Influence of a wiper on transport phenomena in direct chill casting of aluminium alloy 7050

Abstract

A fully transient model of the direct chill casting process is used to examine the influence of implementing a wiper to divert the free falling water from the ingot surface on transport phenomena and segregation profiles for aluminium alloy 7050. The ingot diameter and casting velocity are varied to determine the proper wiper placement as determined by the predicted composition, temperature, and fraction solid fields. The segregation level was evaluated by comparing steady state radial composition profiles. The wiper alters the dominant radial heat transfer mechanism, causing the surface of the ingot to heat up below the wiper. Placing the wiper too close to the mould causes the surface temperature to increase above the solidus, making the ingot susceptible to bleed outs. The optimal wiper location was found to be near the bottom of the sump for all process conditions examined.

Keywords:

• Aluminium direct chill casting
• macrosegregation
• wiper

Acknowledgement

Financial support from the Purdue University Bilsland Dissertation Fellowship and Shandong Nanshan Aluminum Co., Beijing Nanshan Institute of Aeronautical Materials is gratefully acknowledged.