Improved VDC Casting of Aluminium Alloys through an Understanding of the Surface Properties of the Molten Metal

2006 ◽  
Vol 519-521 ◽  
pp. 1693-1698
Author(s):  
John A. Taylor ◽  
Ian F. Bainbridge
Keyword(s):  
Surface Properties ◽  
Molten Metal ◽  
Aluminium Alloys ◽  
Defect Formation ◽  
Direct Chill ◽  
Gradual Change ◽  
Liquid Aluminium ◽  
Hot Top ◽  
Metal Head ◽  
Wide Range

Vertical direct chill (VDC) casting of aluminium alloys is a mature process that has evolved over many decades through gradual change to both equipment design and casting practice. Today, air-pressurised, continuous lubrication, hot top mould systems with advanced station automation are selected as the process of choice for producing extrusion billet. Specific sets of operating parameters are employed on these stations for each alloy and size combination to produce optimal billet quality. The designs and parameters are largely derived from past experience and accumulated know-how. Recent experimental work at the University of Queensland has concentrated on understanding the way in which the surface properties of liquid aluminium alloys, e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of the naturally-stable meniscus for a given alloy, temperature and atmosphere. The wide range of alloyand condition-dependent values measured has led to the consideration of how these properties impact the stability of the enforced molten metal meniscus within the hot top mould cavity. The actual shape and position of the enforced meniscus is controlled by parameters such as the upstream conduction distance (UCD) from sub-mould cooling and the molten metal head. The degree of deviation of this actual meniscus from the predicted stable meniscus is considered to be a key driver in surface defect formation. This paper reports on liquid alloy property results and proposes how this knowledge might be used to better design VDC mould systems and casting practices.

Structure and Defect Formation during DC Casting of Aluminium Alloys

2012 ◽  
Vol 710 ◽  
pp. 43-49
Author(s):  
Laurens Katgerman ◽  
Dmitry G. Eskin
Keyword(s):  
Aluminium Alloys ◽  
Defect Formation ◽  
Systems Approach ◽  
Computer Modelling ◽  
Experimental Studies ◽  
Pilot Scale ◽  
Direct Chill ◽  
Process Conditions ◽  
Production Chain ◽  
Research Activities

Research activities on aluminium production technology focus on the successive steps in the production chain of aluminium wrought products. Direct-chill casting of aluminium alloys is a well-developed technology with a long history. But only in the last 20 years, the development of computer modelling offered a means of better understanding of the physical phenomena involved in solidification. The main scientific challenge is to obtain a fundamental insight into the processing of aluminium alloys and to establish quantitative relationships between materials, processes, and performance. A systems approach is employed, covering theoretical and experimental studies on processing into semi-finished products. Special emphasis is placed on experimental verification and industrial applicability with the availability of pilot scale experimental facilities at M2i-TUD. This facilitates the design of process conditions as desired for experimental validation studies. In this paper we will consider main mechanisms of structure and defect formation during solidification of DC cast billets, mostly based in the results obtained in cooperation between Delft University of Technology and Materials Innovation Institute (M2i).

scholarly journals Tunable Crystalline Phases in UV-Curable PEG-Grafted Ladder-Structured Silsesquioxane/Polyimide Composites

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2295 ◽  
Author(s):  
Ryung Il Kim ◽  
Ju Ho Shin ◽  
Jong Suk Lee ◽  
Jung-Hyun Lee ◽  
Albert S. Lee ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Surface Properties ◽  
Weight Ratio ◽  
Hybrid Polymer ◽  
Water Contact ◽  
Uv Curable ◽  
Wide Range ◽  
Drastic Increase ◽  
Polyimide Composites ◽  
Crystalline Polyethylene

