The measles defect in CA-15 alloy steel castings
Name
32271434-MIT.pdf
Size
7.79 MB
Format
Adobe PDF
Checksum (MD5)
24c86552460adc32dc419ca61bb6b1ef
Author(s)
Fraunhofer, Harold G.
Date Issued
1958
Publisher
Massachusetts Institute of Technology
Abstract
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.
Description
Thesis: B.S., Massachusetts Institute of Technology, Dept. of Metallurgy, 1958
Cataloged from PDF version of thesis.
Includes bibliographical references (leaf 18).
Subjects
Metallurgy.
MIT Department
Massachusetts Institute of Technology. Department of Metallurgy
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