Molding Methods & Materials Silver Anniversary Paper.

In his Silver Anniversary Presentation titled, "Influence of Chemical Binder Core Sand Contamination on Green Sand Molding Properties--25 Years of Controversy" (04-001), Rodney L. Naro, ASI International Ltd., addressed a topic dating back to the 1970s regarding chemical binder-green sand contamination. It was revealed that chemical binders had little impact on green sand properties.

Since then, there has been a significant growth in chemical binder use due to increased demands. In relation to this trend, usage of cold-curing binders has increased while that of heat-curing binders is not as common.

Naro noted that despite past studies on recycled nobake core sand, the question remained: "What effect will core butts and shakeout core sands have on green sand properties as they enter green sand molding systems?"

In addition to brief analyses of past research, laboratory studies and interviews with three facilities that use phenolic urethane coldbox (PUCB) binders helped evaluate the question. Some of Naro's conclusions were:

* adding up to 100% nobake binder shakeout sand to a new green sand system had little to no effect on green sand properties;

* the compressive and shear strengths, compactability and permeability of green sand was determined to be comparable to that of a standard base green sand system;

* lustrous carbon formation from PUCB binder decomposition doesn't deteriorate green sand systems' properties.