A series of UV-curable hybrid composite blends containing a carboxylic acid functionalized polyimidewith varying amounts of high molecular weight (~1 K) PEG-grafted ladder-structured polysilsesquioxanes copolymerized with methacryl groups were fabricated and their structural, thermal, mechanical, and surface properties characterized. At a composite weight ratio of polyimide above 50 wt.%, a stark shift from amorphous to crystalline polyethylene glycol (PEG) phases were observed, accompanied by a drastic increase in both surface moduli and brittleness index. Moreover, fabricated composites were shown to have a wide range water contact angle, 9.8°–73.8°, attesting to the tunable surface properties of these amphiphilic hybrid polymer composites. The enhanced mechanical properties, combined with the utility of tunable surface hydrophilicity allows for the possible use of these hybrid polymer composites to be utilized as photosensitive polyimide negative photoresists for a myriad of semiconductor patterning processes.

Automatic Control of Molten Metal Flow for Improving Casting Performance

2011 ◽  
Vol 693 ◽  
pp. 179-184
Author(s):  
Thomas Jarlsmark ◽  
Jan Strömbeck ◽  
Mikael Terner ◽  
Jerry Wilkins
Keyword(s):  
Molten Metal ◽  
Metal Flow ◽  
Casting Process ◽  
Direct Chill ◽  
Level Control ◽  
Level Measurement ◽  
Cost Efficient ◽  
Molten Metal Flow ◽  
Automatic Level ◽  
Rolling Ingot

The ways to gain better quality and higher casting performance is an urgent topic among aluminium producers today. This issue is also often on the agenda at conferences like this and the subjects and technologies to achieve this varies. Controlling the molten metal flow by maintaining predefined levels or level patterns is one of many powerful tools to reach this goal. Precimeter Control specializes in applications for non-ferrous molten metal level measurement and molten metal flow control. By integration, or retrofitting, any new or existing casting line can easily be automatically controlled and gain improved casting performance in a cost efficient way. This paper will focus on the main benefits from automatic level control and how some plants have achieved improvements in their casting process of DC (Direct Chill) slab (or rolling ingot) casting after implementing such technology.

Direct chill billet casting of aluminium alloys

2016 ◽  
pp. 3-25
Author(s):  
Martin Jarrett ◽  
Bill Neilson ◽  
Estelie Manson-Whitton
Keyword(s):  
Aluminium Alloys ◽  
Direct Chill

scholarly journals Reoxidation Processes Prediction in Gating System by Numerical Simulation for Aluminium Alloys

2017 ◽  
Vol 17 (3) ◽  
pp. 23-26 ◽  
Author(s):  
M. Brůna ◽  
D. Bolibruchová ◽  
R. Pastirčák
Keyword(s):  
Free Surface ◽  
Aluminium Alloys ◽  
Oxide Films ◽  
Front Tracking ◽  
Gating System ◽  
Liquid Aluminium ◽  
Surface Time ◽  
Filling Pattern ◽  
Entrained Air ◽  
Flow Experiments

Abstract Pouring of liquid aluminium is typically accompanied by disturbance of the free surface. During these disturbances, the free surface oxide films can be entrained in the bulk of liquid, also pockets of air can be accidentally trapped in this oxide films. The resultant scattering of porosity in castings seems nearly always to originate from the pockets of entrained air in oxide films. Latest version of ProCast software allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up in casts. During a filling calculation, ProCast can calculate different indicators which allow to better quantify the filling pattern. The fluid front tracking indicator “Free surface time exposure” has the units [cm2*s]. At each point of the free surface, the free surface area is multiplied by the time. This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow. Experiments to validate this new functions were executed.

Material flow and void defect formation in friction stir welding of aluminium alloys

2018 ◽  
Vol 23 (8) ◽  
pp. 677-686 ◽  
Author(s):  
X. H. Zeng ◽  
P. Xue ◽  
D. Wang ◽  
D. R. Ni ◽  
B. L. Xiao ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Aluminium Alloys ◽  
Material Flow ◽  
Defect Formation ◽  
Void Defect ◽  
Friction Stir

Direct chill billet casting of aluminium alloys

2004 ◽  
Author(s):  
Martin Jarrett ◽  
Bill Neilson ◽  
Estelle Manson-Whitton
Keyword(s):  
Aluminium Alloys ◽  
Direct Chill

