Abstract
Spray cooling is a key technology in the continuous casting process and has a marked influence on the product quality. In order to obtain the heat transfer characteristics, which are closer to the actual continuous casting to serve the design, prediction and simulation, we created an experimental laboratory setup to investigate heat transfer characteristics of air mist spray cooling during the continuous casting secondary cooling process. A 200-mm thick sample of carbon steel was heated above 1000 °C, and then cooled in a water flux range of 0.84 to 3.0 L/(m2∙s). Determination of the boundary conditions involved experimental work comprising an evaluation of the thermal history and the heat flux and heat transfer coefficient (HTC) at the casting surface using inverse heat conduction numerical schemes. The results show that the heat fluxes were characterized via boiling curves that were functions of the slab surface temperatures. The heat flux was determined to be 2.9 × 105 W/m2 in the range of 1100 to 800 °C with a water flux of 2.1 L/(m2∙s). The critical heat flux increased with the increase of water flux. The HTC was close to a linear function of water flux. We also obtained the relation between the HTC and the water flux in the transition boiling region for surface temperatures of 850 to 950 °C.
Highlights
In continuous casting, molten steel is poured from a tundish into a water-cooled mould and a partially solidified billet or slab is withdrawn from the bottom of the mould
Precise temperature measurement was a key for a reliable heat transfer measurement [20]
A short distance from the cooling surface to the holes was required to reduce the time delay as the thermocouples responded to the changes in surface heat flux
Summary
Molten steel is poured from a tundish into a water-cooled mould and a partially solidified billet or slab is withdrawn from the bottom of the mould. In the secondary cooling zone, the heat transfer behavior of the billet or slab surface is directly linked to the characteristics of the spray. These can be manipulated to control the solidification process, and in turn the billet or slab quality and the casting productivity. Horský et al [10] developed experimental methods and numerical models for spray-cooled surface heat transfer Those papers discussed heat transfer during spray cooling and optimization of the cooling process. The objective was to explore and obtain data that characterized heat transfer at high temperatures using multiple air mist spray nozzles. The calculated temperature profile, heat flux and HTCs provided insight and useful data for the development of cooling strategies for continuous casting
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