Cast Shop Technology: DC Casting and Macrosegregation
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: David Gildemeister, Arconic Technology Center
Wednesday 8:30 AM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Samuel Wagstaff, MIT
8:30 AM Introductory Comments
A Study on DC Casting Trough/ Launder Design and Material Selection: Bin Zhang1; 1Wagstaff Inc
For successful and consistent casting on ingot DC casting systems, metal heat loss has to be reduced. Metal heat loss is directly influenced by casting trough/launder design and material selection. To assist in developing solutions to reduce metal heat loss from furnace to casting table, Wagstaff« developed a CFD modeling program for heat loss analysis from furnace spout to casting station. The influence of the degasser, CFF units, and automated metal level controls are all included in the program to improve accuracy. Case studies at Wagstaff« R&D facility (DC #1 and DC #6) are reported to reveal the influence of refractory geometry and material selection on metal heat loss.
Critical Role of Thermal Management during Cast Start-up of DC Casting Process: AndrÚ Larouche1; Sabrina Guy1; JosÚe Colbert1; 1Rio Tinto Aluminium
In the past, numerical modeling and measurements in the field have provided insight into direct chill casting of sheet ingot and helped identify critical parameters to achieve successful cast start-ups. The control of these critical parameters is of key importance to maximise performance and throughput of the cast house as well as to meet stringent client requirements. Among these key parameters, management of liquid metal temperature, at start of cast, is critical in regard to casting performance. This paper presents several process variables influencing direct chill casting performance such as ingot recovery, false start and ingot quality.
Modelling and Analysis of a Horizontal Direct Chill Casting Process: Garar Gararsson1; Ůr÷stur Gumundsson2; Magnus Jonsson3; Halldor Palsson3; 1Alcoa Fjaraßl; 2Reykjavik University; 3University of Iceland
The objective of this study is to analyse bleed-outs in Horizontal Direct Chill (HDC) casting process by using a finite element model (FEM). HDC casting machines for aluminium are made for continuous casting with typical duration from 3 to 20 days according to the equipment manufacturer. Reduced duration due to technical difficulties affects capacity, productivity and cost. In order to improve understanding of the operation and the effect of alternative casting parameters an FEM model was developed for a 36 bar HDC machine installed in the Alcoa Fjardaal casthouse. Simulations were done for alternative inlet metal temperatures, cooling water temperatures, cooling water flow rate and casting speed with the focus on extracting information about potential bleed out conditions of a cast bar. Physical measurements were done on the HDC under real casting conditions and compared with the results of the numerical simulation showing good agreement with the measured results.
9:50 AM Cancelled
Casting of Sound, Large Diameter 7050 Billets: Kjerstin Ellingsen1; Mohammed M'Hamdi1; 1SINTEF
Large diameter billets of 7000 series alloys are used for transport applications. The alloys are difficult to cast as they are prone to both hot and cold-cracking due to the large solidifcation interval and low thermal conductivity. When thermally induced stresses overcome the deformation limit of the alloy, cracks are generated either during solidification (hot tears) or during cooling (cold cracks). The difficulty to cast sound billets increase with billet diameter due to large thermal gradients in the billet and associated stress build-up in the center. Fully coupled heat transfer, flow and mechanical simulations for casting of large diameter billets have been performed performed. The simulations provide semi-quantitative predictions of hot tearing and cold cracking susceptibility. The importance the bottom block to avoid start-up hot-cracks using casting simulations is demonstrated. Furthermore, the effect of introducing a wiper on the cold-cracking susceptibility is analysed.
10:15 AM Break