Aluminium and Al–4·5Cu alloy end chill: structural observation and heat flow analysis

El‐Mahallawy, N. A.; Taha, M. A.; Assar, A. M.; Hamouda, Rawia M.

doi:10.1179/026708393790172321

Cited by 3 publications

(2 citation statements)

References 4 publications

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“…One group of scientists performed extensive examination of end-chill directional solidification of Al-Cu alloys and reported the following effects of a higher melt superheat (50 to 200 K): a higher heat-transfer coefficient in the liquid state, a smaller air gap, a longer local solidification time, a larger columnar-grain zone, and faster growth of columnar grains. [10,11,12] Contrasting results are given by Ferreira et al [13] for upward unidirectional solidification of an Al-6.2 pct Cu alloy superheated by 20 to 110 K. They claim that the heat-transfer coefficient between the molten metal and the mold decreases with increasing melt temperature. As a result of the correspondingly slower solidification, the mushy zone becomes thicker and the inverse macrosegregation more severe.…”

Section: Introductionmentioning

confidence: 78%

Effects of melt temperature and casting speed on the structure and defect formation during direct-chill casting of an Al-Cu alloy

Eskin¹,

Savran²,

Katgerman

2005

Metall Mater Trans A

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A thorough experimental investigation of the effects of melt temperature and casting speed on the structure and defect formation during the steady and nonsteady stages of direct-chill (DC) casting of an Al-2.8 pct Cu alloy is performed. In addition, the temperature and melt-flow distributions in the sump of billets cast at different melt temperatures are numerically simulated and used in the discussion on the experimental results. Apart from already known phenomena such as the coarsening of the structure, deepening of the sump, and increased probability of bleed-outs during DC casting with increased casting temperature, a few new observations are made. The increased melt temperature is shown to increase the severity of subsurface segregation, whereas the macrosegregation in the rest of the billet remains virtually unaffected. Hot-tearing susceptibility is strongly diminished by an increased melt superheat. The amount and distribution of "floating" grains is demonstrated to depend on both the melt temperature and the casting speed. The porosity was found to only slightly depend on the melt temperature. The amount of nonequilibrium eutectic in the center of the billet increases with increasing melt temperature. The effects of melt temperature on the dimensions of the sump, transition region, and mushy zone and on the melt-flow pattern in the sump are discussed and used in the interpretation of experimentally observed phenomena.

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Section: Introductionmentioning

confidence: 78%

Effects of melt temperature and casting speed on the structure and defect formation during direct-chill casting of an Al-Cu alloy

Eskin¹,

Savran²,

Katgerman

2005

Metall Mater Trans A

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“…The IHTC was usually determined by using an inverse approach, which aims at minimizing the difference between the measured and simulated temperatures. For the sand and gravity die-casting process, extensive work has been performed for the determination of the IHTC and many factors were found to have an influence on the value of the IHTC, including the die coatings (material and thickness), [4][5][6][7][8][9][10][11][12][13] the die material and preheating, [1,[14][15][16][17] the casting size, [15,18] the application of pressure, [19][20][21][22][23] the orientation of the casting with respect to gravity, [1,15,24] the alloy composition, [14][15][16]25,26] and the surface roughness of the die. [7,14,[27][28][29][30] The heat transfer in HPDC process is different from most of the conventional casting processes.…”

Section: Introductionmentioning

confidence: 99%

Effect of Process Parameters, Casting Thickness, and Alloys on the Interfacial Heat-Transfer Coefficient in the High-Pressure Die-Casting Process

Guo

Xiong

Liu

et al. 2008

Metall Mater Trans A

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The heat transfer at the metal-die interface is believed to have great influence on the solidification process and cast structure of the high-pressure die-casting (HPDC) process. The present article focused on the effects of process parameters, casting thickness, and alloys on the metal-die interfacial heat-transfer coefficient (IHTC) in the HPDC process. Experiment was carried out on a cold-chamber die-casting machine with two casting alloys AM50 and ADC12. A special casting, namely, ''step-shape'' casting, was used and cast against a H13 steel die. The IHTC was determined using an inverse approach based on the temperature measurements inside the die. Results show that the IHTC is different at different steps and changes as the solidification of the casting proceeds. Process parameters only influence the IHTC in its peak value, and for both AM50 and ADC12 alloys, a greater fast shot velocity leads to a greater IHTC peak value at steps 1 and 2. The initial die surface temperature has a more prominent influence on the IHTC peak values at the thicker steps, especially step 5. Results also show that a closer contact between the casting and die could be achieved when the casting alloy is ADC12 instead of AM50, which consequently leads to a higher IHTC.

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Measurements, simulations, and analyses of instantaneous heat fluxes from solidifying steels to the surfaces of twin roll casters and of aluminum to plasma-coated metal substrates

Guthrie

Isac

Kim

et al. 2000

Metall Mater Trans B

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Using implanted thermocouples, and an inverse heat-transfer technique, heat fluxes and associated heat-transfer coefficients during the solidification of steel in a pilot scale 0.6-m-diameter twin roll caster, whose copper contact surfaces had been treated with a propriety coating, were measured. It was found that heat fluxes during initial contact of liquid steel with the rolls were low, rising to maximum values of about 5 to 6 MW per square meter halfway down the sump of liquid steel, but then diminishing toward zero as the strip approached the roll nip. These results corresponded to roll speeds of some 7 m/min, strip thicknesses of 7 mm, and a roll separating force of 20 kN. For higher speeds and thinner strip, a secondary peak in the heat flux was observed. Associated microstructures revealed acicular ferrite, large prior austenite grains, and secondary dendrite arm spacings in keeping with measurements.In parallel experiments simulating a single belt horizontal caster, heat fluxes from strips of various aluminum alloys to coated and uncoated steel and copper substrates were measured. Under these conditions, peak heat fluxes were recorded during the period of initial contact, and depending on the coating characteristics, these reduced to a lower plateau before declining, or continuously decreased toward zero, corresponding to complete solidification of the strip. A theoretical analysis of the maximum heat-transfer rates that can be expected given perfect thermal contact of metal with the rolls, and its moderations by gas films, and substrate coatings illustrates the dominant role of the gas film and the need for dynamic heat flux measurements for quantitative modeling of fluid flows and solidification phenomena in thin strip casting operations. A model for air gap formation is proposed, based on viscous laminar flows within the gas films. Predicted thicknesses are in reasonable accord with those deduced on the basis of heat flux measurements.

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Aluminium and Al–4·5Cu alloy end chill: structural observation and heat flow analysis

Cited by 3 publications

References 4 publications

Effects of melt temperature and casting speed on the structure and defect formation during direct-chill casting of an Al-Cu alloy

Effects of melt temperature and casting speed on the structure and defect formation during direct-chill casting of an Al-Cu alloy

Effect of Process Parameters, Casting Thickness, and Alloys on the Interfacial Heat-Transfer Coefficient in the High-Pressure Die-Casting Process

Measurements, simulations, and analyses of instantaneous heat fluxes from solidifying steels to the surfaces of twin roll casters and of aluminum to plasma-coated metal substrates

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