Single Billet Research Articles

Application of Queuing Theory in Production Efficiency of Direct Rolling Process of Long Product

Based on the mathematical method of queuing theory, the queuing model of billets in the direct rolling process of the long product was established, which represented the conveying process of billets at the casting and rolling interface. Using the billets queuing model, the influence of different steel quantity, length, speed and other factors on the average waiting time of a single billet in the direct rolling production process was analyzed. Combined with the temperature drop of billets, the optimal average waiting time for a single billet was determined. The method improved the conveying connection efficiency of the casting-rolling interface and the direct rolling rate of billets.

Microstructural Evolution during Severe Plastic Deformation by Gradation Extrusion

In this contribution, we study the microstructural evolution of an age-hardenable AA6082 aluminum alloy during severe plastic deformation by gradation extrusion. A novel die design allowing an interruption of processing and nondestructive billet removal was developed. A systematic study on the microstructure gradient at different points of a single billet could be performed with the help of this die. Distinct gradients were investigated using microhardness measurements and electron microscopy. Our results highlight that gradation extrusion is a powerful method to produce graded materials with partially ultrafine-grained microstructures. From the point of view of obtaining an ultrafine-grained surface layer with maximum hardness, only a small number of forming elements is needed. It was also found that large incremental deformation by too many forming elements may result in locally heterogeneous microstructures and failure near the billet surface caused by localization of deformation. Furthermore, considering economical aspects of processing, fewer forming elements are preferred since several processing parameter-related cost factors are then significantly lower.

Leveraging comprehensive baseline datasets to quantify property variability in nuclear-grade graphites

The full characterization of the physical and mechanical properties of candidate nuclear-grade graphites is highly dependent upon an understanding of the distribution of values that are inherent to graphite. Not only do the material properties of graphites vary considerably between grades owing to the raw materials sources, filler particle type and size, methods of compaction, and production process parameters, but variability is observed between billets of the same grade from a single batch and even across spatial positions within a single billet. Properly enveloping the expected properties of interest requires both a substantial amount of data to statistically capture this variability and a representative distribution capable of accurately describing the range of values. A two-parameter Weibull distribution is confirmed to be representative of the distribution of physical (density, modulus) and mechanical (compressive, flexure, and tensile strength) values in five different nuclear-grades of graphite. The fine-grained isomolded grades tend toward higher Weibull modulus and characteristic strength values, while the extruded grade being examined exhibits relatively large distributions in property values. With the number of candidate graphite specimens that can undergo full irradiation exposure and subsequent testing having limited feasibility with regard to economics and timely evaluations, a proper capture of the raw material variability in an unirradiated state can provide crucial supplementary resolution to the limited amount of available data on irradiated candidate grades.

Numerical Assessment of the Influence of Process and Geometric Parameters on Extrusion Welds and Die Deformation after Multiple-cycles

A comprehensive investigation on the correlation between die design and process parameters with extrusion welds (seam and charge) prediction and die deformation after multiple-cycles is presented. In particular, the influence of the number of legs (2,3 and 4) as well of some commonly adopted industrial best design practices in the extrusion of a round tube profile are examined by the ALE code HyperXtrude® for the AA6005A alloy. Then, for the same three designs, the die deformation after multiple-cycles is computed by applying a developed user sub-routine that account for the pressure and temperature maps and for the dwell-time that represents the time required to extrude each single billet. A sensitivity analysis on the influence of process parameters (ram speed, billet length and alloy) on the achieved die deformation after a fixed extruded amount is also performed.

Finite element buckling analysis of stiffened plates with filleted junctions

Modern aircraft wings are thin-walled structures composed of ribs, spars and stiffened panels, where the top skin is subject to compressive forces in flight that can cause buckling instability. If these panels are machined from a single billet of metal then the initial buckling performance can be significantly improved by increasing the fillet radius along the line junction between the stiffener webs and skin. Typically thin-walled structures are usually modelled with two dimensional elements. To model the stiffened panel with fillets three dimensional elements are required. For the stiffened panel selected for the analysis the paper shows that the three dimensional model shows a substantial increase in skin initiated buckling if the fillet is taken account of. A 5mm radius leads to an increase of 34% increase in local buckling load performance for a skin portion of breath to thickness ratio of 100. The associated overall buckling load increases by 1.8%. The mass penalty for a 5mm radius is 5.1%. To avoid local and overall buckling interaction an accurate measure of both buckling loads is very important and may have impact for designers. The three dimensional models with no fillets show very good agreement with the two dimensional models.

