Secondary Cast Research Articles

Performance of Al-6063 Primary and Secondary Billets Used in Hot Aluminum Extrusion

The service life of tooling plays an important part in the economics of the extrusion process. A number of causes are considered responsible for initiating damage to the dies before its designated life is reached. Apart from other factors such as die design and manufacturing, heat treatment, working conditions, etc, the performance of the die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die failure, based on microstructural investigation. A secondary (remelt) billet cast in-house at a local extrusion plant is compared with a primary (smelter) billet by applying different material characterization techniques, including optical microscopy, Vickers microhardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). It is observed that a secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, inclusions, and high hardness that can be associated with poor casting and homogenization practice. In view of present results, some suggestions during in-house billet preparation of secondary billets have been formulated for improved die service life.

Influence of solutionising and aging temperatures on microstructure and mechanical properties of cast Al–Si–Cu alloy

This paper presents the influence of solution and aging temperatures on the microstructure and mechanical properties of 319 secondary cast aluminium alloy. Experimental alloy was subjected to different heat treatment cycles. Heat treatments were designed with two solutionising temperatures (504 and 545°C) at two solutionising times (4 and 8 h), followed by quenching in water at 60°C and artificial aging. The artificial aging was carried out at two temperatures (200 and 154°C) for 6 h. The improvement in mechanical properties was obtained with low solution temperature (504°C) for 8 h followed by quenching in water to 60°C and aging at low temperature (154°C). The increase in the solutionising temperature from 504 to 545°C was recommendable only for short solutionising time (4 h). Increase in the aging temperature from 154 to 200°C has led to the increase in hardness with the corresponding decrease in ductility. Aging under unfavourable conditions (prolonged aging at high temperature) caused coarsening of spheroidised eutectic silicon crystals and precipitated particles resulted in deleterious effect on the tensile strength.

Rissa Bartholomew’s Declaration of Independence (review)

Reviewed by: Rissa Bartholomew’s Declaration of Independence Kate Quealy-Gainer Comerford, Lynda B. Rissa Bartholomew’s Declaration of Independence. Scholastic, 2009 [320p]. ISBN 978-0-545-05058-6 $16.99 Reviewed from galleys R Gr. 4–6 In the summer following fifth grade, Rissa begins to realize that she no longer has anything in common with the girls she has been friends with all her life. Her best friend, Beth, seems like a stranger with her sudden interests in boys and fashion and her insistence that everyone now call her “Bethany.” Rissa decides to “leave the herd,” as she puts it, when several humiliating experiences at the hands of her supposed friends climax in a disastrous birthday party. Although she enters sixth grade friendless and ostracized, Rissa refuses to conform to fit in; instead, she takes the opportunity to discover who she is when she is not Beth’s shadow. The setup seems destined for a “be yourself” morality tale, but Comerford skillfully avoids any sermonizing as she explores the beginnings of the adolescent search for identity. Rissa’s narrative voice is believably that of a young woman who can at once be selfish and compassionate, naïve and perceptive. Her insights into the adult world are pitch perfect in their shrewd honesty, while her preteen awkwardness provides plenty of opportunities for comic relief. The secondary cast is also well drawn, with three-dimensional characters ranging from Violet, a seemingly independent classmate with her own relationship issues, to Rissa’s mother, a woman who has perhaps also had her fill of the pack mentality. There is no tidy conclusion here, since Rissa never does acquire a new and improved best friend, but readers will find that the uncertain ending makes Rissa’s experience all the more relatable. Copyright © 2009 The Board of Trustees of the University of Illinois

Effect of Al-6063 Billet Quality on the Service Life of Hot Extrusion Die: Metallurgical and Statistical Investigation

The current paper presents results about the effect of Al-6063 billet quality on the service life of AISI-H13 hot extrusion dies based on microstructural and statistical investigation. In the first half of the paper, secondary (remelt) billet cast in-house at local extrusion plant is compared with two sources of primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, x-ray diffraction (XRD) analysis, and energy-dispersive spectroscopy (EDS). The second half of the paper evaluates the performance of primary and secondary billet types based on statistical analysis of data collected on 53 hollow-profile dies from a local commercial extrusion setup. It was observed that the secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, and high hardness that can be associated with poor casting and homogenization practice. Statistical analysis covers overall analysis of collected data followed by detailed study of percentagewise use of billet quality in terms of die profile complexity/extrusion ratio. Analysis has shown that dies extruding a high percentage of secondary billets are more susceptible to early die failure on overall basis. For more complex dies with high extrusion ratio, average die life further reduces with increased percentage of secondary billet usage. Regression models are also proposed for prediction of die life in terms of secondary billet usage and extrusion ratio. Considering results of present microstructural and statistical analysis, some suggestions during in-house billet preparation of secondary billets have been formulated to prevent early die failure.

