Papers by Keyword: Unidirectional Solidification

Abstract: In this paper, by using the commercial finite-element software of ProCAST, unidirectional solidification processes in 23t steel ingot were simulated. Emphasis is placed on analysis of required time for complete solidification of steel ingot and temperature distribution about ingot and side wall during the solidification process. By comparing simulation values and measured values of side wall during the solidification process, the simulated results conclusively demonstrate that our developed model is feasible and valuable.

Abstract: The temperature-induced liquid-liquid structural transition has been observed and testified in different kinds of alloys. The effect of liquid-liquid transition on the morphology of solid/liquid interface was investigated by means of the unsteady-state unidirectional solidification. The results showed that the interface instability of Sn-1wt.%Pb was developed after the liquid structural change, which suggested that the solute distribution coefficient decreased due to the structural change of liquid Sn-1wt.%Pb and the solute on the frontier of solid/liquid interface enriched.

Abstract: The interface pattern of Zn-5wt%Al alloy was investigated during unidirectionally solidification with different withdrawal rate and superheat degree. It was showed that the pattern of liquid/solid interface varied with withdrawal rate and superheat degree. While the superheat degree of alloy melt was low and the withdrawal rate was increased, the change of interface pattern was the same as the normal change of interface pattern. While the superheat degree of alloy melt was high and the withdrawal rate was increased too, the change of interface pattern was different. As a result, the pattern and stability of liquid/solid interface was chosen by withdrawal rate and superheat degree mainly.

Abstract: Much attention has been paid to unidirectionally solidified ceramic composites as candidates for high-temperature structural materials. We have recently developed potential ceramic eutectics, which are named Melt Growth Composites (MGC). The Al₂O₃/GAP(GdAlO₃) binary MGC has a novel microstructure, in which continuous networks of single-crystal Al₂O₃ phases and single-crystal GAP phases interpenetrate without grain boundaries. Chain structure in the Al₂O₃/GAP binary system is formed due to the frequent branching of both phases resulted in the entangled structure. Therefore, the Al₂O₃/GAP binary MGC has excellent high-temperature characteristics in the air atmosphere at very high temperatures. In the paper, high temperature strength, thermal stability of microstructure and strength, and fracture toughness of the Al₂O₃/GAP binary MGC are reported.

Abstract: Unidirectional solidification technology is a producing process of cast large-sized ingots industry and control the single orientation microstructure of solidification. Combined with the conditions of production, casting the 23t ingot of unidirectional solidification for experiment, we made numerical simulation of the 23t unidirectional solidification ingot with MARC; these are consistent with the result of experiment, and testified the simulation is feasible, offered gist for the design of the mould and casting, and took on reference to the product field.

Abstract: Unidirectional solidification is a method of producing slab ingot for special heavy plate, when compression radio is more than 2.5, internal soundness of slab ingot is assurance, and the nature of Z orientation and percent of pass through supersonic flaw detecting are increased. Products are used in oil drilling platform in ocean ,separator of steam turbo-alternator with more than 0.6 million kW, anchor gate of large-scale hydropower station, shell of nuclear power plant, armoured plate of aircraft carrier. According to dissection on 28t large-sized slab ingot, simulation experiment of crystal, and analogy calculation of heat transfer and coagulation with CFX software, histology features and key to manufacturing technology of large-size unidirectional solidification slab ingot were mastered.

Abstract: Thin walled copper tube is prepared in vacuum melting and argon protecting continuous unidirectional solidification equipment by a short process method. The size of the thin walled copper tube is ф39×1.8 mm. The effect of process parameters on the solidification structure and the surface quality of the thin walled copper tube is investigated. The mechanical properties and electrical properties are tested and analyzed. The results show that the thin walled tube with columnar crystal structure and good quality surface can be obtained continuously and stably under the most appropriate process of the melting temperature is between 1423K and 1453K, the cooling water volume is 0.2～0.5m3•h-1, the cooling distance is 50mm, the drawing speed is not higher 20m•h-1. The elongation can reach 60%, and conductivity can reach 102.6%IACS.

Abstract: In this study, the influence of pulling velocity on temperature field, fluid field and grain structure of a unidirectionally solidified superalloy DZ417G cylindrical casting was investigated by using a 3D cellular automaton finite element (CAFE) model within commercial software CALCOSOFT. The predictions show that temperature distribution in the casting is well in accordance with the experiment result. The solidification front and fluid field are sensitive to changes in pulling velocity. And the pulling velocity should be controlled less than 0.5 mm/s in our experiment so as to effectively decrease the grain number and mean grain deviation.

Abstract: Lotus-type porous iron was fabricated by continuous zone melting technique through thermal decomposition of chromium nitride(Cr1.18N). Nitrogen dissolves into the molten iron through thermal decomposition of Cr1.18N. When the molten iron is solidified in one direction, insoluble nitrogen forms the directional gas pores aligned along the solidification direction. The porosity increases with increasing transfer velocity. For most of lotus metals fabricated by pressurized gas method, the porosity does not change with the transfer velocity owing to constant gas solubility in liquid and solid phase. On the other hand, the porosity of lotus metal fabricated by thermal decomposition method depends on the transfer velocity. This difference is attributed to the decomposition behavior of gas compound dependent upon the heating rate.

Abstract: Lotus-type porous aluminum was fabricated by continuous casting technique in mixture gas of hydrogen and argon at various transfer velocities in order to understand formation process of pores. The porosity and pore diameter decrease with increasing transfer velocity. The transfer velocity dependence of the porosity in lotus aluminum is different from that in other lotus metals such as stainless steel and copper. It is considered that the difference is attributed to lower solubility in aluminum than that in other metals.