Metallurgical Principles and Practice of Engineering (PE) Study Guide: Question #28

It Is the Policy of The Minerals, Metals & Materials Society (TMS) to Encourage the Professional Registration of Metallurgical Engineers.
A new product is being made as a ductile iron-casting project. The casting has a minimum section size 5 mm. Several attempts to produce this casting in a production facility have been made using various alloy modifications to the base 60-40-10 iron. These attempts have resulted in carbides in the thin section and a fine pearlite matrix. Several suggestions have been made to correct this problem.

A set of 14 castings is found to have a microstructure of graphite flakes, iron carbides and pearlite. Because of the need for test castings for design verification it is suggested that these castings be heat-treated to rectify the microstructure. The proposed heat treatment is to austenitize at 1700°F for 6 hours, cool to 1550°F, and air cool. The most likely resulting microstructure would be:

(A)	graphite flakes and a pearlitic matrix
(B)	graphite temper carbon in a ferritic matrix
(C)	graphite nodules in a pearlitic matrix
(D)	graphite flakes, spherodized carbides in a pearlitic matrix.

The information on this page is maintained by the Nellie Luther (natale@tms.org).

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