Effect of mold temperatures on interface between primary and secondary castings of cast-on method for precision metal frameworks

The purpose of the present study was to obtain fundamental data for application of the cast-on method by evaluating the effect of mold temperatures on the interface between primary and secondary castings in detail. Silver-palladium-gold alloy (Ag-Pd-Au), type-4 gold alloy (Type4), and chromium-cobalt alloy (Cr-Co) were used in the present study. A polished flat, square metal plate, 10.0 mm x10.0 mm x 1.0 mm, was used as the primary casting. A wax pattern, 2.0 mm in diameter and 2.0 mm thick, was prepared for the secondary casting and invested together with the primary casting. The mold was heated at 600, 700 and 800 degrees C for Ag-Pd-Au and Type4, and 700, 800 and 900 degrees C for Cr-Co. After casting, the mold was embedded and sectioned. The cross-section was observed using a scanning electron microscope (SEM) and analyzed using energy dispersive X-ray spectroscopy (EDS). The gaps between the primary and secondary castings were analyzed for each alloy by analysis of variance and Tukey's honestly significant difference test. The significance level was set at 0.05. The heated primary casting without the secondary casting was examined using a thin film X-ray diffractometer (XRD). Gaps were observed between the primary and secondary castings in all examined conditions. The primary casting surface was covered with oxide layers such as CuO and Cr(2)O(3), and became rough with an increase of the mold temperature. The results suggested that the cast-on method was influenced by the mold temperature.

Integrating Casting Simulation into Automotive Wheel Fatigue Analysis

Bending test is the most important performance test of automotive wheel.At present,the fatigue life prediction still based on nominal stress approach or local stress-strain approach.The effect of microstructure and casting defects has not been considered in presently used approaches,there is a considerable difference between prediction results and real practice when these approaches are used to predict the high-cycle fatigue life of the aluminum alloy automotive wheels under low stress level.A fatigue life prediction model concerning secondary dendrite arm spacing and casting defect is built based on small fatigue crack propagation theory.Casting simulation and finite element analysis are integrated into fatigue analysis.An integrated platform to predict wheel mechanical performance that includes casting process,related casting defect and downstream manufacturing process is constructed primarily. The bending fatigue life of a certain type of wheel is predicted by using this model,and the experiment validates that the result is more accurate than Simth-Waston-Topper method.

Effect of melting, refining and casting on product quality and properties

The 16th Annual Conference of the Sheffield Metallurgical and Engineering Association (SMEA), held on 4 and 5 July 2007 at Tapton Hall, University of Sheffield, UK attracted 120 delegates. The aim was to explore the effect of primary processes on the quality and performance of a range of steels, titanium alloys and nickel based superalloys. Attention focused on secondary steelmaking and continuous casting and on vacuum remelting processes, exploring how these are related to product quality and properties. The five sessions comprised 22 presentations.

A sharp interface model for the morphological evolution of precipitates in Al cast alloys§

Efforts to recycle aluminium objects including alloy material are frequently complicated by Fe and Mn components of the alloys, causing the appearance of intermetallic phases during the secondary casting process. A variety of methods exist to reduce the occurrence of such intermetallic phases, such as the introduction of convection via electromagnetic stirring. To gain a deeper understanding of such casting processes we present a sharp interface model which allows us to predict the evolution of precipitate growths under the influence of forced convection. Furthermore, we have also studied the impact of convection on the morphology of these precipitates, as well as the influence of different inflow velocities and Péclet numbers on the volume fraction of the precipitation. §Submitted to the Special Issue of Philosophical Magazine Letters Nucleation and growth kinetics in colloids and metals.

Cementable implant crowns composed of cast superstructure frameworks luted to electroformed primary copings: an in vitro retention study

The aim of this in vitro study was to investigate, on ITI solid abutments, the retention values of single crowns fabricated using an alternative prosthetic solution: secondary cast superstructure luted to an electroformed primary coping. Fifty standard 4.1 mm ITI implants and 5.5 mm high ITI machined abutments were assembled and mounted in acrylic resin. Implant/abutment assemblies were randomly divided into two groups. In the test group, primary galvanic caps were directly fabricated on implant abutments (A.G.C. Micro machine), and a secondary cast noble alloy superstructure was luted on each primary galvanic cap with a resin cement (Nimetic Cem). In the control group, prefabricated burn-out caps were used for casting the metal frameworks. Test and control crowns were cemented using a resin cement (Panavia 21). After storage at 37 degrees for 24 h, the specimens were subjected to a pull-out test using an Instron universal testing machine. The load required to dislodge each sample and the respective mode of failure were recorded. Means and standard deviations of loads at failure were analyzed using ANOVA. Statistical significance was set at P< or =0.05. The retention values (+/-SD) of loads at failure were 67.26 (+/-16.61) for the test group and 44.03 (+/-9.45) for the control group. In the test group no separation occurred between the electroformed (galvanic) primary cap and the secondary superstructure. The results showed that this prosthetic solution is superior on retentive performance than the conventional cast framework. An added clinical advantage of this novel method is its potential to provide a totally passive fit. Further in vitro and in vivo studies involving multiple-unit restorations are needed in order to more generally validate this prosthetic concept.