DEVELOPMENT OF CRYSTALLOGRAPHIC TEXTURE AND GRAIN REFINEMENT IN THE ALUMINUM LAYER OF CU-AL-CU TRI-LAYER COMPOSITE DEFORMED BY EQUAL CHANNEL ANGULAR EXTRUSION

The present research is concerned with the aluminum layer of a loosely packed tri-layer copper-aluminum-copper composite deformed by ECAE process. Electron back scattered diffraction (EBSD), transmission electron microscope, and X-ray technique were employed to investigate the detailed changes occurring in the microtexture, microstructure (cell size and misorientation), and dislocation density evolution during consecutive passes of ECAE process performed on the composite based on route Bc. According to tensile test results, the yield stress of the aluminum layer was increased significantly after application of ECAE throughout the four repeated passes and then slightly decreased. An ultrafine grain size within the range of 500-600 nm was obtained in the Al layer by increasing the thickness of copper layers. It was observed that the reduction of grain size in the aluminum layer is nearly 57% more than that of an ECAE-ed single layer aluminum billet. Also, the grain refinement of the aluminum layer is accelerated throughout 8 passes. This observation was attributed to the higher rate of dislocation interaction, cell formation and texture development during the ECAE of the composite compared to those of the single billet.

Progress in Commercialization of Cable-in-Tube Approach to Manufacturing of Internal-Tin ${\rm Nb}_{3}{\rm Sn}$ Wires

With funding provided by US Department of Energy SSI has been able to reach significant milestones in manufacturing of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires by the innovative cable-in-tube method. Development of wires for consideration for the International Thermonuclear Experimental Reactor (ITER) project has reached the stage where single billets produce single piece-lengths of wire without any breaks. Wires in the range of 1-1.5 km have been produced. An early stage sample wire produced by the CIT approach has shown a non-copper J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of 940 A /mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 12 T and 4.2 K combined with plusmn3 T hysteresis loss of 560 mJ/cc. Another wire designed and produced for High Energy Physics applications has shown a non-copper J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of more than 2200 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . These results and the research to achieve them are described in this article.

Critical Current Measurements on&lt;tex&gt;$rm Nb_3rm Sn$&lt;/tex&gt;Conductors for the NED Project

The Next European Dipole (NED) project is a EU funded program aiming at the realization of a 15 T accelerator-type of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn dipole magnet. The objective of NED phase one is developing high performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn conductor in collaboration with European industry. The envisaged Rutherford type of cable consists of about 40 superconducting strands exhibiting a noncopper critical current density of 1500 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K and 15 T. In the frame of conductor development, adequate critical current measurements in terms of accuracy and reproducibility should be ensured to qualify the ambitious strands produced. Therefore, a NED working group focuses at the establishment and implementation of appropriate and standardized procedures for sample preparation and mounting, critical current measurement, data analysis and reporting. A cross-calibration program between the institutes involved has been initiated by exchanging samples of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn conductor from a single billet for critical current measurements, prepared at each institute. The experimental results of this program and the conclusive procedures for NED critical current measurements are presented and discussed

