Study of Calcium Treatment in Steel Ladles for the Modification of Alumina Inclusions to Avoid Nozzle Clogging during Casting

2020 ◽  
Vol 978 ◽  
pp. 12-20
Author(s):  
Sujata Devi ◽  
R.K. Singh ◽  
Niladri Sen ◽  
N. Pradhan
Keyword(s):  
Volume Fraction ◽  
Submerged Entry Nozzle ◽  
Steel Ladle ◽  
Liquid Inclusion ◽  
Ladle Furnace ◽  
Calcium Treatment ◽  
Total Oxygen ◽  
Nozzle Clogging ◽  
Calcium Addition ◽  
Casting Nozzle

Presence of non-metallic inclusion deteriorates quality of steel and causes nozzle clogging during casting. Nozzle clogging eventually leads to a disruption of normal casting operations. This happens when solid alumina inclusions get accumulate in the nozzle of submerged entry nozzle (SEN). Therefore, it is required to understand the inclusion characteristics (shape, size and chemistry), which forms during the steelmaking process. Calcium is added in the steel ladle furnace (LF) in the form of CaSi wire to modify inclusions and to desulphurize steel. The range in which all the oxides become liquid and no solid sulphides begin to form is regarded as the "optimum window" or “liquid inclusion window” for calcium treatment. It is a target to obtain this calcium addition window, during calcium addition in the ladle furnace. This window mainly depends on the sulfur and total oxygen contents of the liquid steel bath. In the present study, inclusions characteristics such as volume fraction of inclusions, inclusion rating and EDS analysis of inclusions has been carried out using SEM-EDS. Thermodynamic study is carried out using thermodynamic software FACTSAGE and databases to find out formation of various calcium aluminates and the precipitation of CaS. Results show that liquid inclusion window mainly depends mainly on the sulphur level, total oxygen and aluminum content in the steel. These windows will help in calculation of calcium addition range for optimizing the addition of calcium in the ladle. These nomograms have been validated with actual plant condition to reduce the nozzle clogging during continuous casting.

scholarly journals Dependence of the Clogging Possibility of the Submerged Entry Nozzle during Steel Continuous Casting Process on the Liquid Fraction of Non-Metallic Inclusions in the Molten Al-Killed Ca-Treated Steel

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1205
Author(s):  
Weifu Li ◽  
Yi Wang ◽  
Weijian Wang ◽  
Ying Ren ◽  
Lifeng Zhang
Keyword(s):  
Liquid Fraction ◽  
Submerged Entry Nozzle ◽  
Casting Process ◽  
Liquid Inclusion ◽  
Inclusion Composition ◽  
Casting Condition ◽  
Nozzle Clogging ◽  
Liquid Phases ◽  
Metallic Inclusions ◽  
Inclusion Zone

In the current study, the nozzle clogging behavior and inclusion composition in Al-killed Ca-treated steels were observed to investigate the relationship between the liquid fraction of non-metallic inclusions and the clogging possibility of the submerged entry nozzle. Clogging materials were mainly MgO-Al2O3 with less than 20% liquid phases, while most of the inclusions were full liquid CaO-Al2O3-MgO in tundish at the casting temperature. Thus, it was proposed that the nozzle clogging can be effectively avoided by modification of solid inclusions to partial liquid ones rather than full liquid ones. There was a critical value of liquid fraction of inclusions causing the nozzle clogging. A critical condition of the inclusion attachment on the nozzle wall was a function of cosθN−S+cosθI−S<0. With the increase of T.Ca content in steel, the evolution route of inclusions was solid MgO-Al2O3→liquid CaO-Al2O3-MgO→solid CaS and CaO. To avoid the clogging of the submerged entry nozzle (SEN) under the current casting condition, the appropriate T.Ca concentration range in Al-killed Ca-treated steels can be enlarged from the 100% liquid inclusion zone of 10–14 ppm to the 20% liquid inclusion zone of 4–38 ppm.

scholarly journals The Influence of Technological Parameters of X70 Stainless Steel Ladle Refining on the Residual Content of Non-Metallic Inclusions

2015 ◽  
Vol 15 (3) ◽  
pp. 5-10
Author(s):  
A. Babanin ◽  
O. Babanina ◽  
V. Bilousov ◽  
B. Komarov ◽  
D. Pashchuk ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Residence Time ◽  
Steel Ladle ◽  
Minor Effect ◽  
Ladle Furnace ◽  
Technological Parameters ◽  
Residual Content ◽  
Secondary Refining ◽  
Metallic Inclusions ◽  
Dynamic Forces

Abstract It is demonstrated that during secondary refining at the ladle furnace the carbon content of steel and the residence time of the metal in the ladle exert a significant impact on the residual content of non-metallic inclusions (NMI) in steel. Mathematical calculations showed that the dynamic forces have minor effect on the motion of small sized NMI, making it difficult to penetrate deep into the slag.

