Effects of substrate surface conditions on heat transfer and shell morphology in the solidification of a copper alloy

Abstract

The effect of substrate surface conditions on the heat transfer and morphology of solidifying shells of a copper alloy has been characterized by a series of dip tests. Results showed that in the early stages of solidification, rough and grooved surface conditions provide a greater heat transfer than polished ones. The shells solidified on rough and grooved surfaces had significant localized variations in thickness, indicating that heat transfer at the substrate-metal interface was not uniform. The implication of these results on strip casting is discussed.

Control of heat transfer and growth uniformity of solidifying copper shells through substrate temperature

“…work dealing with the surface condition of substrates in the T(N,t) ϭ T measured t Ն 0 [5] solidification of a copper alloy. [18] A special emphasis is…”

“…The coefficients were rithm utilized to solve the inverse heat-conduction problem, separated into two constituents, one for the substrate, the has been published elsewhere. [18] other for the solidified shell, [19][20][21][22] to determine which most The second step involved calculating the surface temperaaffected the heat flow.…”

“…This time corresponded the initial change in the slope (heating rate, in ЊC/s) provided by the thermocouples duce approximate solutions. [26] In addition, in this work, the number of future time steps [18,23,24] used to solve the inverse imbedded near the surface of the block. The entry temperature of the blocks varied between 25 ЊC and 350 ЊC.…”

“…[48] It is noted that the dendrites produced below 200 ЊC are coarser than those above this temperature, and this corroborates the results of Figure 7, since dendrite spacing is inversely proportional to the cooling rate. [48] In an earlier study on the solidification of a copper alloy, [18] it was shown that gains in heat flow produced by roughening or machining grooves on the substrates were at the expense of an uneven shell growth. The present results show that heat-flow intensity and uniformity can be simultaneously improved by increasing the temperature of the substrate.…”

“…The temperature range over which heattransfer enhancement occurred was between 450 ЊC and of an uneven solidification rate at the mold-metal interface and have been reported in other studies dealing with the 580 ЊC, and this coincided with the liquidus and solidus of the molten alloy. The transition at 200 ЊC observed here is solidification of alloys of copper, [18] aluminum, [45] and steel. [46,47] In twin-roll casting, a uniform growth is desired too low to be caused by a similar effect.…”