Secondary cooling in continuous casting and Leidenfrost temperature effects

Raudenský, Miroslav; Horský, Jaroslav

doi:10.1179/174328105x15913

Cited by 45 publications

(32 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For the calculation of h s , it has been assumed that the slab surface temperature is always above Leidenfrost temperature 54) in the spray zone. At high temperature, the cooling water forms a stable film on the slab surface which protects the surface from the direct contact with the coolant.…”

Section: 75mentioning

confidence: 99%

Three Dimensional Turbulent Fluid Flow and Heat Transfer Mathematical Model for the Analysis of a Continuous Slab Caster

Shamsi

Ajmani

2007

ISIJ International

View full text Add to dashboard Cite

Continuous casting of slab caster of Tata Steel has been simulated using a three dimensional mathematical model based on considerations of fluid flow, heat transfer and solidification for better understanding of the process. Liquid metal comes in the mould by bifurcated nozzle. The principal model equations are momentum and heat balances. In various zones, different standard boundary conditions have been used. In the mould region, Savage and Prichard expression for heat flux has been used. In the spray cooling zone, heat transfer coefficient for surface cooling of the slab has been calculated by knowing the water flow rate and nozzle configuration of plant. The turbulence in the molten metal has been modelled by the Realizable k-e model. CFD software (Fluent) has been used for the solution of equations to predict the velocities in the molten pool of the slab, temperature of the entire volume of the slab, heat transfer coefficient in the mould region, heat flux in the spray and radiation region and shell thickness. The variables studied are different casting speed.KEY WORDS: slab caster; turbulence; solidification; shell profile; CFD; radiation cooling; spray cooling; heat flux; heat transfer coefficient; mathematical modelling; steel casting; realizable k-epsilon model. ISIJ International, Vol. 47 (2007), No. 3, pp. 433-442 433 © 2007 ISIJ austenite-ferrite phase transformation, which is accompanied by a sizeable volume change should not occur. To meet the above criteria, after certain length of spray cooling, the strand is allowed to be radiant cooled. The dimensions of the caster are given in Table 1. The spray zone length has been sub divided into six regions for flexibility of cooling. The first is spray ring region (Zone 0) just after the mould and having only water flow. In the narrow face of the slab, the spray ring region (Zone 0 N&S) is also having only water flow. After this region, there is no forced cooling on the narrow face. After spray ring region other spray zones are named as 1A, 1B, Zone 2, Zone 3, Zone 4 and Zone 5 as mentioned in Table 1. Slab cast should be free from surfaces and internal cracks. For a given composition of steel, solidification in the slab casting will depend on fluid flow and heat transfer in different zones. In the mould region, the total heat transfer can be easily obtained by knowing difference of temperature between the inlet and the outlet of water passing through mould cooling jacket and its flow rate. Theoretically, it is difficult to get the heat transfer along the mould length because of air gap formation between mould and slab, resistance of heat flow due to shell formation, mould plate, water-copper plate, thermal contraction of slab and mould plate, bulging due to liquid height pressure.2-6) Singh and Blazek 7) have experimentally measured the heat transfer profile along the mould length by using a bench scale casting facility. Mould was stationary, unlike the actual caster. They have shown the effect of carbon content, casting speeds, pouring practice, mou...

show abstract

Section: 75mentioning

confidence: 99%

Three Dimensional Turbulent Fluid Flow and Heat Transfer Mathematical Model for the Analysis of a Continuous Slab Caster

Shamsi

Ajmani

2007

ISIJ International

View full text Add to dashboard Cite

show abstract

“…Bendig et al [14] indicated that the parameter that controlled heat transfer intensity above Leidenfrost temperature, i.e., within the film boiling regime, was the kinetic energy of drops, which is influenced by p a . In another work, Raudensky and Horsky [15] also reported that the heat transfer is influenced not only by w but that d and v also played significant roles. Even, it was indicated that the heat transfer coefficient was affected by the casting velocity, arguing an effect of the motion of the hot surface on the flow of liquid on it and on the formation of vapor in front and behind the impinging jet; however, no direct evidence of such claims was provided.…”

mentioning

confidence: 95%

Heat Transfer and Observation of Droplet-Surface Interactions During Air-Mist Cooling at CSP Secondary System Temperatures

2015

Metall Mater Trans B

View full text Add to dashboard Cite

Air-mists are key elements in the secondary cooling of modern thin steel slab continuous casters. The selection of water, W, and air, A, flow rates, and pressures in pneumatic nozzles open up a wide spectrum of cooling possibilities by their influence on droplet diameter, d, droplet velocity, v, and water impact flux, w. Nonetheless, due to the harsh environment resulting from the high temperatures and dense mists involved, there is very little information about the correlation between heat flux extracted, Àq, and mist characteristics, and none about the dynamics of drop-wall interactions. For obtaining both kinds of information, this work combines a steady-state heat flux measuring method with a visualization technique based on a high-speed camera and a laser illumination system. For wall temperatures, T w , between~723 K and~1453 K (~450°C and~1180°C), which correspond to film boiling regime, it was confirmed that Àq increases with increase in v, w, and T w and with decrease in d. It should be noticed, however, that the increase in w generally decreases the spray cooling effectiveness because striking drops do not evaporate efficiently due to the interference by liquid remains from previous drops. Visualization of the events happening close to the surface also reveals that the contact time of the liquid with the surface is very brief and that rebounding, splashing, sliding, and levitation of drops lead to ineffective contact with the surface. At the center of the mist footprint, where drops impinge nearly normal to the surface those with enough momentum establish intimate contact with it before forming a vapor layer that pushes away the remaining liquid. Also, some drops are observed sliding upon the surface or levitating close to it; these are drops with low momentum which are influenced by the deflecting air stream. At footprint positions where oblique impingement occurs, frequently drops are spotted sliding or levitating and liquid films flowing in from inner positions are seen generating vapor cushions after having stayed in contact with the surface. Visualization of events taking place under high,~500 kPa, and low,~200 kPa, air nozzle pressure, p a , conditions suggests that the considerably larger heat extraction obtained under high p a is related to more frequent impingement of finer and faster drops that result in the formation of a dense fog of tiny secondary drops that moves tangentially close to the surface.

show abstract

“…Since it is not possible to determine the intensity of the air-water jets on an actual caster, it is necessary to transfer the investigation -of each jet individually -to the experimental laboratory device (Figure 4), which is capable of simulating the surface of a concast slab [8][9][10][11]. This device also allows the measurement of temperatures beneath the surface within the slab.…”

Section: Measuring Of Cooling Effect Of Nozzlesmentioning

confidence: 99%

Importance of the experimental investigation of a concasting technology

et al. 2018

View full text Add to dashboard Cite

Abstract. The solidification and cooling of a continuously cast billet, slab or cylinder, generally of a concasting and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving of such a problem is impossible without numerical models of the temperature field of the concasting itself which it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optímization of the process procedure: real process  input data  numerical analyses  optimization  correction of real process. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling.

show abstract

Secondary cooling in continuous casting and Leidenfrost temperature effects

Cited by 45 publications

References 4 publications

Three Dimensional Turbulent Fluid Flow and Heat Transfer Mathematical Model for the Analysis of a Continuous Slab Caster

Three Dimensional Turbulent Fluid Flow and Heat Transfer Mathematical Model for the Analysis of a Continuous Slab Caster

Heat Transfer and Observation of Droplet-Surface Interactions During Air-Mist Cooling at CSP Secondary System Temperatures

Importance of the experimental investigation of a concasting technology

Contact Info

Product

Resources

About