Printer Friendly

Coreless induction melting conference weighs technology gains, foundry practices.

Coreless Induction Melting Conference Weighs Technology Gains, Foundry Practices

After a particularly interesting, but involved session on furnace refractory lining techniques, furnace design and the different methods of charging a furnace, a young metal shop foreman was heard to remark, "It sure ain't like making bread!"

The young foundryman's comment said a great deal about the nature of the AFS Conference, "Coreless Induction Melting of Steel," held recently in Cincinnati. The conference, coordinated by Ezra Kotzin and Ian Kay, was organized by the Coreless Induction Furnace Committee (8-C) of AFS. The committee's chairman, Kenneth W. Copi, reported that the successful three-day meeting was the first one to encompass a weekend, also including commercial displays as an integral part of the conference.

In his opening remarks, Dr. John M. Svoboda, Center for Metals Production, said that the growth in the use of coreless induction melting has been a major

factor contributing to the technological improvements in quality and productivity experienced by steel foundries in recent years.

Svoboda said that, although most steel foundries use coreless furnaces simply to melt a given alloy in the shortest time, a trend is underway to use the induction furnace as a refining vessel.

He cited three examples of emerging coreless induction melting technologies that will propel the use of this steelmaking technique even faster in the near future. They include liquid metal refining, the Calidus system and vacuum processing.

Liquid Metal Refining (LMR)

This process, developed by the Steel Casting Research and Trade Association (SCRATA), uses a stainless steel ladle placed within an induction coil. The heated ladle is fitted with a slide gate pouring system and a porous plug for the introduction of inert gas.

Svoboda noted that a two-ton pilot facility has proven capable of consistently providing a highly-refined steel heat and holding it effectively for up to 1 1/2 hours. Teaming an induction furnace with a direct arc furnace would allow a foundry the production latitude to supply metal on a semi-continuous basis rather than in batches.

The Calidus System

This system is similar to that described above. Developed in Sweden, it uses a nonconducting ladle shell made of an epoxy-fiberglass composite material which slips into a stationary induction coil. After completing the melt process, the ladle is lifted from the coil and used to pour castings.

Used for the production of highly refined steel, the present composite ladle shell is costly and still relatively fragile for most foundry environments.

Vacuum Processing

A melting trend that is rapidly gaining momentum, vacuum processing is reportedly growing at a 14% annual rate and is expected to capture 50% of the induction furnace market by the year 2000.

The principal benefits of vacuum processing are low hydrogen content and the promotion of deoxidation with carbon under low pressure to provide gaseous deoxidation products rather than potential inclusions. Not new, but not widely used in the U.S. because of its relatively high cost, the growing clamor for "cleaner" steels seems to be tilting the steel foundry industry in the direction of vacuum production.

The importance and diversity of refractories proved to be of considerable interest to conference attendees. Interest was expressed in the most common types of monolithic refractories used for coreless induction production of steel such as the dry vibratables, damp ramming mixes, plastics, castables and patching compounds. Though prefired crucibles, brick and special shapes also were discussed, interest was highest in linings having a single uninterrupted, or so-called monolithic, surface.

The most used refractory is the dry vibratable type, a ground material, moisture free, and mechanically vibrated into place around a form.

Advantages of dry vibratable linings are many. Because they contain no moisture, they can be installed and sintered in a relatively short period of time; they are subject to unique phase sintering, from complete ceramic sintering at the hot face to very little sintering at the cold face, to better guard against crack propagation through the entire lining. In addition, they have longer shelf life than lining materials containing water and are easier to install and remove.

Dry vibratable refractories have some shortcomings. They are highly porous, have low strength and are fragile at the hot face. It was suggested that they should not be used in stressed applications.

A new furnace lining must be burned-in using a controlled temperature rise to force a chemical reaction in lining material. Furnace temperature rise and hold times before charging garnered several opinions; however, it was widely agreed that proper heating during initial sinter will maximize bond formation, increase density and lining strength.

Conversely, rushing a furnace into production definitely reduces the life of a refractory lining, resulting in general metal saturation, cracking during thermal cycling and increased refractory wear.

PHOTO : Ian Kay, Cast Metals Institute, far left, welcomes international attendees to the Coreless

PHOTO : Induction Melting of Steel Conference. They included, from Kay's left to right, Yoshiya

PHOTO : Suzuki, Suzuka Furnace Co/Div of Fuji Electric, Japan; Carlos Luzcano and Dr. Ignacio

PHOTO : Elcoro, both of Hylsa, Monterey, Mexico; Jim Thiessen, Sutherland Steel Foundry,

PHOTO : Saskatchewan, Canada; Maseo Tateno, also from Suzuka Furnace Co; and Hiroo Ikeda, Nippon

PHOTO : Crucible Co, Osaka, Japan.

Tom Bex/Senior Editor
COPYRIGHT 1989 American Foundry Society, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:American Foundrymen's Society
Author:Bex, Tom
Publication:Modern Casting
Date:Dec 1, 1989
Previous Article:Diecasters project steady growth for '90s.
Next Article:Cast iron symposium brings 100 to Tokyo.

Related Articles
New research advances melt control.
Clean steel technology.
Product showcase.
Evaluating operating costs of melt systems.
Melting and pouring.
Over-preheating scrap can cause high levels of melt slag.
Induction melters examine furnace and pouring technology, refractories.
GIFA's 'Technology Summit' unveils world's most advanced production tool.
Speakers Focus on Improving Melt Efficiency, Process Control.
Understanding bottom wear in coreless induction furnaces.

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters