Modeling Direct Chill Casting of Aluminum Alloys

Cathryn Karashin

Advisor: Dr. Krane

Aluminum Applications

Beverage cans, planes, trains, automobiles, boats, spacecraft parts

Used as the mold material in Al casting

Al is very lightweight (1/3 the weight of steel) so it is very useful

Picture courtesy of Aluminum: Technology, Applications, and Environment by Dietrich G. Altenpohl

Direct Chill Casting

Direct chill (DC) casting process is used for 68% of the aluminum ingots processed in the US

Ingot scrap from stress cracks and butt deformation account for a 5% loss in production

Control of scrap levels is important both in terms of energy usage and cost savings

DC Casting: Mold and Ingot

Photos courtesy of M. Krane

Sump Depth

Sump depth at start up? Flood et al. believe the

sump increases at start up, then decreases and plateaus

Through modeling, we hope to have a more definite answer

A scaling Analysis for the Heat Flow, Solidification & Convection in Continuous Casting of Aluminum by Flood, Davidson, & Rogers

Physica Version 2.11

Models thermal and mechanical properties

Puts continuous equations into discrete parts; breaking down into simple algebraic terms

Produces a results file that can be used to generate graphs and analyze data

Photo courtesy of http://www.gre.ac.uk/~physica

Project Objectives

To model heat transfer and solidification phenomena in direct chill casting using Physica software

To study sump shapes during start up as basis for future stress analysis

Progress of Models

1st Model: pure Al, simple cooling using fixed values

2nd Model: pure Al, simple cooling using fixed values, solidification

3rd Model: Al-Cu 5%, cooling using heat transfer coefficient, solidification

Wedge Gone Bad

Started using simulations with a wedge

Axisymmetric properties of wedge made it ideal

Problem with geometry of translating smaller wedge to larger wedge

Wedge to Cube

Simulations with the Cube

pure Al, simple cooling using fixed values, solidification

Pure Al, simple cooling using fixed values, solidification, fluid flow

Pure Al, simple cooling using fixed values from only side mold wall, solidification, fluid flow

Cube Simulations

Cooling from sides and bottom

Notice liquid center (red) and solidified region (blue)

Cube Simulations

Cooling from side only Notice liquid center (red)

and solidified region (blue)

Note large different between this and previous plot

Resultant Velocity at 20s

Liquid Fraction at 400s

Thanks to:

Dr. Krane All the grad students that have helped me

when I’m stuck in the lab Purdue