Riser insert sleeve breaker cores eliminate pock mark defects at Huron. (Case History).Huron Casting, Inc., a 440-employee shell-molding steel foundry in Pigeon, Michigan Pigeon is a village in Huron County in the U.S. state of Michigan. The population was 1,207 at the 2000 census. The village is within Winsor Township. Geography According to the United States Census Bureau, the village has a total area of 2.1 km² (0.8 mi²), all land. , was experiencing a casting defect while using fiber-based riser insert sleeves and breaker breaker: see wave, in oceanography. cores (referred to as cookies). The foundry was using insertable riser sleeves with an attached cookie to improve the yield of its castings. The insert sleeves improve the thermal properties at the surface of the riser so that smaller, more efficient risers can be used and still will yield a solid casting. The cookies aid this technique by reducing the contact area between the casting and the riser and by incorporating a notch into the riser neck that allows the riser to be easily broken off after shakeout and cooling. However, the use of the sleeves with cookies created gas holes and pock pock (pok) a pustule, especially of smallpox. pock n. 1. The characteristic pustular cutaneous lesion of smallpox. 2. A pockmark. mark defects on the surface of the casting underneath the sand of the cookies. Some of these pock mark surfaces were deep enough to require welding above the casting contour. A heat treat tempering operation also was added to relieve welding stresses, and then the area was snag or hand ground to customer specifications. These additional operations added costs, detracted from acceptable surface appearances, hindered ship dates and decreased customer satisfaction. Huron wanted to eliminate the rework re·work tr.v. re·worked, re·work·ing, re·works 1. To work over again; revise. 2. To subject to a repeated or new process. n. operations to correct these defects. The foundry worked with Ashland Specialty Chemical A Specialty chemical is a chemical produced for a specialized use. They are produced in lower volume than bulk chemicals, of which petrochemicals, made from oil feedstocks, are the most common. However, both are produced in a chemical plant. Co.'s Foundry Products Div., Dublin, Ohio Dublin is a city in Delaware, Franklin, and Union counties in the U.S. state of Ohio. The population was 31,392 at the 2000 census. In 2006, the population was estimated to be 36,565[1], and Dublin continues to be one of the fastest-growing suburbs of Columbus. , to find the optimal recipe for shell sand cookies for use with Ashland's Exactcast Riser Sleeves. Several recipes were tried. The final (and successful) recipe tested included a 3.5% low reactivity binder, fine clay and black iron oxide The material used to coat the surfaces of magnetic tapes and lower-capacity disks. . Gas evolution testing showed there was 21% less gas generated from the new recipe. The reformulated shell sand recipe resulted in a cookie that not only solved the pock mark defects but also contained a lower amount of nitrogen. After June 2002, when new recipe cookies were put into production, pock marks under cookies were reduced or eliminated. A comparison to prior data showed that welding was reduced by 85% and hand grinding was reduced by 22%. These figures confirmed what had already been seen on the castings--a greatly improved surface appearance. Select No. 025 at www.moderncasting.com/info |
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