
3
, the saturation concentration of magnesium oxide MgO varies from 3 to 9%. Increase in the B
2
O
3
content to 4% increases the saturation concentration of magnesium oxide MgO to 11–13%. Switching to slags of basicity 3–4 lowers the saturation concentration of magnesium oxide MgO to 2–5% with 1–3% B
2
O
3
and to 7–9% with 3–4% B
2
O
3
in the slag. Slag formation in the region of basicity 4–5 with 1–3% B
2
O
3
does not significantly decrease the saturation concentration of magnesium oxide in the slag. In this basicity range, the saturation concentration of magnesium oxide MgO in the slag varies from 2 to 4% and hardly reaches 7% with increase in B
2
O
3
content to 4%. In that case, the cost of the steel rises, on account of the increase in the consumption of lime and the material containing B
2
O
3
.
The paper summarises experience with using synthetic slags on the CaO - Al2O3 oxide basis in the technological flow of the oxygen converter steelworks in TŘINECKÉ ŽELEZÁRNY, a.s. These slags are used ...as an alternative to slags containing fluorspar which unfavourably affects both the service life of ladle linings and the steelwork's working environment. The content gives the first knowledge of using the Refraflux type synthetic slag to desulphurize steel, and it also provides a basic statistical evaluation of the heat produced.
W pracy podsumowano doświadczenia z użyciem żużli syntetycznych bazujących na tlenkach CaO - Al2O3 w technologii dmuchu tlenu w konwertorze stalowni TŘINECKÉ ŽELEZÁRNY, a.s. Żużle te są stosowane jako alternatywa dla żużli zawierających fluoryt, które niekorzystnie wpływają zarówno na żywotność wyłożenia kadzi i środowisko pracy stalowni. Artykuł przedstawia pierwsze doświadczenia z wykorzystaniem syntetycznych żużli typu Refraflux do odsiarczania stali, a także podstawowe dane statystyczne wytopu.
The viscosity of CaO-SiO
2
-Al
2
O
3
slags with 8% MgO and 4% B
2
O
3
is investigated over a broad range of composition, by means of a simplex-lattice experiment design. For slag of basicity 6–8 in ...the upper left region of the local simplex, with 15–25% Al
2
O
3
, 8% MgO, and 4% B
2
O
3
, the viscosity is high: 9.4–26.4 P over the range 1500–1530°C. Displacement of the slags of basicity 5–8 to the lower region of the local simplex ensures high fluidity in the given range of Al
2
O
3
concentration: the viscosity is 1.5–6.1 P over the range 1500–1530°C.
This paper presents the industrial results of evaluation of efficiency of synthetic slags during the treatment of steel at the equipment of the secondary metallurgy under conditions of the steel ...plant VÍTKOVICE HEAVY MACHINERY a.s. The aim of the heats was to assess the influence of the briquetted and sintered synthetic slags based on Al
aiming the course of the steel desulphurization and slag regime during the production and treatment of steel grade 42CrMo4 with the technology EAF→LF→ VD. Within the plant experiments, basic parameters influencing the steel desulphurization and slag regime were monitored: desulphurization degree, basicity, content of easily reducible oxides, proportion of CaO/Al
and Mannesmann’s index. Obtained results allowed to compare the steel desulphurization and to evaluate the slag regime. It was proved that the synthetic slag presenting the briquetted mixture of secondary corundum raw materials can adequately replace the synthetic slag created from the sintered mixture of natural raw materials.
W pracy tej przedstawiono przemysłowe wyniki oceny efektywności zastosowania żużli syntetycznych podczas obróbki pozapiecowej stali w zakładzie VÍTKOVlCE HEAVY MACHINERY a.s. Celem badań był a ocena wpływu brykietówanych i spiekanych żużli syntetycznych opartych na AI
- na przebieg odsiarczania stali i żużla podczas produkcji i obróbki stali 42CrMo4. zgodnie z technologią EAF → LF → VD. Podczas eksperymentów w zakładzie, monitorowano podstawowe parametry wpływające na odsiarczania stali i żużla: stopień odsiarczania, zasadowość, zawartość tlenków łatwo redukowałnych, stosunek CaO/Al
oraz indeks Mannesniann’a. Uzyskane wyniki pozwoliły na porównanie stopnia odsiarczania stali w kontekście zastosowanych żużli. Wykazano, że syntetyczny żużel składający się z brykietowanej mieszaniny wtórnego korundu, może zastąpić syntetyczny żużel otrzymywany ze spieku mieszaniny surowców naturalnych.
The control of inclusions in tire cord steels and techniques used in the production process are extensively reviewed. Inclusion and segregation requirements for the tire cord steel are discussed. The ...deformability of an inclusion is significantly affected by its Al2O3 content. Inclusions containing 20% Al2O3 has best deformability. The undeformable inclusions can be avoided by controlling the dissolved aluminum in the steel. Low basicity slags favour the generation of deformable inclusions. When the basicity R (=CaO/SiO2) = 0.8‐1.5, the dissolved aluminum in the steel should be 1‐5ppm to achieve 20% Al2O3 in inclusions. With R=1.0‐1.4, in order to control Al in the range of 1‐5ppm, the slag should contain approximately 8% Al2O3. The technologies to control inclusions in tire cord steels are reviewed including steel deoxidizer choice, steel refining method, slag carry over from BOF to the ladle, ladle stirring practice, control of nitrogen pickup and caster curvature. Control methods to decrease the central segregation in the tire cord steel are briefly reviewed, such as electromagnetic stirring during continuous casting.
The effectiveness of a ladle refining process for production of tool steel with focus on the top slag is studied using computational thermodynamic calculations. The theoretical assessment was based ...on compositional data of steel and slag samples collected during trials in a plant equipped with a 65‐t EAF, a ladle furnace and a vacuum degasser. The calculation of slag‐metal equilibrium during ladle treatment was performed for top slag excluding (Case A) and including (Case B) slag carryover and deoxidation products. The predictions showed that slag carryover and deoxidation products in the ladle significantly affect the composition of the top slag. Thus, these conditions must be taken into consideration when predicting the actual top slag composition. It was also found that it is possible to predict the final aluminium and sulphur content in steel based on the same calculation approach.
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