Simulation of Argon Gas Flow Effects in a Continuous Slab Caster
- PDF / 2,392,491 Bytes
- 21 Pages / 603.28 x 783.28 pts Page_size
- 36 Downloads / 250 Views
I.
INTRODUCTION
A R G O N gas is employed at several stages in the continuous casting process (ladle, tundish, and mold) to encourage mixing, to help prevent nozzle clogging, and to promote the flotation of solid inclusion particles from the liquid steel. It usually enters the continuous casting mold after injection into the submerged entry nozzle (SEN), and eventually escapes from the liquid steel surface through the mold flux powder layer. Argon injected into the SEN provides a positive pressure inside the nozzle, which inhibits the natural aspiration of air through cracks, pores, or joints in the nozzle walls, such as the junction between the nozzle and sliding-gate flow-metering plates. This helps to prevent the formation of the associated reoxidation products, such as alumina, which otherwise form detrimental solid inclusions that can adhere to the nozzle walls to block the flow of liquid or enter the mold cavity with the steel to create other quality problems. Argon helps to prevent nozzle clogging in a second way by creating turbulence that discourages adherence of inclusions to the nozzle walls. Once inside the mold cavity, the argon bubbles are believed to preferentially attach with inclusion particles, thus promoting their removal when the argon leaves the surface of the liquid pool. In addition to these beneficial effects, argon can have detrimental side effects. Gas bubbles, and their associated clusters of attached inclusions, may become trapped in the solidifying shell and create serious defects just beneath the slab surface. Alternatively, they may disturb the liquid steel surface when they exit the powder layer, B.G. THOMAS, Associate Professor, and X. HUANG, Postdoctoral Research Associate, are with the Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801. R.C. SUSSMAN, General Manager of Process Research, is with Armco, Inc., Middletown, OH 45043. Manuscript submitted July 6, 1993. METALLURGICAL AND MATERIALS TRANSACTIONS B
generating detrimental surface turbulence and consequent surface defects. These effects are influenced by the amount and size of the argon bubbles and the flow pattern inside the mold cavity. Moreover, the injected argon gas bubbles also influence this flow pattern. In addition, this has corresponding effects on the extraction of superheat, composition intermixing during a grade transition, and the movement of solid inclusion particles. The extent of these effects is intensified by the volume expansion of the gas bubbles in the high-temperature molten steel. These effects have not been quantified previously, and they are the focus of the present modeling study. If.
PREVIOUS WORK
Experimental measurements on an operating continuous casting machine are very difficult, dangerous, and expensive. Multiphase flow phenomena, particularly volumetric expansion of the gas, are also difficult to simulate using physical water models. The recent development of numerical modeling provides an alternative tool for understanding
Data Loading...