Analysis of Extrusion Welding Conditions for AlMg Alloys with High Mg Content

2016 ◽  
Vol 682 ◽  
pp. 401-407 ◽  
Author(s):  
Alicja Wojtyna ◽  
Dariusz Leśniak ◽  
Artur Rękas ◽  
Tomasz Latos ◽  
Krzysztof Zaborowski ◽  
...  
Keyword(s):  
Aluminium Alloys ◽  
Original Method ◽  
Die Design ◽  
High Quality ◽  
Weldability Tests ◽  
Welding Stress ◽  
Porthole Die ◽  
Extrusion Welding ◽  
Wide Range ◽  
Mg Content

In the work, an original method and a special modified device is presented enabling to determine welding conditions of hard deformable aluminium alloys. The main advantage of the proposed method is that it simulates conditions occurring in the welding chamber of the porthole dies. The weldability tests were performed for 5754 (3,5% Mg) and 5019 (5,5% Mg) alloys, in a wide range of temperatures and pressures. The microstructure and joints strength were examined. The welding conditions of AlMg alloys that allowed obtaining high-quality joints were determined. The obtained welding stress values will be the basis for extrusion porthole die design.

Preparation and Pretreatment Effects on Co/SiO2 Catalysts for Fischer-Tropsch Synthesis

1994 ◽  
Vol 368 ◽  
Author(s):  
Kent E. Coulter ◽  
Allen G. Sault
Keyword(s):  
Surface Properties ◽  
Photoelectron Spectroscopy ◽  
Cobalt Catalysts ◽  
Volatile Components ◽  
Cobalt Metal ◽  
Nitrate Hexahydrate ◽  
Incipient Wetness Impregnation ◽  
Supported Metal Catalysts ◽  
Drying Procedures ◽  
Wide Range

ABSTRACTCatalyst drying procedures are often given little attention in the experimental section of papers on supported metal catalysts. In general, drying appears to be regarded as a method to remove water and other volatile components prior to calcining or reduction, but not as a method to affect the surface properties of the catalyst. This study uses x-ray photoelectron spectroscopy (XPS) to examine the surface properties of silica supported cobalt catalysts, prepared using incipient wetness impregnation of cobalt nitrate hexahydrate, and finds a wide range of cobalt distributions, extent of nitrate decomposition, and reducibility for various drying procedures. After UHV annealing and subsequent reduction, the final cobalt surface properties are found to depend on the length of heating and the environment during the drying process. Maximum cobalt metal surface area is obtained for samples exposed to limited amounts of air and dried under conditions where gas phase species generated during the precursor decomposition are rapidly removed from the surface of the sample.

Computational study of Mg insertion into amorphous silicon: advantageous energetics over crystalline silicon for Mg storage

2013 ◽  
Vol 1540 ◽  
Author(s):  
Fleur Legrain ◽  
Oleksandr I. Malyi ◽  
Teck L. Tan ◽  
Sergei Manzhos
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Defect Formation ◽  
Crystalline Silicon ◽  
Computational Study ◽  
Binding Energies ◽  
Functional Theory ◽  
Wide Range ◽  
Insertion Sites ◽  
Formation Energies

ABSTRACTWe show in a theoretical density functional theory study that amorphous Si (a-Si) has more favorable energetics for Mg storage compared to crystalline Si (c-Si). Specifically, Mg and Li insertion is compared in a model a-Si simulation cell. Multiple sites for Mg insertion with a wide range of binding energies are identified. For many sites, Mg defect formation energies are negative, whereas they are positive in c-Si. Moreover, while clustering in c-Si destabilizes the insertion sites (by about 0.1/0.2 eV per atom for nearest-neighbor Li/Mg), it is found to stabilize some of the insertion sites for both Li (by up to 0.27 eV) and Mg (by up to 0.35 eV) in a-Si. This could have significant implications on the performance of Si anodes in Mg batteries.

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