Study of Threading Operations in Austempered Ductile Iron
The focus of this research was to compare three different methods of threading holes into grade 1 ADI and to determine the viability of plastically deforming threads (thread forming) into ADI rather than cutting the material. Identical test specimens were drilled with carbide tipped drills and threaded by cut taps, forming taps, and thread mills. Data used to evaluate the threading methods included cutting force data, surface profilometry, and metallographic analysis. Thread forming was successful and, under the appropriate conditions, can surpass the performance of a cut tap. Threads that were formed had a greater concentration of martensite within the matrix at the threads than those that were cut. Threads formed at 50% thread formation consumed an average of 78% more energy than threads that were cut with a tap. Increasing the thread formation to 75% from 50% in forming operations increased the average energy consumption by 260%. Thread milling was successful but took significantly longer than the other two methods. Threads produced by cutting having an average surface finish Ra that is 27.7% lower (finer) than formed threads.
machinability, austempered, ADI, threading, forming
Candelas, M. (2022). Study of threading operations in austempered ductile iron (Unpublished thesis). Texas State University, San Marcos, Texas.