Effect of reoxidation on inclusions in steel during calcium treatment

2019 ◽  
Vol 116 (2) ◽  
pp. 206 ◽  
Author(s):  
Ming Li ◽  
Yang Liu ◽  
Lifeng Zhang
Keyword(s):  
Contact Angle ◽  
Sulfur Content ◽  
Molten Steel ◽  
Driving Force ◽  
Calcium Content ◽  
Slag Layer ◽  
Calcium Treatment ◽  
Total Oxygen ◽  
Limited Degree ◽  
Inclusions In Steel

In the current study, the effect of reoxidation on inclusions during calcium treatment was studied via adding Fe2O3 into a Al-killed molten steel at 1 min after the addition of calcium. The total oxygen (T.O.) content increased from 10 to 24 ppm just after the reoxidation occurred, while it finally decreased to 14 ppm since inclusions were floated to the top of the steel and absorbed by the formed slag layer. The increased T.O. favored the decomposition of CaS, especially for the heat with high sulfur contents. The vaporization of calcium, which leads to the decrease of calcium content, is the driving force for the evolution of inclusions from CaO-CaS-(Al2O3) to CaO-Al2O3-(CaS) due to the limited degree of reoxidation. The contact angle between inclusions and the molten steel increased with the increase of Al2O3 in calcium alumina, which favored the removal of inclusions. Increased sulfur content decreased the surface tension of molten steel, which led to remove less inclusions since the contact angle between inclusions and the molten steel was decreased. Thus, more inclusions were measured in heats with higher sulfur content.

scholarly journals Characteristics of Inclusions in Low Carbon Al-Killed Steel during Ladle Furnace Refining and Calcium Treatment

2013 ◽  
Vol 53 (8) ◽  
pp. 1401-1410 ◽  
Author(s):  
Wen Yang ◽  
Lifeng Zhang ◽  
Xinhua Wang ◽  
Ying Ren ◽  
Xuefeng Liu ◽  
...  
Keyword(s):  
Ladle Furnace ◽  
Low Carbon ◽  
Calcium Treatment

Operating conditions for the lining of a steel ladle in a ladle-furnace unit at the MMP Istil (Ukraine) Joint-Stock Co.

2004 ◽  
Vol 45 (5) ◽  
pp. 312-316
Author(s):  
G. I. Kas’yan ◽  
A. Ya. Mints ◽  
N. A. Belomerya ◽  
S. M. Fesenko
Keyword(s):  
Furnace Unit ◽  
Operating Conditions ◽  
Steel Ladle ◽  
Ladle Furnace

Determination of defects on a processed disc from S355J2 steel

2015 ◽  
Vol 6 (5) ◽  
pp. 605-616
Author(s):  
Theofani Tzevelekou ◽  
Spyros Papaefthymiou ◽  
Vasiliki Panteleakou ◽  
Athanasios Vazdirvanidis ◽  
Dimitris C. Papamantellos ◽  
...  
Keyword(s):  
Submerged Entry Nozzle ◽  
Nozzle Clogging ◽  
Cause Analysis ◽  
Content Type ◽  
Edx Analysis ◽  
Root Cause ◽  
Microstructure Observation ◽  
Steel Making ◽  
Quality Degradation ◽  
Furnace Steel

