The Observation of Mold Flux Crystallization on Radiative Heat Transfer

Abstract

As an important factor in the moderation of heat transfer in continuous casting mold, mold flux has been researched widely. However, the study of the effect of solid mold flux on radiative heat transfer has not been conducted widely. By using an infrared radiation emitter, which was developed at Carnegie Mellon University, a radiative heat flux was applied to a copper mold to simulate the heat transfer phenomena in continuous casting. The effect of adding a thin slag disc on top of copper mold on radiative heat transfer has been analyzed. It was found that the presence of mold flux enhanced radiative heat transfer rate. The effect of full crystallization of a slag disc was to reduce the heat transfer rate by 20 % compared with a completely glassy sample. The specific effect of full crystalline and glassy parts of the mold flux on radiative heat transfer, and the influence of their properties on heat transfer rate was discussed in this paper.

Radiative Heat Transfer Behavior of Mold Fluxes for Casting Low and Medium Carbon Steels

“…6 and 7 are higher than the bare copper system, which confirmed that the solid mold flux film does enhance the radiative heat transfer rate in continuous casting. 21) An optical-process model to study the radiation energy through the solid mold flux layer to copper mold has been previously developed by Wang and Cramb, 11) and Eq. (3) was given to compute the part of the radiation transferred through the solid flux to the mold, as follows:…”

“…[9][10][11] Furthermore, some research has focused on the study of crystal compounds such as, cuspidine (Ca4Si2O7F2), which is the dominant phase in the crystalline flux films. [12][13][14] Since cuspidine is the primary crystalline phase in almost all commercial mold fluxes; controlling the crystallization of cuspidine is a key component in adjusting the horizontal heat flux.…”

Study of Shell-Mold Thermal Resistance: Laboratory Measurements, Estimation from Compact Strip Production Plant Data, and Observation of Simulated Flux-Mold Interface

“…[22][23][24][25] In the sandwiching methods, measures are taken to establish linear temperature gradients through the measuring system, which consists of hot body, mold flux film, and cold body. This requires that the heating source, simulating the strand, has sufficient power to balance the heat extracted by a water-or air-cooled body simulating the mold and that steady-state conditions are established.…”

“…[22][23][24][25] It was reported that the optical properties among various mold fluxes, for low-and medium-carbon steels, are similar and that the larger radiative heat flux passing through low-carbon steel slags is due to the increase in thickness ratio of molten to crystalline layer. [22] The authors reported that in the molten layer the ratio of radiative to total heat flux amounts to around 40 pct and that in the crystalline layer this ratio is just 7 pct when the total thickness of the flux film is 1.5 mm.…”

“…[22] In another study, where the slag disk was on top of a water-cooled Cu finger, it was reported that full crystallization of the slag disk reduced the heat-transfer rate by 20 pct compared with a completely glassy disk. [23] The reflectivity caused by scattering of radiation at crystal grain boundaries was pointed out as an efficient factor for reducing radiation heat transfer, and thus it was indicated that the heat transfer across the mold flux film is primarily dominated by thermal conduction. [26] Most of the studies regarding the influence of mold powders on heat transfer in the continuous casting mold were concerned with conventional slab casting.…”