Abstract: Physical vapor deposition of GaxIn1−xSb

Films of GaxIn1−xSb have been deposited by the electron-beam evaporation of three-component billets. The films have potential use in low-cost electroabsorptive devices such as switches and modulators. The band gap of the ternary solid solution can be varied from 0.2 to 0.7 eV by changing the film composition. Modulation of this band gap with an electric field will then provide the desired control over the transmittance of the films in the infrared. A typical deposit was made in a vacuum of 10−3 Pa, using 1 kW of electron beam power to cause evaporation of the single billet. The films were usually 10–30 μm thick and were formed on alumina and sapphire substrates. X-ray-diffraction analysis was used for both film and billet samples to identify the phases present and to determine homogeneity. Values of x for the ternary phases were assigned by computing lattice parameters from the x-ray peak positions and then applying Vegard’s law. The values of x ranged from 0.05 to 0.47 for the films consisting of a single phase of ternary solid solution. This range of x was observed because of the use of billets with different compositions. It was further observed that the x values of the deposits were approximately one-half the x values of the billets used to produce them. This relationship can be used to control the x values of deposits. The analysis of the phases present in the films further showed that single-phase deposits of ternary solid solutions were only formed for a particular range of substrate temperatures. Deposits formed at substrate temperatures of 486 °C or less contained free Sb and GaSb in addition to a ternary solid solution. At substrate temperatures of 567° to 655 °C, the films consisted of a single-phase ternary solid solution. The deposits contained free In as well as the ternary solid solution at the higher substrate temperatures of 735° and 820 °C. The films then consisted solely of the ternary solid solution only when the substrate temperatures were in the range T1&amp;lt;T&amp;lt;T2, where 486&amp;lt;T1?567 °C and 655°?T2&amp;lt;735 °C. The compositional homogeneity of the films was checked over two scales of distance. The homogeneity of the deposits from substrate-to-substrate (distance scale ∠5 cm) was confirmed by agreement of the diffraction patterns from three substrates of a given run. Smaller scale homogeneity was evaluated using the width of the 422 x-ray peak. The results showed that the x variation of the ternary solid solution is not more than ±0.015 over the interaction volume (∠0.25 cm2×7×10−4 cm) of the x-ray beam. The x-ray analysis of the billets showed that they were composed of free In and ternary solid solutions. The compositional homogeneity of the billets was confirmed by the agreement of the diffraction patterns from material at different positions in a particular billet. The films and billets were analyzed chemically using atomic absorption spectroscopy and arc spectroscopy. The values of x determined chemically for films of ternary solid solutions agreed to within ±0.05 with the x values determined from the use of Vegard’s law. This agreement is within that expected from considerations of the sources of error, so Vegard’s law is considered to be applicable to the films. In addition, the chemical analysis revealed that two of the six single-phase ternary solutions essentially achieved the stoichiometry represented by the formula GaxIn1−xSb (to within 2%). The remaining four ternary solid solutions contained more than 50 at.% Sb. The analysis also showed that the films were contaminated by impurities from the alumina substrates. The transmission properties of four deposits on sapphire substrates were studied. Static reflection measurements were made in the 2.5–10-μm range at room temperature. The observed absorption edges were in agreement with band-gap data for the two deposits stoichiometric in Sb. The observed edges were at shorter wavelengths than predicted for the two deposits with excess Sb. The maximum transmission observed in this work was 40%. Electroreflectance measurements on the four films at liquid-nitrogen temperature showed that one of the films (a stoichiometric film) could be modulated by an electric field. The above results are encouraging for the synthesis of electroabsorptive materials by this method of physical vapor deposition. Ternary solutions of a given band gap can be deposited and modulation with an electric field is feasible. In order to make good quality devices more work needs to be done in controlling the impurity content and percentage of Sb in the films.

押出しされたMg-Zr合金に起こる微細結晶粒組織について

An anomalous fine-grained structure of Mg-Zr alloy phase was observed in the annealed co-extrusion of Mg-0.5%Zr and Mg-1%Al powders.The present experiment has been carried out to clarify this phenomenon. A cylindrical bimetal billet of pure Mg and Mg-0.5%Zr alloy was extruded at 400°C and the extruded bimetal was annealed at 350°∼550°C for 1, 3 and 9 hr. The grain size of Mg-Zr alloy phase near the interface to the pure Mg phase was measured and plotted in Figs. 2∼4 against the distance from the interface.The fine-grained zone of about 0.3 mm in the Mg-Zr alloy phase adjacent to the pure Mg phase was observed in the as-extruded condition. Annealing the extruded bimetal at 550°C resulted in remarkable grain growth in the opposite side of this zone to the interface. The fine-grained zone, however, remained in the extent of ∼0.1 mm.This fine-grained structure of Mg-Zr alloy phase seems attributable not to an ordinary deformation mechanism in the extrusion process of a single billet but to another mechanism caused by the co-extrusion with a softer material.