The measles defect in CA-15 alloy steel castings

An investigation was made to determine the effects of various mold variables on the surface condition of CA-15 alloy steel castings. This alloy often suffers from a peculiar defect known as measles, and an attempt was made to determine what reactions at the old-metal interface cause this defect. To this end, small cylindrical pins were rammed in sand molds and heated or melted in a small induction furnace. The type of sand and clay used were held constant while various atmospheres were provided in the mold flask. It was found that samples heated to 50°C below the melting point in an oxidizing atmosphere showed the characteristic measles defect encountered in casting CA-15 alloy in green sand molds. Samples melted, cooled to 50°C below the melting point, and held at that temperature in an oxidizing atmosphere showed a combination of the two defects. It was found that the measles defect is due to a liquid state reaction in which the chromium in the melt is oxidized to Cr₂O₃·Fe₂O₃ and Cr₂O₃·FeO. The mechanism was found to be akin to a pitting form of corrosion. The oxidizing atmosphere is provided by moisture in the molding material and carbon dioxide formed by the combustion of organic binders.

Name thesis:degree_name

Bachelor

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Metallurgy

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1958

Author dc:creator

• Fraunhofer, Harold G.

• Metallurgy.

Statement dc:rights

• MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/138709

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/138709