Shared Leadership in a Community Theater Group: Filling the Leadership Role

In contrast to research in which an individual leader is assigned or expected to emerge, musical theater productions provide an opportunity to explore how leadership is shared among the director, assistant director, music director, choreographer, and stage manager in a naturally occurring group. This ethnographic study explores how one community theater group managed the sharing of leadership roles when the primary director assumed a passive or ineffective role. The study explores the communication and affective responses of the secondary leaders and cast members when they perceived that the primary leadership failed to function and then examines how secondary leaders and cast members communicated to share the leadership to produce successful theatrical performances. The results have implications for other groups with shared leadership structures.

Tunneling under compressed air through immersed soft soil strata

The paper presents the problems encountered at the building of main sewer from Braila town, driven with shield under compressed air. The sewer tunnel is built in very difficult conditions: - the shield is driven through immersed silty sands strata and under loessial strata sensitive at humectation; - the sewer trace pass under an urban area (streets, buildings etc.) at variable depth (6 - 8m) and with settlements restrictions; - the hydrostatic level varies along the tunnel from 2m above at 2m below the upper level of shield. The main features of this work are presented: - The shield used (De = 4.15m) of open type with manual digging; - The strength structure of tunnel made of two lining, a primary precasted (six bolted segments of 20cm thick) and a secondary cast in place (25cm thick) and the type of grouting; - Air compressed production and storage equipment and air locks which have been located at the start of tunnel; - The problems and difficulties encountered during the latest 230m of tunnel (compressed air loss, surface settlements, the measures for breaking in final shaft). (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

SHELLEY SALLEE. The Whiteness of Child Labor Reform in the New South. Athens: University of Georgia Press. 2004. Pp. xi, 207. Cloth $49.95, paper $19.95

This case study of child labor reform in Alabama between 1901 and 1919 raises provocative questions and deserves a wide readership. Two middle-class white activists from different social circles spurred Alabama's early twentieth-century anti-child labor crusade. An Episcopal minister, Edgar Gardner Murphy, founded the all-male Alabama Child Labor Committee. His successor, Nellie Kimball Murdoch, revived the issue after Murphy fell ill and, enlarging the importance of female-led reform, helped to establish the Alabama Child Welfare Department as a new branch of state bureaucracy in 1919. Although Shelley Sallee focuses on Murphy's and Murdoch's campaigns, her book also includes a rich secondary cast of characters: the “mill men” intent on creating an industrially modern “new” South; the worker families who left farms for lives in cotton mill villages; the southern clubwomen who provided the most consistent support for restrictions on work by children. Sallee argues that an emphasis on the “whiteness” of reform helped southern anti-child labor advocates sidestep longstanding regional resentment of perceived outside interference. It also offered a solution to a home-grown problem: the declining status of poor white “crackers,” whose high rates of illiteracy, chronic bad health, and supposed tolerance for lives “buried under old tin cans … rags, and chicken feathers” (p. 111) threatened to throw dead weight on efforts at southern economic progress.

La technique du tournage utilisée à l'Âge du Bronze final pour la fabrication d'épingles de bronze trouvées en Bourgogne

A technological study of the two-piece pins from the Villethierry hoard (Yonne, France) has been performed with the help of different approaches. Firstly examinations with a binocular magnifying lens were carried out. Metallographic sections were prepared with samples taken from three pins; they were examined by optical microscopy and analysed with a device associated with a scanning electron microscope. Results from ethnoarchaeology and experimental archaeology were used. Precise answers to technical questions about the shaping process allow us to propose a complete and detailed scheme for the fabrication of this type of pin. The use of several techniques may be underlined. The pin head was formed by secondary casting. A spinning device was used, particularly for the shaping of the wax model of the head. As a last remark, annealing treatment occurred before the finishing steps of the decoration.

