Study of Solidification and Heat Transfer Behavior of Mold Flux Through Mold Flux Heat Transfer Simulator Technique: Part II. Effect of Mold Oscillation on Heat Transfer Behaviors

Abstract

Mold flux solidification and heat transfer experiments under both non-oscillation and oscillation modes have been conducted and compared with the help of Mold Flux Heat Transfer Simulator (MFHTS) technique. The results suggested that the steady-state responding heat flux in the mode of oscillation is smaller than that in non-oscillation operation, and a transition time is observed in the responding temperature and heat flux profiles during the oscillation experiments. The oscillation of mold would introduce the roughness of slag film surface and the enlargement of air gap at the interface of mold/flux film; thus, the interfacial thermal resistance was enhanced. In addition, the thermal conductivity of solid crystalline mold flux and mold/flux film interfacial thermal resistance at steady state were calculated in this work. The thermal conductivity of crystalline mold flux was about 1.43 to 1.76 W m À1 K À1 , and the interfacial thermal resistance R int in oscillation operation was calculated as 17.3 to 22.5 9 10 À4 m 2 (K W À1 ) in the measured region. The obtained interfacial thermal resistance R int in this work is higher than that in non-oscillation operations.

Mold Simulator Study of Heat Transfer Phenomenon During the Initial Solidification in Continuous Casting Mold

“…[52][53][54][55] However, all above techniques for the measurement of thermal resistance cannot represent the real scenario of continuous casting mold where the mold/slag thermal resistance varies with the position below the meniscus. A pilot caster [2,56] had been used to investigate the heat transfer across the slag film, while the thermal resistance of slag film along the casting direction was difficult to be calculated due to the complex and transient heat transfer in the vicinity of the meniscus.…”

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

“…[19] In experiments where the finger included oscillation, the estimated interfacial thermal resistance reached slightly higher values, up tõ 2.25 9 10 À3 m 2 K/W. [9] Apparently, oscillation of the mold caused a rougher surface of the slag layer in contact with the copper finger. An experimental apparatus for simulating the initial solidification of a low-carbon steel produced a slag film, between the mold and the shell, with thickness in the range of 1.4 to 2.4 mm.…”

“…[5,6] Through the liquid and solid layers, heat is transferred by conduction and radiation and reaches the mold by conduction through an air gap that is claimed to form between the solid layer and the mold. [7][8][9] Normally, it is stated that the gap arises because the crystalline phase has a higher density than the glass, and therefore crystallization results in shrinkage of the solid flux layer. [10,11] In an investigation carried out to determine the surface roughness of solidified mold fluxes, it was found that this was in the range of 10 to 30 lm, when the crystalline phase precipitated; [12] this surface roughness was claimed to agree with the calculated thickness of the air gap assumed to form between the mold and the solidified slag layer.…”

“…For studying heat transfer, different methods were devised and, according to their experimental principles, were classified into three categories: (1) sandwiching a mold slag layer between hot and cold solid walls, [7,[14][15][16][17] (2) dipping a cold finger into molten slag [8,9,18,19] or into a bath of molten slag and steel, [20,21] and (3) exposing a mold slag layer to infrared radiation. [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.…”

“…[7,[15][16][17] Cold finger dipping methods deal with freezing a slag shell over a cold body that is immersed into a molten bath and with recording of temperatures, at certain locations, as a function of time. [8,9,[18][19][20][21] The temperature data obtained are converted to heat flux values by solving a one- [9,18,19] or two-dimensional [20] inverse heat conduction problem. In the earlier study, it was reported that for a given composition the effective thermal conductivity was a strong function of superheat and that at high temperatures the dominant heat-transfer mechanism is radiation conduction.…”