50th Steel T&O draws record crowd, diverse presentations.

The milestone 50th annual Steel Founders' Society of America Technical and Operating Conference, November 7-9 in Chicago, fittingly attracted both its highest attendance in a decade and the presentation of some vital work being done at member foundries. The 210 attendees participated in sessions dedicated to materials handling, clean steel, dimensional tolerances, rapid proto-typing, high-alloy production and environmental/safety concerns.

Direct Pouring/Filtration

According to Kenneth Porter, Varicast, Inc., the foundry has been pouring directly into an insulated riser containing a ceramic filter, which allows it to remove the runner, spree and ingates from some of its green sand molds. In operation, the filter is placed on a ledge in the riser, and two nails are used to hold it in place. The nails melt during the pour and, once the mold is filled, the filter floats to the top of the riser where it won't interfere with feeding.

Since initial trials a year ago, more than 20 of the foundry's patterns have been converted for the direct pouring technique. "Ceramic filter pouring techniques are not used on every pattern," Porter said. "The filter must be cost-justified before it is added." He said that the 5-10% improved yield is one of those justifications, as are reduced cleaning times and improved quality. Pouring time with the method is up to 50% shorter, and the greater heat of the delivered metal reduces cold shuts and laps. Also, there is less spree and gating system erosion and fewer metallic oxides are formed in the mold cavity.

"The use of ceramic filters has been cost-effective and beneficial at Varicast," Porter said, "and we continue to look for cost saving opportunities to expand their use."

Furnace Lining Improvements

To combat upper wall erosion near the bezel ring of its 30-ton basic electric are furnace, American Steel Foundries' Alliance, Ohio plant installed cast iron water-cooled panels in that area in 1989. "After the panels were installed our sidewall life immediately doubled," Thomas Benton said.

To compound the benefits, a new blended lime refractory mixture containing 10% magnesium oxide (MgO) was tried at the slag line. "The thinking was if MgO was present in the lime, the slag would be less caustic to the furnace lining. Bingo! Our sidewall life went from 700 heats to 2400 heats."

Furnace roof longevity was another target for improvement, even though the panels had helped in that area too. "We had experienced premature roof failure before," Benton said. "An accumulation of material at the bottom of the furnace raises the scrap charge and reduces the distance between the bath and the roof." To better control bottom refractory thickness, the foundry devised a "profile gauge" - five lengths of chain suspended from an iron frame that spans the diameter of the top of the furnace. The chains represent the proper distance from the top of the hearth to the bottom of the bezel ring, Benton explained. "It the chains don't touch the lining, it's low at that point; if they pile up, it's high." The foundry is currently averaging more than 600 heats per roof, with a record of 872 heats.

Green Sand to Airset

KO Foundry and Machine is a job shop pouring carbon, low alloy, nickel base and corrosion and heat resistant steels. Traditionally, the foundry used green sand jolt-squeeze molding, and added zircon and new silica sands for facing. "Although quality molds and castings were made this way," said Paul Rudd and Howard Lambert, "sand and labor costs were excessive."

In 1994, the decision was made to switch to phenolic urethane molding. With a set of objectives in mind, as well as challenges to overcome, foundry officials designed a molding loop to produce 20 molds per hr by running six boxes simultaneously. "The system provides for core setting of up to 15 cores per mold," the authors said. After pouring, molds are cooled on three oscillating conveyors beneath a dust collection system to eliminate smoke.

The complete system has many carefully planned and innovative features. To convert the tooling with no extra cost to its customers, KO uses universal mold boxes designed to accept the same insert boards used in the green sand operation. Also, on higher production tooling, custom boxes were designed that eliminate any sand on the mold that is not essential, saving on binder and improving the sand to metal ratio. "Each mold has its own shape," they explained. To further save on materials cost, "molds move very slowly to pouring after being made, allowing them to fully set up. That means we can use less catalyst in the sand mix," they said.

Remarkably, during the six-month construction of the new molding loop, the green sand operation continued undisturbed in the same area. Finally, during a routine, one-week shutdown in July 1994, all the green sand and its equipment were removed. "The employees left a green sand foundry," they said, "and 10 days later returned to an airset foundry."