18. El-Mahallawy, N.A., Assar, A.M., “Metal–Mold Heat Transfer Coefficient Using End-Chill Experiments”, Journal of Materials Science, vol. 7, no. 3, pp. 205-208 (1988).
19. Hallam, C.P., Griffiths, W.D., “A Model of Interfacial Heat Transfer Coefficients for the Aluminum Gravity Die Casting Process,” Metallurgical and Materials Transactions B, vol. 35, no. 4, pp.721-733 (2004).
20. Santos, C.A. Quaresma, J.M.V., Garcia, A, “Determination of Transient Interfacial Heat Transfer Coefficients in Chill Mold Castings,” Journal of Alloys and Compounds, vol. 319, issues 1-2, pp. 174–186 (2001).
21. Mortensen, D., “A Mathematical Model of the Heat and Fluid Flows in Direct-Chill casting of Aluminum Sheet Ingots and Billets,” Metallurgical and Materials Transactions B, vol. 30, no. 1, pp. 119-133 (Feb. 1999).
22. Nguyen, T. et al., “Heat Transfer in Permanent Mold Casting,” Proceedings from Materials Solutions Conference, ASM International, pp. 191-197 (12-15 Oct. 1998).
23. Mortensen, D., Henriksen, B.R., M’Hamdi, M. and Fjær H.G., “Coupled Modeling of Air-Gap Formation and Surface Exudation During Extrusion Ingot DC- Casting,” D.H. DeYoung editor, Light Metals 2008, vol. 2, pp. 773-779.
Technical Review and Discussion
Developing a Localized Squeeze Cooling Technique for Improved Casting Solidification D.P.K. Singh, V. Navaneeth, J. R. Lee, CAMTEC, Centre for Advanced Manufacturing Technology, School of Engineering, Auckland University of Technology, New Zealand
Reviewer: It appears that the authors estimated uniform HTC distribution in the interface between copper chill and casting during inverse calculation and simulation. If it is the case, the authors should explain clearly in the manuscript.
Authors: During casting simulation, the temperature of the mold and chill, water flow rate and melt temperature were maintained constant. Different interfacial heat transfer coefficients were calculated to fit the experimentally mea- sured temperature profiles with simulated temperature. This method of calculating heat transfer coefficients is explained under the Computer simulation section. However, the heat flow from the casting to the mold walls and chill housing were assumed to be adiabatic to simplify the calculations.
Reviewer: It appears that the parameter that the researchers are using to judge productivity is time to 540 °C, and figure 19 seems to indicate a three way tie between trials 1, 3, and 4. Authors should comment on whether a simple chill with
no movement and no water cooling is just as effective as the two moving chill scenarios. In sand casting, chills are normally employed at room temperature. In permanent mold dies with water cooling, the passages are normally run un- der PLC control and the overall die temperature will be sig- nificantly above room temperature and cooling passages are typically used to drive directional solidification as much as to decrease cycle time. Some addition to the discussion sec- tion to review these scenarios in light of their results would enhance the value of the paper
Authors: The solidus temperature of the alloy used was 560 °C. The temperature 540 °C was chosen as the temperature slightly below which the casting can be ejected out of the mold during production cycle. The comparison was made between the scenario 1, 3 and 4 with scenario 2 at 540 °C. Scenario 1 (no cooling medium) is equally competitive with movable chill with cooling conditions. However it can be seen from figure 19 that the chill in scenario 1 does not dissipate the heat after 500 sec compared to the movable chills with cooling medium. This would have a wider impact of overheating the dies or creating a higher temperature operating zone for the die. In PM casting dies the cooling circuits are run to remove the heat not only from the casting but also from the die surround- ings. The chills without cooling medium effectively removes the heat from the casting initially but is ineffective in reducing the surrounding die temperature. The paper has been modi- fied to explain this in more detail.
International Journal of Metalcasting/Spring 11
79
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88