Advances in secondary steelmaking and continuous casting

The 13th Conference and Exhibition of the Sheffield Metallurgical Association (SMEA), held on 24 and 25 June 2004, attracted 130 delegates. Twenty-two presentations in five sessions covered the latest developments in secondary steelmaking; development of process routes for increased output; optimisation of product quality; improving the performance of continuous casting; and developments in wide and fast casters and casting thin cast products, with an update on the latest in thin strip casting – Castrip at Nucor.

Improving oxide cleanness on basis of MIDAS method

The MIDAS method (Mannesmann inclusion detection by analysing surfboards) was established in 1987 and enabled steelmakers to detect less frequent macroscopic inclusion particles in large volumes of steel. The basic idea of MIDAS is the flat cross-rolling of a strand sample perpendicular to the casting direction. Improvements in secondary metallurgy and casting technology have been achieved, since it became possible to define macrocleanness in exact numbers. In this paper, MIDAS results are presented for various strand sections: billets, blooms, jumbo blooms, round strands, conventional slabs and thin slabs. The variation of cleanness during sequence casting, at the front portion and end portion of heats, at ladle change and during steady state casting is investigated. The effect of teeming disturbances and accidental casting events on macrocleanness is studied. Selection of clean material can be optimised by adjusting the cutting length and downgrading critical casting portions. Detected inclusion particles in ultrasonic tested 'surfboard' samples are subsequently identified by metallography and by SEM or EPMA. The exogenous sources of contaminations and the formation mechanisms of inclusion particles are elucidated. Fundamental aspects, such as flotation due to buoyancy forces, coagulation of liquid particles, agglomeration of solid particles due to turbulent fluid flow, and the emulsification of slag droplets from ladle, tundish or mould, are now more deeply understood and enable progressive steps towards clean steel practice. MIDAS results correlate with material behaviour and properties at manufacturing and end-use of long and flat steel products. Future objectives should stress the stabilisation of optimised steady state conditions to realise a higher consistency and reproducibility of properties. Revamping of older continuous casting machines with curved moulds and the introduction of vertical sections are most essential for clean steelmaking. To avoid subsurface inclusions at the midwidth of the strand, submerged entry nozzle design and fluid flow pattern in the mould and liquid pool of continuous cast slabs should be reconsidered.

Synthetic casting tapes: benefits and uses of Delta-Cast Conformable.

Casting is a traditional practice that has changed relatively little over thousands of years. Today, however, with the emphasis on evidence-based medicine, health professionals are examining the practice and investigating ways of improving it for the benefit of both patients and those who perform it. Most fractures and many soft tissue injuries are usually managed in a rigid cast, which brings with it complications and disadvantages. The ideal form of fracture fixation would stabilize the fracture while allowing some movement of the fracture site and soft tissue compression. This article explores the use of Delta-Cast Conformable (Johnson and Johnson), a synthetic casting tape, in both primary and secondary casting. The role of Delta-Cast Conformable with regard to focused rigidity casting, a new philosophy in fracture management, is discussed.

Restoring the edentulous maxilla using an implant-supported, matrix-assisted secondary casting.

The selection of appropriate implant treatment modalities for the edentulous maxillary arch is complex. Although many patients are candidates for an implant-supported removable prosthesis, two major considerations affecting choice of treatment type are the amount of residual alveolar bone and soft tissue, and cost. A technique is described that employs a cast milled primary bar and a secondary casting constructed using a vacuum-formed 0.040-in plastic matrix. The secondary casting is intimately adapted to the primary bar and incorporates the retentive elements within it. The resulting prosthesis is less expensive than comparable designs, and retentive elements are easily replaceable. The technique is adaptable to most implant systems. The matrix-assisted secondary casting technique provides a design that is esthetic and hygienic. The prosthesis may also be easier to insert and remove than implant-supported removable prostheses that use plunger- or latch-type retention.

Rolling of secondary casting aluminum alloys

Rolling of secondary casting aluminum alloys

A secondary lingual casting for removable partial dentures

This article describes a technique for constructing a nickel chromium alloy lingual casting that reinforces a removable partial denture against heavy anterior occlusion. The metal can be cast into a thin secondary casting, and it is easily etched and bonded to the resin anterior teeth and associated base. This type of lingual casting has the potential to provide a simple and effective solution to the problem of repeated fracture or displacement of anterior teeth in many restorations.

Structure of secondary cast aluminum alloys obtained by granulation

1. After crystallization of secondary alloys AK5M2 and AK4M4 by granulation the size of dendritic cells is an order lower and that of excess phases 5–7 times smaller than in ingots of the alloys cast in chill molds. The structural components are evenly distributed; initial crystallization of brittle phases containing iron and manganese is suppressed. 2. The concentration of alloying elements in the solid solution is smaller in the granules as-cast than after standard quenching.