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Heat Treat, Penetration Highlighted.

Of the 10 Steel Committee (Div. 9) presentations, the majority focused on preventing defects and treating steel castings to enhance quality.

In their presentation (154), S. Kuyucak, P. Newcombe and R. Zavadil, CANMET/Materials Technology Laboratory, discussed austenitic manganese steels [1.2% carbon, 13% manganese (Mn)], which suffer from intergranular embrittlement. They explored the effect of heat treatment (solution annealing and water quench) and residuals (aluminum, nitrogen and phosphorus) on impact toughness.

Experiments were performed on test blocks cast in Grade B3 and Grade C Mn steel. The authors found that a step-down in annealing temperature did not significantly improve toughness in 1- and 3-in. sections, but reduced distortion in 1-in.-thick plates. As-cast impact toughness increased with larger grain size. Quench water temperatures offered a convenient way to check quench efficiency. A higher temperature anneal can recover some toughness lost due to high nitrogen and aluminum content. Data suggested that more phosphide eutectic formed at lower temperature near the solidus with increasing phosphorous content.

In their exploration of steel penetration in sand molds (130), J.O. Barlow, K.D. Hayes, T.S. Piwonka and D.M. Stefanescu, Univ. of Alabama-Tuscaloosa, developed mathematical models to predict mechanical and chemical penetration. The chemical penetration model shows that when no carbon is present in a green sand mold, penetration always will occur. Foundry experiments demonstrated the validity of their models.

Variables that most affect mechanical penetration are metallostatic head, metal velocity and mold aggragate grain size. To eliminate this penetration, the authors recommended a mold coating, decreased flow rate into the mold and aggregates that are less susceptible to wetting.
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Publication:Modern Casting
Date:May 1, 2000
Previous Article:Aluminum Production Examined.
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