Cylindrical Ingots Research Articles

Solution of inverse problem of solidification of a cylindrical ingot

An inverse problem of heat conduction that involves determination of the density of boundary heat flux providing a prescribed velocity of solidification front motion is solved by an integral method.

連鋳鋳片の内部割れ発生機構

To clarify the mechanism of internal cracking in continuous casting, a series of tensile tests of cylindrical ingot with liquid core and internal cracking tests by intentional misalignment in continuous caster were carried out. By analysing the above experimental results with strain accumulation model, it wad found that internal cracking occurs and grows in the range where the total amount of strain given between ZST and ZDT exceeds the critical strain. Severe longer internal cracks which often generates in continuously cast strand is estimated to be caused with the development of solidification. To prevent internal cracking, not only suppression of each incremental strain, but the determination of casting condition and roll-lavout to suppress total amount of accumulated strain smaller, considering the range between ZST and ZDT is significant.

Upset forged Nd [sbnd]Fe [sbnd]B [sbnd]Cu magnets

Cylindrical ingots of the alloy Nd 17Fe 76.5B 5Cu 1.5 were upset forged in a crank press at an average strain rate of 0.8 s −1 at temperatures of 750, 850 and 950°C. Microstructural development and magnetic properties are treated in terms of the material flow during the semi-solid deformation of the alloy as a function of the forging temperature. The results indicate increasing microstructural inhomogeneity due to the compaction flow at higher forging temperatures.

Processing and properties of AlAl 2O 3 (TiO 2) in situ particle composite

Al-3 wt% TiO 2 particle composite was solidified in the form of a vertical cylindrical ingot to segregate the particles at the top. The machined surface of the ingot showed three regions with varied particle content. Coarse particles were segregated at the top and the particle density was greater at the top zone. The next zone, at the bottom of the ingot, contained less particles, whilst the rest of the ingot appeared to be free from particles. Voids were also present in the particle-enriched zones. The top zone of the composite fractured on hot rolling due to its greater particle content (a volume fraction of 0.10). The middle zone with a 0.05 volume fraction of particles, and the bottom zone, could be rolled successfully. The particle size and the inter-particle, distance reduced on hot rolling. The hardness and tensile strength of the coarse particle-enriched zone was less than that of the bottom part of the composite, as voids were also segregated into the former. The presence of fine Al 3O 3 particles without voids in the bottom part of the composite resulted in better mechanical properties.

Theoretical analysis and design considerations for float-zone refinement of electronic grade silicon sheets

The finite element method is used to solve a detailed model of heat and momentum transport in the vertical float-zone refinement of thin silicon sheets. The model formulation is much like that used to study float-zone refinement of cylindrical ingots, but the dominant physical mechanisms differ because of the much smaller length scale. The curvature of the meniscus remains nearly constant under all conditions due to the dominance of surface tension. The solid-liquid interface deviates considerably from a planar shape, contrary to the assumption of previous studies. The release and uptake of latent heat appear to play only minor roles in determining this shape, which results primarily from the sharp decrease of silicon emissivity upon melting. Strong flow in the melt due to the Marangoni effect is driven by large temperature gradients (O(100 K/cm)) at the melt surface, whereas buoyancy effects are negligible. Effective Reynolds numbers exceeding 10 3 are calculated. Multiple solutions are found under some circumstances. The different solution branches show little difference in the temperature field or free surface shape, but show a large difference in the flow field, which is likely to affect the redistribution of impurities. Transient calculations are used to determine the thickness variation of the sheet during the approach to steady state.

Fabrication of Small Aluminum Ingot by Electromagnetic Casting.

In this study, as the first step to explicate the fundamental phenomena of Electromagnetic Casting (EMC), we provided an electromagnetic force generated by an electric source of 20 kW, 3 kHz and a electromagnetic coil with 18 turns to the molten aluminum. After confirming a stable meniscus in the electromagnetic mold, the bottom block was drawn in vertical direction. And a cylindrical aluminum ingot which size can be varied from 30 to 60 mm in diameter was fabricated. This ingot has the luster and the smooth surface typical for EM cast. Microstructural observation showed that the secondary dendrite arm spacing was 6 to 8 μm.

