| 1. |
- Holmberg, N. Anders, et al.
(författare)
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Analysis of the motion of a flat jet in a direct strip casting feeding system
- 1998
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 69:1, s. 17-21
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Tidskriftsartikel (refereegranskat)abstract
- The motion and shape of a vertically falling flat rectangular jet of liquid metal issuing from an inclined plane is analysed numerically and analytically. The jet is affected by surface tension and gravity. The main interest in this problem originates from the technological application of the direct strip casting process, which is a novel process to cast steel strips in a thickness range from 2 to 15 mm with a minimum or no hot-rolling. In this process the liquid metal is fed onto a single endless horizontal belt that runs between two rollers. The bottom of the belt is cooled by water. One of the techniques to feed the liquid metal is down an inclined plane Due to disturbances in the flow, for instance slag in the liquid metal, the jet issuing from the inclined plane may split into two or several jets. The large convergence of the individual jets causes an unfavourable non uniform distribution of the liquid metal over the belt. In the analysis of the present paper it is shown, using an expansion in the inverse Froude number, that the convergence of a single jet depends to zero order on the inverse square root of the Weber number We'[l/2]= (y/(p[wo][2] lt))[1/2]. Small convergence of the jet is found for large Weber numbers, which can be accomplished with a large initial velocity w[o].
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| 2. |
- Holmberg, N.A.
(författare)
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Distribution of metal onto the belt of a horizontal strip caster
- 1998
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 69:1, s. 22-27
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new method for metal distribution onto the belt of a horizontal single belt strip caster. Water and liquid tin have been used to study the flow conditions in the feeding zone on the conveyor belt. Tests of a method presented in literature for metal distribution have been conducted and a new method that uses multiple parallel jets in order to obtain stable feeding conditions have been tested. This method gives a controlled way of maintaining a continuous liquid film and it also has a stable meniscus. The freezing problem with a triple point will also be eliminated by use of this method.
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| 3. |
- Nedar, Lotta
(författare)
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Dust formation in a BOF converter
- 1996
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 67:8, s. 320-327
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Tidskriftsartikel (refereegranskat)abstract
- Four dust forming mechanisms can be considered in a BOF converter: ejection of metal, ejection of slag, entrainment of charged material and vaporization. In order to determine the importance of the four dust forming mechanisms and to characterise dust, with special emphasis to zinc, the off-gas from a 100-t BOF was sampled during twenty seven heats. The sampling equipment allows the sampling of both solid dust particles and vaporized elements. Samples from the first and the second part of blowing show significant differences both in chemical composition and in the origin of formation. The major dust formation mechanism is the ejection of metal and slag, respectively. Entrainment of solids plays an important role only during the first part of blowing. Vaporization of elements from the bath is most important during the end of blowing. The formation of dust is influenced by process operation control, especially lance position, silica contents and time of charging of slag formers. Zinc is mostly found on the rim of ejected particles where a gradual transition of zinc oxide to zinc ferrite to iron oxide is found. At sampling temperatures of 800-1000°C most of the zinc had already condensed. (
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| 4. |
- Nurni, Viswanathan, et al.
(författare)
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Estimation of escape rate of volatile components from slags containing CaF2 during viscosity measurement
- 1999
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 70:2, s. 53-58
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Tidskriftsartikel (refereegranskat)abstract
- In continuous casting process, the viscosity of the mould powder/flux has direct impact on the size of the gap between the mould wall and the solidified shell, which in turn affect the heat transfer characteristics between the metal and the mould. Numerous experiments have been conducted to determine the viscosity of various mould powders using rotation cylinder method. The pre-melting of the mould powder as well as the viscosity measurement are carried out in a cylindrical crucible placed in a tubular furnace with constant argon flow to maintain inert atmosphere. One of the main difficulties encountered during viscosity measurement is the liberation of volatile fluorides, which in turn changes the flux composition, and consequently the viscosity of the flux. Thermodynamic calculations have shown that SiF4 and HF are major constituents of the volatile matter. Present study aims to estimate the liberation rate of SiF4 and HF from flux samples during viscosity measurement by computing the detailed gas flow pattern inside the tubular furnace. The gas flow pattern is computed by solving momentum and continuity of equations. Further, the effect of argon gas flow rate and slag level in the crucible on liberation rate has been studied to arrive at proper experimental conditions during viscosity measurement.
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| 5. |
- Nurni, Viswanathan, et al.
(författare)
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Mathematical modelling of divided blast cupola
- 1997
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 68:5, s. 192-197
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Tidskriftsartikel (refereegranskat)abstract
- A pseudo 2-D mathematical model has been developed to simulate a cupola with one row and two rows of tuyère. The simulation results predicted higher spout temperature and combustion ratio for cupola with two rows of tuyère compared to that with one row. Further, the model has been used to study the effect of the distance of separation between the two rows of tuyère on cupola performance. The computed results shows that the spout temperature increases with tuyère level separation and attains the maximum at an optimum distance of separation between two rows of tuyère. Above the optimum, the spout temperature starts decreasing. The exit gas temperature and combustion ratio increases monotonously with the increase in tuyère level separation. These results agree well with the reported experimental observations. The mechanism behind the improved cupola performance with two rows of tuyère has been deduced from the computed temperature and composition profiles inside the cupola.
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| 6. |
- Yang, Qixing, et al.
(författare)
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Effects of bubble expansion on wear of refractory for BOF stirring plugs embedding tuyères
- 1997
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 68:3, s. 107-114
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Tidskriftsartikel (refereegranskat)abstract
- Single tuyere wear tests of MgO-C and burnt magnesia bricks were performed to study relations between tuyere characteristics and refractory wear parameters, with emphasis on the wear zone geometry. Either Ar or N2 was used as injected gas and the test temperature for liquid metal was 1400, 1550 and 1700 °C. A bubble expansion wear mechanism was proposed for the mechanical wear of tuyere refractory by comparison of bubble radii and the wear zone geometry of refractory bricks and H3BO3 disks. Equations are derived to predict the deep and shear wear zone radii and the refractory wear rate at values of the nominal Mach number up to one. These equations can be used for an optimum design of single- and multiple-tuyere plugs for combined blowing BOF, as well as for optimization of gas stirring operation to reduce the wear of MgO-C refractory around the tuyere and for the plugs.
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| 7. |
- Zuo, Guangqing, et al.
(författare)
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Some applications of neural networks for prediction of blast furnace irregularities
- 1998
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Ingår i: Steel research. - : Wiley. - 0177-4832. ; 69:2, s. 41-48
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Tidskriftsartikel (refereegranskat)abstract
- The on-line analysis of operational data and prediction of furnace irregularities, though difficult, are essential for the improvement of the control of blast furnace operation. Three models based on artificial neural networks for the recognition of top gas distribution, distributions of the heat fluxes through the furnace wall, and for the prediction of slips have been designed. The off-line test results showed that a trained perceptron network could recognize various types of top gas profiles. A classifier consisting of a self-organizing feature map network and a learning vector quantizer could classify the characteristic patterns of heat flux distribution; and a model based on a back propagation network could properly predict the probability of upcoming slips in advance. The most important operational variables needed for predicting slips have also been extracted. It has been proved that the neural network used has a good capability of predicting furnace irregularities.
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