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A SUPPLIER’S VIEW ON SLEEVE SELECTION


Pure insulating sleeves have their place, but more often than not, exothermic-insulating sleeves provide the greatest benefit in steel casting, according to representatives of Foseco, Cleveland, Ohio. (Foseco refers to its exothermic sleeves as exothermic-insu- lating and traditional insulating sleeves as pure insulating.) “Exothermic-insulating sleeves have a thermal advantage as compared to a pure insulating sleeve. You can feed the same casting section in a modulus-controlled application using an exothermic-insulating sleeve containing less metal volume,” said Bob Sisetski, marketing and technical manager. According to Sisetski, the introduction of pure insulating sleeves allows steel casters to reduce their risers by 1 in. in diam- eter compared to a sand riser. Exothermic-insulating sleeves allow them to reduce riser diameter by an additional inch. The resulting yield advantage, backed by simulation predictions, convinces most steel casting facilities to use exothermic-insulating sleeves, according to Foseco product development manager Tony Midea. “We use a methoding software containing thermal data on all our feeding products to give us an idea what sleeve


not as efficient as the sleeved risers. Te results from the 2 x 2-in. bar


suggested the exothermic sleeve is more efficient on smaller sections. However, it could be argued the difference between insulating and exothermic sleeves are so slight as to


type and configuration is optimal,” Midea said. Steel casters can improve their simulation results by ensuring they have accurate thermal data for their metal and mold materials. “Exothermic-insulating sleeves should be the product of choice, unless the [steel casting facility] is running into some specific constraint,” Sisetski said.


When pouring an alloy sensitive to carbon pickup, insulating sleeves are a safer option, Sisetski said. For alloys sensitive to aluminum-nitride cracking, he pointed out that exothermic-insulat- ing sleeves with a refractory coating, pure insulating sleeves, or mildly exothermic-insulating sleeves with a low aluminum content are possible alternatives.


While exothermic-insulating sleeves cost more than pure insulating sleeves, Midea said for modulus controlled applications, exothermic-insulating sleeves are generally more cost effective than pure insulating sleeves. “There’s just so much benefit when you get that extra 1-in. diameter out of the riser in steel casting,” he said. —Shannon Wetzel, Senior Editor


be negligible. Flask size restrictions and metal availability still should be considered in sleeve choice. Some preliminary work using


both sleeves (3-in. diameter, 6 in. tall) showed the insulating sleeve providing better yield (Fig. 2).


The Responses Following are main points from


each survey respondent, all of which answered the questions anonymously. Company A: Uses sand risers 90% of the time and insulating risers the rest of the time. It has found that


Fig. 2. Facilities using both exothermic and insulating sleeves have conflicting practices when opting for a particular sleeve type. 40 | MODERN CASTING May 2011


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