New evaluation of critical strain for internal crack formation in continuous casting

In order to determine the critical conditions for internal crack formation, tensile tests of cylindrical ingots with liquid core have been carried out. It was found that internal cracking occurred in the solid-fraction range between 0.99 and 0.80 corresponding to zero ductility temperature (ZDT) and zero strength temperature (ZST) respectively, only when strain given in this range exceeded critical value (1.6 %). This critical value was not influenced by strain rate and manner of deformation. At a lower strain rate, successive strain which exceeded the critical value between ZDT and ZST made the cracks longer with solidification progress. New evaluation of strain for internal crack formation in a continuous casting strand was found out.

On the interfacial heat transfer coefficient for cylindrical ingot casting in a metal mould

On the interfacial heat transfer coefficient for cylindrical ingot casting in a metal mould

Simulation of solidification and viscoplastic stresses during vertical semicontinuous direct chill casting of aluminum alloy

Abstract A method to simulate temperature and stress fields in solidifying cylindrical ingots during the vertical semicontinuous direct chill casting process is presented in this paper. As the first approximation of the whole process, a steady state in the casting ingot with enough length is examined, and the steady heat conduction equation with heat generation due to solidification incorporated with material flow is solved by the finite element method. Based on the obtained temperature distribution, elastic-viscoplastic stresses were also calculated to obtain residual stresses. Here, material parameters appearing in the constitutive equation were determined by the data of tensile stress-strain curves under some strain rates at several temperature levels close to the melting temperature. Calculated temperature and residual stress fields were compared with the experimental data to verify the analytical procedure, and discussions are also given on the effect of operating conditions on the fields.

A numerical simulation of the D.C. continuous casting process including nucleate boiling heat transfer

The steady-state thermal problem associated with the direct-chill continuous casting of A6063 aluminum cylindrical ingots is solved using the numerical finite element technique. Excellent correlation is demonstrated between the numerical model and experimental data from ingots cast at two different speeds. By application of the model, effective heat transfer coefficients are calculated as a function of vertical position on the outside surface of the ingot. It is shown that direct application of these coefficients to the modeling of different casting situations will produce substantial errors in the region in which heat transfer is by nucleate boiling. Using theories of nucleate boiling with forced convection and film cooling, a method is developed to calculate the external boundary conditions in the submold region of the ingot, thus making it possible for the first time to define explicitly all of the thermal boundary conditions associated with this casting configuration. These theories are incorporated into the numerical model, and a subsequent simulation shows excellent agreement with experimental data from a third ingot.

Investigation of metal flow in open-die forging with different die and billet geometries

Axisymmetric upsetting and plane-strain analyses have been performed with the finite-element method to predict the press loads and material flow when forging with different die and billet (or ingot) geometries. The calculated press load and final billet geometry compare well with the values from an actual hot upset-forging operation. The billet geometries investigated were cylindrical, octagonal and rectangular prismatic bars, whilst the die geometries studied were flat dies, double-V dies (135°), TFBV (Top Flat Bottom V) dies, and FML (Free of Mannesmann Effect at Lower Press Loads) dies. In order to determine the effect of billet- and tool-geometry on eliminating porosity at the billet center, a comparison of the calculated hydrostatic stresses and strains at the center of the billet has been made. The results of this analysis show that for good consolidation of the material at the centerline the double V dies are effective. Different ingot geometries produced similar strains at the center, but the lowest calculated press load was for the cylindrical ingot.

Modelling Permanent-mould Casting Processes

Numerical and experimental work is carried out to investigate liquid metal flow and heat transfer during the permanent moulding of cast iron. Heat conduction during the pouring and solidification of cast-iron plates, and liquid metal flow and heat transfer during the pouring and solidification of cylindrical cast-iron ingots is numerically and experimentally investigated. The castings are poured in permanent moulds, and temperature distributions in the castings and the moulds are recorded. The mathematical modelling indicates the significance of finite pouring time and liquid metal convection on the temperature distribution. Good agreement is obtained between the experimental data and the predictions of the heat and mass transfer computations. Temperature fields, solidus front shapes and velocity fields during pouring and solidification are simulated for both top and bottom gated cases.

Fraction Solid to Regulate the Shape of Shrinkage Depression of Cylindrical Al-Si Alloy Ingot

Fraction Solid to Regulate the Shape of Shrinkage Depression of Cylindrical Al-Si Alloy Ingot

Simulation of vertical semicontinuous direct chill casting process of cylindrical ingot of aluminum alloy.

