The use of water cooling during the continuous casting of steel and aluminum alloys

Abstract

In both continuous casting of steel slabs and direct chill (DC) casting of aluminum alloy ingots, water is used to cool the mold in the initial stages of solidification, and then below the mold, where it is in direct contact with the newly solidified surface of the metal. Water cooling affects the product quality by (1) controlling the heat removal rate that creates and cools the solid shell and (2) generating thermal stresses and strains inside the solidified metal. This work reviews the current stateof-the-art in water cooling for both processes, and draws insights by comparing and contrasting the different practices used in each process. The heat extraction coefficient during secondary cooling depends greatly on the surface temperature of the ingot, as represented by boiling water-cooling curves. Thus, the heat extraction rate varies dramatically with time, as the slab/ingot surface temperature changes. Sudden fluctuations in the temperature gradients within the solidifying metal cause thermal stresses, which often lead to cracks, especially near the solidification front, where even small tensile stresses can form hot tears. Hence, a tight control of spray cooling for steel, and practices such as CO 2 injection/pulse water cooling for aluminum, are now used to avoid sudden changes in the strand surface temperature. The goal in each process is to match the rate of heat removal at the surface with the internal supply of latent and sensible heat, in order to lower the metal surface temperature monotonically, until cooling is complete.

Effect of water flow rate, casting speed, alloying elements and pull distance on tensile strength, elongation percentage and microstructure of continuous cast copper alloys

“…It has also been previously reported that water flow rate is one of the main process parameters that can change upon direct chill casting because increasing the water flow in the mould increases the heat-transfer rate, and thereby decreases the mould temperature [15,16]. Water-cooling affects the product quality by (1) controlling the heat removal rate that creates and cools the solid shell and (2) generating thermal stresses and strains inside the solidified metal [17]. When the cooling rate is slow, some of the large clusters of atoms in the liquid develop interfaces and become the nuclei for the solid grains that are to form.…”

“…So water flow rate in continuous casting plays a key role in transforming heat from the mould and solidifying metal during the continuous casting of copper and copper alloys. It has also been previously reported that water flow rate is one of the main process parameters that can change upon direct chill casting because increasing the water flow in the mould increases the heat-transfer rate, and thereby decreases the mould temperature [15,16]. Water-cooling affects the product quality by (1) controlling the heat removal rate that creates and cools the solid shell and (2) generating thermal stresses and strains inside the solidified metal [17].…”

Effect of melt temperature, cleanout cycle, continuous casting direction (horizontal / vertical) and super-cooler size on tensile strength, elongation percentage and microstructure of continuous cast copper alloys

“…Melt superheating treatment is an effective method of refinement grain [13]. In the past decades, the effects of melt superheating on aluminium and Magnesium alloy have been studied [14,15].…”

The Effect of Thermophysical Parameters on Temperature Distribution in the Primary Cooling Zone

“…The application of numerical computing for the analysis and identification of the existing processrelated problem can lead to finding an appropriate solution. It results in an improvement of production and the quality of products [1][2][3][4][5][6][7][8][9][10][11][12]. For the continuous casting of steel, it could be analysis of the effect of the interaction between the solidifying metal and the mould wall, the effect of the mould powder, or the effect of the non-metallic inclusions.…”

“…Many numerical models of the continuous steel casting process used in numerical computations are based upon material parameter average values, i.e. specific heat, viscosity, density [2,[12][13][14][15][16]. The use of average values within such a broad temperature range leads to a significant increase in the numerical error concerning the calculated temperature distribution; this is the basis for computing thermal stresses, examining the mould taper, the steel flow within the mould, or predicting cast strand defects.…”