Purpose – A failed disc that was forged from S355J2 round bar was investigated in order to determine the failure route cause. The purpose of this paper is to determine the defects and route cause analysis regarding their origin. Design/methodology/approach – Macroscopic evaluation, microstructure observation using light optical metallography and scanning electron microscopy with EDX analysis were the techniques used to analyse and characterize the defected areas. Findings – Macro-inclusions (up to 850 µm) that correspond to high melting aluminium rich calcium-aluminate particles were detected. Their formation, possibly due to improper calcium treatment during ladle furnace steel refining process might be associated with clogging problems at casting. SEM-EDX analysis revealed whitish spots containing Zr that could be related to submerged entry nozzle (SEN) erosion/breakage. Characteristic is the large size and unusual shape of the traced particles, as well as the presence of low Si, Na, K. The findings indicated that nozzle clogging and/or breakage at casting was most possibly the root cause of the product’s quality degradation. Originality/value – After extended root cause analysis, specific countermeasures are proposed to avoid clogging phenomena. The suggestions are based on the findings taking into account restrains of the steel-making process. Emphasis was laid in detecting the weaknesses that lead to product quality degradation and consequently in optimizing the steel-making process. Such incidents are often found during steelmaking a useful suggestion to steelmakers is to mark and remove cast parts after SEN problems are encountered. In this way quality issues in intermediate and/or final products will be avoided.

scholarly journals Fibre Bridging and Nozzle Clogging in 3D Printing of Discontinuous Carbon Fibre Reinforced Polymer Composites: Coupled CFD-DEM Modelling

2021 ◽  
Author(s):  
Hao Zhang ◽  
Lixing Zhang ◽  
Haoqi Zhang ◽  
Jiang Wu ◽  
Xizhong An ◽  
...  
Keyword(s):  
3D Printing ◽  
Polymer Matrix ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Length ◽  
Fibre Volume ◽  
Nozzle Clogging ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

Abstract A coupled multiphase model based on computational fluid dynamics (CFD) and discrete element method (DEM) is developed to numerically investigate the extrusion-based 3D printing process of discontinuous carbon fibre reinforced polymer composites. Short carbon fibres are modelled as rigid bodies by clumping discrete spheres in DEM, while polymer matrix is treated as an incompressible Newtonian fluid in CFD. A fluid-particle interaction model is adopted to couple DEM and CFD and represent the dynamic fibre/matrix interaction. Collisions between fibres are considered naturally in DEM by using the Hertz-Mindlin contact law. The coupled CFD-DEM is validated, both qualitatively and quantitatively, against X-ray microtomography (µCT) experimental results for the T300/PA6 composite. Parametric study on various fibre lengths, fibre volume fraction and resin viscosity using the CFD-DEM model shows that the nozzle clogging tends to occur when the fibre length and/or the fibre volume fraction are increased. Use of a polymer matrix with a lower viscosity can be effective to eliminate the clogging issue when printing composites with relatively short fibres. The fibre length is dominating when long fibres are used and the clogging is largely independent on the viscosity of the polymer matrix. Finally, a potential solution of using a cone sleeve insert located above the shrinking region to address the nozzle clogging issue is proposed and numerically assessed.

scholarly journals The Use of Barium and Calcium Alloys in the Ladle Furnace Treatment of Selected Grades of Continuously Cast Steels

2015 ◽  
Vol 60 (1) ◽  
pp. 281-288 ◽  
Author(s):  
W. Derda ◽  
P. Lawenda ◽  
P. Pardela
Keyword(s):  
Ladle Furnace ◽  
Total Oxygen ◽  
Finished Steel ◽  
Cast Steels ◽  
Furnace Treatment ◽  
Metallic Inclusions ◽  
Before And After ◽  
Continuously Cast ◽  
The Subject ◽  
Refining Time

AbstractThe subject of the paper are the results of laboratory and industrial investigations into the use of Si - Ca - Ba alloys for modifying non-metallic inclusions. Based on laboratory tests, the morphology and chemical composition of non-metallic inclusions in carbon steel were examined before and after refining with the use of the above-mentioned alloy as a refining addition. In particular tests, variable additions of the alloy were used at a constant refining time and temperature.Comparison of the process of casting of a sequence of seven heats of the same steel grade using the stopper system in the tundish was made under industrial conditions. In these heats, additions of Si - Ca (three heats) and Si - Ca - Ba (four heats) were introduced as a non-metallic inclusion modifier in the form of core wires during the process in the ladle furnace. For the investigated heats, the contents of total oxygen and calcium were assayed in the finished steel. A significant effect of the simultaneous addition of barium and calcium on steel castability, and thus on the process of continuous casting of the investigated heats, was found.

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