An analytical method to estimate the temperature and stress distribution in an ingot due to a steady vertical semicontinuous direct chill casting process in a spatial coordinate system is presented in this paper. The interaction between temperature and phase change is carefully discussed to obtain the heat conduction equation including latent heat generation with the consideration of material flow. A viscoplastic constitutive relationship capable of describing the viscoplastic solid as well as viscous fluid is employed for stress analysis. As an example of the simulation, a casting process for axisymmetric aluminum ingot is examined by use of the finite element method, and the calculated results of temperature, deformation and stress are revealed to simulate the actual behavior during semicontinuous direct chill casting process.

Fluid flow and macrosegregation in cylindrical ingots

The macrosegragation resulting from fluid flow during solidification is calculated. The bulk liquid flow is coupled to the inter-dendritic flow. The calculations carried out on cylindrical Al-4.5wt.%Cu alloy ingots agreed well with the experimental results. The formation of an equiaxed zone at the bottom of an ingot, the thermal contraction of the bulk liquid and the deformation of the ingot due to solidification shrinkage affect the result of the calculations.

Ultrasound assessment of fetal weight at term: Patterson R: Estimation of fetal weight during labor. Obstet Gynecol 65:330, 1985.

The authors discuss application of the Model-View-Controller software design pattern simulate heat and mass transfer in metallurgical production. We scrutinize of this technology in software development for the purpose of modeling the production of high cylindrical steel ingots. The processes occurring in the melt and the mold walls are described through a system of equations in the cylindrical coordinates and the boundary conditions in the Boussinesq approximation.

Synthesis and crystal growth of copper indium diselenide from the melt

A technique for in situ synthesis and crystal growth of CuInSe2 from the melt in an open crucible is described. Cylindrical ingots 55 mm in diameter and weighing up to 200 g exhibited single-crystal grains up to 90 mm2 in area after slowly cooling in the synthesis crucible. A B2O3 liquid encapsulant was used in conjunction with argon gas at 50 to 70 atmospheres pressure to suppress vaporization of the constituents. Liquid encapsulated Czochralski growth was also demonstrated. Electrical and compositional properties of the crystals are presented.

Deformation of graphite during hot extrusion of cast aluminum-silicon-graphite particle composites

Cylindrical ingots (5.2 × 10 −2 in diameter and 2.0 × 10 −1 m long) of cast aluminum-silicon-graphite particle composites were extruded into rods 6 × 10 −3 m in diameter at 723 K. In the extruded composites, dispersed graphite particles were present in the form of stringers lying along the direction of extrusion. An attempt has been made to explain the observed deformation of graphite particles on the basis of hardness values. Microstructural examination indicated good bonding between the graphite stringers and the aluminum alloy matrix. Extruded composites exhibited a higher ultimate tensile strength than that of as-cast composites.

A numerical simulation of the D.C. continuous casting process including nucleate boiling heat transfer

The steady-state thermal problem associated with the direct-chill continuous casting of A6063 aluminum cylindrical ingots is solved using the numerical finite element technique. Excellent correlation is demonstrated between the numerical model and experimental data from ingots cast at two different speeds. By application of the model, effective heat transfer coefficients are calculated as a function of vertical position on the outside surface of the ingot. It is shown that direct application of these coefficients to the modeling of different casting situations will produce substantial errors in the region in which heat transfer is by nucleate boiling. Using theories of nucleate boiling with forced convection and film cooling, a method is developed to calculate the external boundary conditions in the submold region of the ingot, thus making it possible for the first time to define explicitly all of the thermal boundary conditions associated with this casting configuration. These theories are incorporated into the numerical model, and a subsequent simulation shows excellent agreement with experimental data from a third ingot.

アルミニウム合金鋳物の諸性質に及ぼす高圧鋳造の効果

Cylindrical ingots of 12 different casting and die casting alloys were cast under ambient and 2000kgf/cm2 pressures. The specific gravity, proof and tensile strengths, elongation and impact value of high pressure castings are improved to different degrees corresponding to the casting characteristics of the alloys. The alloys having wider solidification temperature ranges and intensified tendencies to hot shortness show higher relative increase in mechanical properties more significant. The effect of high pressure casting is more pronounced for the alloy having poor castability in such casting indices as hot shortness and pressure tightness that are related to occurance of macroscopic casting defects. Based on the above correlation a new castability criterion including mechanical properties of castings is proposed by evaluating the effect of high pressure casting. The alloys suitable for high pressure casting is discussed based on the present experimental vesults.